N4231 -1-F NOX. CO L' O' U A Sf 2 C FED A TR AzUAS DEPARTMENT OF GEOGRAPHY Final roxort vy. (-s Li ID' is a ~Y i Ali~" rin~B ~~ ~~7knJJ Co&qfuDQJ V L tVWth~ Ouartermazter 1"Rostoa hnd Devooprijant Corumand Environmontal Protection Research Division Contract Ho. DA-19-129-OIAV-1655 Natick, Al-assachusotts Admiinisored throuah: Gei arh?962 * cr -.. -.... _~ _i _ _ ~A Iij; pi d?rIL.jV tr trO? '3I~ I I,\ r' I /A b.ff1 Ir LL Pr a (II rr~ Fr.i (r f1 _~ *r. __ _ __ _ _

I.A. Accession No. UN CLASIISX'F, AD Accession No. UNCLASSIFIED The University of Michigan, Office of Research Administration, Ann Arbor ANALYSIS OF GEOGRAPHIC BAND CLIMATIC FACTORS IN COASTAL SOUTHEAST ASIA Report No. 04231-1-F, March 62, 178 pp incl. 31 illus., and 30 tables (Contract DA-19-129-QM-1655) Unclassified Report The University of Michigan, Office of Research Administration, Ann Arbor ANALYSIS OF GEOGRAPHIC AND CLIMATIC FACTORS IN COASTAL SOUTHEAST ASIA Report No. 04231-1-F, March 62, 178 pp incl. 31 illus., and 30 tables ((Contract DA-19-129-9-QM-1655) Unclassified Report Description of' a fifty mile wide strip around the coast of Southeast Asia from Pakistan to China. The topics included are: offshore water depths:. overJ Description of a fifty mile wide strip around the coast of Southeast Asia from Pakistan to China. The topics included are: offshore water depths. coastal analysis; land surface with separate studies of relative relief and slope angles; climate and weather with detailed statistics of some weather stations; vegetative cover with a special study of trafficability of rice paddies in Malaya; soils, described by separate countries; a quantified study of the road system with an. interesting new technique for appraisal; and native animals and diseases of importance to military operations. L4NCLASSIFMD. UNCLASSIFIED UNCLASSIFIED coastal analysis; land surface with separate studies of relative relief and slope angles; climate and weather with detailed statistics of some reather stations; vegetative cover with a special study of trafficability of rice paddies in Malaya; soils, described by separate countries; a quantified study of the road system with an interesting new technique for appraisal; and native animals and diseases of importance to military operations. ~ UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED - __ __ __ J

AD Accession No. UNECLASSIFED The University of Michigan, Office of Research.Administration, Ann Arbor ANALYSIS OF GEOGRAPHIC AND CLIMATIC FACTORS IN COASTAL SOUTHEAST ASIA Report No. 04231-1-F, March 62, 178 pp incl. 31 illus., anud 50 tables (Contract DA-19-129-QM-1655) Unclassified Report I - Accession No. UNCLASSIIED The University of Michigan, Office of Research Administration, Ann Arbor ANALYSIS OF GEOGRAPHIC AND CLIMATIC FACTORS IN COASTAL SOUTHEAST ASIA Report No. 04231-1-F, March 62, 178 pp ncl. 31 illus., and 50 tables (Contract DA-19-129-QM-1655) Unclassified Report Description of a fifty mile wide strip around the coast of Southeast Asia from Pakistan to China. The topics included are: offshore water depths; -~ (over) Description of a fifty mile. vide strip around the coast of Southeast Asia from Pakistan to China. The topics included are: offshore water depths(,,rrI UNCLASSIFIED UNCLASSIFIED _ _ I - I b- --- - - I~ coastal analysis; land surface with separate studies of relative relief and slope angles; climate and weather with detailed statistics of sole weather stations; vegetative cover with a special study of trafficability of rice paddies in Malaya; soils, described by separate countries; a quantified study of the road system with Ln interesting new technique for appraisal; and native animals and diseases. of importance to military operations. UNCLASSIFIED coastal analysis; land surface with separate studies of relative relief and slope angles; climate and weather with detailed statistics of some weather stations; vegetative cover with a special study of trafficability of' rice paddies in Malaya; soils, described by separate countries; a quantif ied study of the road system with an interesting new technique for appraisal; and native animals and diseases of importance to military operations. UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED -- - - i

J, i-.. AcsnNo. CS'.AesoN... S.. r J AD A~Lccessi;' n No. JN CLASSIFED The University of Michigan, Office of Research Administration, Ann Arbor ANALYSIS OF GEOGRAPHIC AND CLIMATIC FACTORS IN COASTAL SOUTHEAST ASIA Report No. 04231-1-F, March 62, 178 pp incl. 31 illus., and 30 tables (Contract DA-19-129-QM-1655) Unclassified Report t i A.Ccession No. UNCLASSIFIETp The University of Michigan, Office of Research Administration, Ann Arbor ANALYSIS OF GEOCRAPHIC AND CLIMATIC FACTORS IN COASTAL SOUTHEAST ASIA Report No. 04231-1-F, March 62, 178 pp incl. 31 illus., and 30 tables (Contract DA-19-129-QM-1655) Unclassified Report Description of a fifty mile wide strip around the coast of Southeast Asia from Pakistan to China. The topics included are: offshore water depths. o rveerl I Description of a fifty mile wide strip around the coast of Southeast Asia from Pakistan to China. The topics included are: offshore water depths' ( rTerY - UNCLASSIFIE UNCLASSIFIED h )V~ ---~ _ w V Fi L of - - - -- - coastal analysis; land surface with separate studies of relative relief and slope angles; climate and weather with detailed statistics of' some weather stations; vegetative cover with a special study of trafficability of rice paddies in Malaya; soils, described by separate countries; a quantified study of the road system with an interesting new technique for appraisal; and native animals and diseases of importance to military operations. UNCLASSIFIED coastal analysis; land surface with separate studies of relative relief and slope angles; climate and weather with detailed statistics of some weather stations; vegetative cover with a special study of trafficability of rice paddies in Malaya; soils, described by separate countries; a quantified study of the road system with an interesting new technique for appraisal; and native animals and diseases of importance to military operations. UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED A -----— -- B

I j --- - I ~ — - AD Accession No. UNCLASSIFED AD Accession No. UNCLASSIFIED The University of Michigan, Office of Research Administration, mnn Arbor ANALYSIS OF GEOGRAPHIC AND CLIMATIC FACTORS IN COASTAL SOUTHEAST ASIA Report No. 04231-1-F, March 62, 178 pp incl. 31 illus., and 50 tables (Contract DA-19-129-QM-1655) Unclassified Report T.e University of Michigan, Office of Research Administration, Ann Arbor ANALYSIS OF GEOGRAPHIC AND CLIMATIC FACTORS I; COASTAL SOUTHEAST ASIA Report No. 04231-1-F, March 62, 178 pp incl. 31 illus., and 30 tables (Contract DA-19-129-QM-1655) Unclassified Report Description of a fifty mile wide strip around the coast of Southeast Asia from Pakistan to China. The topics included are: offshore water depths3 fovep-l Description of a fifty mile wide strip around the coast of Southeast Asia from Pakistan to China. The topics included are: offshore water depths; ( nvrl UNCLASSIFIED UNCLASSIFIED coastal analysis; land surface with separate studies of relative relief and slope angles; climate and weather with detailed statistics of some weather stations; vegetative cover with a special study of trafficability of rice paddies in Malaya; soils, described by separate countries; a quantified study of the road system with an interesting new technique for appraisal; and native animals and diseases of importance to military operations. UNCLASSIFIED coastal analysis; land surface with separate studies of relative relief and slope angles; climate and weather with detailed statistics of some weather stations; vegetative cover with a special study of trafficability of rice paddies in Malaya; soils, described by separate countries; a quantified study of the road system with an interesting new technique for appraisal; and native animals and diseases of importance to military operations. UNCLASSIFIED L.UNCIA~SSIFIE UNCLASSIFIED UC J

T HE U N iVE R SI TY O F MI CH I GA N COLLEGE OF LITERATURE., SCIENCE AN~D THE -ART-S Department of Geography Final Report ANALYSIS OF GEOGRAPHIC AND CLIMATIC FACTORS IN COASTAL SOUTHEAST ASIA ORA Project O04231 under contract with: A ~-~J ---1AD -.' ~lDDEVELOPMENA'T COMMAND EN'IVIRONMIENTAL PROTECTION RESEARCH DIVISION CONTRACT NO. DA-19-129-Qyi-1655 NIlATICK, M.1,ASSACHU9SETTS ad-ministered through: OFFICE OF RES:-EARCH ADMI'NISTRATION ANEARBO)R March 1962

TABLE OF CONTENTS Page LIST OF TABLES v LIST OF FIGURES vii LIST OF MAPS ix I. INTRODUCTION 1 Directive 1 As sumptions 1 Presentation 2 Basic Map Coverage 2 II. APPROACHES TO THE COAST 5 Offshore Water Depths 5 Measurements 5 Coastal Type Analysis 6 Available Map Coverage 6 Variability of Map Data and Nomenclature 13 Coastal Regions and Geomorphology 13 III. SURFACE QUAIITY 31 Lanld Types 4 Physical Regions 35 Analysis of Relative Relief 48 Method used in this Study 48 Analysis of Slope 51 Tmplications 52 MIethod of Slope Analysis 52 IV. CLIMATE AND WEATHER 6 Climatic Controls 6 Climatic Elements 64 Temperature 64 Precipitation 68 Type I. Hill Country, Summer Rain-Winter Drought 70 Type II. Accentuated Summer Maximum with Dry Winters 73 Type III. Normal Summer Maximum 74 Type IV. Accentuated Autumn and Early Winter Maximum 75 Type V. Double Maximum, Transitional Type 76 Storms 76 iii

TABLE OF CONTENTS (Concluded) Page Monthly Analysis of Weather Stations 78 V. NATURAL VEGETATION AND LAND COVER 107 Distribution of Cover Types 110 Cover Type-Analysis from Map Coverage 113 Cultivated Land 115 Rice Paddy Areas and Trafficability in Malaya 120 Sources: Vegetation 123 Maps 127 VI. SOILS 129 Generalized Pattern of Soils 129 The Soils of Burma 130 Arakan Coast 132 Irrawaddy Delta 134 Soils of Malaya 157 Soils of Thailand 139 Soils of Cambodia.39 -Soils of Southl VietNam 140 Soils of North VietNami 141 Sources: Soils 142 VII. ROADS AND CO'U:-TJ ICATIONS 143 Analysis of the Transportation Network 1-5 The Properties of a Transportation Network 145 Sample Design and Measurements 147 Sample Areas and Sample Observations 148 Characteristics of the Transportation Network 150 Quality of Surface and Construction of Transportation Network 157 Directional Trends in the Transportation Network 162 Connectiveness of the Transportation Network 167 Summnary of Transportation Network Analysis 175 VIII. NATIVE iANIMALS AND DISEASES OF ICMPORTANECE TO MILITARY OPERATIONS 177 Native Animals 177 Diseases 177 Sources: Native Animals and Diseases 178 iv

LIST OF TABLES Table Page 1. Offshore Locations of the Five- and Ten-Fathom Contours 7 2, Exact Locations by Place Name, Latitude, Longitude, and Map Number of Sampled Areas with Offshore Distances of Five- and Ten-Fathom Contours 8 35 Areas Covered by Coastal Type Analysis 12 4. Summary of Coastal Type Analysis 16 5. Coastal Types Analyzed by Accessibility 21 6. Distribution of Coastal Types by Geomorphological Areas 22 7o Coastal Analysis 23 8. Relative Relief by Physical Regions 49 9. Percentages of Project Area in Categories of Relative Relief by Physical Regions 51 10. Measurements of Slope Determlination il Complex Hills 55 11. Computations of Slope Determinaition in Complex Hills 58 12. Selected Weather Elements for Weather Stations (JanuaryDecember) 80 13. Map Analysis of Natural and Cultivated Vegetation by Geomorphological Types 114 14. Periods of Possible Trafficability of Rice Areas of Malaya 124 15. Agricultural Calendar for South VietNam 125 16; Square Miles of Area and Number of Sample Observations by Landform Type 148 17. Transportation Network Sample Observations 152 v

LIST OF TABLES (Concluded) Table Page 18. Total Network Mileage Based on Estimated Density of Network in Plains and Uplands Compared with Actual Mileage by Sample Areas 154 19. Distances to Nearest Road from Randomly Chosen Points in Uplands, Plains, and Delta 156 20. Total Mileage and Proportions by Class of Route for Transportation Networks of Coastal Southeast Asia 159 21. Transportation Network Mileage and Proportions by Quality of Surface and Construction 160 22. Medians and Ranges in Proportion of Transportation Network in Each Class of Route by Landform Types 162 23. Directional Trends by Ratio of Boundary Points 164 24. Ratio of Directional Mileage of Transportation Network by Sample Areas 166 25. Area of very Sparse Transportation Network 168 26. Network Events Per 100 Miles of Route 169 27. Internal and External Connections and Endpoints as a Percentage of Total Network Events 171 28. Internal and Boundary Points, Line Segnents and Percentages of Line Densities to Line Density of Minimum Connected Networks 174 29. A Selected List of Insects and other Animals of Lmportance in the Transmission of Disease or as Pests in the Countries of Southeast Asia 179 30. Principal Contagious Diseases of Southeast Asia 182 vi

LIST OF FIGURES Figure Page 1. Cross Section A and B. 3 2. Cross Section C. 39 3. Cross Section D. 40 4. Cross Section E. 42 5. Cross Sections F and G. 44 6. Cross Sections H and I. 4 7. Limestone Hills on the Tonkin Delta. 47 8. The highlands of northeastern Tonkin. 47 9. Country at margin between hi ghlands and Tonkin Delta. 48 10. Distribution of categories of slope frecquencies. 61 11.- Temperature graphs. 67 12. Diurnal distribution of precipitation in Malaya. 70 13. Typhoon tracks in Tndo.ChinR and the South China Sea. 7 14, Climatic -JnformJLation-.Penang. 92 15. Climatic information-WJellesley. 9 16. Climatic information-Malac-1ca. 94 1.Climatic information-Bnko.95 18. Climatic informnation-I.lot Cone. 96 19. Cl imat ic in-fo-riat ion-Phnom Pehn. 97 20. Climatic Information-Ha Tien. _98 vii

LIST OF FIGURES(Concluded) Figure Page 21. Climatic information-Phan Thiet. 99 22. -Climatic information-Dalat. 100 23. Climatic informationi-Nha Trang. 101 24. Climatic information-Quang Ngai 102 25. Climatic infor-mation-Tchepone. 105 26. Climatic information-Dong Mai. lot 27, Climatic inforr-aation-langson. 105 28, Profile of a rain forest. 109 29. Percent of cover on plains. 116 50. Abstract characteristics of transportation network. 146. 31. Transportation network —srimple observations. 152 viii

LIST OF MAPS Map Page 1. Location of depth samples and areas covered by coastal type analysis. 14 2. Sandy coast. 17 3. Hilly coast. 17 4.. Sand dunes and lagoon coast. 18 5. Swamp and mangrove coast. 18 6.Mangrove coast. 19 7. Tidal flats. 19 8. Rocky offshore. 20 9. Geomorphological and physical areas, 32 10. Percent slope at sample points. 5L 11. Average precipitation and prevailing surface winds, June, July, and August. 65 12. Average precipitation and prevailing surface winds, December, January, and February. 66 13. Monthly precipitation. 71 14. Precipitation reginns and weathr stations. 72 15. Generalized vegetation. 1ll 16. Cover of part of South VietNam. 112 17. Malaya-land use. 117 1. Types 'o rice cultivation on Indo-China. 119 1. Times of rice harvest in the Tonkin Delta. 126 ix

LIST OF MAPS (Concluded) Map Page 20. Generalized soil map. 131 21. Soils of North Burma. 133 22. Soils of the Irrawaddy Delta. 136 23. Soils of Malaya. 138 24. Principal roads and railroads. 144 25, Transportation-sample areas. 149 x

I. INTRODUCTION Directive Contract No. DA 19-129-QM-1655 between the Headquarters of Quartermaster Research and Engineering Command, U.S. Army Quartermaster Research and Engineering Center, Natick, Massachusetts, and the Department of Geography, The University of Michigan, directs that the contractor "tshall e^ert his best efforts with a view toward: "1. Determining the environmental elements (e.g., weather and climate, landforms, soils, vegetation, native animals, diseases, and the physical works of man) in the coastal areas of Southeast Asia (Burma, Thailand, and Malay Peninsula, and the countries of former French Indo-China) which should be econsidered in the design and operation of all types of military equipment." As sumpt ions Certain assumptions were made by the contractor within the broad framework of the directive to limit and guide the research work. These were@ A. The "coastal area" was considered to be an area extending inland for an arbitrary distance of fifty miles and included the offshore water. B. That "operation" implied military operation by a commander who would need to know the environmental character of whatever part of the coastal area in which his operations were being conducted. C. That basic i nfo.ation about all of the elements listed in the directive would not be available in the same degree of detail for all of the area, so that the several sections of the report should not be confined to any given degree of detail and that each one should be relatively complete in itself. D. That the report would be used for both of the purposes (design and operation) mentioned in the directive cad should be easily understood by persons without extensive geographic knowledge and vocabulary. 1

Presentat i on The envirornmental elements are presented in topical form with regionalization, when applicable, made on the basis of the individual element. Qualitative descriptions are supplemented by quantitative analyses in those parts of the repnrt where the data lend themselves to quantification. Basic MVap Coverage In several of the tables, maps are referred to by numbers 1 to 85. These represent the numbers given to the maps of several series on the 1:250,000 and similar scales, arranged in series around the Project Area from northwest to northeast. For purposes of identification the exact designations of these numbered maps follows: Number 1 2 5 4..5 6 7 8 9 10 11 12 15 14 15 16 17 18 19 20 21 22 25 24 25 Series and Iindex Number U542 U542 U;42 U542 U542 U542 U542 U542 IJ5c142 u542 U542 L509 U5 42 U542 U542 U542 U542 U5 42 U542 L508 L508 L508 L50.S L'- O NF 46-10 NF 46-14 NF 466-15 NE 46-5 NE 46-7 NE 46-8 NE 46-12 NE 466-15 NE 46- 16 ND 46-4 NE 147-15 NE 47-9 NE 47-14 NE 4.7-14 ND 47-2 ND 47-6 ND 47-10 ND 47-11 NC 47-2 ND 47-6 C 4170 C-47V B-47C B-47D B-47J Scale 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,030 1:250,000 1:250,000 -1: 250,000s 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:255,440 1:253,440 1:255,1040 1:r 53 5L[LO 1:255,440 1:255,4,0 2

Number 26 27 28 29 350 31 32 33 34 35 36 57 38 4o 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 -7 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 Series and Index Number L501 L501 GS GS L501 L501 L501 L501 L501 L501 L501 L501 GS GS GS GS L501 GS GS GS GS GS GS GS GS L501 L508 L508 L508 L5-O L509 L509 L509 L509 L509 L509 L509 L509 r r n.~ L509 L509 L509 L509 T 5o9 i-50 L509 L509 L509 L509 T rL L5 09 L509 - B-47K 2I 4218 13-47R B-47W B-47X 3A 313 A-47L A-47G & part A-48M 3L A-48 0 4218.A-481 4218 A-48H c3 4218 B-48T 4218 B-48S 4218 B-48N 4218 B-48M 4218 B —48G 13-47L B-47E C-47W C-47V C-47P & C-47Q NC 47-7 NC 47-3 ND 47-15 ND 47-11 ND 47-12 ND 48-9 ND L7-16 ND 48-13 NC 48-i NC 48-2 NC 48-5 NC 48-7l NC 48-15 NC 48-1 NC 48-7 NC 48-8 NC, 48-4 NC 49-1 ND 49-13 ND 49-C ND 49-5 Scale 1:255,4140 1:253,440 1:253,440 1:253,k40 1:253,440 1:253,440 1:253,440 1:253,440 1:253,440 1:253,440 1:253,440 1:255,440 1:253,440 1:253,440 1:253,440 1:253,440 1:2535440 1:253,440 1:253,440 1:253,440 1:253,440 1:253,440 1:255,440 1: 255,440 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 1:250,000 3

Nim~ber 715 7)4 75 76 77 78 79 80 0, O-i82 83 8)4 85 -Series and Index Number L509 L509 L509.L509 L509 L509.L509 L509 T509 L50-9 L509-.L509 L509 ND )48-4 ND 149-1 NE )4.9-13 NE t48-16 NE 48-15 NE 48-12 NE 4-i8-11 NE 48-7 NE kL18-3 NF 4i8-15 NF 4v8-16 NF 4i8-11 NF 4i8-12 Scale 1-:250,000 1:250.,000 1:250,000 1:250,000 1:250,9000 1:250, 000 1:250,000o 1:250,9000 1:250,000 1:25 ---0,000 1:250,000 1:250,00 1:250,00 Personnel connected with the research and preparation of this report are: Project Director: Charles M. Davis Research Associates: L.-A. Peter Gosling, David L. Jones., Ian M. Ivatley, John D. Nystuen., Waldo R. Tobler, Paul Vander Meer Research Assistants: Alberta A.. Bella-ire, Donald J. Lenick, Anne Lindgren, Susan.H. Perham., Ann Peterson, Jean P. Ponchie, William Rogell., Helen Thompson. 14

II. APPROACHES TO THE COAST It seems a reasonable assumption that any military operations in Southeast Asia will involve landing of personnel and equipment on the shore. It is also probable in any widespread operations that several such landings would be made because the capacity and extent of the road and railroad system would not permit long supply lines. During World War II the Japanese forces used coastwise amphibious movements to circumvent defense lines across the Malay Peninsula. For these reasons it seemed useful to analyze the coastal conditions of the area. This analysis has been done in two parts: first, a study of the offshore water depths; second, an analysis of the nature of coastal structure and cover which might affect amphibious landings. The offshore water depth study is complete for the entire coastline but the coastal type analysis had to be limited to the areas for which large scale map coverage was available. For both studies the raw material data is presented with some summaries and generalizations. Thn data of the analyses indicate that approximately 30/o oi the examined coast is easily approachable; that about the same percentage is inaccessible, mostly because of mangrove growth; and that the remainder presents problems either in the approach itself or on the inmlediate shore. The inaccessible areas as well as the problem areas are interspersed with accessible areas so that amphibious landings would be possible within almost any considerable strip of the coast. Offshore Water Depths There is a coimnon but not universal relationship between the offshore depths and the coastal geomorphology. This may be stated: deep water is closer onshore along hilly and mountainous coastlines and farther offshore on flat alluvial coasts and deltas; on bay-and-headland coasts the deep water approaches most closely onshore at the headlands and is most distant offshore in the bay bottoms. Considering the whole of the coastline of Southeast Asia and medians of measured samples, the five fathom con-tour will usually be locate-d from one to two miles off:shore and the ten fathom contour two to five miles offshore. NtAS UREM1 S NTS The 1:250000- coverage was used for measuremient because the HO charts were

on smaller scales and the fragmentary coverage of larger scales (1:50,000 and 1:65,5360) did not always include hydrographic. information and also the sheets seldom extended far enough offshore for the purposes of this analysis. The five and ten fath om contours were used in the analysis because they were available on the 1:250,00cvrg nd also because it was probable that transports and larger vessels could approach the shore landward of the ten fathom contour but not beyond the five fathom con-tour. One or more measurements were made on elach of. t~he 85 maps of the area coverage except those with no shoreline. For'summary purposes the data has been divided into distributional areas in terms of location from Burima around to the China border. The'data itsel-f does not show any regionality except for the association with geomorphology mentioned above., The accompanying map (Map 1) shows the locations of the samples; two of the same number means two samples, from the same, map. The names of the locational areas are also shown on the map. Co-astal Type Analysis A survey of incomplete, mapD coverage indica-tes that about. Q olf t~he coast-, line is open to easy access by any kind of landing craflt and about 13% prpesns some but probably not. seriouls offs-h~ore obstacles, such as roc~ks, coral., or san —Idbanks. About 25% Ihas.onshbre conditions that present di f ficulties and some is- 4naccessible, almost entirely because of manngrove growt~h. The poorest coastal conditions were found along the west coast of Thai~land and South, Burma and the best conditions, as judged from incomplete coverage cco-ur alon-g the South China Sea Coast and the southern peart oft.e Gulf of Tor.1un_1i, A survey of coastal types was made from the available lar~~e-scale map coverage to d.1eterm-ine the frequ,1ency an egahcal d1 2stribution of the types. The objective was to asc-er-tain the availability of coastal areas on which landings could be made. AVATLA-BLE MAP COVERAGE J r " e' I fl th 20, 003,0 and smilDar scls a ot- usfu fr h prpse fh obj ectLI'e The l:2?.,O ev~ tl -'st, ald ncct b 1 -ai but- the area 2ov-erecd at this scar' w. -orfined to cn- part ef t'.-, caC-1t a n thercfore did n1-ot -t ake-1 0 _ai ncci dsparP1_e " kc-rrdag 1,,: avi~ar 'n) mn Ot the, west. coast a re a and 1 `0,000 for appyIx1rately Orl-e-1oV 11f ofte c I d. ri na C-.ca st. An atteu-r-ot was_ inacir- to g'-neralize the mis-In r-ap lurm the 1:650,000 Mars but, tLhe results:7 of` 1 -r'a1 clhecks were -net cc!:rparable, 6

TA3LE 1 OFFSHORE LOCATIONS OF THE FIVE- AND -THE TEIN-FATHOM, COIvONTIIS (Arranged by distributional areas in terms of increastng distances from shore) VC - very close, computed as 0.0 in figuring averages. OM - off map, commonly distances of ten miles or more (where OM readings occur the average distances are n ',computed). Measurements in miles perpendicular to shore direction. 5 Fathoms 10 Fathoms [ 5 Fat'homs 10 Fathoms BAY OF BENGAL (9 samples) IVC 0.0 1.0 0.5 1.0 0.5 2.0 1.0 2.0 1.0 2.0 1.0 6.0 2.0 12.0 2.0 13.0 5.5 15.0 Average 1.27 Average 5.77' Median 1.0 Median 2.0 GULF OF MAPTABAN (4 saplea) 1.0. 3.0 2.0 Om 2.0 Om 20.0 O Average 6.25 Average - Median 2.0 Median - ANDAOMAN COAST (9 samples) VCO0.0 0.25 VCO0.O 0.50 VCO0.0 1.25 0.75 2.0 1.0 2.0 2.5 4.0 4.0 4.5 5.0 7.0 5.0O 7.0 Average 2.0 (1.9722) Average 3.166 Median 1.0 Median 2.0 MLCCA STRAIT (11 samples) IC, 0.5 0'.75 1.0 1.0 1.25 1.0 1.50 1.0 2.0 1.5 3.0 1.75 5.0 5. 0 5. 0 3.06. 5i.0 8.o 6.0. 16.0 Average 2.1818 Avei-ug, 4.5409 Median 1.5 Median 5.0 1I MALAYA EAST COAST (8 samples) 'IC 0.0 1.5 VC 0.0 2.0 0.25 2.0 0.5 2.5 0.75 5.5 1.5 50 3.0 5.0 5.0 -6.0 Average 1.1250 Average 5.4375 Median 0.5 Median 2.5 GULF OF SIPAM- (16 samplea) 'IC 0.0 0.5 'IC 0.0 0.75 0.5 2.0 1.0 2.5 1.0 2.5 1.0 4.0 1.5 5.0 1.5 5.5 1.5 6.0 2.0 7.0O.2.0 9.0 2.5 10.0 5.0 10.0 4.0 13.0 7.0 14.0 19.0 Om Average 2.9687 Average -- Median 1.5 Median 5.5 SOUTH, CHINA SEA COAST (11 samples) 'IC 0.25 VC 0.5 'IC 0.5 0.2- u.75 0.25 0.75 0.25 1.0 0.25 1.0 0.5 1.0 1.) 0.75 4.0 5.0 7.5 Average 0.7045 Average 1.7045 Median 0.25 Median 1.0 Averag( Me di am GULF OF TONKIN (5 samplea) 'IC 0.5 0.5 (.0 1..5 8.0 5.0 15.0 114.0 24.0 e 5.8 Average 10.5 Median 8.o 7

TABLE 2 EXACT LOCATIONS BY PLACE NAME, LATITUDE, LONGITUDE, AND MAP NUMBER OF SAMPLED AREAS WITH OFFSHORE DISTANCES OF FIE- AND TEN-FATHOM CONTOURS 5-Fathom Line, 10-Fathom Line, Map No. Locationemiles miles miles (1) (2) (2) (3) (4) (4) (5) (5) (6) a (8) (8) (9) (10) (11) (11) (U) (12), (15): (15)! (16) (16) (1-) N (18) N NF 46-10 NF 46-14 NF 46-14 NF 46-15 NE 46-3 NE 46-3 E 46-7 NE 146-7 & (7) NE 46-15 yx 46-15 Countryt BURMA Out of territory Thawinchaung 20025' N 92~35' E Dahaing 20~10' N 92'50' E No coastline *ICyunzon Taung 19~47' N (an island) 93~02' E West Point 19~20' N (an island named Ramree) 93026' N Thandougzu 18050' N 93~551 E Agat Eatung 18~16' N 94~20' E Sheets off coast Tazin 16~52' N 94*22' E 16'33' N Alegon 91{145' E Sheet off coast Purian Point 15~50' N 94~22' E Both following are in Gulf of Martaban: Tawpalwc - 1615' N 96~00' E adanukkon 16*50' N 97~22' E Off coast Roc.~' LegV 15~l5' N 97~42' E Pagoda 15~55' N 97 35' E White Point 14052' N 97047' E S. of Pagoda Point 14~12' N 98'03' E Th.-n Maw 13'32' N North of Mergui 12'29' N 98'35' E 2 3-1/2 1/2 1 Close off shore 1 1/2 1 12 13 1 2 13 2 1 2 ND 46-4 NE 47-13 NE 47-13 (13), & (14) NrD 47-2 N-D 47-2 ND 47-6 ND 47-6 nD 47-10 U0 47-14 2 6 20 2 Cauiot be found on mip Canunot be found on map Extremely close to shore 1 Extremely close 3 Indefinite 2 2 1/2 4-1/2 8

Map No. TABLE 2 (Continued) Location Country: BURMA (Concluded) 110101 N 98044' E 10036' N 99*29' E 5-Fathom. Line, miles 10-Fathom Line, miles (19) NC 47-2 (20) NC 47..6 Alyne Tutkabo Maw 5 2-1/2.7 4 (21) (22) (22) (23) (24) (25) c-47 0 c-47 U c-47 U B-47.C B-47 D B3-47 J Loam Pho Laimtam Chak Leem Son Laem Nun Nai B Ta Pe B Bau Ched Luk Country: THAILAND 90381 N 98'28' E 8*32' N 98013' E 80021 N 980151 E 70473 N 980163 E 70211 N 99'78' E 60521 N 990403 E 3 3,/4 Extremely close Extremely close 6 5 7 1-1/4 1/2 1/4 (26) B3-47 K (27) Sheet 21 (28) (229) B-47 W (350) B3-47 Y (31) Sheet 3A (32) Sheet 3B (33) A-47 L (34) A-48 G (34) A-4.8G (35)" Sh.eet 3-L (06) A-48 0 Country: MALAYA Kg Kubang 6007' N 1000163 E Yen 500471 N 100*22' E3 No shoreline lBt Batu Tiga 40103 N 1000371 13 No shoreline Tejon~g Sauk 3047' N 100049' 1 West of K Selangor Fort 3022! N 101*10 E Fort Dickson 2*32' N 1010473 E Tg Klinz 21i4' N 1020073 E Kg Jawa 1052' N 102*40' E Tg Friai (Bules) 1151 N 103 *301 E Kg Telok Bamunia 101731 N lo4*15' 13 3 3 3/4 1-3/4 1-1/2 Extremely close 1 1 1 Extremely close S 6-1/2 1 3 3 1/2.1-1/2 1-1/4 2 2 9

Map No. (37) (53).A-48 H (59) A-48. B (;40) (41) B-48 T (42) (h44) B-:8 M (45) 3-h13 G (46) 3-27 L TABLE 2 (Continued) Location Country: MALAYA (Concluded) Very little shoreline Tg Penyabony 2~58' N 103~47' E Kg K Pahang 3~32' N 103~27' E No shoreline Kg Telok Kalong 4~17.' N 103~27' E No shoreline Bt Chenering 5~16' N 103~10' E Kg Mcrang 5~32' N 102052' E Kg Sabak 6~10' N 102~20'- E K, Tauk Ha 6~50' N 101~32' E j=-k 5-Fathom Line, miles 10-Fathom Line, miles 1-1/2 3 5 6 2 Vzry close 1/2 3 3/4 3-1/2 2-1/2 5 1-1/2 i7) (,8) (29) (49) (5. (. -) (.2) ( C,<4) 3-);7 N C-h 7 V "C!" 1,d.. - I -.11 - 1 -, 2 1 ~. Country: THAILAND Songkiila 7~13' N 100~10' E Laem Lurn Phuk 8~30' N.00~1('. E Sichon 9~00' N 99~)5' E Pa'k Chlong 9~07' N 99~53' E North of Kowiang Islrnd l10~0 ' N 9 ~52' E,-;ao Mae RHanlphung l~1'1' N 99~53' E an; h. n;r.ng Tanot 12010' N 100~02' E H:at Pak 'hlo. 15~00o' N.iOO~0' E Laem Chaba:n 15~003 N 100~ 2' E:o coas tline La^em Pu Chao 12~L0' N 10C~ 2' E?ran Th.',i.cc.at L::'n' 12~10':; 10~17' N 10 2-1/2 3 1 1-1/2 Very close 1/2 1-1/2 o 1 V'ery close 14 1.0 9 -f 5/4

TABLE 2 (Continued) Ma N.Loa3o -Fathom Line, l0-Fatlhom Line, Ma o oainmiles miles ( 59) NC 48-1 (6o) (61) NC 48-5 Pointe Kah Kus. No shoreline A point SE ofI kuountry: CAMBODIA sat U1105' N l03-05' E Ream 10"30' N 103138' E 1 1-1/2 2-1/2 (62) NC 48-6 (63) NC 48-10 (64) vs4a o c (65) NC.48-11 (6-6) NC 48-7 (67) NiC 48- 8 (68) (69) NC 49-1 (70) NDo 49-13 (71) riD 49-9 (72) ND 49-5 (73) (74) ND 49-1 (75) NE 49-13 ('(6) NE, 48-16 (77) (78) N-E 48- 12 (79) (Bo) NEr 48-7 Country: MUi Ong Thoa Point South of Lea Mamelles Xam Mui Ap Baa Thanh Cap Saint Jacques Pointe de Ke Ga No shoreline Mui Sung Truu Dam Van 'Phu Oc Vinh Tuy No shoreline Cap Na~m Tram Cap Chon May (east) Vinh Tri No shoreline Cap LAY No shoreline Cap mui Ron Ma:VIETNAP 100083 N 104 5,,8' E 9002' N 1040483 E 8',38' N io4l,43' E 9`40' N 1o6o4o' E 10 020 N 107-15 E 1o04o' N 1o8'oo' E 11018' N 109000' E 12025 N 109"20' E 13018' N lo0918, E 1404o' N 109.05- E 15-25 ' N lo,815o' E 16020' N 108o02' E 1614o' N 107"35' E 17-05' N 107*05' N,L8o18' N lo6928' E 19 7 4 5 Very close 1/4 Very close Very close I.1,, 1/4 1/2 1/4 1/4 1/2 Very close Extremely far 13 5 7-1/2 4 1 1/2 1/4 1 3/4 3/4, 1/2 1-1/2 1 1/2 11

TABLE 2 (Concluded) Map No. Location 5-Fathom Line, 10-Fathom Line, miles smiles Country: VIETNA24 (Concluded) ( IC ~ 4- ~ Cap Talus 19,2-lo 1/27 lo5648' E (891) INE 48Q-5 Cap Chao 190429 N 1-1/2 125-1/2' 105'52' E (82) No appreciable shoreline (85;) mv )48-16 Point nearilon DaU Sight 20*42' N.5 8 w.6048? (84) No shoreline (85) DE 48-12 Nui Cat 21020' N 1424 107037' E Complete coverage was obtainable for the Burma Coast (see Coastal Regions, below) the Gullf of Martaban, and for most of the Andaman Sea Coast and Malacca Straits. For these areas meaningful generalizations can be made. The coverage for the East Malay Coast is all in one section. representing more than haiL' of the coast. There is so little coverag-,e in the Gulf of Siam as to be useless but that on the South China Sea Coast represents a good sample. In the Gulf of Tonkin the parts representing the Red River delta are missing but the rest is complete. TA PLE 3 AREA); M0\DED BY COASTAL TYP'E ANALYSIS P~tnNO. of Estiriated Estimated M4iles C Maps % Covered 1, Missilsg Coiered,. Cu~ O Martatars*"d'iafta Sea os ' Ch'nEast Coast Totals 100 0 0 1.9 100 26 ij25.; 56 (20 169 10) 136 15)4 95 I ek5 >1. 49 155 16 20(2 1 71 5..1 L 12

VARIABILITY OF MAP DATA AND NOMENCLATURE In this part of the survey, we are compelled to rely upon maps which vary from series to series, possibly from map to map, in the criteria and the names used to identify coastal conditions. As examples, the designation "Sand Bank" occurs on only one map and "Mud Bank" on only eight. The entire areas of the South China Sea Coast and the Gulf of Tonkin, represented by 99 maps do not show such designations. On the same 99 maps there is no designation "Tidal Flats" which must be common in most places. On the 58% coverage of the Malay East Coast there is no designation "Mangrove" although some 21% of the covered coast is designated "Swampy." Because of these and many other inconsistencies, the raw material of the survey is presented and implications and assumptions must be understood as being subject to the limitations implied above. COASTAL REGIONS AND GEOMORPHOLOGY For purposes of convenience in analysis, the coastal area has been separated into eight sections. Some of these have recognizable geomorphological differences, but these differences are those of inland structure and are not statistically recognizable in coastal types. The eight sections described below are delineated on Map 1. Burma Coast (15 to 21~ north latitude). Much flat plain north of 20~; Arakan Range, 17 to 200 but fronted with wide plains; tidal and swampy flats around Ramree Island; narrow plains south of 15~ latitude. Gulf of Martaban (15 to 17~ north latitude and 94 to 97~ east longitude). Mostly wide plains and the delta fringe of the Irrawaddy. Andaman Sea Coast (8 to 150 north latitude). Mostly hilly fronted with narrow coastal plains. Islands of the Merugi Archipelago fringe the central part of the coastal stretch. Malacca Straits (2 to 8~ north latitude). Mostly broad plains, some alluvial; protected to south by Sumatra. East Malay Coast (2 to 7~ north latitude). 'Wide coastal plains with a few hilly spurs. Gulf of Siam (7~ north latitude and 101~ east longitude to 8~ north latitude and 105~ east longitude). Wide alluvial plains and delta coasts of the Chao Phraya. Hilly on the east coast between 10 and 13~ north latitude. South China Sea Coast (8 to 18~ north latitude). Wide delta plains at mouths of the Mekong ( to about 11~ north latitude) north of this the coastal zone is hilly with relatively narrow plains with hilly spurs projecting as headlands. Many beaches are covered with blown sand or moving sand dunes in parallel rows. 15

LOCATION OF DEPTH SAMPLES.2 02 o4.4 *5 8AY OF 05 BENGAL 8 Rq I ilI io / ll oa 0,I15 /GULF OF < MiTA BA o 16 el7 *85 *83 GULF OF e81.8 TOANKIN 081 o80.0 0 78 76.:. 75 074 72 0 54 e55 *18 57 53 0 058 52 ~19 3 GULF OF o20 51 SAM 71 70 9 AiNDMA/VN COAST s59:' 6i 21 0 69 67 66 e 0 65 SOUTH CHINA SEA 50 %49 o21 8 48, 22 0 23 / "24 o47 a25 /.46 a 26 o45 e27,62 o63,64 I DOTS INDICATE LOCATION OF SAMPLES NUMBERS FEFER TO MAP SHEETS HEAVY LINES SEPARATE COASTAL REGIONS AREAS COVERED BY COASTAL TYPE ANALYSIS 5 A LAYA.44.43 EAST A, r/ MAT. e291 Ct v 'V o31. 39 -0 32 C ~ V * 33 938 tS>, o 34 f</34 "<p 35.36 O 1. I1 Map I. Location of Depth Samples and Areas Covered by Coastal Type Analysis. 1l

Gulf of Tonkin (18 to 22~ north latitude). Narrow coastal plains in south with delta of the Red River in north. A small hilly area near the Chinese border (about 21~ north). Coastal Types From map analysis of the available coverage the following coastal types were identified and measured for each map. Accessible Types Flat Foreshore. Flat beach area, usually several hundred yards or more in width, not identified as sandy, marshy, or tidal in character; commonly the coastal feature of alluvial plains. Sandy Foreshore. Same as flat foreshore except that maps indicate sand by symbol or name but do not indicate dunes. Probably some dune area included because of differing symbolization on different map sets. In a few places sandy foreshores include lagoons immediately inland from the sandy shoreline (Map 2). *Types with Onshore Terrain' Problems. Hilly Foreshorel. Hills as identified by contours reach to the coast; with or without narrow strand areas between the actual slopes and the shore; limited beach area for assembly or supply functions (Map 5)0 Sand Dunes. Single or multiple sand ridges high enough to be indicated by contours or specifically so labeled on maps. Especially abundant along the South China Sea Coast and southern Gulf of Tonkin (Map 4). Swampy. Fresh or brackish water commonly inland of a beach ridge and othler kinds of indicated swampy land. Probably includes mangroves in some Tidaal Flats. llarshly areas especially in estuaries and along other low coastal types; grassy vegetation where indicated on maps. Probably much overlap with the "swampy" category above (Map 7). Types that Present Difficulties in Approach Rocky Offshore. Rocks in shallow water adjacent to the actual coastline (Map (). -Sand lanks or Mud Banks. In shallow water offshore probably much more I5

TABLE 4 SUMMARY OF COASTAL TYPE ANALYSIS (Coantal Regions by Miles and Percentages) cn (n a o Id 14 co o Cs U Id =A G r- ( O; M EO 0 Eu Mi 136 30 61 123 107 7 5 7 2'; 5C00 Burma Coast 27.3 6.o 12.0 21.7 21.4 1.4 1.0 1.I. 3 100 Gulf of Gulf of Ml 105 12 9 8 151 41 29 9 24 388 Martaban 27.1 3.1 2.3 2.0 38.9 10.6 7.5 2.3 6.2 100 Mi 25 81 64 241 4 17 20 452 Andaman Sea Coast Se Cot 5.5 17.8 14.2 53.5 1.0 3.8 4.4 100 Mi 155 14 19 5 222 188 603 Malacca Straits trat 25.7 2.2 3.1.8 37.0 31.2 100 Malay Eat Mi 89 16 3 39 39 186 M~a lay East Coast st % 41.8 8. 6 6 21.0 21.0 100 lf of Mi 25 5 17 47 1 9 Gulf' of Siam iam 26.3 5.3 27.8 49.5 1.1 100 Sout Cina Mi 36 78 64 50 26 144 118 6 11 53 South China Sea Coast Sea Coast.8 14.8 12.0 9.4 4.9 27.0 22.1 1.1 2.1 100 Gulfof Mi 45 129 6 5 1 11 11 206 Gulf of Tonikin Tokin 20.9 62.6 2.8 2.4.5 5.3 5.3 100 Mi 614 270 255 308 32 144 897 297 51 9 51 5 2963 Totals d0 20.7 9.1 8.6 10.4 1.1 49.3 10. 0 1.7.3 1.7 1.2 100

Map 2. Sandy Coast. From Series L 805, No. 215 77E. 0 1 Statute M!!'. 1000 500 0 1000 2000 Meters _____~.~~m_-n 3 1000 500 0 1000 2000 Ydrds 0 t Nautical Mile N-ap 5. Hilly C-oast. From Series L 805, 'No. 125 5E 1 7

Map 4. Sand Dunes and Lagoon Coast. From Series L 805, No. 125 29E. 1 0 1 Statute Mile -i i ___:_ii_. -- i __r 1000 500 0 1000 20( ~~_l=_ '- -__ --- — __ _ 30 Meters rds 1000 500 0 1000 2000 Yda 0t W k. -- 0 1 I Naultical Mile E - - — jZ —F I L 1.'- j -'.~::; _:-'..;*^;.-'... '*...":-..t *....''.'-: ':.' - ' '.'':.""',-..'.'.:.'..:.'/.. -,:.:,:'.' -'-:':'-..-.: - '.::..;:':.- *.... -.*./':..:-.' ' ''-2 -l _ -,.,. _.. -:...-... ".:..-.:..-...:.:..' -:.:..... -. -.::../:; -r w::A;- *? t.. -*:.:....: *... *.*. *.. i * - ___,_ _,___ 4-4~;,,._.. - /,''*..':,.-',,', ' '. '"'''^ ' '. '''"'''-.'',.~iF-' ' ',-. "'':"'" * "" '-". "" ' 1 '-' '; ' '"'" '', '":''":":'.- ''.1? '....;_.- '.. '... _... ' ** - * *.... '. " _ 5X.' ' ^ *. ' ' ' 1 0 - — ',,,'..'-'.'"'.,'-".'..'',"",,-,''.''.''-'-.j I' 10-_f I Map 5. Swamp and M.angrove Coast. From Series L 805, No. 236 9E. 18

Map 6. Mangroove Coast. From Series L 805, No. 194 70Ter. I 0 r -~~~ —, Ad - 1000 SQO 0O EZZLEr-EET-T _-~~__~ --- --— I_ _ 1000 500 0 I__ __ _ _~ ----__-`- 0 — - 1_._ 1 _- E_;.~-ifl7Z H- T~i i~-L --- — - - -. --- -. — - Z_ 1 Statute Mtle 2000 Meters 2000 Yards I Nautical Mile - ---- ~ -- --- Map. 7 Tidal Flats. From Series L 805, No. 132 36W. 19

1 0 1 Statute Mile 10 '0 I' 20- -----— __1000 2000 Meters --- —._ 1000 500 0 1000 2000 Y eters 1000 500 0O 1000 2000 Yards r-P=->-~I -i i-j i-i i-l * --- —-- -— = ---, --- I0 1 O Nautical Mile Map 8. Rocky Offshore. From Series L 805, No. 1358 50E. common than indicated. Absent on maps east of Gulf of Martaban (Map 3). Coral. Coral barrier in shallow water offshore; uncommon in muddy situations along delta coasts. Inaccessible Types Cliffs. Precipitous slopes actually reaching shore, so designated on maps. Probably wave beaten in storms or high water (Map 3). LManroves. Tree covered tidal shallows presenting a barrier to landing (Map 5T)i. Raw Inventory Data. Pecause of the incomplete coverage and the inconsistencies of data mention(ed earlier in this section the raw data sheets of the coastal inventory are included for their specific locality value. The analyses and surmmaries must be interpreted in terms of these limitations. Coastal Types Analyzed by Accessibility. The following table summarizes the complete mileage inventoried. It is not a statistical sample because of the missing coverage but does present the categories as proportions of the available whole. In telrs of accessibility it shows the following; 20

TABLE 5 COASTAL TYPES ANALYZED BY ACCESSIBILITY Percent Miles of Total Easily Accessible Coast 29.8 Flat 614 20.7 Sandy 270 9.1 Approachable with Difficulty 13.6 Rocky 308 10.4 Sand oa' Mud Banks 60 2.0 Coral Fringe 55 1.2 Inaccessible 31.4 Mangrove 897 30.3 Cliffs 32 1.1 Onshore Problems 25.2 Hilly 255 8.6 Sand Dunes 144 4.9 Swampy 297 10.0 Tidal Flats 51 1.7 2965 100.0 Implications. Within the limitations of the data it may be inferred that there is about as much readily accessible coast as inaccessible coast and that these two categories compose some 60% of the coastal mileso Another 13% (hilly and sand dunes) may not present serious problems to getting onshore or establishing a foothold. Relationship of Accessibility of Geomorphological Structure. Table 6 presents a percentage analysis of the areas in which continuous coverage is available. It indicates some obvious facts. 1. A larger percentage of wet plain coast is inaccessible than dry plains. This comes from the mangrove growth on the wet coasts. 2. All types of coast have enough available areas of ready access for military operations. 3. All types of coast have a surprising percentage of inaccessible mileage. This comes from mangrove growth. Distribution of Inaccessibility and Lack of Easy Accessibility. An analysis of the complete coverage along the west coast between 10 and 21~ N. lati21

r\ P\) TABLE 6 DISTRIBUTION OF COASTAL TYPES BY GECMO:-PHOLCGICAL ARSAS (Percentages of Total Mileage) (B) (c) X U) r: y / (D) U 3 ( A) O ( Map Nos. Location <. ~ C) u C: U2 T -I C,- t.(U + a *rol!- a 0..u.8 H. a i O < ) O C)?, we a n o f f so; re H H o 1 -4 6~ -: tO c 5. a t 2..6 4-. 6. s, c 0 - 0 a C4 a C ri O 2 0 H: 'C 45 '+ o U. 1;rr-a Coa-st 1-8, 20~-21 N. lat. 4].8 22.4 8.2 1.5 20.9 5.2 64.2 13.4 1.5 20.9 Wide dry plains 9-12 1J: O-C20 N. 1 t. 17).2 7.5 28.3 50.9 13.2 7.5 28.3 50.9 Low, wet islands off shore 1-24 l6~-18:50~ N. lat. 23.5 14.8 54.2 16.8 1.53 1.6 7.7 23.5 16.1 45.5 16.8 Wide dry plains Gulf of Martfabian 25-4:5 95~-97:50' E. long. 27.1 5.1 2.3.1 1 38.9 10.6 2.3 7.5 6.2 30.2 20.4 10.6 58.9 Wide alluvial and delta plains Andaman Sea Coast 44-64 10l-16~ N. lat. 5.5 17.9 14.2 53.3 0.9 3.8 4.4 5.5 23.2 18.0 35.5 Narrow wet plains 6~-10~ N. lat. Coverage mrissing Malacca Straits 65-100 2~-6~ N. lat. 25.7 2.3 5.2 0.8 36.8 51.2 27.5 55.5 3.2 57.6 Wide vet piatins (A) Flat or Sa.nd. (B) Hilly, Sand 3D.nes, Swamps, Tidal Flats (C) Rocky, Sand or Md Banks, Coral (D) Cliffs and Mangrove

TABLE 7 COASTAL ANALYSIS (Raw Data) a 5) Map;> a U N.* Index No. Location, > | a. d No.c 'd CC P co U 0 ) EZ C L4 Burma Coast 1 84 C/3 21-15N 92-15 E 7 10 5 22 2 84 c/4 21-OON 92-15 E 2020 5 84 D/5&1 2'0-45N 92-15 E 14 5 1 4 84 D/6 21- 3ON 92-1 5 E 14 5 84 D/10 20-50N3 92-45 E 111 6 84 D/ll 20-15N 92-45 16 19 7 84 H/4 20-OON 93-15 4 5 12 8 84 H/8 20-0N 93-0 E2 2 14 2 20 9 85 E/5 19-45N 95-30 E 3 13 420 10 85 J/1 1845N 94-15 E 16 11 85 J/2 18-5ON 94-15 E 4 7 12 85 J/6 18-5ON 94-50 E 3 1 2 6 15 85 J/7.1315N 94-30 24 15 7 12 40 14 85 J/8 18-00N 94-30 3 8 9 24 15 85 K9&5 17-45N 94-45 E 5 9 20 16 85 K10 17- l)N 94-34 E 9 10 2 7 2 17 85 Kll&7 17-15N 94-45 E6 12 9 2 50 18 85 K12 17-OON 94-45 1 4 2 1 8 19 85 L5 16-45N 94-30 E 1 2 9 1 22 20 85 L6PAr 16-30N 94-0 E 9 6 8 6 29 21 85 L7&L5 16-15N 94-50 E 5 3 9 3 18 22 85 IS 16-0ON 94-50 E 1 2 10 5 51 25 85 L4 16-OON 94-15 E 5 5 9 2 21 24 86 I5&1 15-45N 94-30 E 16 4 11 4 35 Miles of Coast 136 30 61 125 107 7 5 7 24 500 Percentage 27.3 6.0 12.0 24.7 21.4 1.4 1.0 1.4 4.8 100 ro *These numbers refer to this table only for the 1:63,560 and 1:50,000 coverage. They should not be confused with the numbers of the general coverage mentioned in the Introduction.

TABLE 7 (Ccntinued) Map 0 0 0 5) C) P. 5 5,-4cfl-4 45 -4 Index No. Locat'..cG n U+ cC d to r -, 0 ) ZO 0 C Z a5:l) a3 "A 4H OC 0 C o &4r= $ 2-4 Gulf of Martabani 25 86 19 26 86 I13&14 27 86 M l&2 28 36 M5 29 86 M6 50 836 M9 31 85 P12 32 85 Pi6 33 94 D/5&4 34 94 D/7 55 94 D/l0cll 36 94 D/13 o 57 94 C/16 - 94 G4 59 94 HI 40 94 H6&2 41 94 H7&8 42 95 E9 43 95 E10 Miles 15-45N 94-45 E 15-45 N 95-00 E 15-45N 95-15 E 15-45N 95-30 E 15-30N 45-30 E 15-45N 95-45 E 16 -oo 95-45 E 16-oNs 96-00 E 16-15N 96-15 16-15N 96-DO E 16-3oN 96-L5 E 16-45i 97-00 E 17-OON 97-00 E 17-CON 97-15 E 16-45N 97-15 E 16-530 97-30 E 16-15N 97-30 E 15-45N 97-45 E 15-30N 97-45 E of Coast 2 2 1 18 3 10 4 15 12 12 10 3 4 1 5 5 5 19 6 1 5 19 9 11 21 19 22 16 17 7 15 22 13 19 38 17 21 19 18 17 28 20 20 46 13 388 100 18 4 10 5 20 9 12 6 105 3 23 11 12 6 5 3 9 8 S 151 38.9 25 1 41 29 9 24 10.6 7.5 2.3 6.2 Percentages 27.1 3.1 2.3 2.0 Andaman Sea Coast 44 95 E15&1 45 95 E16&12 46 95 F1. 47 95 Fl4 L8 95 F15 49 95 j4 50 95 K1 51 95 K6 52 95 K7 53.95 K12 1.5-15N 98-OC E 15-00. 98-00o 14-45N 98-00 E 14- 30N 98-00 E 14-15N 98-00 E 14-OON 98-15 E 13-45N 93-15 E 13-50N 938-50 13-155s 98-53 E 13-00O; 93-455 6 0 2 2 7 15 3 3 6 8 9 6 7 1 15 3 5 5 5 14 1 9 4 6 9 1 1 5 15 4 42 25 21 24 1 - 18 25 25 18 1 6 J 5 5 L4 4 -r I a J-o

TABLE 7 (Continued) Map 0 li. o o I ~ H d q - o e4 ac o No *. Inex No. Lcation I d ~ ~ I c5 0 o 9 < 5 H O a Andaman Sea Coast (Concluded) 54 95 L9 12-45N 98-45: 2 17 1 20 55 95 L12 12-OON 98-45 E 25 4 29 56 96 19 11-45N 98-45 E 20 12 32 57 96 14 11-30N 99-00 E6 6 58 96 111 11-15N 98-45 E 118 19 59 96 I/12&8 11-OON 98-45 E 27 27 60 96 J/9 10-45N 98-45 E 28 28 61 96 J/o 10 -30N 98-45 E 6 62 96 J11&7 10-15N 98-45 E 9 3 10 22 63 96 J12&8 10-CON 98-45 E 5 4 11 20 64 96 I10 11-30N 98-45 E 2 2 11 15 Miles of Coast 25 81 64 241 4 17 20 452 Percentages 5.5 17.8 14.2 53.5 1.0 3.8 4.4 100 n Malacca Strait 65 2 E/9 6-15N 100-15 E 210 12 66 2 E/15 6-OON 100-15 E 5 5 67 2 E/14 6-OON 100-30 E15 15 68 2 I/2 5-45N 100-0 E 116 17 69 2 I/6 5-30N 100-30 E 4 5 12 21 70 2 I/9&10 5-15N 100-50 E 14 3 17 71 2 1/14 5-OON 100-50 E 21 21 72 2 M/2 4-45N 100-50 E 10 10 75 2 M/5 4-45N 100-45 E 12 12 74 2 M/7 4-30N 100-45 E24 24 75 2 M/11 4-15N 100-45 1 7 12 20 76 2 M/15 4-00N 100-45 E 35 10 18 77 2 M/16 4-CoN 101-00 E8 8 78 5 /53&4 -45N 101-00 oo 21 21 79 5 A/8 5-50N 101-00 E 11 11 80 5 3/5 5-50N 101-15 E15 15 81 5 2/9 5-15N 101-15 17 17 82 ) /1o 5-15N 101-50 1 9 10 9_ 1

TABLE 7 (Continued) Map 0o MT >, 0 ~ rn z,?No.* I o H U4-, 1 3- - ao ) 4 -5 (3 * Qo4 H aa Sro C- c lu 0 e) 0 4 XI0 Q 1 Maacc CSri (Q E-4 i U P E Malacca Strait (Concluded) 83 8,4 85 86 87 88 89 90 91 92 93 94 95 96 ro 97 98 99 100 3 B/13&14 3 F/1&2 3 F/6 3 F/7 3 F/8 3 F/12 3 G/9 3 G/13 3 G/14 3 G/15 3 K/3 3 K/4&8 3 L/5 A L/6 3 L/10&11 3 L/12 4 i/9 4 I/10 3-00 101-30 E 2-45N 101-30 E 2-56N 101-30 E 2-20N 101-45 E 2-30N 102-00 E '-15N 102-00 E 2-15N 102-15 E 2-OON 102-15 E 2-OON 102-50 E 2-OON 102-45 E 1-45N 102-45 E 1-45N 103-00 E 1-30N 103-15 E 1-30N 103-30 E 1-15N 103-37-47 E 1-12N 104-00 E 1-15N 104-15 E 1-15N 104-30 E 3 2 6 6 5 17 14 10 3 19 27 13 7 1 2 15 10 12 21 29 6 19 12 20 14 10 18 10 14 23 21 12 50 3o 27 12 603 100 2 1 4 1 6 12 z6 1 15 11 21 2 27 5 3 12 Miles of Coast Percentages 155 25.7 1 14 19 2.2 5.1 10 11 222 188 37.0 31.2 5.8 101 4 I/5&6 1-45N 104-00 E 102 4 I/1 2-00N 104-00 E 103 3 H/16 2-15N 105-45 E 104 3 H/12 2-30N 103-45 E 105 3 H/8 2-45N 105-45 E 106 3 H/7 2-45N 103-50 E 107 3 D/6 3-45N 103-15 E 108 3 D/2 4-00N 103-15 E 109 2 P/14 4-15N 105-15 E 110 2 K/2 6-0ON 102-15 E Miles of Coast Percentapes 8 2 14 11 7 17 5 15 2 10 89 East Malaya Strait 6 9 4 9 7 1 4 10 3 2 12 8 18 21 18 23 16 18 17 24' 21 10 186 3 16 3 16 5 39 59 n. n 47.8 8.6 1.6 1 n - - 11. - -I V -L.V 22I.0 100

TABLE 7 (Continued) a > Mnap 0 0 0 No Index No. Location S H f O Id CO 4 O H a e No.* 0 3U4 cH zj Id 0 cld c4cdH- -0 0- H 0:J 0 *H -H o0 0 ) = o v m E- 4 EIndo-China - Gulf of Siam 111 5842/2 10-20N 104-30 E 112 5942/3 10-20N 104-45 E 113 5941/4 10-1ON 104-45 E 114 5941/;5 10-OON 104-45 E 115 5941/1 10-10N 105-00 E 116 5941/2 10-OON 105-00 E 117 6041/5 10-OON 105-15 E 118 6040/4 9-5ON 105-15 E Miles of Coast Percentages 8 2 6 2 2 2 1 2 25 26.3 5 2 7 1 7 7 6 2 4 12 5 12 47 1 49.5 1.1 9 13 8 6 14 8 14 95 100 5 17 5.3 17.8 Indo-China. - South China Sea Coast 119 6239/1 120 6339/4 121 6540/5 122 6340/4 125 6541/3 124 641/4 125 6342/5 126 63542/2 127 6442/3 128 6643/4 129 6845/4 130 6846/3 131 6846/4 152 6852/3 133 6852/2 154 6852/1 155 6852/4 136 6853/3 157 6756/1 158 6756/2 19 6658/2 9-40N 106-15 E 9-40N 106-30 E 9-50N 106-50 E 10-O1N 106-30 E 10-ION 106-30 E 10-20N 106-30 E 10-30N 106-30 E 10-30N 106-45 E 10- O)N 107-00 E 11-OON 108-00 E 11-40N 109-00 E 11-50N 109-00 E 12-OON 109-00 E 13- 50N 109-00 E 15-50N 109-15 E 14-OON 109-15 E 14-(oN 109-0Oo 14-o10: 109-00 E 15-20N 108-45 E 15- 0ON 108-45 E 15-rON 108-15 E 6 6 21 3 7 7 7 20 15 7 2. 7 9 6 2 1 5 25 7. 11 5 5 6 3 2 1 2 11 6 2 S I 1.3 1 10 6 21 10 19 26 18 14 2 14 4-3 18 11 22 23 52 13 15 11 2 13 15 12 2 7 2 2 6 16 2 1 11 8 2 4 1 5 2 8 5 2 4 5 7 2 7 i3 13

TABLE 7 (Concluded) 11 aQ Map 0 Index No. Location X o s U d a U c oH No.* c O CH to + 5 c O co I -Ci -4 0-4 H 5 3 a cSao th^- 0 ) C. X. C ) S 0 _ _s COO M E- PU 0 U P E-1 Indo-China - South China Sea Coast (Concluded) 140 141 142 144 1.45 146 147 6658/1 16-OON 108-15 E 6659/2 16-10N 108-15 E 6659/3 16-loN 108-00 E 6659/4 16-20-30N 108-00 E 6560/2 16-30No 107-45 E 6560/4 16-40N 107-50 E 6461/2 16-50N 107-15 E 6461/4 17-OON 107-00 E Miles of Coast Percentages 16 7 5 7 1 8 16 9 4 16 36 78 6.3 14.6 2 1 15 13 16 19 16 19 25 26 18 20 19 16 11 533 2.1 100 64 50 26 144 12.0 9.4 4.9 27.0 118 6 22.1 1.1 ro CD Inco-China - Gulf of Tonkin 2 2 148 6166/2 149 6166/1 150 6167/2 151 6167/3 152 6167/4 153 6169/1 154 6170/2 155 6170/1 156 6270/4 157 6271/3 158 6271/2 159 6271/1 160 6371/4 161 6372/5 162 6372/4 163 6373/3 Miles 18-0oN 105-45 E 18-40N 105-45 E 18- 50N 105-45 E 1 -5 1C 5-50 E 19-00N l0 -50 E 19-40N 105-45 E 19-50DJ 105-45 E 20-OON 105-45 E 20-00N 106-00 E 20-10N 106-00 E 20-20N 106-15 E 20-20N 106-15 E 20-20N 106-30 E 20-30N 106-50 E 20-40N 106-30 E 20-50N 106-50 E of Coast 15 11 10 2 5 11 12 4 8 4 7 10 2 2 11 1 9 5 17 13 10 7 16 12 16 12 14 1 1 4 5 6 11 11 2 7 10 1 1 1 11 11 5.5 5.53 11 15 10 19 22 8 206 100 45 129 6 20.9 62.6 3.0 2.4 1 Percentages.5

tude covering 1340 miles of coastline indicated that short stretches of inaccessibility were scattered through the whole of the coast and that the longest continual stretch of inaccessibility was 146 miles along the wet narrow plains of the Andaman Sea. The areas of lack of easy accessibility followed the same pattern, the longest stretch was 236 miles also along the wet narrow Andaman coastal plain. 29

III. SURFACE QUALITY In coastal Southeast Asia as a military environment the two most important factors in terms of operations are the surface quality and the nature of the climate. In this part of the report the nature of the land surface is presented, first by qualitative description of its components, next by its regional pattern, and finally by quantitative analyses of its roughness and its slopes. The analysis of roughness shows that about 45% of the project area is in plains surface; with less than 600 feet of relative relief; some 355 is in hills with relative relief between 600 and 2000 feet, and the remainder is rough enough to be called mountainous although much of it does not bear typical mountainous landforms. Analysis of the slopes by comprehensive random sampling shows that, within the hill-mountain part of the project area, 19% of the slopes are slight; (5 to i5%) 56% are moderate; (16-35070) and 25o are steep. (31-50%). The surface conditions of coastal strip are most easily understood i.n terms of the general geomorphology of Southeastern Asia for which purpose a short description of the principal elements of the structure is necessary. Geomorphologic al Elements F rom the lard mass of South China four chains of mountainous uplands extend southward to form the skeleton of Southeast Asia. Between these uplands stretch the plains and deltas of the four great rivers. The ocean margin of this complex is rinLned with a generally narrow fringe of coastal plain. The eight principal elements, four uplands and four plains, are briefly described hereafter and their distribution shown on Map 9. 1. The coastal mountains of North Burma between the Bay of Bengal and the Irrawaddy vally are composed of the narrow dissected ridge of the Arakan aarange which diminishes in both width and altitude from the Chin Hill country of the -north to its termin-ation at Cape Negris west of the Irrawaddy delta. 2. The valley of the Irrawaddy together with that of the Sittang on the east compose a lowland some 150 miles in breadth extending from the north and temnninating in the flat and poorly drained delta area. 51

CEOMIORPHOLOGICAL AND PHY.SICAL CHIN HILLS CHINA MASSIF TON/KIN HIGHLANDS AN/DAMAN COAST CH/A/NE IRR9AWADDY DELTA MEKONG VALLEY TENASSER/M COAST 7 PL.AI N MEK-ONG DELTrA SOU/THERN THA IL AND MAL AYA GEOMORPHOLOGICAL ELEMENTS AND PHYSICAL REGIONS A LOCATION OF TRAVERSE EAST wEST COA ST7 COAsT SINGAPORE LOWL AND -Map. 9'. Geomorphological anid Physical Areas. 32

3. The hill country of northern Burma separates the drainage of the Irrawaddy and Sittang from that of the Thailand rivers. This upland extends to the south over the Malay Peninsula almost to the equator and terminates in the mountains of Malaya. The northern part is formed by the Dawna and the Eilauktaung ranges. To the south through the Kra Isthmus it is a discontinuous series of hilly strips. 4. The lowland of Thailand is separated into the watershed of the Chao Phraya on the west and that of the Mekong on the east by a low, hilly waterdivide. The western part of the lowland is the valley of the Chao Phraya, some 150 miles wide which terminates in the Bangkok plain formed of the deltas of the Chao Phraya and the Tachin. 5. The low water-divide mentioned above is the central portion of the third narrow upland which depends -to the south from the China massif. Its northern part is rugged as is also its southern extension which, through coastal Cambodia, is composed of the Cardasmomes and the high (4)000 ft) Chaine de '1Elephant that reaches the coast and forms the western margin of the Mekong Valley. 6. The Mekong Valley: a broad lowland, up to 200 miles wide, extending through eastern Thailand and terminating in the river delta in South VietNam. 7. The fourth upland belt is the widest. This is the'Chaine Annamitique, from 50 to 150 miles in breadth extending in a broad arc paralleling the South China Sea Coast between the Tonkin and Mekong Deltas. It is a succession of eroded plateaus bearing high peaks and has relatively steep slopes toward the eastern coast. 8. The most easterly lowland is that of Tonkin, -formed by the valleys and deltas of the Red River and its neighbors,. thle Ma, the Chu, and the Ca. It lies between the Chaine Annamitique on the south and the China massif on the north. These eight elements are narrow in proportion to their lengths and extend generally in north-south directions. They give a "grain" to Southeast Asia formed by the alternation of broad flat riverine lowlands with narrower, rl(gged and dissected strips of hilly uplands. The 50-mile w.ride strip of coastal country which comprises the area of this st ldy orntains only the edges of these major geomorphological elements: thie flanks and foothills of the upland surfaces, the seaward margins of the deltas, but it does include almost all of the fringing coastal plain.

Land Types The landforms of the area may be grouped into four associations, called the Land Types. Three of these are lowland types characterized by plains and the fourth is composed of the rougher upland surfaces. They are: delta plains, alluvial coastal plains, complex plains, and complex hills. Delta Plains are the most uniform of the land types. They are level alluvial surfaces on which elevations are rare and the most conspicuous surface forms other than the plains themselves are man-made dikes and barriers constructed to prevent flooding. Gradients inland from the coast are almost impreceptable, usually less than 1 in./mile. The most important facts of military environment in delta country are those of drainage and water-logged soils. The gradual slope toward the sea produces an indefinite coast line including a broad shallow tida.l zone which may be a mangrove swamp extending several miles inland from lowtide water. Alluvial Coastal Plains have one character in cormmon with deltas: basically they are flat alluvial surfaces. The difference is found in the presence of several kinds of minor landforms which are absent in deltas. These include beach ridges, sand dunes, coastal lagoons, offshore rocks, and also in many places, tidal mangrove fringes. Complex Plains are in a wTay transitional between the purely alluvial types and the hill country. They are associations of various flat or subdued landforms such as recent alluvial coastal and riverine plains, older, upraised and dissected alluvium (diluvium), river terraces, and degraded or structurally flat surfaces. Their common characteristic is that their component landforms are all relatively low and that such erosion slopes as are present are short even though they may be steep. The complex plains offer more variety, less waterlogging and less poor drainage than either the deltas of the coastal alluvial plains and therefore would be better passageways from the coast to the interior of the country. Complex Hills. All of the rougher and higher surface, that is, all of the area not classified as plains, has been grouped into a single category, complex hills. It includes areas with such landforms as elevated but smooth plateau ci: faces, rolling foothill land, stream-cut uplands, low rounded m-o'untains, residual blocks, limestone erosion forms (karst topography) and such parts of tiruly mountainous areas as come within the 50-mile strip of the Project Area. This is not a homogeneous category because it covers a wide range of relative relief as w.ell as of structure and erosional stages. An early attempt was made to separate the areas wit-i-high relative relief (over 2000 ft) and make categories for low mountains and rugged mountains. This produced small and patchy distributions resulting principally from area with deep

stream cutting rather than of mountainous forms such as ridges. In a statistical sense it is possible to separate these rougher areas. The study of relative relief which follows in this chapter indicates that the complex hills category which occupies 55% of the area is composed of: Hills (relative relief from 600 to 2000 ft), 54% Low mountains (relative relief from 2000 to 3000 ft), 32% Rugged mountains (relative relief over 3000 ft), 14%. The common characteristic of the complex hills category is that of steep slopes which form considerable local relief. On a few of the smoother upland plateau area (such as that of eastern Thailand) this characteristic is subdued. The operational problems of the hilly country would be those of slopes which would limit movement and observation, in contrast to those of the plains types in which drainage and bearing strength of the soil would be of greatest importance Physical Regions For purposes of description and analysis the Project Area has been divided into eleven physical regions from the northwest around to the northeast. These are not homogeneous regions but in each of them the associations of the land types and their landforms differ from those in adjoining regions. The four delta areas are generally similar but each has some individually in its structure. The eleven regions, shown on Map 9, are: 1. Arakan 2. Irrawaddy Delta 5. Tenasserim Coast 4. South Thailand 5. Malaya 6. Bangkok Plain 7. Mountains and Plateaus of Western Cambodia and Eastern Thailand 8. Mekong Delta 9. Chaine Annamiitique 10. Tonkin Delta 11. East Tonkin Highlands. 1. The Arakan Coast of North Burma extends southward from the Pakistan border to Cape Negris between the crest of the Arakan Range and the sea coast. Thel northern part is some 50 miles in width but the area tapers to the south where the range borders on the Andaman Sea. It consists of three differing sections: a. The Northern Section is composed of the narrow, parallel northsouth belts of complex hills which are the outlyers of the Arakan Range.

Between these ridges there extends from the south, strips of the alluvial plain of the Kaladan, Mayu, and Lempo Rivers. North of Akyab there is only a narrow, sandy coastal plain between the seas and the Mayu Range. The ridges rise sharply above the alluvial lowland to heights of 500 to 1800 ft. The Arakan Range which is the eastern boundary of the area reaches heights of 4500 ft. It 2ontains local relief of 1500 to 2000 ft and slope angles of 25 to 30%. The local relief stated in the remainder of this description is measured by the differences between the highest and lowest contours within the squares of the 10,000 yard or 10,000 meter grid of the L501, L508, L509, and U542 and GSGS 4218 series, an area of approximately 50 square miles. Slope angles are taken from the study which is a later part of this chapter. Cross-section A, Fig. 1, shows a profile of the area on a line just south of Akyab. This section and others used in the descriptions have been made from the map series mentioned above with considerable vertical exageration to emphasize the surface roughness. The local relief shown by the figures, in feet, above each section on these profiles is taken along the profile line itself by 5-mile intervals. The section shows the lowland of the Kaladin and other rivers and the low hilly strips of the outlyers of the Arakan Range. b. The Central Section extends southward from Akyab to Sandoway. Throughout most of its length offshore islands protect the mainland coast from heavy surf and permit a wide belt of mangrove growth between the sea and the inland foothills. The low, swampy coast is additionally described in the section. on soils. The hilly chain is some 50 miles in width and drops off sharply on the east intro the Irrawaddy Valley, The local relief and slope angles.are about the same as those in the nort.hern section. c. The Southern Section. South cf Sandoway the rarnge decreases in altitudle and width anl its foothills. lie directly cr the coast. Ai Cape Negris it terminatles in the low hilly peninsula between the Irrawaddy Delta and the sea, The coas al fritne is a na-rrow and swampy pl.ain cc.on:ly frined with angrove.ro wth. In the sol'thern hills tle local relief has decreased to O0 to ' to00 f'.t andr the slopes from 17 to 2. The I rrae.addy.! Del+ta, At. Cape Negris 'he coastline turn; eastward for somne.50 mileC al-onr l*e Gulf nf I, cinl_ no rtar to the mothl of the Sittant 'iver. r Te co':t.r inl'an is a flat delta '.o wland intricately rivided tby the dist.ib ai, L o. C,'hore il.o.f.e T.rwdy. Tere

NORTH BUR-IA PROFILE A Latitude 20030 N 800 200 0 600 400 600 0 0 0 100 feet 0 0 5 10 15 25 miles 30 35 40 45 50 TENASSERIM COAST PROFILE B LATITUDE 14~30'N 4000 feet. 2000 0 1500 1700 800 2000 1400 1500 1700 2100 500 600 ^ —^\ A /i/L 5 10 15 20 miles 25 30 35 40 45 50 Fig. 1. Cross Section A and B.

are no conspicuous landforms except in the extreme northern part (of the 50 -mile strip of the Project Area) where the southern extremities of the Pegu Range form belts of hill country. In general the delta is low, flat, and wet. It is described in some detail in the section on soils. 3. The Tenasserim Coast extends southward from-the Irrawaddy Delta to the southern end of the mountain country at about latitude 8 north and includes part of southern Thailand, South of latitude 13, and to the border of Malaya, it includes the entire width of the Maylay Peninsula. In structure and appearance it resembles the Arakan Coast and is composed of two sections. a, The Northern Section is the area between the crest of the Dwana Range and the ocean. It encloses the broad alluvial plain of the Salween and other rivers between the mountains and the low coastal hills. Cross-section B, Fig. 1, shows the coastal hills, Tavoy River Valley, and inland mountains. b. The Southern Section, between latitudes 8 and 13 north, includes the width of the peninsula and the coasts of both the Andaman Sea and the Gulf of Siam. The western or Andaman Coast, protected by the islands of the Mergui Archipelago, is low and wet and covered, nearly to the foothills of the Belauktaun Range with mangrove forests. The eastern coast is also narrow and in places outlyers of the range reach the gulf coast, This plain, however, is generally dry and its margins bear sand and sand dune strips. The Belauktaun Range which forms the boundary between Burma and Thailand is narrow, and generally below 5000 ft in altitude, Within the range local relief varies from 1000 to 2000 ft and slopes from 25 to 37%0 Cross-section C, Fig. 2, shows a profile of the area from the Andnaan Sea to the Gulf of Siam. 4. South Thailand is the low, central part of the Malay Peninsula, some 100 miles in width lying between the latitudes of 6 and 8~ north. Within it the hilly chains are present onlY as isolated hills and mountain masses which rise above the general level of the rolling lowland. The eastern coastal plains along the Gulf of Siam are alluvial in nature and some of them extend inland for many miles, They commonly bear coastal fringes of sand or sand dunes. The western plains are complex in nature formed of undulating surfaces cut by shallow stream erosion. Cross-section D, Fig. 3, shows the generally level nature of the area.with the individual hills and one of the —isolated mountain masses. 5, Malaya is described in three parts because the most of the central upland is outside +.he 50-mile strip of the Project Area. The parts are: the west coast, the Singapore Lowland, and the east coast. ao The West Coast consists of a coastal plain generally about 15 to 20 miles wide backed by mountains reaching elevations of 5000 to 6000 ft. Thle plain is generally of alluvium and broken in a few places by mountain 38

NORTH THAILAND PENINSULA PROFILE C Latitude 12~30'N 0 0 400 1000 900 900 900 1200 600 2400 700 1800 900 1000 900 900 0 4000 \ feet 'o0 2000 0 el-4t I - A..... Af I 7 y I I I I I Xh I % 11) Ir ) )c c^ n il - r J JIV J:. zV Z.) 35 40 45 50 55 60 65 miles Fig. 2. Cross Section C. 70 75 80 85 o sea

KRA ISTHMUS PROFILE D Latitude 8030'1N 700 1000 700 500 700 6000 4000 feet 2000 0 300 700 200 500 400 0 300 200 0 nA ^ 0 5 10 15 26 25 30 35 40 45.0 5~ 6b 65 70 0 0 200 700 200 700 1500 4000 4200 0 0 6000 4000 2000 7. 7 8 8 10 5 110 l.5 120 1f miles sea Fig. 3. Cross Section D.

spurs or outlyers which make parts of it of complex character. It contains an extensive swampy area extending between latitudes 30'01 and 4~30'. The coastline is marked by a narrow sandy strand, commonly wet, and in many places covered with a mangrove fringe. The mountains rise sharply from the coastal plain. Local relief increases from north where it will average 1500 ft to the south where it reaches 5000 ft. Slopes vary between 21 and 31%. b. Singapore Low.rland. The mountains extend as ranges to about latitude 2~30' where they break up into discontinuous and individual hilly masses. The general upland surface is a composite of wtet lowlands of negligible elevations and somrwhat higher but flattish areas of complex plain with altitudes of 100 to 300 ft. Along the east side of this lowland is a large area of freshwater swamp extending from the coastal sand dunes to the margins of a large isolated hilly mass. Singapore island and the city itself at the extremity of the Malay Peninsula are a center for the communications lines; roads and railroads from the peninsula. East Coast is formed by an alluvial plain some 20 miles in width which is consistently swampy immediately inland from the strand. The coast itself is sandy and probably bears low dunes which are not high enough to show within the contour interval of the maps (250 ft) but are indicated by presence of short streams parallel to the coast. Mangrove is uncommon except in the river estuaries. The northern part of the plain is of complex character and holds small individual.rounded hills which rise sharply from the level surface to heights of 600 to 1000 ft. The country behind -the coastal plain is a hilly upland cut by stream erosion. The summits are between 2000 and 5500 ft in elevation with local relief near the coastal plain of 15O to 2000 ft and inland up to 5.000 ft. Slopes average 'from 19 to 26%0. Cross-section E, Fig. 4, covers the entire width of the peninsula. The difference between the high mountains of the wst and the hill country and plains of the east is apparent, (. The Ban.kok Plain. The flat -alluvial lowland formed by the delta of the Chao Phraya, and three other rivers, is a plain about 100 miles in breadth along the ocean. The coast is fringed with a narrow tidl- sltrip f!tan!grove. The surface is relatively well drained by agricultural canals a.nd contains no extensive swampy areas. It is entirely under paddy cultivation and has a road and railroad system centering on Bangkok. 7. lMountains and Plateaus of.iestern Cambodia and Eastern Thailand. Between the- Banglkok Plain and tile Mekong Delta extends an area of uplandis composed of plateau and mountainous surface which approaches the coast closely throughout most of its extent. In the western, or Thailand, part of this is an undulating surface, 700 to 1000 ft in altitude, with tabular mountains and ranges rising to 2000 ft. The coastal alluvial strip is only two to three

MALAYA PROFILE E Latitude 4~30'N 0 600o0 4000 feet - 2000 -0 0 250 250 1000 800 0 1300 1450 1600 1450 1250 2500. -A /- ^ A \,.... 0 10 15 20 25 30 35 40 45 50 55 60 65 2000 2250 750 500 500 C ) 0 0 500 1250 1000 750 250 I - - I X I-I 65 70 75 0a 85 90 95 d 100 ids l0-T53 0 0 1750 1000 750 1000 750 750 750 1000 1250 1000 75C i jo 0 i45 14i5 16o0 165 110 175 1. 85 10 6000 -4000 feet -2000 L o a miles se Fig. 4. Cross Section E. 42

miles wide but extends farther inland along rivers and the bays. Local relief in the foothill and coastal areas is from 300 to 600 ft but reaches 2000 ft in the isolated mountain ranges. Slope samples in the area average from 16 to 18%. The eastern or Cambodian side, somewhat higher and rougher, is formed by the Chaine des Ca.rda^ones and the Chaine de 1'Eiephant with summit elevations within the 50-mile zone reaching 3000 ft. The mountains extend to the coast as headlands and the discontinuous coastal strips are very narrow. Local relief in the coastal foothill areas is from 900 to 1200 ft but in the mountain spurs is as high as 2400. Slopes in the coastal zone average 16 to 18% but are as steep as 34i in the mountains. Cross-section F, Fig. 5, is drawn across the Thailand-Cambodia border. It shows the low plateau and the isolated hill group of the Thailand (western) side and the Cardamones on the eastern interior. 8. The Mekong Delta extends southward from the end of the Cambodian mountains for about 100 miles lto Point de Camau (Cape Cambodia), the southern extremity of the Indo-China Peninsula, and thence northeastward along the South China Sea. It reaches inland for 400 miles or more. This is a level, featureless lowland intricately patterned by drainage ditches and the distributaries of the Mekong. Much of the western part for 1.5 or 20 miles inland is permanently flooded and covered with ~wet forest. The northeast-southwest (eastern) coast bears a mangrove fringe two or ncore miles wide along most of its extent. Most of this lowland is subject to disastrous floods, it would be a difficult area for cross country movement but does have a relatively good system of roads. 9e Chaine Annanitique is the extensive area of hills and mountains which stretches for G00 miles along the coast of the South China Sea between the delta of the Mekong and the Tonkin TL.owland. I-t; extends inland somewhat beyond the limits of the 50-mile Project Area and on the west drops onto the Mekong drainage basin, The chain is a succession of eroded plateaus with a general elevation of 1000 ft or higher and capped by erosional remnant s of individual mountains and ranges reaching elevations of 5000 to 6000 ft. Spurs of the upland reach the sea and cut the coastal plain into separate segnents. The upland has been strongly dissected into a hill and valley surface. The southern end of -the-chain, fo about 100 to 150 miles north of the,lekong Lowla.nd is an un;iulaatin;g upland about 50 miles in width between the coast and the Mekong drainage to the west. It has surface elevations of about 00 to 6QO ft with individual mcuntains reaching to 20G ft. Local relief on the uIndulating surface is from 150 to 300 ft and slopes are of about 5 to ils. The isolated mountains contain local relief of 25(00 ft and slopes of 27 to 29S.

EAST THAILAND PROFILE F Map # 58 Latitude 12~30'N 4000 1 feet 2000 - 600 600 0 600 1200 00 0 0 0 I 0, 0 t I I I I 5 10 15 20 25 miles I I I40 45 30 35 40 45 50 SOUTH VIETNAM PROFILE G Latitude 12005'N 8000 600 1500 3100 1200 1800 1500 2100 1500 I1010 0 6000 - feet 4000 - 2000 - C 5 50 4 40 35 30 miles 25 20 15 10 0 Fig. 5. Cross Sections F and G.

From about latitude 13 to the beginning of the Tonkin Lowland the chain is a rough dissected upland into which the short streams flowing into the South China Sea have cut deep valleys. In the rougher, middle parts of the chain local relief between the valley bottoms and the higher crests reaches 2500 to 3000 ft with slopes as steep as 35 to 50%, The coastal strip along the chain is broken into nine segments by headlands. These alluvial areas are usually ten miles or less in width but extend much farther into the hill country along the valleys of the larger streams. On their seaward fringes they are characterized by sand dune ridges, lagoons, and offshore sand bars. Inland of the dunes the lowlands are commonly in paddy cultivation. North of latitude 18~ the coastal strip becomes wider and merges with the Tonkin Lowland. Cross-section G, Fig. 5, shows the ruggedness of the terrain-of the Chaine Annamitique, the large local relief and narrow coastal plains. Sections H and I, Fig. 6, indicate the same general character as well as the sharp drop into the Tonkin Lowland on the east. 3.0. The Tonkin Laowland is the alluvial plain formed in the north by the delta of the Red River and its distributaries and in the south by the wide coastal lowlands and narrow delta deposits of the Ma, the Ca, and the Chu Rivers. It is a flat, featureless area which is only 2 or 3 ft above the sea along the coast and more than half of its entire area is below the elevation of 10 ft. An intricate pattern of ditches and low dykes provide drainage and protection for the densely settled and intensively cultivated low ground. Its coastal extent is about 200 miles. The lowland is divided approximately in half by a ridge of limestone hills which reach within ten miles of the coast at latitude 20~. (See Fig. 7.) Thle northern part, the delta of the Red River, extends inland for 150 miles, constantly narrowing in width. The coast of this part consists generally of sand or mud banks with much mangrove swamp. The southern half is narrower, some 25 to 55 miles in width and is broken into two sections by a hilly upland which reaches the coast at latitude 19Q15'. Its coastal fringe is sandy with some dunes, but generally open and smooth. 11, Highlands of Northeast Tonkin. Between the Tonkin Lowland and the Chinese border is a rough hilly area formed by the southern extension of the massif of China. It is a dissected plateau with short ranges extending generally at right angles with the coastline. The lhighest elevations, 5000 ft, and the steepest slopes, 26r, are in the extreme northeast adjoining the Chinese border. Over most of the hilly area the local relief is betw.een 1200 and 2000 ft. Figures e8 and 9 drawn from photographs show the nature of the hill and valley terrain close to the Chinese border and near the Tonkin Delta. The coast of the northern half of the upland is an alluvial strip some five miles wide, bordered by sand an-d muid fla:ts and priotected by a chain of islands lyin:g two to three miles offshore. *45

SOUTH VIETNAM PROFILE H Latitude 14 30'N 6000 800 300 300 600 300 200 1400 1800 1500 0 4000 feet 2000 O...,.- _.-.../. 50 45 40 35 30 25 20 15 10 5 0 miles NORTH VIETNAM PROFILE I Latitude 17~30'N 1800 1500 600 300 900 1800 2400 3300 0 0 4000 4 -H 2000 0.~ 50 45 40 35 30 25 20 15 10 5 0 Laos North Vietnam Sea miles Fig. 6. Cross Sections H and I.

The hills rise abruptly from the flat lowland of the delta and are covered with forest to their suimmits. In the left foreground there is a coffee plantation and large modern farm buildings. Source: P. Gourou, Les Paysans du Delta tonkinois, plate 5 (Paris, 1936). Fig. 7 Limestone Hills on the Tonkin Delta. Fig. S The highlands of northeastern Tonkin. 47

Fig. 9'. Country at Margin Between Highlands and Tonkin Delta. From: Geographical Handbook Series, 1R.R. 510, Naval Intelligence Division, London. Analysis of Rela~tive.Relief Relative relief is a, measure of local roughness. It. is obtained by measuiring the diff,-,:1erence between the highest and the lowest elevation within a limited arela. It is one of the elements of the environment of importance in calculating the diffL"iculty of off-road movement. MT11T3I0D USED IN7" T11IS STUDY The m,.ilitary; grid squares, 10,000 yards on a side (or 10,000 meters on some maps) was uised as the basic area. Within each square the difference in e leva~tion we~ts, calculated for th-e pa-rts of each map within the Project Area. The maps uised were the 1l"_50,000 and simrilar scale of the U542., L509, L508, and L501 ser'!es. The dilfference in area between the 1-0,000 yar-d and the 10,000 me-ter sq-lip'-es was not con —sidered sigliificant. 'The contou-1-r -irterval vaie I ~~e'isto a-other. T I e use in the analysis were 100 ft. 2 00 ft,~100 neters, and 500 ft (for one map only). A total of sqiia2-tq s we.e co zited. Thec ave been -divided -into the Physical Region c at egori e s, c'ei rp.evioisly I n thIs sect ion on ipand Su_,rface and alre presented iLn Table..ed o n of tuhe fn d i ngs o f.I re1 a tive relief -into the simple c 9t e g o",-,es >-1 ca Ks.and mo-antains follows in the mra>, categori esby the Ai '' c- "or. the samz-e maps but calculated b: th,,e "'S on '5,000

9 t T 1 o ~ n9~z s1 1o 0 Omd~~~d ra"iiI 006m~ OC9 N ~ ~ E 0 I Joe,: OD:I r:::4 ill~il ~ At 7 A::::: In 1 1" 001 0I:-~::-: I 49

yard squares. The AMS classification is: Plains: under 600 ft of relative relief Hills: 600 to 2000 ft of relative relief Mountains: over 2000 ft of relative relief. For the purposes of this project, the area of the mountain category was included within our general category "complex hills." Our original map analysis, made by counting these some 6572 squares for vegetation and geomorphological nature showed that W5I% of the area was in plains of one or another character and 55% in complex hills. The relative relief analysis shows that exactly 45% of the squares have relative relief of 600 ft or under, so that we have taken this flgure which is the same as that used by AMS as the limit of "plains." The AMS limit of 2000 ft or under for "hills" includes (together with plains) 79% of the surface and that of 3000 ft or under, 94-io of the surface. Because we have no geomorphological data to separate hills from mountains we have taken the AMS limit of more than 2000 ft of relative relief as the hill-mountain boundary. We have also subdivided the mountains into two categories: low mountains with relative relief between 2000 and 3000 ft; and rugged mountains with relative relief over 5000 ft. On this.basis the categories of relative relief presented in Table 9 are: Plains: under O00 ft of relative relief Hills: 600 to 2000 ft of relative relief Low mountains: 2000 to 5000 ft of relative relief Rugged mountains: over 3000 ft of relative relief. The physical regions presented above may be described in terms of their relative relief from the study surmarized in Table 9. In reading these figures it should be considered that the flat areas such as the Tonkin Delta include also their silrrc.lunding, mou,:tains to the boundaries of the Project Area. '0

TAB LE 9 PERCENTAGES OF PROJECT ARE.PA TN CATEGORIES OF RELATIVE RELIEF BY PHYSICAL REGIONS Low Rugged Physical Region Plains Hilly Mou ntains Mountains.Arakan Cst. N. 314.8 142.0 17,2 6,o Arakan. Cst. C~ent. 34. 6.14 11. 6 98 Arakan Cst. South 78.8 16,3 9,14 1,5 Irrawaddy 71.35 18,7 5,9 14.1 Tenasserim (N) 10.6 144.1 55.0 12.5 Tenasserim (S) 19.9 66.8 12.8 0,5 Malaya (West) 58.5 57,3 12141.8 Singapore 62030. 6,3.1.5 Malaya (Eas-:t) ~ 4.5 15,,297 S. Thailand East 56~. 0 141,5 15.1 7,14 S. Thailand West 55.5 51.4 11,855 Bangkok 62,8 22,5 15,,21. Camb. Thail. Mts. 57.1 14o,0 15.6 7,5 M4ekong 95.14 6.14 0.2 -Ch. Annam (South) 27,5 29,5 23,1 19.9 Ch, Annam. (Cent'.) i14.3 50.-5.28,9q 26,,5 Tonkin Delta 214.0 5 8.0 19,14 18.6 E. Tonkin Highlands 5o.6 36.14 9.038 Analysis of Slope Of the t-wo general geomor-phologic divisions with in area of th-e stud'y, plainls and comolilex hills, the form,1er presents few problems in terms of' slope anigles. Imnpedimen-rts to trafficability on the plains stem from low s-oil s-tr ent Ifor w7hich we h'ave no measura ble data, from poorly'dratined areasj anI, d from pad die s. -L the com,1plex hlI' one o the factors of trafficability is the- slope angle.Evia points out that vehicles "seldom bog dow-n on steep slopes al — thouh thy ma not b e able to cliimb them"; therefore, weasume that the slope angle is the controll-ing ocondition although Soil strength may be a factor in valley bottoms. An an~alysis -was madn,,Ie from 75 sa-mples, each s elected at random from the 1:2 0,OOO apus which in 1in.-ear sequence cover the coastal area from the Pakistan border to the (!1rm border, using Wentworth's formu'la for acrle withal e miLe rVadi1-us and couni-ting alon —)g six or less radii. Each observation is, there 51

fore, an average of a sample of some 300 square miles. The quantitative distribution of these samples is shown in three magnitudes of category in Fig, 10, and the actual readings and computations in Tables 10 and 11, When arranged by the categories used in Envinal the following distribution is found: 5-15% (slight) 16-530 (moderate) 31-50% (steep) 14 samples 42 samples 19 samples 19' of samples 56% of samples 25% of samples There is no recognizable, or at least measuabl-e, geographical distribution of the categories as can be seen by running down the columns for numbers of contours, as well as percent or degree of slope in Tables 10 and 11. IMPLICATIONS It is recognized that vehicles do not climb "average" slopes but are limited by the steepest slopes. Hlowever vehicles are not usually forced to travel "across the grain" of a surface and may select the easiest way, conmnmonly along the valleys rather than up the hills. By this reasoning, the average slope of' a. saple may be a pretty good indication of its trafficability in terms of slope alone. Envinal gives the following capabilities (disregarding the factor of soil.st;rength). 0-15,'/ (slight) 15-50% (moderate) 30-)45 (steep) All wheel-drive trucks, trailed vehicles, heavy tanks. Medium tanks, tractors with high contact pressures, trucks with low contact pressures., Tractors with average contact pressures, tanks with low contact pressures. Under these criteria almost all of the area should be trafficable for light tanks. It should be stated however, that such conclusions are directly opposed to those of a military reconnaissance party which reported that in the steeper parts of the country (somewhat inland from the area under analysis) cross counitry movements except by foot parties were impractical. Method of Slope Analysis To give some indication of the character of slope in the complex hills regions this analysis employed a met.hodl described in -the Headquarters Quarter 52

master Research and Engineering Command, U.S. Army, Technical Report EP-124, "A Quantitative System for Classifying Landforms," issued by the Quartermaster Research and Engineering Center, Environmental Protection Research Division, Natick, Massachusetts, February 1960, page 7, was used. "(5) Average slope - As yet, no quick method has been devised for obtaining the data needed to describe the statistical and spatial distribution of slopes within an area. Therefore the only indication of the angle at which the surface departs from the horizontal is the average slope. "A measure for average slope is obtained by drawing traverses across the area in several directions, counting the number of contours which cross these traverses, and computing -the slope tangent by the Wentworth equation (5): S tan = I x M/33561, where S tan is the slope tangent; I is the contour interval in feet; and M is the number of contours crossed per mile of random traverse." After selecting 75 random locations (Map 10) a count of contours was made along six (north, northeast, southeast, south, southwest, northwest) ten mile traverses from the random spots. To preserve the maps however no lines were drawn directly on the maps. Instead the traverse lines were drawn as radii on transparent plastic as illustrated and the count of contours made along the inked lines. Since most of our working maps are at a scale of 1:250,000 the star was constructed with a ten mile. radius at that scale. No adjustments were made for those maps whose scale was 1:253,440, inasmuch as the difference is negligible. (Data enclosed.) Kno win_ g the contour interval and having counted the number of contour crossings per mile the data were readily applied to the Wentworth equation. The procedural and concluding figures are attached as Tables 10 and 11. The final solu=ns of the T'able 11 show the slope in percentage and degree respectively. Three different histograms (Fig. 10) constructed from findings show the mean and median figures and to some extent the deviation. 53

PERCENT SLOPE AT SAMPLE SITES *38 24 34 32 ~34 *36 17 *21 *27.21.33.24 14.32.34 *19 022 *11 o20 o 29.50 25 35 e41 029.33 o29 020 09 23022 31,32 037 028. 27.34 15 019 % II 29 1 17 ' 020 17 013 029,25 027.29 04 e22. 15 21.22 * o2 o11 * 13. 23 *25 ~16 DOTS INDICATE LOCATION OF SAMPLES *27 * 22 *20.12 e26 NUMBERS REFER TO THE PERCENTAGE OF SLOPE AT THE SAMPLE LOCATIONS 21 *31 18 * 16 810 *28 Map 10. Percent Slope at Sample Points.

TA!BLE 10 MTEASUREMENTS OF SLOPE DETEPRMINATION INI COMPLEX HILLS Stratified random sample - 15 regions n, numrber of observations = 75 1 t T 2nd. 3rd Total Map Contour. -. --- — Observation o o o No. f No. of No. of No. Interval Miles Miles Miles Miles Contours Contours Contours Contours.,J 1 2 5 4 5 0 7 8 9 10 11 12 13 14 15 17 18 19 20 21 '22 -.25 27 1 500 t, 3 200 ft 3 200 ft 3 200 ft 4 200 ft 5 200 ft 6 200 ft 7 200 ft 7 200 ft 12 200 ft 12 200 ft 14 200 ft 15 200 ft 15 200 f t 16 200 ft 17 200 ft 17 200 ft 17 200 ft 18 200 ft 21 250 ft 21 0j.' t 21. 20 ft 22 20 ft 24.328. ft 27 S20 ft 2250 f-t 2 2250 ft 10 10 10 10 10 9 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10> 2O 38 62 56 43 14 44 69 22 27 32 48 22 50 29 23 41 41 57 48 37 26 20 25 11 40 24 54 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 26 42 51 58 38 19 33 55 32 40 32 18 7 49 32 10 36 38 47 31 31 31 20 57 11 30 18. 34 10 23 10 44 10 60 10 56 10 49 10 16 10 31 10 57 10 34 10 40 10 33 10 44 10 24 10 49 10 41 10 14 10 33 10 38 10 55 10 42 10 21 10 29 10 20 10 25, - 7 1o 29 10 24 30 77 30 124 30 173 30 170 30 160 29 49 30 108 30 181 30 88 30 107 30 97 50 110 50 53 30 148 30 102 30 47 () 110 30 117 30 159 30 161 30 89 30 86 50 60 30 87 25 29 50 99 70 66 30 107 I - -.1) 10 39. t_ = _ _ _ _ -------- - - i- I I _ ~~)CP-.~IC~-CI-IP~-~-~-DCLI ---- -- ---- n _

TAB3LE 10 (Continued) 29 30 31 52 55 54 35 36 57 38 \J1 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57.58 52 250 ft 32 250 ft 54 250 ft 34 250 ft 35 250 ft 36 100 ft (form lines) 59 250 ft 4i.250 ft 44 250 ft 44 250 ft 46 250 ft 46 250 ft 49 250 ft 52 100 m 52 100 m 53 100 m 3 100 m 54 100 m 56 100 m 57 100 m 58 100 m 8 100 m 58 100 m 59 100 m 59 100 m 60 100 m 67 100 m 68 lOO0 m 69o 100 m o' 100 n:LO 50 10 24 10 25 10 3) 7 22 5 12 10 36 10 31 1o 25 10 16 5 21 10 15 10 37 10 12 10 23 10 28 1.0 17 10 45 10 54 10 28 10 35 10 55 10 29 10 29 10 15 10 26 10 28 10 30 10 15 10 21 10 24 10 22 10 6 10 35 10 50 10 24 10 35 10 19 10 30 10 26 10 12 10 23 10 29 10 54 10 29 10 28 10 41 10 350 10 7 10 11 10 28 10 47 10 9 10 13 10 21 10 20 10 6 10 21 10 30 10 28 10 10 10 10 10 10 10 10 10 10 10 10 10 5 10 10 10 10 10 10 10 10 10 10 55 19 27 36 22 25 28 20 41 25 45 37 25 11 52 28 11 17 18 11 2 27 29 25 10 40 10 31 10 14 8 18 5 21 10 11 30 126 30 86 30 64 28 67 17 64 25 58 (form lines) 30 105 50 50 50 80 3D 90 33 51 0 933 30 91 50 82 30 105 30 86 50 115 50 96 50 45 25 48 50 88 30 105 30 55 30 51 350 63 30 53 30 14 0o 83 50 89 50 77

TABLE 10 (Concluded) 1st 2nd, 3rd Total o:, t o.. -o -- —, ----............. ObSrvtion to of o. of No. of No. of No. Interval MileCs Co rs Miles CMi les Miles C Contours Contours Contous Contours 59 60 61 62 65 64 65 66 67 68 69 70 71 72 73 74 75 70 100 m 70 100 m 72 100 m 73 i00 m 73 100 m 74 100 mr 76 100 m 76 100 m 76 100 m 79 100 rn 79 100 m 79 100 m 80 100 mr 80 00 m 81 100 m 85 100 rM 10 19 10 52 10 28 10 35 10 355 10 45 10 351 io 55 10 32 10 35 10 40 10 55 10 14 10 43 10 18 10 22 10 27 10 15 10 36 10 16 10 26 10 26 10 38.10 34 10 50 10 19 10 35 10 29 10 58 10 16 10 29 10 28 10 21 10 30 10 8 10 20 10 18 10 30 10 29 10 42 10 37 10 49 10 27 10 39 10 30 10 33 10 14 10 29 10 29 10 23 10 25 30 42 30 88 30 62 30 89 30 90 50 125 30 102 30 154 50 78 30 109 30 99 30 106 30 44 30 101 50 75 30 66 30 82 - -- --

TABLE 11 COMPUTATIONS OF SLOPE DETERMINATION IN COMPLEX HILLS Wentworth formula: I x M. slope =- 56 M = contour I = contour crossings per mile interval in feet ap I, I x M of Degree Observation M I x M No. ft 361 Slope (approx) -J1 1 2:; 1, 't 5 /, 7 LC -11 2. 10 fL 14 15 16 17 18 19 20 21 22 25 0 r, 26, 1 3. 5 5 5 6 7 7 12 12 14 19 15 16 17 17 17 13 21 21 21 2. _ i 500 200 200O 200 2-00 200:200 200 '200 200.)OO 200 200 200 200 200 200 250 250 2008 250 2r_0 32:)O 2.566 4.133 5.766 5.666 5.332 1.690 5.560 6.033 2.933 3.566 5.255 5.666 1.766 4.933 5.340 1. 67 3.666 5.900 5.299 5.366 9.966 2.866 2.000 2.900 1.160 5.300 1283.0 826.60 1155.2 1133.2 1066.4 338.0 712.0 1206.6 586.6 713.2 646.6 733.2 555.2 986.6 668.0 313.4 73355.2 780.0 1059.8 1073.2 741.50 716.5 500.0 725.0 30 596 825.D.5817.2459.53451.3372.3175.1006.ioo6.2118 3590.1745.2122.1924.2181.1051.29355.1988.0932.2181.2321.3}.3.53195.2206.2132.1488.2157.1152 2455 58.17 24.59 54.31 33572 31.73 10.06 21.18 35.90 17.45 21.22 19.24 21.81 10.51 29.355 19.88 9.32 21.81 23.21 31.55 51.95 22.06 21.52 14.88 21.57 11.32 24.55 20053' 13~49' 18056' 18 38' 17036' 5045 11~58' 19~45' 9054' 11059, 10~54, 12~18' 60oo00 16022' 11~15' 5.20' 12~18' 135041 17~50' 17453' 12~27' 12~02' 8~10' 12010' 6~28' 13~48'._. ---. _. -

TABLE 11 (Continued) M.p I, I x M % of Degree Observation No. M i x M (po,_oA. i-t_ 3361 Slope (approx) 27 28 29 50 32 35!4 56 36 59 to 44 46 43 49 52 54 57,9. 28 29 32 52 54 34 55 36 59 41 44 44 46 46 49 52 52 55 53 54 56 57 58 58 58 59 59 6o 67 68 69 69 70 - 250 2)0 250 1z00 250 25.00 250 250 250 250 250G 528.1 528.1 528.1 528.1 52&8.1 328.1 528.1 32 3.1 325.L 1 328.1 328.1 32(3.1 328.1 328. 1 2.200 3. 566 4.200 2.866 2.155 2.595 5.765 6.655 5.500 1.667. 000 1.700 5.100 5.055 2.75533 3.500 2.866 3.833 5.200 1.500 1.920 2.955 5.500 1.100 1.700 2.100 1.766 1.65 2.766 2.966 2.566 1..00 550.0 891.5 1030.0 716.5 55335.25 598.25 941.25 331.50 875.0 416.75 666.5 750.0 425.0 775.0 758.25 896.6973 n148.55 940.3346 1257.6075 1049.92' 492.15 629.952 962.3173 1148.55 360.91 557.77 689.01 579.4246 133.66 907.5246 9735.1446 841.9046 459. 34.1636.2652.3124.2132.1586.1780.2801.0986.2603.1240.1983.2231.1265.2306.2256.2668 ~.3417.2798.3742.5124.1464.1874.2863.5417.1074.1660.2025.1724.0598.2700.2895.2505.1367 16.36 26.52 31.24 21.32 15.86 17.80 28.01 9,86 26.03 12.40 19.85 22.31 12.65 23.06 22.56 26.68 54.17 27.98 37.42 51.24 14.64 18.74 28.65 34.17 10.74 16.60 20.25 17.24 3.98 27.00 28.95 25.05 15.67 9~181 14051' 17021' 12002' 9~01' 10~06t l5~o39 5038, 14036, 7~041 11~13' 12035' 7013' 12~59' 120435 14~0 6' 18~52' 15~38' 20~531 17021' 8~201 10034' 15059' 18~52' 600o8 9026, 11~31' 9047 -20171 150071.6~ 09 14~04, 70471 --- - __, _ --- - -- -v -

TABLE 11 (Concludedd) I pI, I x M. of Degree Observation M I x M.'o..:t......:t 3 361 Slope (approx) 70 2 2.9355 962. 175.2863 28.63 15~59 6172 28.. o06 677 o846.22017 20.7 1124 62 72 28.1 2.966 973.1446.2895 28.95 16~09' 65 73 328.1 3.000 984.3.2929 29.29 16~20' 64 73 2 1 4.166 1.66.8646.4067 40.67 22~08' 65 74 528. 3.400 1115.54.3319 33.19 18~22' 66 76 358.1.15 1684.1373.5011 50.11 26037' 7 76 528.1 2.560 839.96.2500 25.00 14~03' 68 76 28.1.633 1191.9873.5547 35.47 19~32' 69 79 321 500 1082.73. 3221 32.21 17051' 70 79528.15 3-5 1159.1773.3449 34.49 19~02' 71 79 328.1 1.467 481.3227.1432 14.32 80og9 72 28.1 3.566 1104.3846.5286 32.86 18~12' 7 28.1 2.500 820.25.2441 24.4 15343' 74 81 358.1 2.200 721.82.2148 21.48 12~08' 75 858.1 2.73333 896.6973.2668 26.68 14056' Mean = 24.05015333 or 13532' 0 Standard Devia-tion Ex2 = 4.88875912 v * 2 v2 (?<)2 Z(xi-x) = Zx -( ) n S2 = X S = n-l S =.08626 = 4~551 (5') - 18.0376 7.5 x =.240501333 or 13032' S =.00744152 variance

DISTRIBUTION OF SLOPE FREQUENCIES Slopes calculated in percentages by the Wentworth method from ten mile traverses intersecting at each sample point. Based on 75 Random Samples z 0 E-4 14 o H o o X:*: 14 -12-!~iiii~.t.......... b6*::;.......................::-::::o:::::::: ~ ~ 1.-.. '...............................................................................................:::::::::*:*:*:::::: 4 -...............,................o.....4..,..................................... 4+-:::::::::::::::::::::::::: 2 -.-...-.-....%.......-..,..,. PERCENT SLOPE ( five-percent class intervals).,.......... * t.....................................................s..,.-............. O ""''" i~ ) b2 3 05 PRCET LP ~~ ~ ( fveprcen classinte~als 0 r. O0 14 12 z; 0 10 H I8 -r 6 -C 4 -0 2.O:... *~:::-!ii.!....:....... —.-.-..,,.. -:*..........:::::..... -.:................................................................... 612 1'8 24 3'0 3'6 4'2 4'8 PERCENT SLOPE.......................................... -...:: —: **:::::........................ - ~ ~- -X -........................................ -..-.. ---::-: -::: —:: —............................... *~~~ -.*-.t ---.....:~r:- - -.......- --- ~. -.~::.. - -.... -.... -- ~~~n. ~~~~=;:~~~ ~~ ~? ~l 2430 6ts24 PECN SLOPE ~~~~~~ (three-percent class intervals) Z < Q0 rJ4 10 -8 -6 -4 -2 0......................................................................................................................................................................................................................................................................................................................................... 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 PERCENT SLOPE (one-percent class intervals) Fig. 10. Distribution of Categories of Slope Frequencies.

IV. CLIMATE AND WEATHER The climate of Southeast Asia may be described as tropical and monsoonal. The temperatures are constantly warm and their variation from season to season is small by midlatitude standards. The annual alternation of -the monsoon winds produces in most places a wet season and a dry season and a relatively large amount of annual precipitation. The rainfall in its quantitative and distributional aspects is the most important fact which will affect military operations in the climatic environment. The rains of the wet season produce soft and boggy lowlands, flooded river valleys, and slippery surfaces even on gentle slopes. Together with inadequate and indifferent roads and lack of bridges, these conditions will strictly limit the operation of heavy equipment. Climatic Controls The climatic character of any part or any place in the coastal strip may be explained in the combinations of the following three factors: latitude, altitude, and exposure to wind and nature of local topography. The functions of each of these are briefly described as preliminary to the general climatic description. Latitude. The position of a place in latitude determines in a broad way its temperature. All of the Southeast Asian coasts lie between the equator and the Tropic of Cancer in the zone where there are few cool and no cold monthly temperatures and seasonal variation of about five to twenty degrees between the warmlest and the coolest months. Altitude. Temperatures decline roughly three degrees per 1000 ft increase in altitude. In coastal Southeast Asia about 45% of the area is low plain and 55, is hilly, the highest elevations of which are around 5,000 ft. Comparison of the temperatures in degrees of the following -two stations within about 50 miles of each other will illustrate the altitude factor, J F M A M J J A S 0 N D Yr. Nahtrang Alt 20 ft 75 76 78 81 85 83 83 84 82 80 78 66 80 Dalat Alt 4q21 ft 62 63 6, 67 68 68 67 67 66 65 (64 61 65

Exposure to Winds. All of Southeast Asia lies under the regimen of the monsoonal system which in combination with local topography is the principal factor in the amount and distribution of rainfall. The monsoons alternate their directions with the seasons. In summer they blow into Asia from the south and southwest and in winter blow out of Asia from the north and east as illustrated on Maps 11 and 12. The southwest winds bring heavy summer rainfall to the coasts that face their directions. The northeast monsoons are dry winds except where they pass over the South China Sea and bring rain to east-facing coasts. As a generalization the rainfall regimens may be expressed thus: For west-facing coasts, summer rains and winter droughts; for east facing coasts, winter rains and stumer droughts; for peninsular extremities affected by the monsoons of both seasons, double-maximum patterns with peaks of precipitation in spring and autumn. Climatic Elements TEMPERATURE As the area lies wholly within the tropics, almost all weather stations except those of the highlands and the extreme northeast corner (Tonkin) show normal monthly mean temperature above 70~. The range of temperatures between the warmest and the coldest months is low by midlatitude standards, varying from about two degrees at Singapore near the equator to 22~ at Hanoi near the Chinese border in North VietNa.m- The maximum temperatures lie some 10~ to 15~ above the means and vary within a range of approximately 10~. The mean maximum temperatures (see monthly analysis charts) range from the low 80's to the mid 90's with the seasons and the extreme maxima from the 90's to slightly above 100~ (Fig. 11), Temperature Regimens. Four types of temperature regimens may be recognized in the area. These are: 1. Low range-high average temperatures. These occur in the equatorial and sube-quatorial stations protected from or outside of the full. monsoonal alternation. Monthly temperatures are high, above and below 80~, with a low ann-ual range of less than ten degrees Such a regimen occurs around Singapore and the Malacca Straits area and around Saigon. 2. Sumner maximum temperatures, warm. This is the normal pattern for the coastal lowlands. Low month temperatures in the 70's high month temperature s in the 8O's. 3. Highland regimen. This corresponds with the usual suirmer maximum warm ty pe except that -the temperatures for all -mnonths a.re liowered as a function 6f

95 100, 105 110 ' i A | ND IJ A2 \ 1E N S F W nAIND - I a N25" 50/ ",' 50 4 \\ 2 4 i,} 2 T NI.,/ -/ O 15 ___- __ 2,\ ' ^hO 5 N'N i A' S 7i10 Map? 9.. A I A 4n D j0 |nl \0 and: \ -.'Yb,: ~ — 5 EVAI.IN SURFACE WIND..6 July, nJ and AJUNst. From: AUAn n i e r So ____. A ( __ __ July, and August. From: "An Environmental Comparison of Southeast Asia RStudy EEVAILNR-8 S(6RFAC).E WIND65 Study RE~R-38 (i?61). 65 I

SE S E A AVERAGE PRECIPITATION AND PREVAILING SURFACE WINDS PEC. JAN. FEB. ( Inchl,s) [7 MORE THAN 50 i 1 20.50 i- 5 - 2o I - 5 '] LESS THAN I "^ —( StURFACE \IND FLOW Map 12. Average Precipitation and Prevailing Surface Winds During December, January, and February. From: "An Environmental Comparison of Southeast Asia and the Island of Hawaii,' by J. V. Chambers. QMR&E Command Research Study RER-58 (1961).

TEMPERATURE S Monthly Averages for Selected Stations 90 r f: 80 E-4 So U4 UT 0 C 60 u I I,, ,,,, __ J F M A J J A MONTHS Fig. 11. Temperature Graphs. S 0 N D

of elevation. The figures given above for Nahtrang and Dalat will serve as an example. 4. The Tonkin regimen. The northeastern extremity of the Project Area differs in temperature characteristics from the other types because of its higher latitude as well as the effects of winter weather conditions on the Chinese mainland. The Tonkin area has the coldest winter months, in the low 60's; the highest annual ranges of temperature, up to 22~; and the greatest diurnal ranges with variation as much as 30' in a winter day. Significance of Temperature Regimens. By themselves the temperatures and their regimens are not of critical importance in military operations. Few of the monthly average temperature-humidity combinations at various hours (see the sheets of monthly analysis) 'Jie near the Envinal thermal strain value of 30 at which performances deteriorate. It is probable that individual days produce more severe strain conditions but it is doubtful if these would persist very long. PRECIPITATION Precipitation occurs almost entirely in the form of rain. Snow is absent except for some of the highest elevations.in the northeast; hail and fog, while present are not coirnon and furnish a negligible amount of the total precipitationo Rainfall is derived from the streams of oceanic air which constitute the monsoonal flow. It occurs in greatest amounts at times when the boundaries of the opposing airflows of the monsoonal system pass over coasts where highland margins induce a lift of the humid air, The most intense rains occur, therefore, at the "break" of the wet monsoon along the mountain-flanked coast of northern Burma where they produce the accentuated rainy maximum described in Type II regimen. Rainfall Intensity in a Single Day. From statistics of indifferent rel.isbility, individual 24 hr periods on the north.ern Burma coast seem to receive up to 50 in. of rain during the June or July break of the monsoons. Che-rrapunji, to tle north in India, has an official record of 40,79 in, in 24 hr. From a study of Malayan rainfall between 1.951 arid 1940, the maximum precipitation for any day in mcst of the 7 stations was between two and eight inches. Thie greatest falls recorded during this study period were: Pekan 19.18 in. Penang 14.29 in. Kuala Krai 12-15 in. Port Dickson 12.72 in. Kuantan 11.05 in. The absolute maximum daily rainfall repor-ted for the fourteen "I" type stations 68

appears on Tables 12 a to 12 1. Over a period of ten years in almost all cases, the occurence of very high daily rainfall, for the approximately 1680 (14 x 12 x 1C observed months was 19 in. 2 months 13 in. 1 month 12 in. 2 months 11 in. 2 months 10 in. 4 months 9 in. 3 months 8 in. 1 month A total of 15 months out of 1680 recorded have received the very heavy rainfall of 8 in. or more in a 24-lhr reriod. Diurnal Distribution of Rainfall. It is a generalization that precipit-l.otiLon ov,;r land is more frequent in the afternoon and over seas in the early morning. This is somewhat modified for coastal stations which may be affected by the seaward rainfall. The graphs on Fig. 12 are taken from a manuscript study of diurnal variation of precipitation in Malaya. They are made by plotting the hours of day against the percentage of days of the month in which rain falls during the hour. For the inland station, Temerloh, the generalization of afternoon rains is apparent. For the coastal stations the pattern is complicated by exposure. Westfacing coasts (Sitiawan), exposed to the southwest monsoon have a preponderance of rain in the afternoon during the dry season. During the rainy season the daily distribution is more even. On east-facing coasts with rainfall maxima in fall and early winter, (Kota Bharu) the "inter-monsoon" months, February-April, show fairly even daily distribution; during the summer monsoon, which brings little rain to such-located stations, the afternoon maxima appear; during the rainy months mid-October to January, there are no very rainless hours of the day. Rainfall Regimens. For the purposes of analysis, records of rainfall were obtained for some available stations. The data are not strictly comparable in the sense of covering similar periods and some are from very old sources. They do however serve the purpose of establishing patterns of rainfall for the area (Mao 153 F-ive precipitation regimens can be recognized, one in the hill country and four on the ccast.al lowlands. Each of the lowland regimens appears in two separate places to form precipitations regions shown on Map 14.

KOTA BHARU 20 10I 20 10 Jan. Fe b. Afar. Ap r. A4{ay June SIT[AWAN __ _ _ _ _ _ _ _ Jul~ IuY. Sep. Oct. No v. Dec. 10 20 10 12 18 0 6 12 IS a 6 1 2 10 a 6 12? Ig o 6 u1.2i o 6 12.Timne of Day (AlT) Fig. 12. Diurnal. Distribution of Precipitation in Malaya. After Lea, C. A. "fDiurnal Variation in Rainfall Over Malaya" (unpublished)., cited in Watts, L.E.M1-.,, Equatorial Weather', University of Lonidon Press,, 1955. Tyye I. Hill Country,, Stum'ner Rain-Winter Drought Only a few stations are avail-able within the relatively narrow zone of hill country included In the project area but these do not seem to dl',-,fer sIgnificantly in their precipitation re-gimens from other upland stations more di'stant from the coast. The hill stations present a remarkably uniform regimen of rainy s~ mer months (April-May t.o September-October) and dry winter montIIIhs (November-March). This pattern is a result of the seasonal alternation of a summer air flow of warm, moist, maritime air with-.a winter flow of cooler, 70

OVAL&OUTEAST AZ MONTHLY PRECIPITATION *MONG3AY~ (121) AKYAB (198) SANOOWAY (211) BASSEIN (i0l) DIAMOND I S. (124) HANOI (77). I I; I. I I a 1 HAO * THAN~ (GE IJH RANGOON (101) 0 TAVOY (197). AOULMEIN (190) 0 DONG' HOI (79) * HUE BANGKOK (53) 0a MERGU I (157). CHUMPHON (72) NHAT T F *SATTAHIIB (6 (51) L PRACHUAP LOT GONE DLT PRCUP(133) * __ (74) KHIRI KHAN (49) PHNOM PENH (55) 0 _ _ _ SAIGON (83) SOGHA(88)!(90) KT BAi (124) PENA~NG (100) KUALA TRENGGANU (120) (1I16) RANG 62) PHUKET (95) ALOR STAR RAINFALL IN INCHES 601 401 201 AVERAGE YEARLY TOTAL GIVEN IN BRACKETS -Li KUALA S LUMPUR (94) ji 0 MALACCA (88)-.0SINGAPORE (95) Map 13. Monthly Precipitation. 7'

PRECIPITATION REGIONS HANOI CROW OWMONGAY HAIPHo ~ I K) LANGSON NAN DINHo NORWAY IS. AKYAB 'PHU LIEN *THAN HAO 1 0 VINH CM) DONG HOI *(L) TCHEPONE 0 RANGOON f H~UEAI (K) QUANG NGAI TAVOYo SD AGO ONG SON IQUI NHON TUY HOA I 3Z CJ) NHA TRANG (F) PHNOM PENH DALAT f CE orCN PODA RAN R IA (H) PFINAN THIET VICTORIAo (G) H AT E N CAP ST. JACQUES *CANTHO T POULO CONDORE POULO 081 ALUR STAR0 KOTA BHARU WEATHER STATIONS AND (A) PNANG PRECIPITATION REGIONS 8)WELLESLEY DOTS INDICATE WEATHE R STATIONSI *PAHANG STATION NAMES PREFIXED' WITH KJALA LUMPUR A L-ETTER DENOTE STATIONS WITH N-TYPE SUMMARY (C) MALACCA hff NUMERALS INDICATE PRECIPITATION REGIONS SINGAPORE Mlap 14. Precipitation Regions and Weather Stations 72

more dry, air of continental origin; a circulation uncomplicated by facts of coastal exposure. The differences between lowland and upland precipitation regimens may be illustrated by again citing the two.stations, Nahtrang and Dalat, in South VietNan of about the same latitude and within 50 miles of each other: J F M A M J J A S 0 N D Yr Nahtrang Alt 20 ft 2.3 0.9 1.7 0.9 2.6 1.8 1.8 2.0 6.7 13.4 15.1 7.4 56.6 Dalat Alt 4921 ft 0.4 1.0 2.2 6.5 8.5 7.3 9.6 8.3 12.1 10.0 3.9 1.1 71.0 Significance. Traffic through the hill country is difficult at any season and off-road movement is probably impossible during the wet season. In places where the lowland precipitation regimens correspond in season with those of the adjoining Hill Country regimen, the winter months from November to April are best for operations. However where there is a discordance of season, such as along the South China Sea Coast (from which the two examples above are taken) the common dry months for uplands and lowlands are only those from January to March. The Lowland Precipitation Regimens which occur along the coasts from Pakistan around to China are differentiated by the factors of exposure and latitude into four patterns: 1. Accentuated Summer Maximum with Dry Winters (Type II). 2. Normal Summner Maximum (Type III). 5. Accentuated Autumn and Early Winter Maximum (Type IV). 1. Dble Maximum Transition Type (Type V). Each of these types is distributed in terms of exposure and protection and each occurs in two separate areas within the strip of the coastal lowlands. Type II. Accentuated Sunmer Maximum with Dry Winters r-'om Novemler to April he rainfall is relatively light, the monthly mean arying from less thlan one in.ch to less than five. With the onset of the southest c monsoon thhe rmontihly precipitation increased sharply to the wettest month (t;e orA July) which receives from twenty-five to fifty cr more inches. The total yearly pre cipitation is usually in excess of 100 in., half or more of 75

which is concentrated in the months of June, July, and August. Distribution. The type is Ic,.ted on unprotected west-facing coasts with hilly backgrounds in two areas: a. The Burma-Thailand West Coast from the Pakistan border to 8~ north latitude. This coast is open to the full force of the summer monsoon which begins in May and the wettest months, June or July, may receive as much as 60 in. of rain. The winter months are very dry; in the northern threequarters of this coastal strip, the three winter months, December, January, and February together receive less than one inch of rain. b. Thailand and Cambodia Coast, facing west on the Gulf of Siam from the eastern point of the Bight of Bangkok (Cape Liant) to Isle de Phu Quoc (10~ north latitude). In this area the rainy summer months receive somewhat less precipitation, 30 to 40 in., and. the dry winter months somewhat more than those of the Burma coast. Significance. In this type the occurence of three or more months in which 30 to 60 in. of rain fall on coastal lowlands with indifferent drainage suggests that military operations would be difficult during this period. Type III. Normal Summer Maximum The precipitation regimen in these two areas resembles that of the Hill Country (Type I). From November to March the dry season months receive rainfall of only a few inches. During the wet summer -months, June, July, and August, some 40 to 50 in. will be received, which amount represents about onehalf of the total annual. These areas lack the accentuation occurring in the rainy months of Type I; the winter months although much drier than those of the summer, are rainy when compared to the nearly absolute drought of those in Type I. Distribution. This type occurs in situations protected from the direct force of both the southwest and the northeast monsoons. Two such protected areas are located along the coastal zone: a. The shores of the Bight of Bangkok and extending southward along the west coast of the Gulf of Siam to about the Kra Isthmus (10~ north latitude). The winter months are relatively warn and dry, the summers are hot and wet. b. Coasts of the Tonkin Delta in the Gulf of Tonkin and the adjoining coastal lowland south to about 19~ north latitude. This area is protected by the configuration cf the Gulf of Tonkin and tIai-Nan Island. Because of its proximity to the Asiatic imainland as well as its latitudp, the winters

are quite cool, in the low 60's, and the seasonal ranges (22~ at Hanoi) are highest of any part of the coastal strip. Winter precipitation to the amount of one or two inches per month occurs in the form of drizzles, called "crachin," possibly caused by mainland cyclonic passages. Significance. The absence of an accentuated maximum of precipitation make the summer period somewhat more acceptable for operations. Winters in the Tonkin lowland. would be less favorable than those in the Bangkok area because of lower temperatures and poorer visability. Type IV. Accentuated Autumn and Early Winter Maximum This type is marked by an accentuated rainy period occurring from September to December with the remainder of the year receiving only light; rainfall in the magnitude of three or four inches per month. This regimen is the result of exposure of east-facing coasts to the force of the northeast monsoon after it has passed across the waters of the South China Sea. The total rainfall is considerably less than that in the accentuated sumnmer maximum type (Type II). Distribution. This type occurs in two places where east-facing coasts with hilly backgrounds are exposed to the force o-f the northeast monsoon. a. Malaya and Thailand east coast, unsheltered by Indo-China extending south from the Kra Isthmus (10~ north latitude) to the lowlands around Singapore. With the onset of northeast monsoon in November and lasting through December the coast and a strip extending inland for about 30 miles receive heavy rains in the amount of 20 to 25 in. per month. From February through Sept-mber the monthly means are below eight inches. b. The VietNam east Coast extending from about Cape Padaran (10~ north latitude) nortLhw-ard to the Tonrkin Delta (19~ north latitude) where the coast comes under the shelter of Hai-Nan Island. The rainfall pattern is similar to that of eastern Malaya with heavy rain from Sept ember through December and dry months of 3 to 6 in. from February through August. Significance, This distribution while it covers considerable latitudeis confined to t',ie coastal lowla.nds; the hill country which lies behind these distributions* has the regular summer rain pattern. For the east-facing coasts, lowlands and hills together, the only common dry period is from January to March. 75

Type V. Double Maximum, Transitional Type This is characterized by a double maximum of precipitation in spring and autumn, April-May and September-October respectively. The summer maximum and Type II is replaced by somewhat drier months which receive from 5 to 10 in. of rainfall per month. The type is transitional both in character and distribution between the two accentuated maximum types (II and IV). Distribution. The two occurrences within the coastal strip are somewhat different in their characteristics. a. Malacca Straits Coast from about 8~ north latitude to and including the lowland at the Southern extremity of the Malay Peninsula around Singapore. This area is protected from the southwest monsoons by Sumatra and from the effects of the northeast winds by the hilly country of southern Malaya. The summer maximum of the accentuated type iI is replaced by a drier period leaving the spring and fall rainfall to form two maxima. The wettest months of these periods have less than 15 in. and the drier summer months have considerable rain, 10 in. or so. The November to March period shows the characteristic monsoonal dry months of one to four inches. In the vicinity of Singapore the protection of the hill country is lost but in this equatorial latitude the force of the monsoon is somewhat attenuated and the pattern of precipitation smooths out to a fairly constant monthly mean. b. The Saigon Area in the lowland extremi'ty at the south of the IndoChina land mass from about Isle de Phu Quoc (10~ north latitude) on the western side to Cape Padaran (11~ north latitude) on the eastern coast. This is an area of heavy summler rain with a drier but not very dry period in July and August. The resulting pattern shows double maxima with that in the autumn and early winter being the most pronounced. From December to April the months are quite dry. Significancec 'heo absence of accentuated maxima in either sul.ner or fall is probably of small significance because all of the sumnmer is wet. The best operating period is during the dry winter months from December through March. Storms Thunderstorms are much more common in the tropics than in the midlatitudes. In inland areas they occur mainly in the afternoon, along the coast this afternoon maximum is supplemented by morning occurrences from offshore conditions. Thunderstorms not only bring heavy local rains but are also of importance to air operations because of the up and dowen drafts in their convections. 76

Typhoons. Typhoons are circulations of winds around intense low pressure spots. Their high winds, 70 miles per hour or faster, cause destruction to installations and the waves they generate make landing operations impos-. sible and sweep sea water far inland over lowlands. Typhoons form over tropical oceans north of 100 latitude and move slowly, 10 to 15 miles per hour, toward the west. They curve to the north and northeast and lose their force on entering the midlatitudes. In the Bay of Bengal an average of 15 such storms per year are formed. These occur about one each month from May to July with two in August. Few occur from January through March. In April-May and November-December the storms pass onto the coast north of Rangoon. During other months and south of Rangoon, the typhoon menace is slight. About 20 typhoons are generated each year in the South China Sea and approximately half of these affect the east-facing coast of Indo-China. They are most common from July to October and negligible from January to April. Figure 13 shows the typhoon tracks in this area during the years 1911-1929. Source: E. Bruzon and P. Carton, Le C'lilat tie!Ilndochine et les Typhons de la >A>er die Chine, following p. 274 (IHanoi, 1930). Fig. 13. Typhoon Tracks in Indo-China and the South China Sea. From: IndoChina, Geographical Handbook Series, B.R. 510, Naval Intelligence Division, London.

Monthly Analysis of Weather Stations For 41 weather station records, selected values have been abstracted and set down on monthly tables (Table 12). For 14 of the stations "N" type summaries were available at the National Weather Records Center, Ashville, N. C. These are designated by letters, A through N and their distribution is shown on Map 14. Selected items fro these 14 stations are displayed graphically on Figs. 14 through 27. The data on the monthly charts present: 1. The average number of dry days and dry spells of various duration for the month. 2. The average number of wet days in three categories, the absolute maximum of rain during a single day in the record period, and average number of wet spells of varying durations. 5. The mean, mean maximum, and mean minimum rainfall for the month. 4. The mean maximum and extreme maximum temperatures for the month and the average number of cool, warm and hot days. 5. The average relative humidity and temperature at two times during the day. 6. The average number of days suitable for contact flying at two times during the day. The values used in the items are defined as: Location: Taken from maps. It should be noted that there are few upland stations for which detailed data are available. Period of Record. As stated on the source material. Dry Days and Rainy Days. Dry days are these without trace of precipitation. Rainy days are those with a trace or more. Dry Spells and Rainy Spells are derived from the number of occurrences during the record?,riod divided by the numrber of years of the record. It should be noted that these are a'ceraie occu;rrences (not days ) for the month over the re cord period.,ight, Heavy, and Very Heavy Rainy Days are the mean number for the month over the period of the record. 78

Cool, Warm, and Hot Days are daily averages for the months of the record period. Days Suitable for Contact Flight (at various hours) defined as: Ceiling must be equal to or greater than 1000 feet with visibility equal to or greater than 2-1/2 miles. 79

TABLE 12 SELECTED WEATHER ELEMENTS FOR WEATHER STATIONS (January-December) 0 COASTAL.%LK.1 TA. COASTAL; (A) COASTA0L Ai.'i. P COASTAL '0.qA s *:'IC.OR,, C'- STAL \LJ< STr.;''.. COiST/.g.::-C;5S.'Y (C);COASTAL:'?.'AA L'A4 'J R I.)i'.0'L I'LO-COCCA (C) COASTAL ':C-.:,-OR. C;-iAST.L CJAO.?,'A;AC COAS7/I. c/TA 3S'AST COASTA4L;.'.;O:'<0: (D) I:;0 x J ILOI-CO:.A (C) COAST.'L 60 ":1.SS?'.l:/: " P'2H (F) I. L-V -) 1', TIZ:; (0) COASr*C-?OU'LO 031 I SL,'L. POU'L CO:'DOORE I SLSD 50 MILSS C..'; T:iO IN)L\:;D CA? ST JACQL:ZS COASTAL 30 ''ILES S.,I'C': I';NL;.D 7:':.'; T'-I5T (H) CO-.STJ.L -' DA.-',.':; COASTAL 50 MIIES ~ '."::; - ('J) CIA;T-.D T"',' '!A C:ASTAL ','I:r'i:; C.%CI STAL COASTAL C'"A:;.: A: (K) COASTL T?. - '.- COASTAL COASTAL 50:OILZS 0C'Z."'O:; (L).::.T) -.';:1tOI (M) COAST.AL '; l' i COASTAL 20 IL.ES;.S::'DH i'HLA.D '!'.; LI:; COASTAL L-.W;$0n'; (';) COASTAL;,iPIO:' Ci COASTAL 50 >nIS -';O I I':LA,.D;,rOW.J, COASTAL MONCAY COAST.L V) W L1 a 1~ C!., 11 cn Ccn i).vr o v, r;;t co ~ro tz 0 z m rn L1 O.~1 F ", r: W r:~ d ri: LL' Y L:U id i-~ 3 r;: 9 )-~ c: O C 3:: le i: ~r.s: o:; r 7 o, c:11 u? LJ 1 ~ -C O rl MONOn.IEY AVORLCE > > -.0 301 0 I11 t5 ~-5 g.; r::' >;,. - - I r 0; i1:4.,r F.-, ~ H v; ~ r,._7?,:.'. c 27.2.?: ''.2. l; 0. 25.[?). 5 1._ 2~f..i ' 3.3 A.. 2. 5 25 -,i 3.0 9 D.i. 2 2.? l..' C,:. - I. 2 2 5 l, 5c,. 5. 5rR 3.2 - 1.20 3. c,.2. C,. 2..92 4j;' C _.yq 8G.' '. 1. 14 l.o,, / '._.5 0. 6.02 -7. _. i.," 5.3 0.,. I. 0.3 'j.36 0.35 0. 0 O 0.00 0. 33 -.00 o. 3) i, T rac, 0. 06 0O.0. 0' 022 94 9 32 '6 92 7 50 93 9 -3 78 91 0a.6 2v. i'; 0. -;;. 0.9 O.,9 "ox, < ('Lfv C.57;.G: o.S' 52 5 G~.S-', l.S,3 'J.i_ 2 C, D i' O. 2DC.40 1 2 5. i2 2. I~ r; 7r;i iZ 2.Gj i;., 5.744 '.2. 55.!.53,!. C9 2.C:;X i I 79.0 72.4 7i.!c 92.9 'rr. o 73.9 96.4 90.7 9i.3 91.7 90.7 86.6 36.7 9'.0 93.2 34.9 37.3 92.7 82.1 33. 5 90.4 92.5 95.5 92.5.7 39.3 93.1 ~.4 2.5 3.2 79.1 f3r; 67. 0 0.4 72.44 53.4 79.5 72.1 72.4 57.7 C1 02;64.3 81.'6 63.2 73.2 59.3 74-.2 66. 75. 1 71.7 74.9 72.0 69.3 51.3 72.3 60.6 71.2 52.0 72. 66.7 71.7 32.5 74.5 76.2 73.6 5.82 72.2 70.1 70;9 51.5 69.6 62.83 6.9.,' 64.4 70.7 72.6 70.3 72.4 67.9 60.5 67.3 74.3 67.4 73.9 65.2 1.7 59.4 65.5 6c.4 62.0 7i.7 61.5 72.9 63.2 67.4 60.2 72.5 62.5 70.7 57.2 59.6 61.6 67.8 59.6 69.0 62.0 71.4 61.0 63.4 g d.: c; 73. -: 33.0 - < 7.3. o - 79.9 - 2 87.1 - 24.4 4 23.7 35.7 83.2 76.3 78.9 36.7 30.4 35.9 32.9 77.7 73.1 77.0 77.7 78.1 76.6 74.7 73.2 76.4 72.8.9 69. 0 70.3 11.3 67.5 65.6 13.4 6.9 13.3 63.2 13.0 67.5 10.3 65.8 67.6 30.4 13.5 28.6 11.3 12.7 6.5 12.7 18.5 26.2 31.0;11, 0 -ta!: 0 0 tO 0 0.000::, I a ". w Q 1. L. 0.6 17.5 2.4 19.7 18.3 24.5 18.3 12.5 4.8 31.82 30.52 30.22 30.71 23.11 31.CA 29.71 28.31 27.8 29.2 30.6 27.9 28.8 26.3 30.4 I6.8 25.9 30.6 23.1 29.5 27.5 27.9 21.1 17.4 25.8 21.0 26.4 18.1 9.0 13.9 7.41 20.0 27. 3 1,.0, 22.61 13.9 16.51 23.7 31.03 30.33 30.3 30.3 30.9 30.7 30.5 29.6 31.0 31.0 29.3 30.8 31.0 30.2 23.2 30.2 30.4 27.4 26.4 26.2 29.5 26.9 22.9 24.6 18. 4 26.7 29.1 23.2 26.4 26.3 24.8 28.5 - *Letters indicate stations with complete records. 1 --- 700 HR 2 --- 900 HR 3 --- 1800 HR 4 --- 300 0n5 5 --- 1200 II 6 --- 1500 oo MOhT'i JA}A1I/Y '.r n.i 1 - 0 |:.2 I- A. A. o I" |l, 7 I. ~- 2 2.5 1-~ i.:S 1., -.95 L.3, 7.1,: -. _., 4 I. 2,. C...1 o.! 16.9 I l.5 ' 1 L. i i. Q.., 1.67 1.5 0 r 3 71. 7 L i 3,5 94 95 91 72 32 22.0 - 19.6 - 17.7 17.2 13.0 20.6 - 31.0 - 12.5 0.2 -.C', 1.2 0.9 -.,...l 1, G - 3.0 O. 2 3.0 0.27 I

rd 0 r. E-9 CM U _z: 0 L \ 2 0 C! o~cl IV~ 1pollia 0 0`1 1 1 4 0'J'1 A 04. 0 0 0 0. 4 j cl oI " 0 o l 0 -.4 -N o (. q o l C j - N o ' o e 0 0 4 4 4 3 H H 0 4444 C'4 0 4 C' rnmu4LnI1s SAya 0090 IV l021 I A 444 40 O H — I H.1 -4 H4 H1 1-4 -44 444 (4.0 c9 4-0 O] 4 ~ - 0 4 0 ' 4 o 0 co,O 4 - o0 0 0 'L.4. O\ C ' HO1 31ovll ~v n n o Ml I o r ( ( c. c t tr a\006301I 4 o O6 URAO "4 C' \ I N svC"C 10001;t\ j ) LI S s.0100 01 44-' 4 C 444 - 4 n (\I a 4 A ' O C o C 4 (C 4 4 t 4 (4 1 sonicoos C' ". 04'. 4:4 4. 1 1 0: " 'V4 4 ' - 4 4 4 -4 3 1 1'. 1 4 4 1 1 0L 0 S'JH OOET 1 '04 11:4 z 0090C) 0 61 a;~7I~Z ' ' 44"4 4444044 4'CL~? ~r il f Sint 3:0(f i C- - I:-I?L 4 4 I V C -\ C \00 4 C' 4. \'4J \4 H C ' ' H 211144121LA TP'! 04490 y N 1 44 -4' 1,j 4". 4'C 4.4-' 4444 0 4 SIM'4cC 0090 4 1 1 0 0 4 1 1 C 'V 1 3ALLV13 ld 0'\ 0r(17,.: C \6 1 01 O.6 0 1 ZC I'd In-4 144.14.1, 0.419 I 144044 0 0 0 4 4 1 '3 ' ~ I,; I'j _,rvJ:l.;v::V:-I3 1 nj., n G~OT\('-"[ C33 ~: i.: I I N,0041 '4\42' 066'1 (1 Os,.. 0; 0 0 14401 - '; ( ' 4 40412 '4 -' - ''' slykll CI 3? M2)1'44 XiG DIid l SAYC [-IA,8a T "-i ~ ~ ( ANG~ - ''. S'd, lk 0X( - <~1 d ti.\*;:: 4: J;c~ 01~ NIS in 0 C;2 5 s.I~v 3 i ~- ~f — Z ST~~3;S A 31

TABLE 12 (Continued) I a I F6 ~ o r F B 3 'A r4 ') t..? cn Q tn IM >- 0 '4 z: a 'A ). c 4I 4 - If C Z '' ~4H~A4 W. -0 -4c -293 i-1)7 0.-b,~ L... it. t v. - "P -j -1 XO2CSCLY AVERAGE ~-9 9 9 -~ '4 <4O ~; i o 4 C9g o 8 It ", 1 v, a% u 21- = 0 E H -t!H - -417 t;~:a 8 a MONTH Ma rch L - I ' --- —--- ArYAB RANGOON TAVOC V ICTCRIA.LOR STAR P:-:NASC (A)* WELLESLZY (S) KUALA LULU'R.AL\aCCA (C) S IN;APORE KIALA PAHANG KOTA BIAR'J EA:2C KOK (D) ILCT-CONE (E) PtNOM F EN (F') H A TIE:; (2)?OLL P O OBI I POULO CONDORE C4!: nTo CA? ST JACQLES SA IOON F1i.1 THIET (H) PADARAN DALAT (t).'tA TRAlNC (J) TLY HOA QUI RiGS BOGC SON QUANC NCAI (X) TOURAAE HUE TCtEPONE (L) DOG HOI (M) TlAgl HAO NANMD INH PHU LIEN NORWAY IS. LS.CSON (N) il AIPH{ONG HASOI COWTOA 10NCAY I I I I I I I I I II I c I.c 5 I c c c c c c c 5 1 c c c 2 1 c I Cl Cl 51 1 c C( COASTAL 30 MILES L NLA'. COASTAL COASTAL COASTAL COASTAL COASTAL 25 MILES COASTAL COAST:'.L COASTidL COASTAL 20 m.I^ES I NLA D COASTAL 60.IfLES I:.A:,D COASTA.L I SLAN'D S SIA';D I SLAN D I NLAS D COAST.L COASTAL 50 RILES r 1'.0ND COASTAL COASTAL COASTAL COASTAL COASTAL COASTAL C(AST.AL 50 HI. LES INLAOJD COASTAL COASTAL COASTAL 20 XILZS COASTAL ISLA:D COASTAL:OASTAL O.I LES I NL.LND COAS:AL:OASTAL L-. 5 '5. 2c. 6 5. '' It I. -,3.. L.0 ';,.5 1!,. L)j.4 3.: _;1.)+?+ 10 1..5 27 24 7J 3-1 1. 4l,' 16. 2. 1.,i 0. 2 1 - C~.2 2. C.I 3~ ' r7. 22. 3 Ir 5. 7.,.. o. 2.23 7.3 1.2 0. 6:. 5 7.1 3. o 0.3 3..30 -:.C - 1.57 3.7.3 50.3. 2. 3. 9. 2.. 0. - 1. 9. 0.. 5,0 3.2 0 7. 1.5 9.0 1.4 4.7 10.3 i i.:, 3.7 O.0 13.7 i.0 6.1 0.6 21.7 0, 13.1 1.3 0. 31 0.2 3.35 - 1.70 0.3.96 4I.93 9.23 2.21 1.32 27.0 2.t! 5.13 9.31 2.51 _. 5 3.11 Trace.51 4.53 0.00 2.26 7.13 0.C.;,,9 3.5. 5. 0.17 i~. 1i.- 5.C7 O.C0 Trace O.C1 0. r, 1.35 P.35 o.00 1.,6.3 0.02 3.76 12. 2 o. CO 2.01 5.21 S.C1 2..37 9.C7 0.0? 1. 3.5. 0 C, 2.',0.2;1 0.22 1. 3 3.42 '. 25.9 4.2 G-0.33 l.;3 ~.3j o.'5 1.56 2.92 O.14 2. 6 5. 3' 0.31 93 79 32 999 97 102 90 98 91 96 92 57 3 101 92 5 6 39 35 2 94 7 92 9: 9_ I 91 9 3) 99 103 92 33 94 101 36 73. 2 76.q0' 9.6 1. 69.4 80.7o 54.2 C9.3" 76.4 '32.4; 70.2 83.6 '5.6 73.3, 55.1 90. 4 77.3 83.1,:: t5.5 83.9 76.2. '7' 64. 3.9 6.6 72.1 57.3 8'9. 93.1 75.3 71.0 P85.2 94 3 76.3 70.5 85.9 97.0 7!4.3 66.4 86.1 92.2 76.3 53.9 93.1 39.7 i6.l 63.4 87.4 90.6 75.9 50.6 91.2 92.1 76.5 73.3 85.7 91.3 7,4. 75.0 2.0 6.7 75.5 (6.o 35.5 90.2 76.5 55.7 93.0 85.6 76.7 72.1 83.3 90.0 76.0 51.3 9.5 r6.6 74.0 66.9 8;3.5 1. 76.1 70.9 83.0 39.I 5-7.6i l9.6 75.5 91, 7L2.3 69.5 85.4 93.1 73.4 66.9 33.3 89.9 74.1 72.0 82. 91.8 71.6 57.4; 85.6 95.5 71.83 70.3 83.2 91.9 72. 7-.3.8 0.0 94. 7o.7 '779.2 79.3 92.7 6'.; - 84.9 37.5 69.1 77.6 76.1 95. G67.8 0 o.9 74.2 94!5 66.6 79.4 72.5 S5.3 65.7 76.2 71.7 93.7 65.4 83.1 70.5 37.2647.2.767.1 74.6 1. 6 73 4 79.5 67.1 73.1 71.9 95.1 65.7 75.7 72.8 53.4 61.9 79.0 66.7 85.7 62.5 69.5 69.6 - l3.3 12.7 - 1.4 29. - 12.9 18.1 -.0 24.0 - 2.7 28.3 - 2.9 28.1 - 4.4 26.6 - 13.6 17.4 - 203.4 10.6 - 26.5 4.5 3.9 24.8 2.3 10.1 20.3.6 16.2 14.9 13.1 16.6 1.2 6.8 2.8.3 8.0 22.0 1.0 20.7 10.3 - 30. 2 30. 3 20.32 30.53 30. 30.23 30.0 30.7 25.I1 31.0 33.7' 29.3 30 3 31.0 28.3 31.0 27.9 28.3 24.9 30.7 27.1 30.8 30.1 30.7 23.8 29.3 19.3 31.0 30.8 31.0 19.9 30.6 28.6 31.0 30.3 31.0 21.1 26.9 30., 31.0 28.9 30.2 30.1 30.6 25.3 30.8 19.2 30.7 25. 3o0. I 25. L 23.4 24.1 29.9 16.5 25.4 9.6 23.2 1t.7 24.0 8.21 17.8 16.1 23.6 22.7 24.8 13.4 25.8 20.91 25.0 9.1 27.5 24.31 25.4 20.7 27.0 *Lettcrs indicate stations with complete records. 1 --- 700o ' 2 --- 900 1R 3 --- 1800 }R 4 --- 300 IiR 5 --- 1200 Hl 6 --- 1500 HR L; LC * 0 1I 0.1 2.03 C.3 3.62 - 1.23 1.72 - 1.24 0.1.2 o 7'7 1'J3 'i'5 102 4 102 72 51 74 93 74 93 71 95 13 15'. 3.0 -1..7.7 - 7.1 o.6 i5.1 3.6 1.3 3. 5 1.5

TABLE 12 (Continued) i I RA.N; OON TAVOY VICTORIA ALOR STAR PG';,;C (A)';LL~OSLEY (B) K1C-ALA L,'STUR MALACCA (C) S I':;lAPOR. KUALA PA'ANG KOTA BILARU BAK';OK (D) ILOT-CONZ (E) P"LNOM PENH (F):lA TIEN (C) pO'ULO OBI POULO CONDORE CAN T1HO CAP S;T JACQUES SAIGON PNHA2 THIET (H) PADARAN DALAT (I) NIA TRANG (1) TUY i{OA QU I?NION BOSG SON QUA'NC CAI (K) TroU'A.'rE HUE TC1ZPONE (L) Do0N 1101 (M) VINi T!AWH HAO NAMDINH r.(U LIE. NORWAY IS. LANCSON (i) HAIFSONC HANOI.ONCAY _5 CGASTAL 3C.ILES COASTAL COASTAL COASTAL COASTAL COASTAL 2)5 ILES COASTAL COASTAL COASTAL COASTAL COASTAL 60 MILES I.L'ND COAST.AL I S L,'.D ISLAND 50.MILES:LA';cO COASTAL COASTAL COASTAL 50 MIaLES.INLA.:D CO'STAL COASTAL COASTAL COASTAL COASTAL COASTAL COASTAL 50 MOLES COASTAL COASTAL CCASAkL I Ia';D COASTAL I SLA'D COASTAL COASTAL 50.,ILES I LA.'D COASTAL COASTAL In w I: n - VI s-;? 14 " >.. 1.4-4: vn b- >0: ". N"! Q cn - 'A, N O;~-;-S O - ~58 _ o Ne.-.. N N -.A N<0 Na. NA NAN3 N A 05( N( AN (-.. N9. a!.- C MONTHLY AVERAPV b 0o!s P o" r m AD O 3 2 i- O - 0 I 5 o > - 1 -A50 - CNA (O N.-.o% - 0 e - rs r. O rx s/ "* W 0 t4 W. >4 v CW -C as >- P o) a of-t O C oOv s8 u 3L 0 8.4! v C V)0 d '. u = L) I.. I. I IO L.', 5.6 O.5 L0 3.4 I. L 1.5 MONTH April LO L7.5 4.0 G.I 5 2 10 LO 203. 2.3 0.4 25.7 0.5 4.5 20.8 2.5 2.2 21.7 3.0 1.6.5~ 3. 5 9.2 4 4. 3 3. 5 32 4. 0 5.5 2. P, 2.5 2. C 4.), LI. 3, j.;; 1.1?,. C5.; i. 3D;.. r; 5.C, 1.0 4. O00 7.2 1. 0.6 3.1 i. 1.7 1.3 3.11 4.2 L.1 0.2 2.13 3.7 5.6 - 1.)3 7.0 -0.6 0. 3.5 1.. 3 2.3 3. 0.5. 3.2Y L2.5.2 0.4 3.f 5.7 0.3 0.1 2.26 6. 1.0 - 1.19 3.2 1.C 0.2 3.4 I; LO 10 10!0 i10 ' C 25-7 0.) 0.9 2.5 1.2 C,. 2f. 5 L. 2 C. 25.6 0.,3 L. 12. 3.. 2 9 1. 1.7 23.o o. 6 t.,, '2.. 25.5 25.5 '0.:-. '.0.7.6 2.3 17.5 2. 2.6 -.5 3.5 2.0 2.4 2.05 12.5 2.. 2.0 11.12 13.935 6..' '. 65 13.1 3.20 3.,-' 6., Trace 5.46 11.36.35 4.39 14.14 0.93 6.61 13.41 2.60 2.01 6.28 O.C00 1.12 6.22 O.CO 2.20 5.5L 0.06;.1L 5.59 G.(; i.09; 3.61. (. 11 6.49 l'.l7 2.92 0.?2 3.6j O.CO J.0., 3. ) 0.1.6 3. C.?5 O. 1G 6.95 0.00 2.03 7. 5 O0.J2 2.,5 4.,L 0.!;. 2.51- 5.2 0.9, 3.57,.. 9 2.23 5.3' 0.62 3.65 7.55 1.2 4-50 lt..6 CO.79 '27 93 9 91 95 93 100 Ci 94 ' 95 31; 90 94 96.4 113.7 93 105 go 8" 90 5 104,7 95 97 102 3 2 107 ~32 i07 199 *4 F35, 79 99!81 101 79 93 73.4 23.3,4 7 0.933. 71.3.1 66.8 87.9 72.7 83. 1 79. 2. 96.1 75.5 63 3 89.3 79.1,3.2 69.4 1.1 77.3,4. 24 6t,.6 88. 1 96.7 75.2 62.6 83.5 94.0 76.0 75.5 4l.6 92.6 77.7 72.2 85.3 95.5 76.1 6!.6 8.1.3.5 0.0 56.8 93.6 88.6 78.5 67.6 83.5 92.0 73.1 54.3 91.7 90.8 79.2 72.4 '37.0 90.6 77.3 74.2 84.7 83.7 79.1 66.4.7.1 /3.9 7(3.0 58.3 90.3 85.4 79.0 70.7 85.7 3.5 79.0 53.7 90.7 84. 77'i.7 66.7 86.9 33.3 78.3 71.6 38.2 2. 62.1 57.9 75.2 90.2 76.0 70.4 66 91.5 76.4 67.0 n5.7.0 77.1 71.5 85.2 90.2 74. 54.1 8.1 94 74.86,.o 86.3 89.5 75-2 72.9 82.9 92.7 7'. 3 77.7 82.6 93.3 72.5 - 86.7 86.2 72.9 70.6 79.7 9l.8, 72.2 75.8 80.2 93.0 71.5 74:.2 71.6 79.9 71.5 6.6 78.4 82.2 71.7 75.6 76.4 91.3 70.3 70.2 73.7 3.6 69.4 69.0 73.3 2o.0 5.59 74.0 76.6 - 15.6 14.4 2.2 25.8 - 18.7 11.3 - 6.0 24.0 - 3.7 26. 3 - 3.8 26.2 - 6.4 23.6 - 14.9 15.1 - 22.4 7.6 - 12.1 18.0 0.5 25.2 4.3 30.2 30.03 28.42 23.63 29.32 26.73 28.71 30.0 21.41 30.0 30.01 27.0 29.0 29.7 29.71 30.0 28.2 23.8 24.5 28.4 27.5 29.8 29.1 29.2 29.5 29.2 22.2 29.2 28.9 29.3 21.0 28.7 23.7 28.6 29.1 29.3 17.7 25.7 29.3 29.7 28.2 29.6 29.7 29.9 27. 4 29.0 241.3 29.3 28.1 29.6 26.1 29. 3 22.1 30.0 19.9 26.9 14.7 27. 17.0 26.7 8.51 18.6 22.1 25.8 17.91 2.0 21.7 26.3 20.91 25.4 13.1 27.5 19.31 23.3 21.2 27.6 'Letters indicate stations vith complete records. L.. — 700 TM 2 --- 900 RU 3 --- 1800!H 4 -- 300 It 5 --- 1200 Itp 6 --- 1500 HE ~ 4.5 11.3 12.5 15.5 2.0 3.2 4.0 L.O '5;3 0.5 0.2 1.2 0. o.8 lO LO 20.5 13.1 13." 2.2 1.5 1'0. 0. LL. i 1.2 -3.I i.5!3. 1.5 1.5 1.S lO.7 2.5 0. 3 2. 0.2 2.15 0.1 2.12 0. 3 2.?,' 0.3 2.? 2.9 22.7 9.1 21.0 8.6 12.8 2.2 27.2 2.3 23.1 2.1 25.7 84. 8.6.6 4.6 2.1 LO 16.93 to 16.2 3.7 4. 1.2 L.;

TABLE 12 (Continued) I..m-YAB RAIN.OON "AVOY VICTORIA ALOR STAR. P:;ANVG (A)* WELLESLZY (B) KUALA LLUMPUR MALACCA (C) SINCAPONE KUALA PARANG KOTrA BARAU BANGKOK (D) ILOT-CONE (E) P'LNOM1 PE. (F) "A TIEN (G) CD POULL OBI POULO CONDORE CAN THO CAP ST JACQUES SAICON PIAS; THIET (H) PADARAN DALAT (I) SIA TREANG (J) TUY HOA QU I 5HoN BONG SON Q'ANG NGAI (K) TOIRANE H UE TCZP(ON.E (L) DONG HOI (H) VINH NAMD IN. PIU LIEN NO'RAY IS. LA.N SON tN) HAIPH ONG HAN1OI CO.WTO. MONGCAY 3 F: COASTAL 30 MILES I NLAND COASTAL COAS'.AL COAS:AL COAS.'AL COAS':.AL 25 MJLES IL.N'L,'D COASTAL COAST'.L COAST;L COASTAL 20.ILES COASTAL 60 'ILS I 'SLAND COAST.-1 ISLAND 50.fILES ISL..;D COASTAL 30 LES INDLAi COASTAL COASTAL 53 MILES I:ILAN:D C 'vS AL COASTAL COASTAL COASTAL COASTAL COASTAL COASTAL 50 aILlS I:..%'ND COASTAL COASTAL COASTAL COASTAL COASTAL COASTAL 20 MILES IELAID COASTAL OASTAL i~" W '" 0W 9z t o L 'A I E 1.1.,. >0cn < =~ 0 a 1 a v~ i~ '. -3 a A 3 - cnv, <B": 0."5~ 1 -— 4 - g E W, 0 ' Pi Su.4 Io 5 0 LO L. 0 I I. 5.0 5.7 7.6.2.3 5.?.L.J 1.3. ' 2. 4.2 I.3 2.3 2.5 2. 3 13.3 3. 2,1. 33 2, -3 2 10.5.3 1.5 21.3 1 1.2 '5. 7 5.; 15.6.' 1.6 4. 2.0 I:. 7 5.7 I'. 2 1-.7 5.: 2.5 I 5.9.-j 1.1 2. *. 1.3 5.0 1;.9 2. i. 9.1. 0.2 2.. i' 12.5 R. _., 20.! L. 15.3 5.;; o.? 9.6 1.9. 1. 3.?3.1 5. 1.4 5.20 ".4 -.5 0..95 l,.3 3. 0.6 3.: - 1.1. 4.3 3.94 12.2 3.0 0.2 2.91. 5.3 1.1:.,0 12.4.; 5 3 0...2.5 -.9 '. 3 3.07,12.- 4 C-6 4.10 6.5 3.3 C-2 2.32 3.2 1 0 2. 6.1 5.1.1. 3.6 1C 1.5 6.1 3.9 1.59 3-9 0.9 0.2 2.80. 6. 1L 3..: L.142 28.29 4.65 t.44 11.39 1.99 6.:12 9.23,.30 23. 3 32.40 1,.91 5.31 3.43 l.. io.3 15,.85 -.55 7.04 11.35 2.72 7.64 15.01 2._0 5.25 22.07.325, 6.67 2.29 2.-1 4.S3 0.67 7.50 12.53 3. 4.31 3.45 0.CO..69 6.2o 0.11 1.72 7.25 0.00 6.81 15.15 2.11 3.48 12.86 0.71 3.75 6.70 0.81 7.21 11.01 3.22 7.00 16.83 1.05 7.07 12.4 2.49..77 15.5; 2.51 1.70 20.63 2.32 36 96 91 99.119 35 93 90 9I 92 199 90 1:0 32 98 39 91 90 13 92 1.O2 92 102 79 87 91 10 90 1 03 9-3 10 ONTSHLY AVERAGE S X f 79.2 o2. 77.6 8215 7. o1l 72 6F 13O 3.6 78.4 1 7.282.85 G.6 8.7 7.5 4 3.I I9.3 75.0 75.0 75.2 93.4 78.2 7.5 82.15 91.6 78.4 7.2 85. 91.2 79.2 62.3 2.0 93. 78.7 62.0 89,8 90.279-2 73.3~6.0 0.6 8.5 7.2 8.4 3.7 5.9 79.2 75 6 85.2 93.2 78.2 72.5 86.5 87.0 79.1 76.3 85.1 3.1 78.7 66.2 89.2 36.8 78.1 56.9 8 9. 2.7 78.1 65.190.7.3 79.2 70.0 87.31 3. 78.4 71.5 8.8.0 2.9 74.4 - 86.4 2. 4 '77.5 71.0 84.0 2.1 8077.2 74.2 865.0 0.9 671.5. 6.2 74.7?1.3 72.4 793.0 93.8 39.277.9.90.1 0.4 6.855 75.7 59. 89.8 2.45 79.4 75.41 9.7 ~3.3 7'. 7 064.80 8.1 88.8 78.4 71.5 Sv3.o 776 0. 7. 6.3,. 6 37.677.7 78.1 83.6 0,7 22.4 7.9 - 10.3 20.7 - 23.7 7.3 - r,'. R 13.8 - 8.1 22.9 9.4 2L6 - 9.4 21.6 - 20.2 10.8 -27.0 4.0 - 14.5 16.5 - 8.6 22.3 - 13.1 17.8 - 29.1 1.9 - i.8 17.2.7 18.8 11.4 - 11.0 20.1 - 27.2 3.9 27.02 28.93 27.92 23.43 28.02 2063 30.31 31.0 22.71 30.3 31.0 28.3 30.3 31.0 31.l 31.0 25. 27.6 27.3 29.5 28.7 30.4 28.3 27.3 27.7 26.3 21.9 27.7 30.4 30.5 25.7 29.3 26.5 30.0 30.6 30.1 24.9 27.9 31.0 31.0 30.8 30.8 31.0 30.6 30.3 30.8 30.7 30.5 30. 4 30.4 30.8 30.7 22.0 28.3 28.5 30.2 22.3 28.4 24.7 30.5 21. ' 23.6 26.7 29.7 28.41 27.4 26.5 29.1 25.11 29.3 23.5 30.1 20.71 29.2 27.5 31.0 0 'n ' c n o:- od Ng c Q c.: 0 n a -8 3 I __ I "O 8i Ca 0 - 60F u 0 w L. 0 t. t. Letters. nicnc-te ststions with complete records. 1 --- 700 IUR 2 --- 900 HE 3 --- 1800 Hi.: 4 --- 300 5 --- 1200 HR 6 --- 1500 HR MONTH May I.0.0.0 5.4 3.3 7.8 1.6 9.4 1.8 8.6 3.1 15.5 3.5 o1..7 3.5 12.3 3.3 1.3.1 4.7 0.6 3.92 0.3 5.61 0.5 2.93 0.3 6.82 1. 5.89 1.1 4.87 1..1 4.46 1.3 _.~ 65 91 91 81 8,, 89 87 108 106 107 99 90 104 97 c09 100. 1:3.3.0 14..9 4.2

'r 4, 0 0 Cr OJ r-1 E-4 25 &) C, CC 25 2 13I64 0 r 1 00490 V nI II A 0 6 0 ' ij Ni I - H n H. N J C SAVOKHY! SAW '0 0090 IV r l fld u cu Cvr L - I? N L'\ CI-...N.-. i. - H. CC)% -, N. H - o H - N - o o ( j,o — * 0 - O: ), c co d \ J C\.-.... C\ C"... A: oO o,.,0 H N06 NaH.: - --, SIV 0090GH-Ifl 9ASi 0 IV^ C; H cr- ~ JI- C, tO- Z:c L t — tc M C, g<C —I-H L C'U.Y a3 20a -o ri N N N. N H H o _- r > ' N ' N~ "i -t - N I N N O N I N H- N C,i F; C-, (' C - o c o N N\ H c N < ' TT- \6 - IV\0 _f* d cj en o 'o \0 "o Ci3 Z3 () d ' H- H N N -- - I H NH H S O C ' - ', i. i. 0 A0 Y '00911 5 3 0 \ I H " J] H N * I.V 0o1 3\ \.1. SAVA I.- I:: H H- H o- (1. ' ).i st W006311. t. 102 0 — (- t -o. o,o ~m., - C6\,0, Ce -- N\N'- H No, ---- Ni-,,1 - I33 S014 ' - r -4 o o, o 1 o - o,.o, r- o 0.Sm.0090. ' % %,oU" " '_-' - -4__ _e C......ll-, JI, S 3 3- d S -O N H - i I "j, ( '.. i 0 i| I |J N I5 j I " 0 i 350 5 -5 I gi0 13 cii, o o q co -.,~ o-,, _ - tr,,.o 51aa 16o m ) OT V t wO i J-t J - c '0, d W; j oj C,r; (A oi, A' C7 03 ccr.~ u W. ~u c " -4 I\ b;', rILaa5 - a ~;t BFr ' ' ' o,,c '' c r: E Ac~J.: 85

c od S.. 0 Ei~ 0 01 u -4 IN In - I Id U) Irs 4-, 14 -0 0 ('-, N 0 0 % 1 I V 1. 6 3 1 1 A 'C' 0 C o c H - - 0 0 1 0 0 0 1 -4 — o~ o0 o -..0 O.V. 40 1 0 CD 0 0 - 0 0 1'> 0 Cl 0 7 0 \ > C\ 0 - -: 0 " O - 0 0 O O ' 1 1, T, TIMMIOS S~kIN 0090 IV 1.140111 0'? '. \ 0- c0 0`)-0 0 0`J 1I -0C 0. 010> C —. -0 0. 1' 00 10' 0 0 1- 0. -\ JY 1 03 K 43 o o o -o o Hu orc '1~- o~ q co cO -o c ~i ~~.1 0 0 0 0 0 1 0 0 1 0101>O 'O o o1~ ~ oco o-C Ti' LIoSSA OJ 0 4 0 S k\0 C)-40 0 O l 1 0..0 0.0'.- 1 0 C 0 0 1 0 C 2 - 4 O O 11C\ 0 1 0 1 0101 0-410.0 0. A 0061414 A 0) 6 2 0 -. 0 0 -CJ 00 1 0 1.0 1 1 0 Hc~ ~ ~ J C ~ ~U 011444 U A.014 - C 10 Hr 1 0 0~-I o o 0 o 0 6 011JC ' H' '1-.4 0, cN t 00 0 '1 J0001 '1003 S O H O O C IC.. I.0O 00 0 0 O 0 O H H H H\0 0 o. -. C C - 1 0141410090c~~; I N 0'~ H0 J \ 0 - 0 0 - 0 1'n '. ' 0 H H0-~: I-r ~ O H - >. > 0 H o oo( SUH aocU Ir i CT\ - ji `3 t C-' C-\ 0i C- N L;" C C-\ (\J 1 C-,' 1,j n; -~ 'c~ - - -C -3, CD c) '-c, c ci a- cC' C3 C-, C: C.-: c"I Y\ C-\ c~C\C ( ClCaU Cacr C: -3- r~c7 OUT 01fV.V 1 - c0G\ c I- '0- -0 --- L I 1-C: 1-0-1-' 010- 07 C 0-0C1-. " 1 4 A 1. '1 1 4 0 0 0 0. 0 - 0 1 - 1.-.ID " )o - ~ l - c ~ t - U 0 0 0 1 0 7 0 0L I - - ' 1 0 - 1 L I\ 07 \ _ \ 0 0- 0 1 t- 0. 0 0 o, 0. 0 - 3AUMN.-1 OJ ccvr~~c CO;cC o.ox o o N 0 0 1\1 H 1 0 0 1 - _ t4 H O 0 0)r- N ~ 4 0 0 > ~ 4 0~ ~I~QT~ n0- Ill.0 0 0.0 t-Ci 010. D.0.0'C. 1 1 7 1 > H O?\ W I\I 3 r1 1 0 1 1 1 4H. 1 - - ~Su I 0090 IV Cf-C~~~~ -i-l-\ 1 7r fI C — r- Io C — C,- Cj CD C~ r-i --- I` ET-ICWI-CC~L C.Y) co ~cc- C-)0.- cocr r ~ cc O CO C 00900\, IV IVNMI lI 001 0"'I l\0nil C) IS 0101 r 1- 0 ' CIS 001111, 10103C11 N r - 0\1' C ]4 k L \ 0" cH 01 1 ', c0 0 01 o S I N S H 'H 1.0014.0140 01 0CsIH 0- -" 0 1 "H-I' C,1 '.\. 0ILN 1 11N 0-O CV N - r I oJN'U 011C \ _:0 _\ C,\ r! (r:01. 0 I.' 1 1 7. 0 1.1 1 0 0 1'J -4 C-)? 11;3 C VT\ ' D \o C\l 01140 0''>.,A.-66 'I r1 011 AN 11140 V0 11 S11300 A M 11,111 S~k I I S I IH H.44 4 4 4 A0'-'yyo ""5,4 AN V cJ o; ("J "J N. SIMIA C C C) ( 14 OJ 0~~l Uoa 41 to'C '".l0 "c C~ ~? ~ 4~-~ e c 1 AMm IUnCHSu=r;r:C SAYG 4 0 2O <. < 86

TABLE 12 (Continued) rn, ~ VI I I- C. & N ". 'n.(A v A I 0: S =?-5.-. r.:. c. 18 i- -. 4: F i3 O us _; s-b.s 1-0o dC ~C 03A 3535p -.46 o 9.n" ~i 1 I-, MONtIS.Y AVENACG 94 0,, 96' z.4.40 9. 50, H3WP 0 m r! 5 ~'- =.4 3 5" 8 t - 8 8 cnE5& V)0 (j u!;li MONTH Aigust _ I I- - - AKYA8 RANGOON TAVOY VICTORIA ALOR STkR PE.SANG (A)* WELLESLEY (B) KIJALA LOPUR MALACCA (C) SI;,APOR". KUALA PAHANC KOTA B1LAU BANGKOK (D) ILOT-CONE (t) {.NOM PmNH (F) CD HA TLEN; (C) POULO OBI POULO CONDORS CAN nHO CAP ST JACQIES SAtIGON PtAJ THIZT (H) PADAAAN DAIAT (I) I.NhA TIRNC (J) TrY HOA QuI smoN BONC SON QUANG NCAI (K) TOUAE HL'E TCltZPCiN' (L) DONG 1OI (M) V INDI T' lsl O PIL' LIZN NORWAY IS. LA.NGSO3 (N.) RAIPIHONG HANSOI COWTOW MONCAY CCASTAL 30 MILES t NLA"D COASTAL COASTAL COASTAL COASTAL COASTAL 25 HILS I LAND COASTAL COASTAL COASTAL COASTAL 20 S>IlS INLAND COASTAL 60 MILES INLAND COASTAL 50 MILES ILXAN D INLAND CO STAL COASTAL 50 MILES I.COASAD COASTAL COASTAL COASTAL COASTAL COASTAL COASTAL SO KIS S I %1J'.'D COASTAL COASTAL COASTAL 20 MILES COASTAL IS LAN1D COASTAL COASTAL 50 HILES INLAND COASTAL COASTAL Co0sMILE II I I I 10 13.1 10 1E. 4 5.2; 1.1 5.3 1.o 5.5 0.9 r r -- I --- I - -- I J _ I -- 12.9 12. 1'). 3 5.) 1.2!5 L. 3.0 16.7 7.0 4.3 1.6 6.6c 7.5 2. 2.3 6.37 6.9 5.5, 1.5.:,.6 2.6 v.6 3.- L6.6.7 3.0 0.6 3.1 J.1 5.3 1.0 5.07 9 2 10 IO 8,,, 4.5j 1.2 13. 5.C) 1.0 10.7 '4.4 i.6:4.6,.3 1.3 2,.9 5.2 1.; '-.' 3.5 2.5 20.3!4.2 1.16.4 3.6 1.2 10 io.9 1C. l's I' I 131 5 10 ') 10 10 10 6.3 20.3 23.0 16.1 13.6 21.9 5.1 1.2 5.1 1.1 4..2 2.0 L.6 1.9 3.4 0.3 1.3 2. 0.9!.7 2.1 1.7 20.1;.8 21.7 4.3 52. ') 3 _ 25.4 2.3 1..7. 3 12.4 2.0 9.1 3.2 =.3 1.7 1.1 1.2 0.1 C.3 01.! 1i4.8 5. C.3 1.6.1 5.;.2 13.0 5.6 1.1 4. 5.8. 1, '7,.2.7 o.1 19.5 5.8 0.1 13.1 I 1.0 0.6 1C. 3 1,4 0.2 5.4 3-2.5 2.34 2.61 6.35 2. 3 3.56 2.60 10.75 1i.56 2.65 11.38 2r7.53 1.74 12.03 1!.15 5',F 6.'6 10.22 2,5 2'; 21 49., 12. '9i 6.7 11.75 2.59 10.35 19.95 2 '9 7. 14 11.54 5.,0-7 6.9) >.17 3.P5 7.51 10.U3 5.Co L.4C 3.35 (.1i5 P.Z-, 12.59' 3.33 2.,, 4.23 1.I 2.70 8.01O.c 5.'3 i1.5 0.'17. '9 24.4.7:J.2.29 1.39I 1.71 5.26, lC.01 0.72 17.!.- 16.6 3,4!; l4.5-6 3.67 6.3' I.9o0 22.91 6.'2 17.41 35.61 5.20 22.70 47. 0.0- - 4 6 35 93 86 87 89 931 92,93 90 95 95,) 31; 91.0 95'.3 9 97 7690 86 go 74 85 92 101 51 106 95 1C4 92 107 2 107 "7 97 95 90 10C 90 99 )1.2 79.55' 90.3 80.65 41.2 57.6 79.54 87.1 79.45.7 79.04 88.2 79.6 6,o 75.32 69.5 86.26 82.9 81.82 75.4 P5.5 76.1 83.0 -66.8 87.6 1;;6 73.3 o 60.6 f..12.4; 750 83.5 ':9 7q, '73 728 84.6 4,95 75.0 65.9 P7.1 2.,1 77.9 65.2 P8., 0.59 77.9 30.9 82.9 51.5 77.6 67.5 83.1 39.5 73.9 '3.4 4.0 51.7 76.2 86.8 79.9 6.7 78.3 77.6 82.4 3,- 77.6 73.1 85.8 '.3 77.1 31.4 82.5 )4.0 7.6 74.6 85.4 '9.7 77.1 68.5 86.6 72.9 73.3 77.6 82.1 3.3 63.6 79.4 71.1 7.4 77.7 69.2 88. O.6 79.6 59.5 90.4!7.7 81.5 53.9 91.2.5 79.7 51.8 91.9 1.3 78.2 62.3 92.1 5.2 79.1 63.4 78.2.479.0 6.0 91.1 )4.0 74.3 - 82.5 0.5!.0 65.2 90.0 31.2 73.9 63.9 87.8 3.1 78.9 73.1 86.4 '9.6 "2.7 7,.9 83.0 4.2 73.1 81.4 84.2 7.1 81.9 79.2 f5.1 '9.2 76.9 73.6 84.7?3.2 81.0 79.7 86.6 5.1 7.9 74.2 84.0 17.1 1.8 79.5 36.3 2.8 79.4; 80.6 8,6. I,- - I_ - 30.0 1.0 - 27.7 3.3 - 31.0 - - 23.0 8.0 - 17.8 13.2 - 6.2 214.8 - 1.1.2 19.9 - 26.1 4.9 28.6 2.41 -18.5 12.5 - 4.1 26.9 - 8.7 22.3 - 17.7 13.3 - 19.; 11.6 - 14.4 16.6 - 12.0 19.0 - 10.3 20.7 19.82 25.63 16.32 15.03 25.22 26.23 31.0 31.0 29.31 30.3 3 1.0 26.0 '30.7 30.71 30.7 19.2 24.0 30.6 30.6 27.9 2 9.2 28.1 27.3 26.6 28.7 27.6 28.9 28.2 28.6 24.3 28.2 23.4 28.5 30.2 30.4 23.8 26.3 30.6 30.7 30.7 30.4 30.7 30.7 29.4 30.4 30.3 30.5 30.5 30.7 30.2 30.7 14.1 29.0 29.4 30.2 27.1 28. 1 25.8 29.2 24.81 26.3 25.51 28.3 29.6 30.1 17.9 27.2 29.51 30. 3 25.9 28.7 27.61 28.2 28.9 30.4 *Letters indicate stations with complete records. 1 --- 700 R 2 --- 900oo 3 --- 1P00O 4 --- 300 m 5, - 1200 O' 6 --- 1500 m 1'C 10 10 10:14.6 2.' 1. 5,3.2 2.3 2.0 18.4 1.9 1.5 14.5 4.0 1.6 10.5 4.0 1.5 10.4 3.9 1.1 10 10 1".!; 16. 12.6 16.5 20.5 20.6 13.9 19.5 0.6 1.5 2.5 1. 5:. 0.5 1.2 1.2 3.9. 3.1 2.0 2.2 2.6 6.3 10.5 II.5 1i2.. 9.9 9.5 7. 2.3 5.22.3.5 6.'4 2., v.5 6.66 4.64 1.6 6.61 5.7 2.0 7.47 6.7 1.1 5.67 5.9 3.1 7.;C 6.5 3.5.11 10 12.1 10 11.5 4.2 0.9

TABLE 12 (Continued) ceLd CZ. t~ o k 4< w 11a C 8 g r 5 m —f1. EC mm -C 5 Q W 4 3 1- 0 A A (. k. 00. b H p r, 5 I - J I C. z " R u~ 0mM!.': AEVEAcE 1y CO, 0 1.0 2 1- o 10n 8! V' 8 aFi at = 8 8:1 N m Q t $ 8 IQ, MONTH September t _ I I I I 1. 1 — - AXYAB RANCGON TAVOY VICTORIA ALOR STAR PE.NANC (A)* WELLESLEY (B) KUALA LLUMiR MALACCA (C) S IN;CAPORZ KUALA PAHANG KOTA BKARU BANGKOK CD) ILOT-COZ (ZC) PINOH PENH (F) CD HA TIEN (G) CD POL'LO OBI PO'LO CONDORE CAN Tr10 CAP ST JACQUES SAIG ON PuA2N THIET (H) PADARAN DALAT (I).I.A TRANG (J) TUY HOA Qu'l.tON SONC SON QUANC NCAI (S) TOURANS HL' TCHEPONhE (L) DONG HOI (M) T'1AlW HAO SA.MD IN PHU LIEN NOIRAY I S. LANGSON (N) RAIt HONl HANOI GOWTOW HONCAY I CO STAL 30 MILeS INLAND COASTAL COASTAL COASTAL COASTAL COASTAL 25 MILES INLAND COASTAL COASTAL COASTAL COASTAL 20 MILES I NLAOD COASTAL 60 MILES I NLA'D COASTAL 7 SLA;D ISLAND 50 KILES COASTAL 30 MILES I N"N D COASTAL COASTAL 50 MILES I.SLA.'ND COASTAL COASTAL COASTAL COASTAL COASTAL Cahor Arl COASTAL COASTAL COASTAL INwaM) COASTAL COASTAL 20 MILES INLAND COASTAL IASTAND COASTAL 50 MILLS INLAD COA^TAL COTAL I I I I I I I I 1' LO 10 '2.1 2.9, 14. 3.6 15. 5.; 1i3.3 5.0,,.9 ' 5. Pl.j ) 3 1.3 D r 2.2 O. 4 i.1.0c 10 10 10 J 1C10,3 s O0 10 13 13 10 10 iO 10,., 4,... -':, 2. 2 4.2 3.3 2.3 3.3;.2. -.7 1.5 13.3 2.6 2.0 2.-? 1.7 1.i:2. 5 3.' 4.8 3. 6 1.5 12.1 3. 1_.3 8..3 2.6.. 16.5 17.9 3.0 1.7 1.. 4.3 143 5,*!. D.5.6 3...2. _.15.2 1.2 13- 5 - - 2'_-...;., 3. -2 _7.5 3.- -.; 11.7 3.9 0.7 13.5 -.2.1 3.' 1.. 7 5.7 2...r/,, 5. 5.3 '. 9 13. 9.2 4.4 0.7,.15 5.4,.2 5.7 5.9 5.3 5.5 5. 3.5 _Ic. - w.;,l_ - _,. -.C 4 - 240. * _,.2 3.72 0.0 0ci l_ _;, J 4 ^,', '5.05 5G.024 3.30 3.70 15.43 3.0 10.73 16.70 6. C 12.;3 27.51 0,.0' 3.!)1 _ 0 J.,j J 3 J 14.'72 49.263. 'L 12.?2 1 {.66 D. 5.72 1.3 76.67 3.L5 c.67 L.', c_.-n 12.55 3.,1 L1.47 19.46.71 L2.92 46.9; 2.36 5.90 15.00 0.87 9.84 17.04 2.10 L3.27 27.S7 4.29 33 93 91 1' 90 3 90 5C1.: 799 87 91 3 93 901 95. 4 35 9 10., _., 90 9 36 93 3 99 39 1(;2 ~7 53 9,6 93 88 99 83 102 ';.3, 0.64 5.4 3&1.75 0;.5 3o.534 4. 40.55 93.4 770.9 P33.0 77.35 56 3.6 'r4.96 G. 74. '!9 72.85 R4.9,4. 1.5 71.9 85.06 76.6.2.92 (63.5 6.8 95.3 74.0 602. 86.7 32.9 75.2 74.7 P3.3 90.0 7.0 1.7 34.7 35.1 75.1 66.L 86.6 34.3 77.4 67.93 7.9 93.1 76.7 80.8 82.9 '1. 7'.0 '1.9 86.9 9. 73.3 79.5 834.1 2 75.9 37.9 78.7 '12 773.9,7.2 7 7 79.9 81.8 9,-.3 77.7 7 6.0 84.4 91.1 6. 6 79.8 2.4 4. 77.2 75.0 84.5 1.1 7'5.9 70.6 85.7 ',.j 7O.0 73.6 33. l39 63.1 7.07 1.8 3 7.5 69.3 87.3 3.7 77,4 65.9 87.4 -.3 7673.3 67.2 37.4 0.2 6 62.C 87.3 34.2 76.571.. 37.* 2.2 76.6 71.3 5.9 2.1 75.9 74-. 87.0 -6.4 73.. - 83.4.7.67 T.8 74.1 86.5.4 77.1 72.2 85.0 53.8 77.0 76.' 85.0 3-.2 79.0 73.7 34.6 53. 76.7 79.4 84.4 77.3 79.9 64.5 83.6 9 3 72.3 70.3 P1.0:0.5 783. 78.3 84.9 '1.5 77.1 73.0 3,5. 0.9 78.7 78.0 3.4 8.9 73.4 69.o 4.9 - 28.1 1.9 - 27.2 2.8 - 30.0 - 26.8 3.3 - 22.1 7.9 - 9.2 20.8 - 12.8 17.2 2'7.6 2.4 - 27.8 2.2 - 23.0 7.0 - 12.3 17.7 - 17.7 12.2 - 20.0 10.0 - 19.4 10.6 - 22.8 7.2 - 8.0 11.9 - 26.6 3.3 22.42 26.33 17.92 20.73 26.72 27.23 29.3 29.7 25. 1 29.7 29.7 29.7 27.21 30.0 29.71 30.0 18.5 24.8 29.0 2f.9 27.8 27.9 27.7 27.1 25.3 26.1 27.0 28.8 27.0 28.5 19.3 29.3 19.7 28.3 28.6 -28.8 25.3 27.2 29.9 29.6 23.5 29.3 28.4 28.9 26.7 28.2 25.7 29.0 27.5 28.3 28.1 23.9 13.1 26.1 26.3 28.1 23.9 27.1 23.7 26.9 23.41 26.3 2.1 28.1 2.71 27.9 20.6, 26.8 27.5 27.8 21.31 29.0 92.7 27.9 28.329.9 *Letters ind( ate stations vIth complete ec-rds. 1 --- 70.: H, 2 --- 90C IL; 3 --- 1800 HI. 4 --- 30C. R 5 --- 1200 Im 6 --- 1500 HR I '10.5 9. -^ 3.9 8.2 6.0. - 2.6 '. 31 3.9 2.3 6.32 1.5 2.71 5.I 1.2 19.31 2.1 0.7 6.26 3.9 I.- 5.59 4.2 1.9 1. ' 0 ' 2,.;

TABLE 12 (Continued) 2 WI i. 'A in d <d I.. ml n0 t! cl n 4ca4 cn C~, >. " - ". E;:j,. 0100 > 0 0 = 8 P S-< i:~ g 3 u:, w, ~.4;- 1 et -3 i' — - - I -4OCIOY AVERACE vr o 0o - 0 0 t/0 = 10 " 14( CC l. B" tC I ~ Z s"~"~ OtobeH October i i RA.NGOON TAVOY VICTORIA ALOR STAJ: PENANG (A)* WELLESLEY (,) KUALA LLUPUR MALACCA (C) S INiAfORE IKALA PAHN.G KOTA BHARU BANG.rKO (D) ILOT-CONE (E) P-60NM PENH (F) CD3 HA TIEN (G) o POU OBI POULO CONDORE CAN THO CAP ST JACQUES SAIGON PHAN THITr (H) PADARAN DALAT (I) SHA TRANC (J) TIrY HOA QUI N:ON BONG SON QUANC NGAI (K) TOURANE HULE TCHt PONE (L) DONG HOI CH) THA9i HAO NAMDICNH PHU LIEN NCRyAY IS. LANCSON (N) RAIPHONG IANOI GO0Tow 4NGCAY COASTAL 30G HILES COASTAL COASTAL COASTAL COASTAL COASTAL 25 MILES INLAND COASTAL COASTAL COASTAL COASTAL 20 MILES INLAND COASTAL 60 MILES COASTAL ISLAND ISLA'ND 50 MILES I N'LAN D COASTAL 30 HILES ISLAND COASTAL COASTAL 50 MILES I NLA D COASTAL COASTAL COASTAL COASTAL COASTAL COASTAL COASTAL 50 MILES I NLAN-D COASTAL COASTAL COASTAL 20 HILES I SLAND COASTAL ISLAND COASTAL COASTAL 50 MILES INLA.'D COASTAL COASTAL f1 I 4. i I I - -__ _ 10 1C 9.4 2.7 2.5:-.0 3.5 1.7 15.0 4.3 1.6 2'1.6 04o (.9 22.0 4.4 C). 7 L6.0 5.1L 0.9 5 2 1o 10 10 10 9+ 5 1C '9+ 10 'C Lcv 14.5 2.4 25.3 1.0 L1.7.'*5 15.S 3.6 12.2 6.5 14.2 3.7 8.c, 2L.3 2.2 16.2 3.3 10.7 2.7 1.5 3.9 7.8 2.7 14.3 3.3 1.2 2.0 0.9 1.7 1.4 1.4 1.2 1.7 0.7 1.2 1.3 1.3 16.5 2. 5.7 3.5 -.3 4-.c 15.2 4.0 6.' 3.1 '0.3 2.3 20.5 4.2 23.2 2.2 6.7 3.2 0.K 0.0 1.5 O.9 1.4 1.4 0.6 1.C 1.-5..1 1.7 I-5 i1.9 7.9. 6. 9 -1.9 6.5 3.6 5.50 10.3 5. 0. 3.. 10.9 4. 1.1 3.79 2.0.7 - 1.97 13.7 0.7 3.92 7.6 6. 0.3. 08 11.3 6.8.. 3.60 12.7 3.3 0.8 5.91 15.5 5.6 1.0 3.6 3. 2.9 0.5;. 1i.6 2.6 0.6 3.31 13.7 5.7 0.9 3.6C 12.7 5.4 2.4 7.25 15.2 5.2 2.3 7.25.3 5.9 2.8 19.30 2. 1.2 0. 6.55 10.2 04.4 2.9 9.04 8.7 3.1 1.9 6.33 6.7 i.5 1.0 2.0. 11.2 1.6 0.3 5.13 6. 1 0.1 2.40 7.9 1.7 0.4 s.77 6.1 2.3 0.6 6.59 16.38 32.11 10.17 20.10 32.C/i 9.,6 3.73 16.51 1.15 3.47 14.32 2.23 5.61 13.11,:.o; 3.,5 17.31 4.41 10.; 6 7.02 6.05 10.42 19.22 5.76 7.3 16.61 2.02 9.57 15.33 3.53 5.47 15.17 1.39 5.30 9.81 0.49 9.90 18.94 2.52 06.73 35.52 3.51 17.74 28.97 6.74 22.16 35.97 5.C6 6.03 1.13.03 17.51 29.73 5.90 11.54 5.16 1.93 6.50 19.52 2.!0C 3.30 10.9O 0.72 2.64 6.44 0.82 3.82 7.55 0.19 6.00 19.06 0.55 86 9g 89 98 84 84 37 92 ^V 92 90 93 C933 96 83 92 37 9; 92 39.6 95.2 36 91 84 87 10 10 10 1C 10 26.6 o.6 1.o 13.5 2.4 1.6 17.3 2.5 2.1 o.38 1.3 2.0 17.9 1.5 1.6 22.7 1.9 2.3 4.4 2.0 0.2. 17.5 2.6 L.9 3.7 3.6 -1.5 9.2 3.0 2.6 3.1 2.7 (0.5 3.3 3.5 o.3 85 84 88 83 75 26 8i 25 84 53 53 85 51 85 I 5 89 92 940 92 82 95 99 3!j 94 91 39 99 99 91 313 94 931 96 98 83.4 79.34 8.9 80.75 79.3 82.74 76.3 33.45 35.8 79.84.1 78.05 96.6 74.9 74.4 84.;5 82.5 81.52 74.6 35.2 78.2 82.5 71.5 85.8 95.5 74.5 65.2 86.0 92.4 75.5 74.2 83.4?1.5 77.3 71.5 84.9 95.5 75.2 69.6 85.3 93. 77.1 68.6 67.0 91.8 75.6 75.12' 2.9 92.0 77.7 70.2 85.8 91.6 77.4 76.8 8 3.9 93.9 75.4 86.7 79.3 83.1 77.7 79.9 32.5 91.5 78.5 71.8 85.5 90.9 76.0 78.8 81.7 94.6 76.4 71.9 84.8 93.1 75.4 73.1 54.6 86.2 76.2 76.3 82.3 91.4 61.9 78 '.5 '72.8 91.4 75.4 71.7 85.5 93.4 76.1 73..5 2.7 39.7 76.7 73.7 33.8 90.6 74.8 64.9 84.0 '9.7 75.1 73.7 83.2 31.2 75.4 75.2 82.2 93.4 74.5 76.6 P2.5 94.6 70.3 - 32.9 35.0 75.5 74.6 82.7 93.5 73.6 64.3 i.8 92.5 72.8 63.1 82.3,Pl 4 7, ti 2. 0 75.2 72.3 67.7 81.6 77.6 65.7 58.0 79.2 55.9 75.2 65.7 82.6 93.9 72.8 59.3 82.7 80., 75.5 66.2 8;.1 76.8 73.3 67.2 81.4 - 28.5 2.5 - 15.2 15.8 - 31 - 27.6 3.4 - 22.9 8.1 - 12.3 18.7 - 16.2 14.8 - 27.3 3.7 28.6 2.4 - 28.2 2.8 - 23.7 7.3 1.2 24.8 5.0 - 31.0 - - 31.0 - 27.2 3.8 - 26.0 5.0 - 15.7 10.3 25.02 29.03 29.22 29.43 28.62 30.03 297.7 31.0 27.6- 30.7 31.01 30.7 29.7 31.0 30,7 31.0 26.8 29.5 28.9 30.0 28.8 29.0 26.5 28.6 26.2 29.3 29.6 30.1 28.7 29.5 24.1 30.1 20.1 27.9 28.2 29.0 29.0 29.0 29.3 30.5 25.6 27.5 27.6 28.1 25.2 28.3 24.4 27.0 26.7 27.2 28.2 28.2 23.5 29.9 26.1 27.5 21.8 28.0 24.3 28.3 23.0 26.3 27.5 28.5 31.0 30.4 20.8 28.0 29.3 29.6 22.61 30.1 27.3 29.9 28.6 30.6 *Letters indicate stations with complete records. 1 --- 700 FM 2 --- 900 HR 3 --- 1800 R --- 300 HR 5 --- 1200 Fo 6 --- 1500 H 10 21.0 10 22.0 2.0 1.5 10.0 9.0 2.8 0.7

I; " '% V1 Cu i~ 4 Y:;ZYO cn ' " ( " c, r5~-'" a cn v, cn v,,~ 2~ v, : VIV) O F 2~ czl YO awP a cn ISmcr IV) tr S -a - l -5, S~ Z~ 5 ~.0.005 OI rn 0. r el teBE! e14: r L I L4 C~ I-~0( v d iIOI-'rHl.Y AVERACE HOg 50~~(.800...D a rV> W 0. o l|| U o ZCi Sn >e c " > c O nn lc O 8 n Y O 9 t;c tt' 3= 3 cng o cn m o eES @j L~rL. a a a MONTH riovember -- RANC:OON TAVOY VICTORIA ALOP STAR FE:,ANC, (A) WELLESLEY (B) KL'ALA LUMPUR,LA CCA (C) S INC APORE KUOALA PAItANC KOTA BIlARU CANGKOK (D) ILOT-CO.'S (E) PNOM P2E t (F) MA TIS?; (3) 3OULo OBI POUtO CODOOiR CA:; THO CAP ST JACQUES SAICGON P'IAN THIET (H) PADARAN DALAT (I) '.A TRASNC (J) TTfY tlOA.QLc SrtON jO;(N SON QUANC NGAI (K) TONRANS HU'S TC:IEPON- (L) DONG HOI (M) V I:.H 'niANl HAO NA^'OD I.N P{' LIEN NORWAY IS. iAI HONcL':GSON (N) OHANOI MONCAY COASTAL 10.MILES I LAND COAf TA L COASTAL C.A ST. L COASTAL COASTAL 25.MILES I.'LASD COASTAL COASTAL COASTAL COASTAL 20.'< LES INLA. D COASTAL 60 MILES I '.'LAND COASTAL I SL,AVD ISLt';D 50 MILES COASTAL 30 MILZS I''LAN D COASTAL COASTAL 50 MILES I;LAND: COASTAL COASTAL COASTAL COASTAL COASTAL COASTAL COASTAL 50 MIILS:;.1A'. COASTAL COASTAL 20.MiLS I.'hL';D COASTAL ISLA'MD COASTAL COASTAL 50 MILES INLAND COASTAL COASTAL 1..I _ t I -TI1' 1 5' 1 1 I;1 5 lu ''; i0:<,; 4. ');* 3 2!., 3.;; 0S 20.3. 2.0 1q.1 1.2.. 3. L. 2.0 il,0 I 1;. ' I;. 7 _ _ r.c L.2 '' 2 2.4 1 5 15.?.? c.2:.2-, 2. 7 '~ O_. 1 l~,. 4 i'. 5. B1J-5 '.3 2.G 2o.a - -.. 2" 9. 5;. q; R 7L: -. 6. * 1. 0.3 3,. o L.,;-.2 12.2!.7 15.2^ _:12.'~ 2.1 2.9 1. o.?.r:. r~.7 'o r.5 10. 7.D7 0.5 3. 5...;.;+ -.,;7. '?. ', - _ 5.6 ' 7 2.2 12.2 6.f 00. C. c. 0.3 G.' - 3.2 2.6 0.3 S'.2 3.1 1.0 I 1.63 5.12. 7.03 6.4 6.20 o. 3 2. 31 0. 2 0.3 3.3 O. 7 - v, 11.5 3.2 0.5 1.2 O.1 O.1.9 5.3 2.6 0. 5.91.3 2.7 O. r 2.56 15.38.3? 3.5 12.17 a 5.- 5.3 1!. j9!2.31 2C.22 h.23 17.37 33.75 3.7 -0.54 11.51!0.31 3.2, 5.72 1.31 0.3 0.i 30.00 2.L5 1.56 1.10 7.12 14.57 O.C00 7.62 1. '' 3.20 29. '4..5 0. 20 A6.L5 0.12 3.22 1.35 6.57 'o.Co 6.7:) 15.27 0.76 4.5'..27 0.02 20. y.} 66.33...02. 1.2- 5.-77 '-.71 o.r, 2.1 C.G'00 3.,r r7.5L; 7.1D 6.15 18.1p G.' i.53 6.31 0.37 1.72:.6.13 0.97 4.35 0.!1 o.~3 1.5,' o.o'? 90 37.J7 87..2 85;35 91 100 86 92 92 96 90 93 92 90 95.9 93 92 95 92 93 90 53 92 91 6 82 91 97 90 21.2 -75.54 79.0 77.95 75.6 79.'4 69.2 ~2.25 79. 77.8:';79,3 77.75?7.0 74.* ',71.6 f 5..!20.9 8l.'2 7060 8.3 '9.5 31.92 73.3 85.2j 96.3 71. 65.08 36.0 93.5 75.2 73.5 83.6 92.3 76.7 72.4 e8.9 96.6 75.1 77.9 82.4 91.5 75.7 65.9 86.6 9.4 75.7 69.7 5.3 39.1 76. 663.2 35.9 92.7 76.2 75.0 83.0 03.8 70.6 05.9 79.4 23.8 77.0 78.7 81.2 900. 77.6 69.3 "6.1 90.5 75.6 77.0 82.0?3.0 75.4 67.6 05.9 932.3 7;.5 6.o. 95.5 |7.'; 75.7 79.t 79.6 '3.3 f;2.2 72.0 71.8 91.7 7!.7 7?.6 o 2.7 92. 7. 2 0. '. 77.0 79.f,:1.0 *9.9 73 - 72.8 81.3 93.9 73.6 81.2 80.3 31.3 73.5 82. L 7n.5 3.5 72. 1 8.5 77.7, 0 71. 73.3 77.3 2.569.0' 71.5 70.0 90.6 67. 3.0 76.1 0.,3 69.7 65.2 75.9,6.7 67.0 67.4 75.0 69.9 71.8 66.4 75.4 77.1 6o.3 58.6 71.1 3. 69.9 60.3 775 91.9 67.1 62.3 76.3 17.= 70.3 71.3 75.3 7.9 66.2 62.7 75.5 283.1 0.9 15.0 15.0 - 30.0 - 24.6 5.4 - 24.6 5.0i - 1'.5 15.5 - 17.0 13.0 - 26.1 3.9 - 26.0 4.0 - 29.8 0.2 2.0 27.9 1.6 28.0 - 2.7 27.2 - 12.9 17.2 - 2.4 27.6 - 2.3 27.8 -:'o data 27.72 29.63 29.32 26.13 29.32 29.13 23.0 29.7 25.31 29.3 30.0 29.3 27.7 30.0 29.01 28.3 28.9 27.8 29.0 29.0 29.1 29.3 25.1 25.5 28.7 28.0 26.8 29.1 29.3 29.9 23.4 29.7 20.9 28.9 27.4 2.8 27.0 27.9 27.9 28.8 24.7 24.7 25.1 27.0 20.1 25.4 20.1 24.4 24.2 24.2 24.7 25.9 2'. 7 28.0 23.0 24.1 19.4 23.1 20.2 27.3 18.71 24.5 26.91 23.8 29.4 30.0 18.1 26.8 27.71 28.7 20.3 28.8 28.2' 27.9 27.2 29.0 1 *Letters inoicate stations with complete records. 1 --- 700 0iI 2 --- 900 Hi; 3 --- lvvo0 H{i 4 --- 300 0ii 5 --- 1203 hi 6 --- 1500!l;< 0.6 12.0 -9.7 j.3,.3 10 Iiv: 0.5j.1 2.' 2.7 0.7 21 0.7. '. w 0.5 o.2.7 0.4 - 0.91 1~.0 -. L 73 77 78( 80 77 74 30 |7, 7;l' |;.. 2.2 O.. -.6 0. C.2 6.49.2.21 8.92- O.Co

TABLE 12 (Concluded) j CA 0 -3 m I <r 1."$ 0 9. I < Z m A c, 011l 2?". - - >. 8 y: c n =! o rn- n _ ur B cO ~SO O r O, ra ~ s e o N Wf r OHWa t~-e -.CY CIIL- 'ijtJC iZE a Si: gq $Z i, - 2 13 0 9:-.3 I4""Z YORMLCY AVERAGEt 0;. ) e -. 8 8 -C!"!Z.4v 0.i V) "0 P48:,! MOYM5 Den-mber. AJCYAB HANCGOON TAVOY V'C TORIA A.UJR STAR F'F!A.NG (A)* UWLLUSLzY (B) 'UALA LLKPUR MALACCA (C) S:CHAPORC KgLALA PAA.NG KOTA BHAP.U BAhKOK (D) ILO:-CONE (E) P1?.1NOM 'N (') \0 HA TIEN (C) H- POULO 031 POtrLO CONDORSCAN T1O CP? ST JACQOES.SAI'ON PHA; THIET (H) PADAPRA DALAT (I) IN.A TRASG (T.) TL'T HOA Q' I Nt(ON BO?; SON QuANCA SGAI (K) TOO;A2'5E 'C:. SPPO~t' (L) DOCIG HOI (M> VINS I T'N' HRAO F'UH LIEN NORWAY IS. L"'NSON (N) HAI PHON' HANOI 0NCAY.,to.,'A COASAL 30 MIL2S IrNLAND COASTAL COASTAL COASTAL COASTAL COASTAL 25 KILES COASTAL COASTAL COASTAL COASTAL COASTAL 2 0 I LE S I.LAN D COASTAL 60 MILS I %IA.S'D COASTAL I SLAN-) INTAND IS LASTAL 30!<IL~ C ASALE I. I.ANO COASTAL COASTAL 50 -ILES COASTIAL COAST.AL COASTAL COASTA.L COASTAL COASTAL 50 MILS I r.>t. COASTAL COASTAL COASTAL 20 ILE2S I I..ND COASTAL SLATD COASTAL COASTAL SO.ILzS INLAND COASTAL COASTAL _ _ I I I I I I I 1 r I I -i i i i + i I: ) I:i IC';-4 11 i i. D I i L-3.; ',. i 0.7 Lf. (I. 9 L1. 4 f.', O..9 0. C, tL 7 1;. 0.0 3CJ - 0.5.'5..3 j. 1 L. 5 2;. C C.7 1.2 1 3.; '" 12.9 ''.'J 5.2 1.7 i.0',. 7,,,.. 1^., '. I, I 1.5 r. -,. 0. 0.2,.: 2.( 10.5 3.: 0.2 2.'.,' 1...3; G.? 3.33 0.0 - 3. i. 2. 2 1_. 2.2 *. _., 2.52 3.5;'. 3.. 1.3 2. 3 * o, r'. _.;7 C., _ D. 5 |-. 7 C. C.,.7 2 _.20 2- 5 0. 5.2' 2 q 2 H T-.7:.i.J 9; a 0.9;,. -{ *'.. 0 7.-'2 1.3 ' ".3 12.31 2.7 o. S 3 2. o. ol.l3 3;5 0O.C_ 2 6.0, v. 1.35 10.2: j.00. 1.'32C.01 7 5'i.13 3 '.j36 5 C-5 *..2. _ 7 5.1^ 7.0 0.'2 I 31 2-. I, 3.. 1. 24 2. 2 0.0' ',5. 32. I -.5 e2 903 89;7.3 35 -n.2 7 fl-, 73 89 34.9 69.2 75.8 73.65 94 71.7 77.0D4 62.5 82.95 3.63 "3., 794!' 76.6 70.15 92 16.C0 i72. 65.1 6. 4.,3. 23 1.; 71.6 5. 97 i3. 7 3.22 9.5,6.2 95 ''.o 73 1..5 36.7 91 93.2 4.6 70.8 84.o 92 '3.7 57 7 30. 84.7 957.5;4.6 77.2 31.5 95.2 5'j.5 70.1 53.0 85.6 '6. 72.5 64.3 82.6 92 i'6.1 72.0 57.8 84.0 8 50.8 72.6 67.7 82.1 1.4 71.4 83.7 76.7.3 74 5.; 74.4 80.0 3 C9.o 74.5 6.3 34.8 91. 72. 74.2 80.0 7,. 7L., 7.7 6 - 3. 7-.6 63.8 82. 3 8 2. 72.7 75.4 77.8. *1 58.5 67.3 69.2 9 1. 71.4 6.5 8.7;,,' 7,71. 75.Q 77.; 50 7 H7j 65.0 7' t; -7',.9 6 5. 97. 9,.3 -. 775.37. 3 3.9 66.1 3.6 73.0 5 9.7 62. - 72.5 '5 0.2 t4.2 70.38 7. 39 9 3.0 6-9.0 69.9 2 59.. 70.2 ' 3. 0. 63.3 69.7 3 17;, 0 63.:5 67.5 67.7 593. 59.20 82.5 62.5 34 3 6.3.8 6.8 89 )L.6 5-.5 73.6 6.2 67.3 65.3: 535 3. 559.2 61.5 67.7 1 - 31.0 - 11.7 19.3 - 31.0 - - 23.6 7.4 - 21.5 6.5 - 13.0 18.C - 16.9 1.4.1 - 27.2 3.8 - 25.8 5.2 - 31.0 - 5.0 25.0 1.0 2.4 1.6 - 18.6 12.4 24.1 6.9 - 11.i 19.2 3.0 18.0 i'o data 28.02 30.23 30.32 28.63 30.42 30.13 31. 0 30.'23.8 31.0 31.0 31.0 30.71 31.0 30.31 29.7 30.1 31.0 29.8 30.7 30.6 30.6 23.9 29.7 29.9 30.5 27.8 30.7 29.9 30.0 20.5 29.3 24.0 30.4 '9.7 29.3 27.9 30.5 29.2 30.6 214. I 27.2 27.3 29.0 22.6 29. 4 2. 26.1 25.9 28.5 23.7 27.8 27.6 3o0.6 24.6 25.7 14.9 23. 13.2 26.2 12.41 24.4 20.3 29.1 2.351 29.3 19.2 24.3 24.21 29.0 24.81 25.7 18.5 28.0 24.6 29.5 *Letters indicate stations with complete records. 1 --- 700!m 2 --- 900 HP 3 --- 1800 HR 4 --- 300 HI 5 --- 1200 Ht 6 --- 1500 KH '' I - I -. - 2. I r" I 1._ 2 L: }. _,.;I _....... _ i. B * I ')!. ' _- _ $~ 4vl 3~.i. v.,, 2 ';'i |. -3 3-. ' D I

CLIMATIC INFORMATION FOR PENANG (5021'N-100015'E) _ ~ - MEAN MAXIMUM TEMPERATURE J R) 'C DAYS WITH RAIN (TRACE OR MORE D HEAVY RAINY DAYS (.5 TO 199 INCHES) A J I15 I I VERY HEAVY RAINY DAYS (2 INCHES OR MORE) J 10 D F ~ 8 N M 01 i i i I.:i:-:::. E i i I IA A, 2 I I, - I - 2 DAYS r M LJ J ' —' 5 SPELLS I I Fig. 14. Climatic Information —Penang.

LL I --.. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _...... _ _....._......:....... ~~..-.~~..~~.~...~..,~.................~.~.....................1................. i........... 0U!! X j.. 1- J In TnII H...... U- -) IL - ) I~~ i~ LAJ ' C) T 0 gr >-: 11i z *1z -0 T rA Q).......::~:... - X.............................................................................'' ~ ~~~ - ~ -- -- -t -- t-:~.'; T~.i~t::::::::~..............~~............ O~v iI i.........................................1lI11II1 i:.::::~-ljlfj...........r:f.......... C) z

c) 0 C) cd ~r — H I 0 ~'.) 0 TH 4-) Hc r-i r-i *HA PLI Q 94

CLIMATIC INFORMATION FOR BANGKOK (13~45'N-100~30'E) MEAN MAXIMUM TEMPERATURE J DAYS WITH RAIN (TRACE OR MORE) D \0 I* aj 5 DAYS I HEAVY RAINY DAYS (.5 TO 1.99 INCHES) VERY HEAVY RAINY DAYS S M A J J L -' 2 SPELL I 5 SPELLS I_ _ _ _ _ _ _ _ _ I.. Fig. 17. Climat;ic Informatiorn-Bangkok.

I 1 1LC C\........ ---. --- —t-. ---^gg||||BIII...I... —... o - ---------------------------- 0 >< 0 I I s o 0 + > z 1Z - - T | o T -I- Hi 0 - 4 -> i — ----- -> I -- - - ' F 5 ' " ' "r *O A ye 0 / 6 - j- ' _ — \- I ^ Qy / - t - -9 I O bC / " \- / 2 -; E | T *< - - -, a U I 0 ~ X - |' X ' I i1 o o; { w — L Ll Q< Qw /H \ r — | J' - j I -I I'0 I4 — 0 x 0................................... c r- ------— $ -~-0 LL < < h 2 2 I v t h3 i v < C1 LLJ w. J i

I I I I___ Lii LL I..... -.. - -= I / \ I I s H ~ V 0 Z 0r /- 2 < a5 j oU I!_ I J 0 a 0 0 I L + - LL 0 a \!. \ I::/? /: )4 o1 LL \\ z.....Z.. J 2................. o.? igi o........~.........______ c r -..l.l1 1!..~.... / "'.... i.. x -jiii- I I 7"' S > __........_.__ z VI::::::::::C~:::::::: t c) r-4:: ~~-~%::: ~~~~::: o ~::::::::::::::::::: i-; ~~: ~~: ~~:~.:-..~:;~.::~::~:,:~::CC 0:............................................................................. IZ)........................!Afri: can!: 3............................................................................................................................... - - -)......................................... LT O............................................................

CLIMATIC INFORMATION FOR HA TIEN (18~21'N-105~55'E) d C' A K 1 d A Y | I I is A r CA A n c' D A 'T I I n rl- i..... _. _. _ _ _. _ I MLMN MAXIMUM TEMPERATIUR 0 DAYS WITH RAIN (TRACE OR MORE) HEAVY RAINY DAYS (.5 TO 1.99 INCHES A C&; I _ 5 DAYS J VERY HEAVY RAINY DAYS '(2 I^NCES OR MORE) J 0-10 D / _i - ": - N. M 0- 1 - 1 4 A S - 1 2 I * S' M\ J LONG RAINY SPELLS (4 DAYS OF, LONGER) J 15 D F 10 N 5 S........ A J '-._ 5 SPELLS L- 2 SPELLS i I_ _ _ Fig. 20. Climatic Inforration-Ha Tien.

A 0 -. ---:l I 5 DAYS L ___ 5.DAYS Fig. 21. Climatic Information-Phan Thiet.

CLIMATIC INFORMATION FOR DALAT (I1158'N-108~28'E) MEAN MAXIMUM TEMPERATURE DAYS WITH RAIN (TRACE OR MORE) D HEAVY RAINY DAYS (.5 TO 1.99 INCHES ) A 0 L. 5 DAYS J A -' 2 DAYS J A ' 5 SPELLS I ' 2 SPELLS I _ Fig. 22. Climatic Information-Dalat.

'I LL o r,, 2:-:::i::i::: ':::::::: J - c,.X —' 1........ ^ / o z O ~ Z-Z................ liii: 3 t: v, J:~:~: J w a Q '" cn v) bo r. 1 ctl a O cn ri C) co a r<t.r-i F-I v) >0 y, 101

CLIMATIC INFORMATION FOR QUANG NGAI (5~8'N-108047'E) MEAN MAXIMUM TEMPERATURE DAYS WITH RAIN (TRACE OR MORF) j D * F \ —..:: t M:,::;:::::::::::.::::::S:::::::::: tte. flD / A { J ' 5 DAYS J HEAVY RAINY DAYS (.5 TO 199 INCHES) 0 N \ I k:::::::::_: -15 F -10 / I -y A L %,.! U....::' '.: A S A I 5 DAYS ' M J 0 Io J 5 DEGREES (FAtRi) VERY HEAVY RAINY DAYS (2 INCHES OR MORE: J "- O D N V I F -8 - 6 / >M 2/ *:. I i i I I M J S. AYS > ---;'. DauS J J - - 2 SPELLS ' 5 SPELLS - I L Fig. 24. Climatic In:formation-Quang Ngai.

0 A J ---- 5 D rEF', (FAHR) RY HEAVY RAINY DAYS ( z INCHE3 OR MORE) J T 10 I 1 S DA { Fig. 25. Climatic Information-Tchepone.

:::,::::::: /. ^::::: \ ',- \ 0 o....r-+-. -, -J. ]z J( I -- Z4 -I1 > L I -- \ 1. > _;: J >l'~Y:j~f~~~~; —)l-~ ---::wi~~~~IZ:::~~:i~ iii 104

105

V. NATIURAL VEGETATION,ND LAND COVER About two-thirds of the project area, including almost all of the hillmountain country and 20C of the plain surface is covered with one or another kind of forest growth. Most of the remainder of the identifiable cover on the plains is rice paddy fields. Because of the concealment it offers, the forest growth is an important part of the military environment as demonstrated by the current guerrilla fighting in the area. Broad areas of rice paddies present a special kind of military environment in which, during the wet season at least, heavy equipment cannot be used to advantage. The character of this cover together with the facts of surface and climate which have been presented earlier point toward an assumption that inilitary operations in this area are likely to be done by relatively.small bodies of troops, 3with hand weapons, and will require strong air support for communication and supply. The land cover of the coastal strip of Southeast Asia may be separated into the following broad categories: 1. Littoral Forests 2c Tropical Rain Forests-primary and secondary 53 Tropical Dry Deciduous forests., Savanna Grasslands with thin forests and brush 5. Freshwater Swamrps-coastal and riverine 6. Cultivated Land-tree plantations and rice paddy Each of the natural categories is a composition of associations of ve<gettation varying in species and density as — well as in changes resulting from enturies of human occup.tion. iNone of them are homogeneous types and all have great interspersion and differences resulting from edaphic drainage, and exposure in their local environments. The following generalized descriptions are composites from those obtained in the United States as well as locally in Southeast Asia. Littoral Forests. These are those found actually on the sea coast or 107

within a few hundred yards of it and extending inland in some places along river estuaries. Mangrove. This is a term applied to forest growth of a variety of trees which have a common habit of growth. They occur in the shallow water of muddy coasts which are protected against strong waves and heavy surf. Mangroves form a relatively thick growth consisting of trees of two characters: one bears "stilt" roots which support the main trunk from the sides and form "knees" that make an impassable tangle at low tide; they are about awash at high tide; the other is supported by a wide lateral root system and is therefore somewhat more easy to traverse than the former. The available maps do not differentiate these two kinds of mangrove growth. The barrier effect of mangroves occurs partly from the density of the stand and partly from the mud ir.. which they grow. On the landward side this may be only a foot or more in depth but on the seaward side is deeper so that it is impossible to wade ashore through and over the slippery stilt roots. Other Littoral Cover. On fairly stable sand dunes and sandy coasts there is a sparce cover of herbaceous plants and small trees which presents no problems of penetration. On waterlogged coastal soils, in places inland of the mangrove fringe, there may be a relatively dense forest growth of thin-stemmed trees-"tram" in the Indo-China parts-together with heavy brush. Some is of swampy nature in whi-ch "visibility at eye level is seldom more than ten yards." This cover is known from description but is not identified as a separate type on the available maps; probably it is a kind of fresh water swamp. Tropical Rain Forest. This is a dense. storied forest, the typical growth of those parts of the area where the distribution and amount of precipitation is such that there is no effective dry season in the soil. It is of evergreen-broadleaf character and is composed of an intimate mixture of many specieso The rain forest occurs in two different aspects, its primary form and its secondary fornm, Primary Rain Forest. Is an association of tall trees with interlocking crovwns which form a closed canopy over the ground, A few tall trees thrust their crown.s up through the canopy, and on the forest floor there is a clumpy growth of' shade-tolera-nt brush and rseedlings. It is not difficult to traverse the tropical rain forest because of the open nature of the ground but ma;ny of the trees are supported by buttress roots that extend out from the tree trunks narrowing the space between. There Is an abundance of epiphytes and lianas. The closed canopy pr obably would cut idown radio communication. Fig 28 is a generalized drawing of this forest. It is outr belief thlat little primary rain forest occurs within the coastal strirp un:der description because of the centuries of occupation by shifting cultivatorsc Most of that indicated on the general map is probably secondary forest of somewhati different character. Map 16 shows the interspersion of primary and secondary forest along the VietNam coast. lo0

Fig. 28. Profile of a Rain Forest. From: Indo-China, Geographical Handbook Series, B.R. 510, Naval Intelligence Division, London. Secondary Rain Forest. For some centuries the rain forest has been used by shifting cultivators who girdle trees to let in light for crops. Within a few years the resulting jungle growth prohibits cultivation and the site is abandoned. It is estimated that several hundred years are required for the rain forest to regain its climax condition. The secondary forests are, therefore, any stage between abandonment and climax development. Clearings are first invaded by heavy grass growth which survives under repeated burnings that destroy some of the other immature vegetation. The forest floor develops a heavy brushy growth containing numerous small trees with lianas and climbers to form junglle thickets so dense as to require cutting for penetration. However this thicket growth occurs in clumps and may be circumvented. Tree reproduction in secondary forests consists of a dense growth of saplings. s1ma and close together. For these reasons the secondary forest is not so readily traversable as the primary type but probably is much better for radio communication. Subtropical Mountain Forest. Above altitudes of 2500 ft this replaces the rain forest. It is a broadleaf-evergreen forest commonly not with a dense, closed canopy; somewhat similar in appearance to a midlatitude open forest. In wet situations there is a heavy brushy growth on the forest floor; in dry places this may consist of a low cover of bracken fern or herbaceous plants. In the coastal area under description this occurs only in one narrow distribution on the flanks of the mountains of northern Burma. Tropical Dry Deciduous Forest. Are found in situations where there is an effective dry season in the climate that causes the trees to shed all or 109

some of their leaves. It consists of a relatively open forest with patches of dense brush, especially along streams. It is also called "monsoon Forest" from its climatic association. In terrAs of its trafficability, the dry deciduous forest resembles secondary rain forest but because of the rarity of lianas and brushy patches is much more easy to traverse. During the dry season most of the trees are bare so that visibility and radio communication probably are good. The fallen leaves burn readily and the forest may be subject to repeated firings. Grassland, Forest, and Brush. This category appears in four places on the general vegetation map but probably is not a climax type in itself. Grass and brush have been described as components of both the secondary rain forests and the dry deciduous forests and the map distributions may be considered as somewhat mere extensive areas of these components. The grassy savanna areas occur in climatic situations where deciduous forests would be expected and possibly represent poorer soils where tree generation is slow or which have been repeatedly burned. Swamps. The area of fresh-water swamp is less than 6% of the total plains area probably because much of it has been converted to rice paddy. The remaining parts occur characteristically in strips along river courses, around lakes, on flat delta plains, or on coasts inland from the area subject to salt water invasion. The general map of vegetation cannot show these small patches but there are extensive area long the south.western and the southeastern coast of Malaya where even now soil surveys are in progress to determine their suitability for paddy development. Swamps are commonly inundated during the period of heavy rains and retain high water tables throughout the remainder of the year. The character of the cover varies widely with soil differences, the duration of flooding, and human utilization. Some swamps are covered with tropical forest and support considerable undergrowth; others bear a thick growth of small trees. Some are repeatedly burned so that the vegetative cover consists largely of tall grass. In almost all situations the swamps would constitute barriers to easy movement of vehicles but only in a few places are tvy enxte i ve enough to constitute a special environment for military rriovement. The upper Mekong and the country around the Tonlc- Sap, outside the area under desoript:i on, is an exampnle of such environment wherein the military operations of August, 1961, utilized landirg cralt in ditches and creeks (Time Magazine -August 25, 1961). Distribution of Cover Types Thie general surface configuration of coastal southeast Asia consists of a wider or narrower coastal plain backed by hill country and. interrupted by river plains and broad deltas. Wherever the coast opposes the course of the sulmier (southwest) ilmonsoon relatively heavy rainfall occurs and the resultant 110

'...... 4~ G ENESTRALIZED VEGETATIN O: ~. ~~'. ~...... Map;15 e:e:ralz- Vg::<taion 1 1 TROPICAL RAINFOREST MANGROVE TROPICAL o.RY DECIDUOUS FOREST -_ WETLAND RICE, SOME DRY CULTIVATION RUBBER PLANTATIONS AND DRY CULTIVATION.; Map 15. Generalized Vegetation. ill i.

COVER MAP No data SOUTH VIETNAM ' ' COVER TYPES | % Pt___ Primary Rain Forest Secondary Rain Forest |I | Savanna and Open Forest - Dunes Vegetation 'zz/,/ Pine Plantings Highland Vegetation s% Cultivated Land A a'........ No data 0. O50 Scale of Miles _0 106 017 108 1'09 Map 16. Cover of Part of Soeuth VietNiam. 112

vegetation in the non-swampy plains and hills to elevations of 2500 ft is tropical rain forest. Such conditions with local exceptions mark the entire western coastline from Pakistan to Singapore (Map 15). Most delta plains and some riverine plains have been cleared as rice areas and in western Malaya there is a large area of tree plantations and other dry cropping. The east coast of the Gulf of Siam is similarly situated and covered in general by tropical rain forest and strips of rice cultivation. On coasts protected from the direct force of the southwest monsoon there are areas where not enough moisture is received to support the rain forest, these are covered by dry deciduous forest, A stretch of such coast occurs along the west side of the Gulf of Siam and spotty distributions appear in parts of eastern Malaya and North and South VietNamo The minor vegetation types, grasslands, mangroves, and swamps are incidental to this major distribution pattern, It should be understood that these broad distributions are not of homogeneous cover types but are based upon dominance of the indicated cover. In particular the difference between primary rain forest and secondary rain forest is; not indicated on the general map and is of considerable importance in terms of trafficability and radio coimnunication. The patchy interspersion of cover types is welL illustrated by Map 16 which shows a section of the South Vietrnm coast northward from Saigon. Cover Type-Analysis from Map Coverage A cover survey was made tby an analysis of the 87 maps forming the 1:250,000 and similar coverage of the area, recording the indicated cover for each grid square in telrs of its geeonorphological character. This provided about ten thousand smnples; not all sqiuares could be identified and the coverage in Thailand did not commonly carry coverr overprints so that estimates had to be made from such vegetatlion maps as were available. The summary by square miles follows as Table 15.. Vegetation of Plains. If the alluvial, delta, and complex plains are combined, they form 74,752 square miles or 45o of the area under description. From the map survey, their cover types are as follows:,Tye Square Miles Percentage Forest 19,6- 2,C72 Paddy 41,2 45.25 t'ree Pl1ant at'ion:; 14 7 5 iMangrove, 5 5252 Swamnp 5' 3.93 6.74 Sacdy Shore 71L. 78 ot Id, ent ied '.17.76:_.,t..'~e... c~?

vegetation in the non-swampy plains and hills to elevations of 2500 ft is tropical rain forest. Such conditions with local exceptions mark the entire western coastline from Pakistan to Singapore (Map 15). Most delta plains and some riverine plains have been cleared as rice areas and in western Malaya there is a large area of tree plantations and other dry croppingo The east coast of the Gulf of Siam is similarly situated and covered in general by tropical rain forest and strips of rice cultivation. On coasts protected from the direct force of the southwest monsoon there are areas where not enough moisture is received to support the rain forest, these are covered by dry deciduous forest, A stretch of such coast occurs along the west side of the Gulf of Siam and spotty distributions appear in parts of eastern Malaya and North and South VietNam. The minor vegetation types, grasslands, mangroves, and swamps are incidental to this major distribution pattern, It should be understood that these broad distributions are not of homogeneous cover types but are based upon dominance of the indicated cover. In particular the difference between primary rain forest and secondary rain forest is not indicated on the general map and is of considerable importance in terms of trafficability and radio communication. The patchy interspersion of cover types is well illustrated by Map 16 which shows a section of the South Vietiam coast northward from Saigon, Cover Type ---Analysis from Map Coverage A cover survey was made by an analysis of t.'he 87 maps forming the 1:250,000 and similar coverage of the area, recording the indicated cover for each grid square in terms of its geonorphological character. This provided about ten thousand samples; not all squares could be identified and the coverage in Thailand did not. commnlonly carry cover overprints so that. estimates had to be made from suc.h vegetation maps as were available. The summary by square miles follows as Table 1.. Vegetation of Plains. If the alluvial, delta, and complex plains are combined, they form 7^4,752 square miles or 45o of the area under description.. From the map survey, their cover types are as follows: Type Square Miles Percentage Forest 19,62- 20 C72 Paddy 41,02 43 25 Tree F1 aita ion,.17 5,45.angrove 4 525 5.52 -wanmp,595. 74 Jandy Shor e 74' 0.7. ot rdei:' 'ied.L85 17.76 1 1A

TALE 13 MAP ANALYSIS CF NATURAL AND CULTIVATED VECGTATION BY GEOMORPHOLOGICAL TYPES (By grid squares from 1:250,C00 (approximate) maps in square miles) Alluvial Delta Co-plex Plain Plain Plain - u~ Complex Hills Total Notes Forests Padidy Tree Plantation nMangrove Inland Swa.p Sandy Shore Not Identified Totals 3200 3852 58 1819 78 47.L2!537-9 569 4697 930 344 1221 7761 35286 39055 8549 538 2749 422 6o0o,6863 Concentrated in Irrawaddy Delta No sm:bol on maps 97 35383 Fcre,;ts Paddy Tree Plantation Mangrove Inland Swar.p Sandy Shore Not Identified Totals 2528 1537 5011 591 3780 81 17339 17567 Ma!laya 53 12599 64 526 I1 176 j2 2 62 9. 10C7 6530!7S? 19904 15481 1601 5537 741 3967 152 12076 39555 All on west coast No sry.b:ol on naps Fores to Paddy Tree Plantation Mangrove Inland Swaur San -y 'hore Not idlentified Totals 2555 1095 50 98 5 667 4470 6960,915 1095 78 7! 70358 ll!0 No sy.mbol or, Ir.:ap Forests Fadiy Tree FiPntation Mangrllove Ina: - ' wr;-.p 3-.:;dy, hore Total. s 25C09 10 10 59 +oq 99 00 i2 1680 11517.cS 955 1741 k 1725 17460 26229;O0 81 20 5 7205 55740 3i.045o 1 5( 15'9 985 601 *, 1' No symbol on: r;np. o:'e s %: 20650 c a!`r D v r C; c" -.- t l ~~~-,C7 CI1~: ~L~lto.n T,-:c v;;;' e o:; ":' ' w,-cp.: S..n Fy Shore l.t i es ot-ls;-; ~'i. - 7 - 114

The percentage of each cover for the three types of plains is illustrated graphically in Figure 29. Vegetation of the Hill Country. The hilly country is almost entirely in forest of one or another type. The map analysis by square miles shows: Type Square Miles Percentage Forest area 101,699 87% Not Identified 15,910 12% Other 1,144 1% It seems probable that most of the unidentified area is actually forest. Cultivated Land Almost half of the plains country is under cultivation. This cover consists of rice paddy, 435.25% and -tree plantations and dry agriculture 5.143%. The hill area is almost entirely in forest and the scattered plantations within it are unimportant in reference to the general forest cover. On the plains, the tree plantation areas are almost entirely confined to a single area in western Malaya (Map 17). Tree Plantations in Malaya. In a belt some 20 to 40 miles wide extending along the entire Malayan west coast, tree plantations are the principal land cover. There are several paddy rice districts (descriptions below) that have been reclaimed. from swampy areas. These occupy perhaps one-quarter -of the land. The principal crop is rubber with minor areas of coconut palms especially along the immrediate coast in Malacca Strait. Tree plantation areas in contrast to rice paddies are easy to reach and traverse. They are situated mostly on well drained ground and are serviced by good roads which connect them with the principal highways or railroads. Plantation headquarters are nodes of settlement and communication. In plantations the native vegetationr had been almost entirely removed and replaced by the crop trees. These have been planted precisely so that there will be no shading of one by another with the result that the space between the trunks is wide enough for ordinary vehicular passage. The absence of undergrowth makes good visability. Although tree crowns touch to form an almost complete canopy, this is not thick enough to shut out all sunlight from the ground and is much more permeable to light and presumably to radio waves than is that of the dense and storied tropical rain forest. The plantation areas are by no means solidly in crop trees. There is 115

COVER ON THE PLAINS Diagrammatic Represenitation of Identifiable Types ALLUVIAL PLAINS Sea Hills Mangrove Forest Paddy Tree SwampPlantation DELTA PLAINS S ea Hi I11s Mangrove Paddy Forest Swamp COMPLEX PLAINS Se a _ \\ Hill1s Mangrove Paddy Forest Te P 1Ia t a to Ion. scaled in percentages observed Fig. 29. Percent of Cover on Plains. 116

MALAYAA LAND USE N \4 N,."\~ I'l-N, N. I.:i.iiii RICE AREAS \ TREE PLANTATION S E LETTERS INDICATE RICE AREAS DESCRIBED IN TEXT I M', ES. I Map 17. Malaya-Land Use. 117

much undeveloped forest land within the actual limit of any plantation and more between plantations. The wetter parts along streams are in heavy brushy jungle growth. However the plantations present few problems to trafficability because of their open character and the presence of the road network which serves them. Rice Lands. Rice is an aquatic food plant which grows in fields constructed to hold soime water during the growing season. Most rice areas are developed from swamp lands by drainage and accompanying irrigation systems and are divided into small fields, usually by solid dikes which give some individual control of water height, or in new areas with common water systems by landmarking soft dikes of raked vegetation. The dual requirement of level land and a plentiful water supply confines paddy cultivation to plains areas. The delta plains with their smooth surface and abundant water are the best sites and 71% of the delta plain surface is used for rice cultivation. The coastal alluvial plains are 29% covered with rice paddies, somewhat less than their forest cover and the complex plains, most of which is river flood plain, are 420 in paddy rice. Rice cultivation consists of four periods. The rice seedlings are grown in beds; they are transplanted into flooded fields; they mature and ripen as the water supply dwindles into the dry season; the crop is harvested in relatively dry fields. After harvest there is a period of two to five months when the fields are dry until the next planting season. Variations of this cycle occur in places where the water supply permits two crops to be raised in a single season extending the wet period to ten months as some fields are harvested while others are being planted. In a few places, particularly on the Mekong, deeply flooded paddies produce "floating" rice, which is planted in dry land, then deeply flooded and harvested from boats (Map 18). The rhytUhmn of rice operations would be an important factor in military operations because of the barrier character of flooded paddies (see the study of;a laya rice areas). N o sound generalization can be made concerning specific dry seasons for the whole area. In most places winter months bring northerly winds, dry weather, and t-rafficable rice paddies (Table 14), but on protected coasts with north-south extent the dry paddy time may be through the summer months. If river w.ater is. avai la'ble from irrigation works two or even three overlapping crops may keep some paddies flooded throughout the year. Rice Areas as Military Environments. In areas where rice paddies are interspersed with other cover types such as the paddy strips along river valleys, they represent only another type of locality in which movement is limited by the cover. However the broad continuous paddy areas such as those of the deltas of the Irrawaddy, Chao Phraya, the Mekong, and the Red Rivers, represent a unique environmvent for military operations. Some of the 118

Source: Exposition Coloniale Jntern-n-ioai-, Paris, 1931. Rizicullt"r en -fr- ~ine, following p. +4 (Hanoi, 10,31). Map 18. Types of Rice Cultivation in Indo-China. From: Indo-China. Geographical Handbook Series B.R. ~1lO. Naval Intelligence Division, Tcondon.! elements of this environment are: 1. rur ing flooded periods or in wet places there wrould be great difficulties in deployment, lateral movements, circumvention of roadblocks, etc. 2. Area would be open to constant air observation because of the absence of concealing cover. 3. Opeerations would be completely dependent on roads. 1ig

4. Any off-road operations would be carried out with hand weapons and the advantage of mechanization and armour would be negligibte. 5. Extensive paddy areas are densely populated. Rice Paddy Areas and Trafficability in Malaya So little information could be obtained about the nature of paddy areas in terms of trafficability that a special report was obtained covering eleven rice producing areas in Malaya. The questions asked were these: 1. What are the usual field sizes? 2. How high and wide are the dikes: 3. What is the trafficability of the rice area and adjoining ground in various seasons for wheeled vehicles such as jeeps? The eleven areas are located on Map 17. A. Kelantan Delta. The fields are very small; few of them are as large as one-half acre. They are separated by field dikes about 2 ft high and some 18 in. wide at the top. The fields dry out about the first of March and remain dry under ordinary weather conditions until the middle of July or the first of August. During this time vehicles could be driven across them because the water table is far below the surface. During the remainder of the year they are wet; the monsoon period from October to February spreads water over the whole area. Trafficability would be good during the dry sea.son. At other times there is a good sysstem of Kamo:ong roads that do not show on our ma.s that are passable some of the time. The structure of the delta with old beach ridges and levees is such that there are dry ridges between wet sloughs that hold some water at all times except at the height of the dry season. These are arranged parallel to the coast so that inland movement would have to -pass ove.r the wet sloughs and lagoons between the ridges which, themselves, are passable at all times. There is one local place, tie Sal(.)r area in the graeat bend of the Kel- antarn, where an irrigation scheme allows dry season flooding from pumped water. This area could be circumvented or the pumpir-ig stopped. It is not a very large area anyway. P. Trengganu.Delt. a. Condiltions are- almost the same as those in Kelarntan.- -nclud ing a pul pib (go'rat'ion near 'bkit Basar which can flood a small area 120

during the dry season for double cropping practices. C. The Pahang River. All the way upstream to Kuala Lipis there are small, scattered paddy areas known as "Paya Paddy" or swamp paddy. These are in old river channels, Oxbow meander scars, lagoons, and similar low spots behind the river levees. They are usually wet throughout the year although some of them dry up during July. By September they are all wet again. Wheeled movement could go along the high levees any time except in rare years when the levees are flooded in late December. The paddies are long strips with few dikes and little water control and therefore diffi ult to cross at right angles. However they are small and discontinuous and crossing is possible where they end in high ground. The paddy areas themselves would not be a serious barrier to movement because they do not form a continuous broad expanse of wet land; it would always be possible to get through or around area. In this district there are distributions of swamp forest which would probably be:nore serious barriers than the paddy land. D. North Jahore. The area is included in the paddy summary although most of it is not yet under paddy but is part of the planned reclamation, now alienated and under development. However the development is slow. The general conditions are about the same as in Kelantan (A) but with a shorter dry season. Only in April and May would the well drained areas support wheeled traffic. In this newly developed area there would be fewer dikes and larger field sizes, some several acres in extent. Drainage canals are being dug wrhich, as they increase in number, would be all-season barriers to traffic. E. Malacca. The wettest period is from July through October and the dry period from February through June. Many of the lower fields will be wet even in the dry season. During April, May, and June most of the area would be passable for wheeled vehicles. The field size is small and fields are separated by 2-ft dikes. The paddy areas are not so continuous as in Kelantan and commonly separated by strips of rubber plantation upland, easily passable at any time. During the dry season the fields near the town of Mialacca are planted to vegetables by their C-hinese owners in heaped-up beds which might bog down jeep traffic. Field dikes are not wide enough for jeep travel but there is a good network of Kmpo.ng roads passable in all but the height of the rainy season. F. Negri-Sembilan. In this area paddy is c1onmonly confined to the stream flood plains. The ribbons of rice land on either side of the streams is usually flanked on the higher ground with rtubber plantings and villages. The rice la!nd is divided into small plots with many dikes, few of which would /O-ar jeep traffic. Most of the villages arc- joined to the main highways by short lateral Kamcong roadzs that are passable in all but the most rainy part 121

of the season. The fields are wet from March to November but most of them dry out by January. Those nearest the stream stay wet throughout most of the year but the higher ones would be passable from January to April. G. Kuala Selangor. This is a new paddy area recently reclaimed from swamp forest and because much of the land is low, near the coast, and not yet well drained, the dry period of the fields is short, December through March. Near the town of Kuala Selangor there is much double cropping in fields that can be flooded from the river. The cropped areas nearest the sea are never dry enough for wheeled vehicles and in addition, this part of the area is cut up by drainage canals which would be additional barriers to transportation. The fields are large and continuous; some consist of several hundred acres owned by many people with the ownerships separated only by strips of uncut vegetation that do not now provide trafficable roads. Vehicular traffic off main roads would be difficult in this area at any time and probably impossible during the rainy season. H. Telok Anson (Sangei Manik) and the Perak River. This is much like Kuala Selangor (G) except that there is no double-cropped areas. The fields are somewhat smaller but still several acres in extent. The dikes are low, small, weak, and discontinuous. The area is wet throughout most of the year and should be considered passable only by tracked vehicles with great difficulty, except during the months of March and April. The Perak River is bordered by strips of paddy which are discontinuous along either bank. The fields are small and separated by firm dikes. The paddy strips are subject to deep flood during the rainy season but dry out to a greater extent than do the larger areas near Telok Anson. Travel is possible at all seasons along the high ground of the river levees. I. Krian District. This area is wet throughout the year. It is somewhat like Kuala Selangor (G) and Telok Anson (H) but even more wet. Most of it is deep ex-swamp and probably impassable at any time. The inland margins might be passable during February and March but this is not certain. The fields are smaller than either of the two preceding areas jbecause this has been established longer. Field dikes have been built up from vegetation and are not firm enough for passage of wheeled vehicles at any time. J. Province Wellesley. This is the largest. double cropping area in Malaya and the fields are wet throughout the year except a week or two in late October and again in Mr h; these dates vary a little with the growing season. The normal climatic dry period is in January and February. Field sizes are small, few are more than an acre in extent. Most of the dikes are firm and solid but some are of raked vegetation so the whole system may not be trusted for passage. There are good roads following the north-south h b iac-h ri s -;these provide access into the area but it would be difficult to move across it wit+h jeeps. 122

K. North Kedah-Perlis Plain. This is the most extensive area of paddy in Malaya. It dries out from January through May. There is much variation in soil moisture from the coast inland. The coastal areas are generally much wetter and do not dry out thoroughly at any time. Near the coast the fields are large, over an acre in extent but become smaller inland. The dikes are high and firm away from the coast but usually not wide enough for jeep travel. The area is cut up by drainage canals that carry some water even through the four-month dry season. The inland parts probably are passable during the February or March period and then only with difficulty. An analysis of this report is presented by Table 14. It indicates clearly the differences between dthe drv p ricds on the side that faces *the southwest monsoon (G through K) and those which are on the lee, eastern, side of the peninsula (A through D) and also Negri Sembilan (F) protected by Sumatra, In the former group the rains come earlier and probably in greater amounts so that the. land is wet by April or May and does not dry out until December or January, On the other side the paddies are not flooded until August and remain wet.until March or April. In addition to this field study fcr Malaya, the Agricultural Calendar of South VietNam (Table 15) shows- the co.nd-itions on another east coast. Here the rice areas would. appear to be -looe!.d by May or June and not dry until December. It should be noted that w'here irrigation water is available local areas will produce two crops (Map 18) and therefore field.s will be wet during the otherwise dry season. Because of water supply and probably also from market condition.s the rice harve-t w.thin a sitngle area (Map 19) may occur at two or more times during the ye.ar. T'ralffcicability predictions should therefore be made in terms cf spci fic studies, such. as that presentedc for thMalaya, rather than upo. general dry Iseason climatic assumptions. Sources: Vege tation Coi, Jin-Fte, "The Nature and Di-stribution of Natural Vegetation in Malaya,".acific Vie.,oint, 1;.' 'I 0) pp. S5-20 o o.... F '-, Forets o., r:. ur.a Pamp!lets No. 5, Longmans, Green;... * t t.i ~,v.... \.., -1i,. Wa -t-S+0 J., "A T T- ot'h Frshar amp Lcwland anrd Hill Forest i',t s of Malay" Te aya-,.L _ a1. 1S iG ) pp. 110-121.

TABLE i4 TRAFFICABILITI PERIOD OF POSSIBLE OF RICE AREAS OF MALAYA F-) 4= Jan. Feb. Mar. Apro May June July Aug. Sept. Oct. Nov. Dec. A) Kelantan x x x x x B) Trengganux x x x C) Pahang River? D) North Jahore x x E) Malacca x x x F) Negri Sembilan x x x G) Kuala Selangor x x x H) Telok Anson x x x I) Krian?? J) Wellesley? K) North Kedah-Perlis x x x x x...., -__........... X =? - probably passable possibly passable

3aPBBPIBB3BPlgsgslL! —,_ —,,,.., ___ __L_ __ _P-. I ---- -U~ — 0 r4 0 H E0. ~o Q w —v J 0X 0o 2 o I s o 2 o IV 1 FQ 2 z i; 0 - ff r IZ g 2 a W U 16 u. O Z o V -I O o 5 UJ u a >* cn I 125

Source: P. Gourou, Les Paysans du Delta tonkinois, p. 396 (Pthris, 1936). Map 19. Times of Rice Harvest in the Tonkin Delta. From: Ind( Geographical Handbook Series B.R. 510. Naval Intelligence Divii Davis, John H., The Forests of Burma. 23 pp. The University of Florida (I960). McKinley, T. W., Forests of Free VietNam. 152 pp. USOM, Saigon (1957). rempsey, J. M., Agricultural Calendar of VietNam. USOM, Saigon (1961). Gittinger, J. P., Vietnamese Agricultural Calendar, USCM, Saigon (1959). 126

"La Foret Cambodgienne" in Cambodge d'Aujourdthui Duexieme Anne No. 1 (1939). Nguyen, Van Chi), "Les Forets Indonees au VietNam," in Causeries sur le Developpment des Ressources Naturelles au VietNam. Le Secretariat d'etat d' l'Agriculture (1960) pp. 23-66. Ma-1 Dia Do-Phan Loai Rung-VietNam (Vegetation of VietNam) manuscript, 1:1,000,000. Probably from the South VietNam Forest-Agency. Land Utilization Map of Malaya,y Surveyor General of Malaya 1:760,520 (1953). IndoChine Forestiere, Institut des Recherclhes Agronomiques de 1' Indo-China 1:2,000,000, not dated (probably before 1954). 127

VI. SOILS It is only during the last decade that systematic work has been done on the soils of Southeast Asia. At the present time surveys are being carried out in a few countries but the results have not yet been generally distributed. So little information could be obtained in the United States that it was necessary for this report to secure the material directly from the soil services of the countries. In Burma the survey is conducted with the assistance of a technical group of advisors from the USSR and its preliminary maps are difficult to obtain. All of the soil information for North VietNam comes through Russian sources. Soil descriptions from the various surveys cannot readily be correlated in detail. In some cases they are collected for agricultural purposes with emphasis on productivity rather +han genetic classification. There is the difference bctween actaal soil mapping and soil sampling with boundaries run out on imperfect geological maps. For these reasons the descriptions are presented separately for each country. The map of major soil distributions has been made from such information as could be obtained and in itself is a generalization of that presented by countries. From a military point of view the principal deficiency of the material lies in the absence of data on which trafficability and bearing-strength estimates can be made. No such information could be obtained; if it has been collected by the Russian technical groups in Burnma and North VietNam it is understandably not available for general distribution, Generalized Pattern of Soils The geomorphological pattern of coastal Southeast Asia is composed of three general entities: the relatively steep slopes of mountains, dissected plateaus, and footlands composed of igneous and hard sedimentary rocks; the intermediate slopes, mostly on sedimentary rocks9 and the alluvial coastal, riverine and delta plains of recent deposition, The soils of each of these entities vary widely in texture and structure but they form board groupings of recogniza! e,'T characteristics. 1, Mlountain, Hill-Country, Dissected Plateaus with Steep Slopes. As a group the soils of these areas are inmutiiture, shallowl and commonly well drained. Somre slopes have little soil and arae Ureas of crushed stone surface from which the finer materials -have been removed by strong sheet erosion. The valley soils are ren-eral4l lateritic red-yellow and red-brown earths of 'heavy texture which may have stony profiles. 129

2. Intermediate Slopes. The gently to strongly sloping surfaces between the mountain-hill land and the alluvial plains are covered by residual soils mostly derived from sedimentary rocks. In almost all situations these are redbrown or red-yellow forest soils or latosoils although some of the older alluviums in VietNam are podsolized. The iateritic process develops clays rather than sands so the soils are generally heavy with high water-holding capacities and probably slippery when wet. 3. Alluvial Soils are those o.: the coastal, riverine and delta plains, in somie places fringed by mangro-ve or sand strips. Tn general the alluvial soils are soft, water-logged during the rainy season, and have a high water table. The study of the Malayan rice lands indicates that they are passable with great difficulty during the wet season. The alluvial soils may be grouped into three subcategories. a. Water-logged, muddy and sandy soils bearing mangrove forests. b. Intrazonal meadow soils of the broad river valleys and freshwater swamps. These are of heavy texture and dark color, some are of gley (sticky, compact, structureless) nature. Included in the group are the soils of the deltas of the great rivers, b. Sandy Coastal Soils. These are most common along the east facing coasts of Indo-China and Malaya where they form bands some few miles in width. Probably they originate from fossil sand dunes. It should be noted that the coastal survey presented earlier shows many more miles of coast line with narrow sandy strips than is indicated by the sandy category on the soil maps because coast lines of other classifications may bear narrow sandy strands along the tidal zone. The distribution of these.lasses is fairly regular as may be seen on May 20. The hi.lly core-land is fringed by alluvial soils which penetrate into the interior along river valleys and over the greab deltas. On the flanks of the hills lie residual latosoils but not in all places. Along the VietNeam coast. where the hills approach the coast closely and in places actually reach the lateritic belt i s very nar row or ahsent although it occurs on the inland side of the mountains. Such detail as could be obtained is presented in the discussions of the soils of the several countries. This politicel organization is necessitated by the differences in e xtent and character of the soil investigations done on national bases. The Soils of Burma iThe i soil rvey of Purn.a, wit.h the assistance of a technical mission 1:0

GENERALIZED SOIL MAP SOIL TYPES \.'~ MOUNTAIN AND HILL SOILS: RESIDUAL BROWN AND YELLOW FOREST SOILS AND LATOSOILS.... ALLUVIUMS COASTAL RIVERINE AND DELTA PLAINS SOME WITH SANDY OR SWAMPY SEA MARGINS Map 20. Generalized Soil Map. 131

from the USSR has progressed since 1956. In 1959 some 42% of the total area had been covered by mapping on approximately 1:250,000 field scale. The following descriptions make extensive use of such parts of this mapping as could be secured. The Burmese coast may be separated into three parts: the northern or Arakan coast strip, the Irrawaddy Delta, and the Southern or Tennasserim coast. The first two of these are the best covered by soil surveys. ARAKAN COAST On the northern section, from the Pakistan border to Akyab, the mountains lie principally inland beyond the arbitrary 50-mile limit of this study, Their long parallel outlying ridges give a nor-thwest-southeast grain to the area. The soils of the ridges have not been mapped in detail but probably are Mountainous Red Earths of shallow depths and stony composition. The valleys between the ridges and the lower hill slopes are covered with red-yellow forest soils betw-een the elevations of 300 and 1500 ft. Red-brown forest soils occur above these elevations up to 4000 ft. These two soil categories are similar; both are residuals developed by lateritic leaching. The higher, red-browns, occur where there is heavy rainfall, 80 to 200 in./yr and have no dry period in the soil. They bear heavy tropical evergreen forests. The red-yellows are in areas of lower rainfall with seasonal soil drought, and bear deciduous or semideciduolus forests, The red-brown scils are shallow on the steeper hills 'ut 5 to 7 ft in depth on level ground. They are usually heavy loasms with some stoniness in the lower parts of the surface layer. They contain little humus and are previous in the upper layers. The red-yellow i-oils are interrmedi.ate between the coastal alluviums and the red-browns. 'Thle are light in texture, 3 to 6 ft.eep with a heavy layer which would hold up water in the rainy season, South of Ramwee Island the main mass of the Arakan Range approaches to within 5 to 10 miles of the coast. In this area the strip of the residual forest soils is much rmore narrow than in the north. The alluvial soils of -th-le Northll Burma coast are of two general categories: the meaidow soils arnd th'pe mang rovre soils. The lowland formed by the basin of the Kaladin Rivcr together swith the Ler.po and t;he M'ayu extends inland to the north for some ', C miles. It is covered by alluvium which forms intrazonal. meado.w soils of heavy text:ure, hiig-,h humus content, and large water-holding capacity. The water table is close to the surface even during the dry season and probably at. the surface during the wet 'season. Some of the soils are gleyey, i.e., sti.cy, compact, and structureless. The lo;er, tidal parts of 1 2

BURMA SOILS OF NORTHERN BURMA GENERAL SOIL CATEGORIES OF NORTH BURMA COAST...... MOUNTAINOUS RED EARTHS, IM-MATUFIE, TURFY, CRUSlHED STONE,/,RED-BROWN AND YELLOW-BROWN FOREST SOILS 4Z' ALLUVIAL INTERZONAL SOILS: MEADO ikA ALLUVIUMS AND MEADOW GLEYS V:SALINE SWAMPY SOILS. BEARING MANGROVE FORESTS % SANDY COASTAL STRAND AT TIDAL ZONE SCALE OF MILES Map 21. Soils -of North Bu~rma. 1331

the river banks are swampy and bordered with mangrove forest. Much of the plain is in paddy. From Akyab wouthward in the areas of Hunter's and Combermere Bays, the coast, sheltered from heavy surf action, is covered with swampy saline soils bearing mangrove forests which reach inland along the tidal streams for distances up to 25 miles. In the lower parts of this area, affected. by daily tides, the soil is deep mud, certainly impassable at any time. The higher ground, flooded only at seasonal high tides is much more firm and the mangrove forest less dense. The seaward coast of Ramree Island and the mainland coast to the south bears a discontinuous narrow sandy strand strip. IRRAWADDY DELTA The alluvial delta plain of the Irrawaddy is some 100 miles wide at the coast and extends as an entity for about the same distance inland. It is continued northward along the river valley for another 100 or more miles. The following report on the soils includes also the area between the delta and the Sittang River. The material presented is taken principally from the unpublished maps of tile Burmese Soil Survey covering the Districts of Hanthawaddy, Insein, Toungoo, Pyapon, Tharrawaddy, Henzada, and Ma-ubin. For simplification several of the original mapped categories have been combined. These are: Meadow Soils: in which have been placed meadow soils, meadow loams, medorllW '11 viurs, alluvial soils and meadow light brown. Meadow Swampy Soils: meadow sw.ampy, s.wamnpy gley, swampy soils. Saline Soils: meadow saline, solonchoks, Saline - Mangrove Soils: salty-muddy, saline gley-mangrove. Latosoils: lateritic brown and yellow, dark brown, forest soils, cinnamPon soils, light and hea.-y loams (nonsedimentary). Iil 11y-iMout ainous red mount'ainous earths, crushed stone, -turfy. The soils o' the area i:s3y be separated into fcur general groups, similar in nature to those described for 'North Burma.. These are: coastal soils, intrazonal alluviums, latCosoi,s and illly-mountainous soils. The Coastal Soils occupy a narr-ow band along the tidal fringe of the delta coast and the large' river i.rouths. There is a strip of mangrove, five miles or less i1n width bordering directly on the c!ean on the west side of i>

the delta but fronted with a wet sandy tidal strand of about equal width on the east. The meadow soils behind this eastern part are also saline, probably inundated at seasonally high tides. Meadow Soils. The delta plain and the northern valleys into which it extends are covered with a group of intrazonal alluvium originating from river detritus. This parent material has been separated into 12 soil groups by the Burmese mappers. It seems probable from the maps alone (these are preliminary manuscript maps for which no textual material is available) that more than one of the cateogires may apply to the samne soil grouping and that such broad ones as "alluviums" are themselves inclusive of others. For the intended purposes of this report it is convenient to regroup these meadow soil categories in terms of drainage into the following: Meadow Soils: generally good drainage Meadow Gley Soils: sticky, heavy, with poorer drainage Swampy Meadow Soils: poor drainage, probably wet at all seasons Meadow Saline Soils: subject to seasonal high tides. The pattern of distribution of these meadow soils is delineated on Map 22. Few generalizations about distribution can be made because the drainage seems to be related to the complexities of the pattern of the distributaries of the Irrawaddy as well as to centuries of agricultural use iwhereby drainage conditions have been changed. The saline meadow soils are located Just inlanid from the coastal soils along the estuary of the Sittang where the tidal bore characteristics of this estuary or the force of the souithwest monsoon winds cause seasonal flooding by sea water. The swampy soils are usually in areas of small extent, partly or wholly surrounded by better drained soils. This suggests that they may be remnants of much larger areas now drained artificially. The significance of this distribution pattern lies in the probability that the well drained and the gley meadow soils are trafficable during the dry season and that the smaller areas of swamp may be circtunvented. There are no continuous east-west all-weather roads or railroads across the lower delta but the waterways formed by the distributaries could be utilized. Hill-Mountain and Latosoil Areas of.the North. Finger-like projections of the hill country extend southward west of the Irrawaddy, east of the Sittang, and in the area between these rivers. The soils of these steep areas are described as shallow, turfy, of crushed stone, and lateritic in nature. It seems probable that they are similar to the red-brown mountainous soils described for the hilly mountainous area of North Burma in view of the fact that the western area is a continuation of the Arakan Range of North Burma. Along the footlands of these southward-extending ridges are broad belts of forest soils and latosoils. Like those of northern Burma, they are on gently to strongly sloping terrain and are usually covered with forest or Jungle growth. 135

r\) Co rJ) 0 Hp H (n CI) H 0 01 Fl II 0 U Ct? H H' 0 - I 5j.r " 0 0u ct P 0i C o 0 0 H- H- H' CIU) CI) cI en\ 00 H- C:I ( l ( < 2 o 0 0. 0 Cl r) O O G r O 0 0 0 r 0 H- H H- H UC cI [) 0 cn m r -I 0 r (I) - -.-dh.-w-. o - - - a~ 35C;v!/ ~~J ~ -

Soils of Malaya The Department of Agriculture of Mala.ya has assembled a map of soils made from all useful information available extended along lines of geological reconnaissance. It is in manuscript form and is intended by the Department for early publication. From this map the distributional information which follows is taken and the map of Malaya soils (Map 23) of this report is generalized from it by combining the original fertility categories of the latosoils and disregarding the separation of the alluvial soils into categories based on the amount of organic matter and the completeness of the drainage. The blank spaces on the m;p represent unknowrn soil areas, The pattern of distribution is fairly regular; the soils are distributed in concentric bands around the central hilly-mountainous core in the following sequence toward the sea: irnmature hilly-mountainous soils, lateritic residual soils, lowland alluviums, and coastal fringe soils. The hilly-mountainous soils are poorly known. They are stony and shallow except in the valleys. The texture characteristics seem to be a function in the amount of quartz contained in the parent material. Where this is abundant the soils are light-colored and coarse textured. Where quartz is scarce the soils are heavier and darker, probably similar to the Mountainous Red Earths. The latosoils belt is formed by residual soils developed almost entirely on sedimentary rocks of gently to strongly sloping surfaces, They are mostly yellow la.tosoils which correspond in situation to the red-yellow forest soils of Burma. The belt of residuals in the northwest at altitudes above 2000 ft, is probably bears of red-brown latosoils. The soils of the blank, unsurveyed area on the map, from what is known about its geological character, probably also are mainly yellow latosoils. Alluvial soils cover the broad river basins and the coastal plains in a belt of some 20 miles or less in width. The riverine and inland alluviums are better drained than those near the coast and are relatively firm for wheeled passage. There is much broad swamp area in the river basins, where the soils are heavy enough to be classed as organic (peats and mucks). The western co-a-tal fringe bears strips of saline mangrove soil which ar.e neither so br-oad or so continuous as those of the Burma coast. On the east are relatively wide sandy -strands similar to those of the VietNam coast, n somne places there are clay strips between the sandy ridges.

MALY SO LS I I__ _ _ _ _ _ _ _ L 2 SOIL TYPES... ALLUVIAL MOSTLY POORLY DRAINEC RESIDUAL LATERITIC MOSTLY 'YELLOW LATOSOI LS,1,1 SALINE COASTAL MOSTLY MANGROVE "'> COARSE TEXTURED WELL DRAINED -11IMMATURE ON MOUNTAINS I - - VILL -.7. Map 23. Soils 158"

Soils of Thailand The soils of Thailand are less well known than those of either Burma or Malaya. The best source of distributional information is an article and accompaying provisional map by Pendleton and Montrakun, "The Soils of Thailand," reprinted from the Proceedings of the Ninth Pacific Science Congress (1960) by the Department of Agriculture of Thailand. It presents 21 categories based on agricultural utility. These are grouped into three divisions, lowland soils, soils of flat to gently sloping land, and soils of steep uplands. The geomorphological association of these three divisions is obvious. Coastal Thailand can be conveniently divided into three entities: the Bangkok Lowland, the peninsular west coast, and the short east coast between the lowland and Cambodia. The Bangkok Lowland is formed by the alluvial deposits of the Naman Chao Phya and neighboring rivers. The soils are described as dark, heavy, poorly drained clays and are differentiated into subcategories for which distribution is not shown on the map. The soils are permanently saturated at depths of 6 ft or less. This delta does not have the complex pattern of distributaries that. occurs on the Irrawaddy Plain and much less swamp area inland from the ocean. It is probable that these lowland soils are passable during the dry mo:-+hs but no specific information to that effect is available. The delta is fringed along the ocean by a belt some 5 miles of saline mangrove mud and tidal marshes. Peninsular Thailand. The narrow strip of Thailand that extends southward along the Malay Peninsula consists principally of hilly land that reaches the coast in several places. This hill country bears shallow and generally sandy soils derived from quartzite sandstone. The lower slopes contain coarse sandy loams of about the same nature. Strips of recent alluvium extend along the coast and into the valleys and lolans b.etween thle hi l s. Little is stated about their composition. Close to the Malaya border the coast contains the alternating sand and clay complex previously described for eastern Malaya. East Coast. Between the Bight of Bangkok and the Cambodia border the coastline is formed by fine sandy loams of lateritic character located on the plateau surface. These are penetrated cy short and discontinuous intrusions of alluvial soils in the valleys of streams.arising in the mountainous country some 40 miles inland. Soils of Cambrodia The 200 mile stretch of Cfmbodian coastline contained within the limits 13>9

of this description is formed by the plateaus, mountains, and hills of the rough country of the Cardomones and the Chaine de 1'Elephant mountains which approach near the coast. The soils of these areas are unknown but probably are of well drained, stony nature similar to those of the Chaine Annamitique of South VietNam. The very narrow coastal strip is sandy and a few alluvial penetrations of the upland occur along the streams. At the west extremity of the coast, near the Mekong Delta, there is a saline mangrove fringe. Soils of South VietNamn Material on the soils of South VietNam is derived from a map entitled "General Soil Map of the Republic of South VietNam" published in 1961 by the National Geographic Service (Dalat). It was surveyed and compiled by Dr. F. R. Moorman, with technical and financial support of the FAO (United Nations) and the ICA (U.S.A.). It shows 25 categories of which nine are not present or not important within the 50-mile belt of the coastal area. The remaining 16 fall into three general divisions: 1. Alluvial soils of the Makong Delta. 2. The complex of red and yellow podsols and lithosols which occur in -the plateau and mountainous country. 5 The discontinuous coastal complex of sands and alluviums which cover the generally narrow belt between the coast and the hills. Mekong Delta. This is an area of low, level, alluvial land cut up by the several distributaries of the Mekong and the lateral drainage ditches which connect them. The map lists six classes of' alluviums differentiated principally on their acidity (agricultural value). For about 10 miles inland from the delta margins the soils are tidal and saline muds supporting mangrove forests. Along the west side of the delta coast is a rather extensive area of mixed peat and mud, presu;mably swampy, w-hich supports mangrove and forest growsth. The delta soils as a group are soft, dark in color, level and generally wet. The eastern half of plain is thickly settled and extensively cultivated. It is subject to severe flooding (such as that in 1961) and would be a difficult area for operations except during the dry months, December to Marclh. North of Saigon there is a transitional zone of about 100 miles between the low delta country and the higher and rougher plateau surface. This is an area of flat to rolling topography bearing soils which are in part podsoli.ed alluviums, now uplifted, and in part reddish latosoils on various kinds of sedimentary and basaltic rocks. No additional soil information is available but, in terms of its soils and slopes this transitional area would offer few imrediments to traffic. 140

Chaine Annamitique Beginning at about 11~ north latitude, most of the width of the 50-mile coastal area is occupied by the Chaine Annamitique, a succession of eroded plateaus which present a relatively steep slope to the east and in several places actually reaching the coast as hilly or cliff headlands. All of the soils of the uplands of this chain are grouped into an inclusive category entitled "complex of mountainous soils"; mostly red and yellow podolic soils and lithosoils. This same structure extends into North VietNam where the Russian soil mappers classify the soils as "mountain lateritic." The genetic difference is probably unimportant for operational purposes..From title alone the soils of the hilly areas would seem to be shallow, sandy or rocky, and well drained. Coastal Complex. The uplands reach to the sea in places and cut the coastal complex into a number of discontinuous strips which have a characteristic composition. The immnediate coast is marked by an area of sand or of sand dunes extending inland for a few miles, in places up to ten miles. The soils are white or yellow dune sands. When these do not reach to the base of the plateau slopes, the intervening area is covered with strips of alluvium, recent or older which extend up the valleys into the plateau country in places for as much as 50 miles. Some of this older inland alluvium is podsolized and apparently not subject to annual flooding. Soils of North VietNam Information on the soils of North VietNam comes from material obtained through the FAO (United Nations) in Rome. It consists of a Russian map with legend translated into Rnglish, This is from a publication "The Nature of North VietNam" by V. M, Fridland, Scientific-Popularized Series, published by the USSR Academy of Sciences, 1961, The Table of Contents was also obtained, but not the text. Presumably the soil mapping represented was done by or with the assistance of a technical mission from the USSR because the soil classification follows closely that used by the Russian mission in Burma, From the South VietNam border north to the beginning of the lowland of Tonkin,.the geomorphology and the soils are similar to those described for the adjoining area in Sou-th VietNam, The plateau bears lateritic soils (analagous to those classed as "podsolic" in South VietNam) and a coastal complex of sand dune strips and alluvium extending up the valleys. Towland of Tonkin and 'Nortkhern Annam. This is formed by the delta deposits of the Red River and its neighbors the Ma, Ca, and the Chu. It is a flat, alluvial area narrowing inland for about 50 miles. The soils are separated into categories which include gleyey, and those "receiving annual fresh deposits" mlong other subclassifications. Presumably they are like those of the other river deltas of Southeast Asia: dark colored, heavy, and bearing 141

high water tables. No areas of inland swampy soils are shown. The coastal fringe of the delta is bordered by a narrow strip of sand, sand dunes, and mangrove mud. Highlands of East Tonkin. This is the upland between the Tonkin and the Chinese border. The plateau or hilly country approaches within 20 miles of the coast; its soils are the same as those of the plateau belt south of the Tonkin Lowland. The immediate coast is fringed with sandy and mangrove mud soils and the area between this coastal strip and the hills is composed of old lateritic alluvium. Sources: Soils Moore, E.C.J. and Van Baren, F. A. Troi Soils. Interscience Publishers, London, 1954. Bramad, D. L. and Dudal, R. Tropical Soils. (Manuscript), F.A.0. Rome, 1957. Dudal, R. "Les Sols du Bassin du Mlekong Inferieur et leur Utilization." Pedolog, 10: (1960), pp. 24-47. Compy, E.Z.W. (Soils Advisor USOM), End of Tour Report Project No. 442-12 -054 (1960), Cambodia. (Manuscript.) Coulter, J. K., M. MIaster, A. R., and Arnott, G. W. "Trans Perak Swr;sp." (Malaya), Soil Survey Report No. 3. Ministry of Agriculture, Malaya. Moorman, F. Note Explicative de la Carte General des Sols, VietNam. Mimeographed, F.A.O. Rome (1960), 50 pp. Panton, W. P. Reconnaissance Soil Survey of Trengganu. Ministry of Agriculture (Malaya), Bull. 105?Kuala Lumpur (1958). Rozanov, Boris G, (Soviet Soil Expert), Explanatory Note to the Soils Map of Burma. (Typewritten Engli.-h translation), 22 pp. (1959). Pendelton, R. L., Sarat, M0ontrakan. "Soils of Thailand." Department of Agriculture, Ministry of Agriculture, Bangkok (1960). Reprinted from the Proceedings of the Ninth Pac ific Clcience Congress, 53 pp. Pendleton, R. L. Notes of Soils and LaD-ild Utilization in Southeastern Sian with so.me Comm:enlts upon the improvement of the Agriculture of the Area. Tech. Pull. 4 (1.,50), 12.. pp. Thailand Department of Agriculture. Note also the maps and informatioon contained in the soil presentations under the separate countries. 1i42

VII. ROADS AND COMMUNICATIONS The importance of roads in conducting operations in an area such as the one under description needs no elaboration. The nature of the land surface, the va-ge;ta-tion, and the drainage inhibits vehicular travel away from roads. It is obvious from 1LMap 24 that the communication network is thin, consisting for the most part of long tentacle roads designed for commcnications between parts rather than within parts. It did not seem useful to delineate the transportation system because this exists on the general map coverage as well as in the usual road maps issued for the several countries by gasoline producerso In place of this we attempted an analysis, by quantitative methods, of the effectiveness of the road system. By sampling methods we sought the answers to these four questions: 1. How accessible is any point within the Project Area to the transportation network? 2. What is the quality of the surface and construction of the roads, especially their seasonal quality? 35 Is the coastal transportation system trend inland or laterally along t;he coast? 4, How well is the transportation network connected? These questions needed answers for the two general types of surface within the area: plains, and hills and mountains. An analytical method was devised and 221 sa.mrpl taken. These are analyzed in the following pages. iluch useful information is contained in the several analyses for the areas covered by the samples. It was our expectation that the findings of the samples would hold true for the Project Area as a whole or at least for the several areas into which It. was divided for the purposes of road analysis. Some characteristics of the road network vary over wide ranges, and as a result there are large deviatinns between the ctully me-asured miles of various kinds of roads and the prediction from the sanpied areas. Thils occurs, we think, because the actual mileage of road is a very small quantity in relation to the very large size of sample areas, and the roads are quite unevenly distributed. This attempt to reduce a road net to measurable numbers is based on map analysis alone. We do not nw just how:much and; in what ways the measured

PRINCIPAL ROADS AND RAIL-ROA'DS -K-MAIN ROADS -~~~~ —RAILROADS (MAIN LINES) - — `MAIN ROADS EITHER UNDER CONSTRUCTION OR NOT ALL WEATHER Mlap 2. Principal Roads a-nd. Railroads. 144

qualities will affect military operations. But when experience has demonstrated what these road net qualities mean in operations in one area, we can predict in some measure at least, what they will mean in other areas. Analysis of the Transportation Network This section presents a description of the transportation network in the Project Areao Important properties of the network are identified and measured by statistical samples. For some properties a complete enumeration is made. The adequacy of the sampling of these samse properties is suggested by comparison of the actual with the sample estimate. The transportation network is defined as all roads and railroads, but not including tracks and paths. The entire analysis is based on information obtained from Army Map Service 1:250,000 and similar scale maps, (See list in Introduction,) Minor adjustments and interpretations were made on the basis of other information sources-particularly first-hand accounts. The first part of this section describes the properties of a transportation network and defines methods for measuring these properties. The second part describes the sampling procedure and methods of analysis. The last section presents the results of the analysis and a general impression of the transportation network in various parts of the study area, THE PROPERTIES OF A TRANSPORTATION NETWORK A road network has several characteristics which are quite independent of one another. A complete description of the network thus requires several kinds of measures~ For exanpie, one characteristic of the network is the relation of road to area. The density of the network defined as miles of road per square mile is one measure of this characteristic. But two networks with identical density may look entirely different. Figure 30a shows a grid pattern network and Fig. 30b a dendritic lattice. The density of the road network is the same for both diagrams. In fact the diagrams have the same nlmb.er of boundary points, road segments and intersections respectively. The difference between the diagram is in the number of endpoints and in the number of road segmcents radiating from the intersections. In,'Figs, Cc a.nd >Od all of the above variables are constant, but the spacings between roads vary, The standard deviation of the distances to the nearest road from. a set of randomly chosen points would reflect this difference in -spacing..Figures g Oe and SC)f show orierat+i on or directional trend -in the road network wit h respect to the coastline. Whether the net-work tends to be con 145

ABSTRACT CHARACTERISTICS OF TRANSPORTATION NETWORK (a) MODIFIED G-91D PATTERN i (b) DENDRIT1C PATTERN (c) EVEN SPACING (d) VARIABLE SPACING (e) LATERAL ORIENTATION (t) SEAWARD-INLAND ORIENTATION SEAWARD Fig. 30. Abstract Characteristics of Transportation Network. 146

nected, on the average, more in an inland-seaward direction than laterally is of interest. This may be observed by counting boundary crossings of the sample area in four quadrants with one direction oriented seaward, or by resolving the road mileage into orthogonal components with one component oriented seaward. We recognize four general characteristics of the transportation network. In the following analysis we attempt to obtain one or more adequate measures of each of them. The characteristics are: 1. network to area relations; 2. quality of construction and surface material of roads and rail roads; 3. orientation or directional tendency; and 4. connectiveness or extent of strategic points and alternate routes. These characteristics were singled out in an attempt to throw some light on answers to the following questions: 1. How accessible is the study area or any point in the study area to the transportation network? 2. What is the quality of surface and construction of rail and road in the area especially with respect to seasonal weather conditions? 35 Is the coastal region transportation network trend inland-seaward or is the trend laterally along the coast? 4, How connected is the transportation network? Are there strategic points and how often do they appear? To what degree are alternate routes available? The measures described below attempt to answier these questions. S.AILE DESIGN AITD MEASUREMIENTS The transportation network analyzed is that shown on the Army Map Service at 1:250,000 and 1:255,440. These maps are based on British, French, and American sources. They are believed to be the most reliable and current coverage of the area. The reliability varies from survey to survey and from sheet to sheet. Most sheets 'iclude a reliability diagram. Most sheets were compiled or revised by air reconnaissance in the period 1950-1958 and printed by the Armzy Map Service in the period 1954-1960. 17'

The study region is a coastal strip extending 50 miles inland and including major adjacent islands (islands appearing on the sheets showing coastline). The region includes all the coastal areas of Burma, Malaya, Thailand, Cambodia, South VietNam, and North VietNam. Three landform types were defined: (1) mountains and complex hills (called upland); (2) complex and alluvial plains (plains); and (3) delta plains (delta). Total square miles of each landform type was computed. The sample was stratified by proportion of area in each landform type because the transportation network varied considerably by landform type. SAMPLE AREAS AND SAMPLE OBSERVATIONS The 221 sample observations were grouped into sample areas containing from 3 to 12 observations, depending upon how many square miles of each landform type were represented. Sixteen of the sample areas were designated as the upland sample. These areas have an M in their code number. Ten sample areas represent plains and six represent delta. Their code numbers carry a P and D respectively. All 52 areas are shown in Map 25. TABLE 16 SQUARE MILES OF AREA AND NUMBER OF SAMIPLE OBSERVATIONS BY LANDFORM "TYPE Total in Noo of Sq Miles _ Observations Upland 119,731 55 120 54 Plains 68,353 32 68 31 Delta 27,90 13 55 15 Total 216,074 100 221 100 Sample observations were chosen at random for each area in the following manner. A square mile grid templ-te was placed on the maps of each sample area on which the physiographic boundaries had been marked. The total square imiles of each landform type was counted and a table of random numbers was used to pick the appropriate number of sample observations in that sample area. The center of the square mile choser was Lutsed. as the center of *the sample observation. This rather involved procedure was an attempt to insure equal opportunity for every square mile to be included in the sraple. The physiographic regions sampled were very irregl:ar in shape and deeply interlaced with one another and with water surfaces. The method allowed narrow valleys, isolated hlumnrocks and/or islands to be in the sample. 148

TRANSPORTATION SAMPLE AREAS I P- 15 SAMPLE AREAS USED IN ANALYSIS OF THE TRANSPORTATION NETWORK M- HiLLS AND MOUNTAINS P-LOWLAND PLAINS 0 - DELTA k~4M-5-Z EXAMPLE OBSERVATION AND CODE NUMBER (5 OF 221 SHOWN) EACH A 500 SQ MILE CIRCULAR AREA SAMPLE STRATIFIED BY 50. MILES IN EACH TERRAIN TYPE. OBSERVATIONS MADE ON A MS 1 250.000 SHE ETS, map 25. Trkansportation-Sampie Areas. 149

Five-Hundred Square Mile Sample Observations. Each sample observation serves as the source of several types of information regarding the transportation network, such as density of network, type of roads, number of intersections, endpoints, and direction trends. A circular area of 500 square miles, with the randomly sampled point as the center, was chosen in order to obtain sufficient observations of these varied elements in a region where the transportation network is generally rather light and simple. The 500 square mile size was arbitrarily chosen and used throughout the study. The circular shape was considered necessary to avoid bias in the directional measurements. Figure 31 and Table 17 give five examnples of the sample observations. The measurements and counts made for each of t'hese observations were systematically recorded in the forml g-iven in T'able I Most of the subsequent analysis is based on these observations. One exception is the analysis of the quality of the roads.. The quality varied so greatly from area to area that the sample was an inadequate measure of quality. A total network enumeration was -taker, measuring the miles of rail or road in each route classification, This total c ou r also provided a check on the method of estimating density using the sample observation;. With the total count available it was possible to compare actual road mileage with estimated mileage, CHARACTERISTICS OF THE?TRAISPORTATION NE TWORK in the section below. each of the four general properties of a transportation network is measured for the coastal Southeast Asia study area. Network to.Area Relations. iThree measures characterize accessibility of the land area to the transportation net.,work-.. They are the density, the average distance to the nearest road from randormly chosen points in the area, anc tlhe standard deviation of the distribution of the distances to the nearest road. Density of the Network. The method of counting boundary erossings of an arbitrary circle tc determine density of the network is not appropriate here because of the interlaci -g of upland, plains, and wat-er in most of the 500 square mile circles ucsed as sarple observations. Road and railroad mileage are measured in eac' l ad orn area and, using a square mile tempilate, the numbe:r of square miles in each of these areas is also measured. The density of the n;etork is estirated fo- plains and upland by dividing the road mileage by total. sql:are mliles in the.apprcpriate landform areas. The density f or tr: entiriie are has little meaning because of the large i'if 'ferences in densit- n the twor 1 n'fo0m types. However, the separate density estim;ates iay be used to estimate -the road and railroad mileae in -the entire area. s imnpl by marr.ki separate estimates for each landform type and sunuinug. Be fore this Is (,one successfully an ad.'ustment must be made to take into account, he e-av density of road netw.ork in ur'ban areas. i5)

TRANSPORTATION NETWORK SAMPLE OBSERVATIONS PLAINS UPLAND ), _ = == _,E.,) _ 52 (MAP::2. _.. UPLAND M-7-6 MAP 36 TEMPLATE PLAINS DELTA LEGEND IrJL PNi) tri —t-t-it c —$ —c —i —i~ 1 I i -i~ —c —l — —-c —C —L -Ck —f-C.Ci~-L-CIlli: — ~ti — — ~-r-* ---n+~-l I,-eC —; Lc-C UPLAND '; WATER PLAINS TRANSPORT NETWORK ill N LEFT l_. _L- - -—._- RIGHT — LATERAL- -.-' *-.:-4 --- — l -4 LATERAL I. -.-71,'... i: ---- —, — ^ METALLED ROAD (PRINCIPAL). ---- OTHER ALL WEATHER............. DRY WEATHER ONLY RAILROAD CLUSTER @ TWO OR MORE INTERSECTIONS WITHIN i/9 M'LE ( INT-'RNAL INTERSECTIONS NOT SHOWN) CUI FOINT. -.t- -.SEAWARD ( —../ COMOLETE TEMPLATE IS A FULL CIRCLE AREA: 500 SO MILES RADIUS i2.62 CiPCUMFFRENE 73 24 Fig. 31. Transportation Network-Sample Observations.

TABIE 17 7iPANSPORITATION:~0TWORK SA;MPLE OBSERVATIONS (5 of 221 -hown) observation number P-4-1 M-5-2 M-7-6 P-11-2 D-16-4 map number 14 21 36 58 82 plains upland total lains upland total plains upland total plains upland total plains upland total Road to Area Relations Distance to nearest road from center of sample area (miles) 2.5 7.0 5.5 5.0 0.0 Square miles in water 22 11 70 240 12 plains 415 415 44 44 152 278 152 227 227 488 488 upland 63 63 445 4A5 278 33 33 0 0 Total miles of road and railroad 100 4 104 5 16 21 13 30 43 33 1 34 350 350 Quality of Road and Rail Network,' rtalled (principal) 3 0 23 0 0 0 6 24 23 1 24 58 - 58 1 ota e r all weather 33 5 1 21 0 0 0 0 0 130 130 miles - dry weather only 28 3 31 0 0 0 3 6 9 0 10 10 157 - 157 [railroad (all classes) 7 0 17 0 0 0 4 0 4 0 5 - 5 Conjkectivencss of Network components 4 1 1 1 9 intersections 12 0 0 1 1 1 2 3 4 7 2 0 2 57 - 57 sum of degrees 30 - 30 3 3 6 9 13 22 6 - 6 182 - 182 clusters 4 0 0 00 00 4 0 4 4 sum of degrees 18 - 18 - - - - - - - 24 - 24 internal intersection 14 - - 10- 10 segments 38 5 14 5 118 endpoints 11 3 4 2 17 Orientation of Network boundary points inland ( j ) 1 0 2 1 9 seaward ( - ) 2 0 0 1 6 right lateral (4) 3 0 2 0 11 left lateral ( - ) 2 1 0 1 12 directional mileage. inland 42 0 17 12 98 seaward 26 5 0 3 114 right lateral 18 3 18 9 97 left lateral 28 13 8 17 93 I I I I I i I I

A Cluster on the Transportation Network. The urban areas represent a density of settlement much higher than the average. This difference! is probably even greater than the differences between upland and pl ains. These large variances in density make accuracy of sampling estimates poor. Furthermnore, the maps do not show the urban areas with any consistency. An adjustment to eliminate the effects of these urban areas is made. Because the analysis is of the transportation network, these built-up areas are defined in terms of the network itself. We define a cluster as being a portion of the transportation network in which an intersection is within one-half mile of at least one other intersection. This definition corresponds rather too broadly to settlements with improved road systems. A more restrictive definition might perhaps have served better but the above definition was employed throughout. Clusters were delimited in each sample observation using the above definitiono The amount of road mileage within the cluster was then deleted from the total mileage in the sample observation and replaced with the sum of two dimensions of the area in clusters. The dimensions used are the longest length and the width at right angles to the direction of that length. This procedure is simply an attempt to replace the close network of an urban-like settlement, whose primary function is internal connection, with a rough estimate of cluster's contribution to regional transportation. Results of Network Density Measures, Table 18 displays the results of the analysis described above along with the actual mileage determined by a complete measurement of the network in the coastal region under study. The tabl e indicates a total of 25,572 miles estimated compared with 24,076 miles in the complete inventory. This represents a 5% overestimate. Individual sample areas show much greater discrepancies. Four areas have over +25% error, two of which have over +50% error, All of these large overestimates are in areas of very low network density in Burma and Thailand. The average density of the plains and delta regions is 20.38 miles per 100 square miles compared with 3.71 miles per 100 square miles in the uplands. Notice this density in 1the plains corresponds to approximately an average of two roads crossing a ten mile square, The 5.71 miles per 100 square miles in the uplands corresponds to a single road extending 1/5 of the way across a ten mile square. Only in Malaya is the road network in the hills comparable with that in the plains. However, the heaviest network is in the Tonkin Delta of North VietNamn, followed by the Mekong Delta near Saigon, and then both plains and uplands of the west coast of Malaya and the plains on the east coast of Malaya. The sample results compared to the complete inventory of road mileage su.gests the reliability of the sample is low and adequate estimates will result.only if care is taken to separate areas of greatly differing densities. Road network densities vary considerably in a region such as the one under study. and this inh1ierent varaiability will necessarily result in rather loose estimates of true density. 1'5

TABLE 18 TOTAL V*99P0 MILEAGE BASED ON EISTIMATED DSSIT OF NETWORK IN PLAINS AND UtLABL' COMP.ARED WITH ACTUAL MIZAGEf BY SJAPLE AREAS Sample Azra Coda Number 2 Bum& (liangoon) 3 4 Thailand 5 ('eore town) 6 (luala Lumpur) (SLngapors) 7 4- ___- 8 7halland 9 (Saagkok) 10 Caornelia 11 12 South ViaetsM (Saigon) 13 Pltnis nd DeltJ jUplnndt total square oetilated total aoqure ailsa in notwork miles in x plains density t upland (square mlles) (ailae/100 sq. miles) (quare miles) ( 5139 10.25 7922 65956 5856 3.99 /781 17.80 3400 5119 11.10 13619 4459 6.81 7670 7260 23,42 8540 8677 18.53 7813 7103 20.06 6781 5896 17.43 9495 5587 12.7n 4719 5016 14.30 8908 7771 17.72 663 7839 39.68 0 5323 32.31 7909 9706 5876 24.70 7103 4619 57.;5 1s/47 96321 20.;8 119731 eatlnated estimated natwork - total network dencity mileage (mile/l0O0 aq. ol-as) (miles) 0.42 1.88 691 234 1.91 916 1.17 727 1.47 417 10.39 2587 28.99 3873 3.31 1649 * 1110 * 750 0.86 794 *0 1377 3111 actual % total notwork error 'uileage (mile.) 771 + 10 152 f 54 796 + 15 964 - 26 351 + 19 2483 + 4 3200 + 21 1346 + 23 703 + 57 900 - 17 566 + 40 1.168 f 18 2916 j+ 7 lotoS * No roads were in s=ple oboervations. Upland road deasity was eatimated using area M-ll estimate of density -- 0.86 miles/100 sq. miles. ** to sample observtieons were made in this small area. 14 15 North VietNam:16 TOTJUL 8.30 2.84 0.89 3.86 2652 1514 2970 2892 - 8 164; - 8 3219 - 8 24076 * 5 - 3.71 25372

The Distance to Nearest Road. Choosing a set of random locations in the study area and measuring the shortest distance to the nearest road gives some information about the spacing of the road network. The center of the sample observations is used as the point from which this measurement is made. The nearest road is used regardless of which landform type in which it is located. Table 19 presents the results of this tabulation for each sample area. Notice from Thailand north and east to North VietNam the distance to nearest roads in upland areas is from three to eight times farther than in the plains for the same area. This is also true of Burma where the coastal plains are narrow (areas 1 and 4). The average ratio for the entire coastal region is 2,5. Only in area 7 is the distance to the nearest road significantly greater in the lowland than in the upl-ndo This may be understood by the fact that Singapore is in this area and is located on an island classified primarily as complex hills (uplands). This same area, on the other hand, has considerable area in inaccessible mangrove swamps in the plains sample area. In other areas of Malaya distances to the road in upland and plains are about the same within 50 miles from the coast. The shortest distances to the road are in the delta regions of North and South VietNam. Approximately the same short distances are also found in the narrow coastal plains of South VietNam. The areas classified as delta around Rangoon and Bangkok have some of the longest distances to roads, reflecting the rather low and uneven road densities in these areas. Variations in Distances to Nearest Road. The variation in distances to nearest road is extreme. This fact is shown in Table 19 by the large standard deviations compared with the average values for each sample area. The distribution of the distances tends to be skewed to the right although both tails of the distribution are sometimes large. The flatter the distribution, the more uneven is the transportation network. The standard devia+.ion seems roughly roportional to the means. This fact suggests the distances -to the nearest road from a randomly chosen point may be described as a Poisson population in certain circumstances. We suspect the distribution of distances to the nearest road is a Poisson distribution for the ideal case of a perfectly even transportation network. No analysis was attempted to prove this statement but we consider it a very fruitfu " avenue of research. If this measure could be related to the Poisson curve, the degree to which a network varied from an even distribution could be established by comparison with the Poisson distributiono Differences in the Variation of Distances to Nearest Road. The plains and delta of North and South Viet7am again display least variation in transport network spacing. mThe deltas and plains around Rangoon and Bangkok show great variation in spacing (areas D-2, D-5, and D-10). Malaya has a. medium.n variation in spacing except for great unevenness in the southern tip of the peninsula in the vicinity of Singapore where, as noted above, mangrove swamp and urban road densities are adjacent. 155

TABLE 19 DISTANCES TO NEAREST ROAD FROM RANDOMLY CHOSEN POINTS IN UPLANDS, PLAINS, AND DELTA Average Number of Miles from Standard Deviations of.Miles Sample Random Point to Nearest Road to the Nearest Road Area Plains Ratio of Plains Ratio of Plains Plains Code U Plains & & U Plains & Number Uplands Delta to De Uplands Delta to Delta Delta ______ ~Upland______________ Uplands 5.9 16.6 16.9 2.8 2.8 2r.i 10.6 15.2 2.3 2.8 2 9.7 8.8 6.8 4. 5 6 7 2.5 15.6 2.7 11.1 7.0 20.0 135.1 5.8 3.3 8.6 1.0 11.4 8.0 2.3 12.0 1.0 7 Z i. _, 0,2 8.0o o0.6 2.2 0.8 1.5 8 2.1 0.3 1.8 5.3 3.5 4.4 2.2 12.0 6.1 2.7 11.7 a. 14 4.9 10.3 8.0 9 4.1 21e9 9.4 10 11 12 9.3 4.2 5.1 30.8 18.7 5.0 0.4 13.6 7.8 1.0 1.5 14 1.8 5.8 9.1 11.6 9.9 5.1 6.8 8.2 1.4 1.0 1, 4 7:3 9.9 9.1 9.0 5.2 7.1 9.1 6.4 15 1.7 1.2 Land fo rm Area Average ELtire Area: 13.1 2. 7.5 11.7 1. 6 mean 9.5 miles, standard deviation 10.7 miles. 156

The variation of the distances to nearest roads is greater in the uplands than in the plains for most areas, but this difference is not as pronounced as the difference in average miles to the nearest road. The standard deviation of the distances is 10.7 for the entire region. The standard deviations for the upland areas of Burma, Thailand, and Cambodia are near this value, but have large average distances to the nearest road. This implies a very light road network, but with average variation in spacing in these areas. QUALITY OF SURFACE AND CONSTRUCTION OF TRANSPORTATION NETWORK The capacity of a transportation network depends upon the quality of the surface and construction of the roadway. We distinguished three classes of roads plus one class of railroad. It is difficult to be consistent because of differing classifications of roads on different map series. The British maps had at least two classifications and the American maps still another. Some British maps (group 1) classify roads as: 1. Road, all weather motorable with milestones and bridge 2. Road, fair weather motorable 5. Road, unclassified 4. Pack-track 5. Foot-path Another British classification (group 2) is: 1. Road, 1st class. metalled (unrestricted), with milestone and bridge 2. Road, 2nd class, metalled or gravel 5. Road, indifferent 4. Cart or jeep-track 5. Foot-path The American classification for maps compiled from either American or French sources is: Roads 1. Al1 weather, hard surface, two or more lanes wide 2. All weather, hard surface, one lane wide 5. All weather, loose or light surface, principal 4. All weather, loose or light surface, other 5. Fair or dry weather, loose surface, principal 6. Fair or dry weather, loose surfce, other 7., Cart-track;-..,Footpath-trai a 157

Railroads were classified as normal guage (3.3'), narrow gauge; single or multiple track; light, milestone and bridge, or simply railroad. The classification adopted in this study to combine these classifications is: All Weather Routes 1. Railroad (all classes) 2. Metalled (principal) roads British group 1-1 British group 2-1 American 1,2 5, Other all weather roads British group 2-2 American 3,4 Dry Weather Routes 4, Dry weather roads only British group 1-2, 3 British group 2-5 American 5,6. Cart, jeep-track, pack-track, foot-path, and trail were not included in the study. Persons with experience in -the area claim the British 2nd class road in Malaya is indeed an all year metalled road. The cart-track and trail are normally unreliable for motor vehicles. Bridges and ferries for larger streamns are available on all the metalled (principal) roads. Fords are not uncommon on the other all weather roads and dry weather roads only. The railroads have bridges, and (normally) displayed cuts, fills, and tunnels. Construction (embankmnents, slopes, etc.) of the railroads are considered at least as good as those of the metalled roads. Distribution of Routes by Type. There is a total of slightly over 24 000 miles of all classes of road and railroad in the study area, 19,700 miles (82%/) in the plains and delta and 4500 miles in upland regions. Of this total 9445 miles or nearly 40%o of the network consists of dry weather roads only. Forty-three percent of the network in the uplands is dry weather roads only while:58- of the net-.ork on the plains is dry weather road. Recall that these totals excluded the network within large cities except for the diameter of the cities. There is probably an additional 500 miles of road and railway in the cities.btit mapping is so inconsistent that.no measure was attempted. Table 20 is the breakdown by class of routes for the entire coastal region by landform type. In addition, by looking at Table 4 vertically we calculated the pcropotion of each route class by landform type. Thus the 158

uplands have 16% of the railroads, 23% of the metalled roads, 8% of the other all weather roads, and 20% of t:he dry weather roads only. TABLE 20 TOTAL MILEAGE AND PROPORTIONS BY CLASS OF ROUTE FOR TRANSPORTATION, I;ETWORKS OF COASTAL STOUTIHEAST ASIA All Weather Routes Dry Weather Total!n_ _ yRoutes Metalled Other all DryWeather Railr oads Roads Weather Roads Only I Roads Only I ________ (P rincipcal) RoadsI___ I.__ Miles % Mles Miles Miles %o Miles Miles Plains | - & Delta 3101 16 5368 27 5692 19 7602 38 19,763 100 Upland. 576 13 1572 36 | 522 7 18534.45 4, 313 100 Total 3677 15 69140 29 1 4014 17 9 59 24,076 100 The reciprocal of these values gives the proportion of each route class in plains and delta areas. Table 21 (a and b) is similar to Table 20, being a detailed breakdown by class of road for each sample area. This Table shows that the quality of the transportation network varies considerably from area to area, The variation in quality of route is very large. This variation is summarized in Table 22 for sample areas by listing the median proportion in each class of route and the range, i.e., the largest and smallest proportions. The variability makes it difficult to make any statements about expected quality of the road. That no mileage was classified as "other all weather road" in Malaya probably means the classification system is faulty-not that this is an actual. characteristic of the routes in that region. Certain patterns can be seen in Table 21. Bqurma has a higher proportion of d.-ry weather roads than the rest of the region. In Burmas something like 75~'- of all routes are dry weather roads only, whereas this lowest class of road accounts for approximately one-third of the total mileage in other areas. North VTietNar also has a higher proportion of poorer roads. Close -to onehalf of its roads are dry weather roads only. 159

TABLE 21 t..;:;CSPORTATION:r;:T'I;CK MILEAGE A'ID PROP.ORTIONS BY QUALITY OF SURFACE EAND CONSTRUCTION I Samp e Area Code Number all weather routes _ dry weather routes Burma (Rangoon) 1 plains upland upo lnd total. 2 delta 3 del ta upland Cot.al 4 plains upland total railroads metalled roads other all _ (principal) weather roads miles percent miles percent miles percent 64 12 62 11 28 5 0 0 7 16 0 0 0 0 0 0 10 6 64 8 69 9 38 5 28 18 0 0 12 8 262 35 163 22 182 25 2 4 24 44 8 15 264 33 187 23 190 24 122 16 102 13 180 23 14 7 8 4 22 12 136 14 110 11 202 21 46 15 58 18 8 3 0 0 6 18 8 24 46 13 64 18 16 5 343 20 946 55 0 0 118 16 493 65 0 0 461 19 1439 58 266 13 1026 52 0 0 112 9 606 50 0 0 378 12 1632 51 262 23 444 39 0 0 76 35 30 14 0 0 338 25 474 35 dry weather roads on lr An. -d. on1' Thailand (west coast) 5 plains up land total miles percent 398 72 36 84 166 94 600 78 112 74 135 18 20 37 155 19 368 48 148 77 516 54 205 65 20 59 225 64 437 25 146 19 583 23 692 35 498 41 1190 37 422 37 112 51 534 40 I I 152 742 54 772 192 317 34 1726 757 1984 L216 1128 218 Malaya (Georgetown (Kuala Lumpur) (Singapore) Totals by land combined form type sample area miles miles 552 43 176 771 152 6 plains up land total 7 plains up land total 8 plains upland total 796 964 351 2483 3200 1346 Thailand

TABLE 21 (Conciuded) Sample Area Code Number 9 plains Thailand upland total (Bangkok) 10 delta upland total _ 11 plains Cambodia upland total o 12 delta upland South VictNam total (Saigon) 13 delta 14 plains upl and up lan.d to tal 15 pl.:lins upland _ total North VietN.un 16 delta upland total _all weather routes railroads metalled roads other all __(principal) weather roads miles percent miles percent miles percent 37C0 59 78 13 48 8 45 56 8 10 C 0 415 59 86 12 48 7 268 31 264 30 56 6 20 83 4 17 0 0 288 32 268 30 56 6 0 0 220 46 134 28 0 0 16 20 20 24 236 42 154 27 0 0 364 36 316 31 24 16 50 33 20 13 24 1 414 35 336 29 92 3 324 11 1500 51 405 21 676 34 372 19 124 21 156 26 124 21 22 7 60 18 62 19 551 19 892 31 558 19 393 26 260 17 174 11 13 12 44 39 2 2 406 25 304 18 176 11 180 6 381 13 682 23 6 2 60 24 46 18 186 6 441 14 728 23 dry weather routes dry weather roads only miles percent 128 21 28 35 156 22 288 33 0 0 288 32 130 27 46 56 176 31 334 33 60 39 394 34 1000 34 519 26 190 32 182 56 891 31 708 46 53 47 761 46 1726 58 138 55 1864 58 Totals by land combined for type sample area miles miles 624 81 705 876 24 484 82 1014 154 2916 1972 594 326 1535 112 2969 250 900 566 1168 2916 2892 1647 3219

TABLE 22 MEDIANS AND RANGES IN PROPORTION OF TR/ANSPORTATION NETWORK IN EACH CLASS OF ROUTE BY LANDFORM TYPES Class of T Plains and Delta | Uplands Total Route 4 Median Range Median Range Median Range Railroad 17% 0-59% 8% 0-83o 17% 0-59% Metalled Roads 20% 0-55% 19% 0-65% 27% 9-58% Other all Weather Roads 10,% 0-51%o 1% 0-24% o9% 0-29% Dry Weather Only 55% 18-74X% 49% o-94,%!. -6% 19-78% Note also that there is no coastal rail connection between Thailand and Cambodia, although one exists at greater than 50 miles inland. Also there is no -iail connection between Thailand and Burma. DIRECTIONAL TRENDS IN THE TRANSPORTATION NEiWVORK A natural orientation or direction suggested in a coastal study is the coastline. Directions parallel and perpendicular to the coastline may be used as a basis for establishing directional tendencies in the transportation network. This orientation is defined in the sample observations by establishing a line from the center of the sample area to the nearest open seacoast. The direction of this line is called the inland-seaward direction. A line perpendicular to it will be parallel to the coast and is called the lateral direction. It is convenient to establish a right and left lateral direction by viewing the sample area from seaward towards the inland direction. A grid coordinate system so oriented with the origin at the center of the observation area divides the area into the familiar positive and negative coordinates where inland and right lateral are-positive values and seaward and left lateral are negative values. The sample observations in.diagram display these directions. A circlular observation area was chosen to avoid a bias in measuring directional mileage, boundary crossings, etc. Intuitively we know what direction means and can conceive of a transportation network that tends to be better connected in one direction than anct her. However, some difficulty is encountered in trying to define an operational definition for directIonal 162

bias. In a map projection, directional distortion is usually defined around a single point; that is, if angles are the same in all directions from any point on a map, no angular deformation exists in the transformation of a coordinate system from a sp1here to a plane and the projection is conformal. Many projections have angular deformation present and Tissot's indicatrix provides one method of measuring this deformation. See for example, Arthur H. Robinson, Elerents of Cartography, New York: John Wiley, 2nd edition, 1960, p. 59ff. We can think of a road network as deforming the accessibility in different directions from any given point, but some radius of observation is required to measure it, The radius of observation may be made infinitely small in a map transformation because of. the continuous nature of the transformation. The road network is a discrete rather than a continuous phenomena over space and Tissot's indicatrix is not appropriate. The problem is to choose a meaningful radius of observation. If the radius is too large the measure will reflect "in the large" influences such as the shape of the study region-the Southeast Asia coastal region under study here being an example of an extremely odd-shaped region. If the radius is too small, the observations will lack data because of -the discrete nature of roads. A 500 square mile area was chosen rather arbitrarily after indications from a pre-test that most samples of this size would contain examples of the road net in the study region. More study is needed on an appropriate radius of observation. Given a lnetwork withi a certain bias, we sus —pect srple measures designed to reveal th at. bias would have 1 arge varianrces if the radius of observation was small compared to the average spacing of the network and that the variance in sampling would decline to some minimum value as the radius of observation was broadened. When "in the large" effects set in, the sample variance would increase again. This implies some best radius. to +" stimate directional trends exists. Proof of these assertions require furthe.r research. In this report, a 500 square mile area is used, which means that directional measures refer to the transportation network in a circle cf just over 12 miles radius around +t.samiP pointsA...^ n:td blCO. J-.l$ d-id no work well in areas of extremely sparse road networks. Directional Trend in Nmuimber of Boundar Points. Using the seaward line to orient the samsple observations, the circumferencre of the circle is divided,nto four arcs, each celtered on one axis of 'the coord-inate system. A count is made of the number of times a road or railroad crosses each arc. The intersections are boundary points and -their sum by direction is a measure of direct.ional'. trend. The absolu-te stum of the righlt and left lateral boundary points divided by the absolute sum of the iniand-se aw.ard boundary points yields a ratio wi..o.h h -e va.lue 1.0 if no directional trend is present. Th-e \val~ue;-.ill be less-tai-o when 4e t r[ is inland-seward and greaterthan-one wh.en the trend is lateral to thable e. shows these clJcuat ions fo:r the sar.ple areas. IC

TABLE 23 DIRECTIONAL TRENDS BY RATIO OF BOUNDARY POINTS Plains and Delta Uplands Sample Boundary Points Ratio Boundary Points Ratio Ara Sum Sum Lateral to Stun Sum Lateral to Coe Inland- Right-Left Inland- Inland- Right-Left InlandNube eaward Lateral- Seaward Seaward Lateral IS-eaward 1 6 17 2.8 1 4 4.0o 1.0 2 5 0.8 5 4.5 2 2 2 1.0 4 8 ) 1 6 -58 7 19 8 29 9 55 29 13 10 12 82 1. 1 4.0o 40 0. 9 57 2.,5 2.0 I b `5 1.4 5 1.5 1.0 9 15 1.4 9 9 5 ) 1.7 - 10 10 1.5; 1.4 * 11 7 1 5 5.0 *I10 19 0. 6 0.9 15 - 00D 1 C; 1.9 6 22 11 0.8 1.8 10 13I 21 55 r) -, 2.1 1.0 1.2 19 Et ir e coastal r eg i.o n 22 175: 214 4.8 0.7 1.2,527 i'-Et roads in Observation area. 164

A predominance of lateral trends is characteristic of both uplands and plains. Four plains and delta areas are nearly balanced including the Mekong and Red River Deltas and the east coast of Malaya. Five areas have over a c2:1- ratio in favor of a lateral orientation. These areas include Rangoon and Singapore zones and certain narrow coastal areas such as in Burma and North VietNam. The narrow coastal valley of South VietNam (area 14) almost reaches a 2:1 ratio in the plains sample-l.9:':L The other areas with narrow coastal valley do not seem to have an unusually high lateral orientation, e. g., area 4, 1.1:1; area 11, 1.4:1. The most extreme lateral orientation in the uplands is in areas adjacent to the narrow coastal valleys (areas, 4, 11, and 15)0 A large portion of the upland roads in these areas is in fact, connecting lowland areas along the coast rather than penetrating inland from the sea. The rest of the upland areas seem rather evenly balanced with some tendency for lateral orientation. An expected inland-seaward orientation did not materialize. Directional Mileage. It is possible to divide a road crossing diagonally to the inland-seaward direction into components of inland-seaward mileage and lateral mileage. Of course, this procedure yields more nileage than a direct measure of the road yields. This is of no consequence, because the objective is again to form a ratio of the sum of the lateral mileage to the sum of inland-seward mileage. The measurements were accomplished with a square-mile grid template covering the area To establish the sum of the lateral road mileage, simply count the number of miles (grid lines) the road crosses in the lateral direction regardless of how far it extends inland-seaward. If a road waves back and forth within a mile in a lateral direction while extending a long distance inland-seaward, to facilitate the count, no lateral mileage is counted. Lateral mileage is counted only when it crosses entirely between grid lines. This procedure tends to underestimate the component mileage, but one might argue that one is getting nowhere on a road that waves back and forth within a mile width anyway. If -the road extends several miles laterally and then doubles back the total lateral mileage is counted. In this sense the road represents two routes for lateral movement. Table 24 is the result of the analysis of directional mileage of the networks The entire coastal region again shows a slight lateral orientation to the transportation network. Although the magnitudes of the directional trends are somewhat dampened by using directional mileage as the index compared to the boundary point index, roughly comparable ranks are found. The rank-correlation coefficient for the two indices is.7, for the plains area. This is a sig:nificant correlation. On the other hand the rank correlation of the two indices for the upland aren is only.05, which is not significant. This low correlation resulted from, such changes between the indices as area 11 going from. the most laterally trending in the boundary count to the most inland-seaward trending in -the directional mileage count. Very small mileage is involved in the calculation 165

TABLE 24 RATIO OF DIRECTIONAL MILEAGE NETWORK BY SAMPLE OF TRTASPORTATION AREAS Plains and Delta Uplands Sanple....... Sample DirectionalMile Aea Directional Mileage Ratio Directional Mileage Ratio Code Inland- Right-Left nlteral to Inland- Right-Left Ineral andto Number Seaward Lateral e.aeaw.ard Lateral Slad ______________ Seaward.Seaward 1 101 1.7 17 5z;I 48 76 2.8 2.2 2 5 4 5 6 7 8 9 10 11 12 153 14 15 i6 coastal region 71 148 117 22 518 433 250 96 150 91 270 1065 255 167 668 64 216 110 34 528 455 321 202 180 94 208 1002 525 296 657 0.9 1.5 0.9 1.5 1.0 1.0 1.3 1.2 1.0 0.8 0.9 1., 1.8 1.0 i1.1 17 44 3o 364 809 162 38 39 155 59 C2 154 1954 14 67 4p 485 761 168 62 24 311 118 161 242,,'~. '7C 9 o.8 1,.5 1. 1.5 0.9 1.0 1.6 0.6 2.0 2.0 2.0 1.5 4422 166

for these areas, apparently too small to be of any significance in the analysis of directional trends. Thus in upland sample areas 1 through 5 and 9 through 12 there are too few roads upon which to make any generalizations about directional trends. This is an area of 62,770 square miles of upland witbh (by actual count) a total of 686 miles of road and railroad combined-slightly over 1 mile of road per 100 square miles of area. From map inspection no directional trend is apparent for this mileage. Sometimes it is a single lateral connector between coastal valleys and sometimes a single spur heading inland. CONNECTIVENESS OF THE TRANSPORTATION NETWORK The road and rail network of the Project Area is now investigated to establish the prevalence of strategic points or alternate routes in the system. These elements depend upon the connectiveness of the network. To measure this property the frequency of events such as intersections, deadends, and sample observation boundary crossings is counted. The relative proportions of deadends to branching, or deadends to connections beyond the sample observation (boundary crossings) are important variables for describing the connectiveness of the network. The number of lines (road segments) incident with intersections is another variable. That is, intersections may be three-way, four-way, or larger. The number of road segments radiating from an intersection is defined as the degree of the intersection. The larger the average degree of the network, the more alternate routes there are and, most likely, the morn interconnected is the network. This is not neces'arily truie however, and a better measure of interconnection is the ratio of road segments to intersections-here called the line density. The matter of the size of the sample observation area is again a problem. There may be a snarl of roads and intersections locally. Two examples of such areas are on a plantation and in a built-up urban area. In these areas, local m&nuverability is great but at the same tim..e there may be but a single connector to the outside-or perhaps no outside links at all. Local connectiveness may be compared to external connection by noting the proportion of boundary points, internal connections, and end-points. In using these measures, the size of the sample area is critical, for it defines a "neighborhood" or local area, The question of what a meaningful neighborhood is has not been answered here. The same 5'00 square mile circular area with a i.2.c mile radiused throughout the study is chosen as the "local area." A set of int+ersections, any one of which is within one-half miles of an-,foPr, s cefined as a cluster. Clusters may often be strategic locations.,xample, tfor a,ilitary point of view, it.ould be fairly simple to control t.wo or ore iItersections within one-half mile of one another. Also clusters norIm.l.y have h1iher degr:ees than intersections giving them greater strategic value in t.-ie net. ork 1t7 I

In summary, the list of the "events" uefined in the network is: clusters, intersections, endpoints, and boundary points, Anal]ysis of the connectiveness of the network did not extend into the upland regions where the roads are so sparse that extremely few observations of branching, endpoints, etc., are possible. Identification of these excluded regions is given in Table 25. TABLE 25 AREA OF VERY SPARSE TRANSPORTATION NET'WORK Route Miles Sample Area Upland in Total Route Country Code No. Square Miles Miles in Sample Observations Burma and M-1 west coast through of Thlailand M-5 59, 567 499 197 Thailand M-9 and through Caubodia M-ll11 998- 187 41 Total 69,55'0 686 238 These areas not included in the gions contain 58^ of the upland routes) analysis of route connectiveness. These rearea and 15% of the upland routes ( 3%o of all Frequency cf Network Events. Table 26 summrarizes the events per 100 miles of route. Twvo groups are distinguished in addition to the regions of very sparse networks. The heaviest networks are in the lowlands of Malaya and the urlands in the Singapore region and the deltas near Rangoon, Saigon, and in North VietNam. In these areas there is, on the average, an intersection, a cluster, or an endpoint just over every two miles. Sturprisingly enough, there is only a small correlation between the density of the network in m.iles per squlaIre mfle anrJ the number of events per 100 miles of roads. The highest net-,work effect is in Malaya where r.any short plantation roads from a complicated network, but with less total route mileage than the delta areas display. The delta areas, on the other hand, havve a fairly high density of road to area, but the network is rather disconnected with endpoints more common. This is due, no doubt, to the emphasis on canal transportation in the delta area. If the canal network is connected, then the road network in the area is broken p into sepa rate components because bridges are not common. The variation in 'he nulmber of components is snown in Table 26 where a component is defined s a co'rnnected port ion of' the net'work found in the.ample observations. 160

TABLE 26 IEiTWORK EVENTS PER 100 MIIES OF ROUTE Total miiles of route (adjusted for urban areas) total evants per 100 miles Network events average — u --- wnumber clusters inter- end boundary of sections points _ pints Icomponents CIrlev 30 s.tat per 100 M1les location Burmi __,n-, oon)_. Malaya (Cuala Lumpur) (Singapore) _ (east cost) Thaiit.ad (eastern coastal, plais) South VietNam (Saigon) North VietNam (Tonkin delta) sample area landform code number type D-2 D-3 delta P-6 plains P-7 plains M-7 upland 2-8 plains P-11 plains D-13 delta D-16 delta average 0C, \10 95 296 854 843 819 510 173 1729 1060 215 192 320 101 270 276 425 484 308 102 143 32.7 49.6 47.0 47.3 53.3 39.6 35.4 45.3 33.3 42.6 23.3 26.6 27.7 27.7 21.4 20.3 26.5 25.0 17.8 14.8 20.3 22.9 4.2 9.8 5.3 5.3 7.7 2.5 1.2 3.4 2.6 4.7 1.9 2.1 1.9 4.0 2.6 1.1 1.6 2.3 0.3 1.0 1.4 1.8 7.4 11.5 18.0 22.3 24.1 18.2 8.1 21.0 14.3 16.1 5.1 7.3 13.4 7.9 6.3 5.1 8.7 8.5 2.9 2.0 3.5 6.4 13.7 20.9 13.0 12.9 14.5 7.5 11.6 11.1 6.2 12.4i 5.6 8.3 3.8 7.9 4.4 5.8 8.9 4.5 6.8 5.9 4.2 7.4 7.4 10.7 6.8 7.0 11.4 14.5 10.1 10.2 9,5 10.7 8.9 8.6 7.9 8.1 8.3 7.3 9.7 7.8 5.9 11.2 8.6 2 3 2 3 1~ 3 2 2 5 5 2 2 3 1 1 2 4 2 2 1 1 Leas thanl 30 evt var,!A0 mtles~ Burua (coastal plains) Maleya _(Bagkok) _ South VietNam P-1 plains P-4 plains M-6 uplands M-8 uplands P-9 plains D-10 delta D-12 delta P-14 plains M-13 upland M-14 upland M-16 upland average North VietNam Very sparse network Very spazse network in uplands of Burma, Thailand, and Cambodia -- sample areas M-1 through M-5, M-9 through M-11, M-15 and the lowlands of west coast Thailand (area P-15).

The regions with an average of 22 events per 100 miles (an event every 14.5 miles) are primarily the long coastal plains throughout1 the Project Area and the delta area around Bangkk- Teradntwr n h angkok region is considerably less dense and complicated than the network in the vicinity of the other large cities in the area. The regilon must depend very heavily on canal t-raffic. The Proportion of Internal aund Do~te rnal Connections and En~dpoints. How often a traveler willbe faced" w.,ith a deadend rather than a choice of routes or an opportunity to leave a neighborhood is indicated by the relative freB yof enpoints internal connections, and boirnclqrv points abe27i a sumbmary of these values- for the sample areas arranged in order of dJecreasing percentage of internal- connections. In all of Malaya a~nd the deltas, excepting that around- Bangkok., over 4k0% of all route events are internal branching. Thffe proportion of.-boundary points is generally inversely related to per-~ centage ofP intlernal, connections. The highest proportion o boundary points is in the coastal r Iplains and uplands where sJimple networks cr1oss th-Ie observation area without- m-uch branching. The percent of endpoints- is not s6I gn Ificanty correlatedl wit-k-h either of these two events. Endtpoints are slightly more common in t~he narrow coastal valleys and upland than, elsewhiere. The exception 1to this observation is the delta region near Rangoon, wrhere 4i2% of the road segm_~r.ents lead to deadends. Thie Line Density of the N,1etwork. The num,,,ber of linie segments in a networik is equal to one-half the sum. of the degrees of the route events, Let q be the numhber of line segments and p be the ntumber1 of points. Define di as the d-Iegree of the ith point. Then, the -above statemient may be expressed as: p q L 2 di; i =1.() The line densit-y of a net-work is the ratio olf numb1-111er ofI- l-ine to one-half t'Uhe ns 1rber of points. The numnber o-fL points is divided by one-half because i-t t-akes two points to estarb-lish each line. Call the line density p; then: q (2) A- I LI I: k 1~ Lu. th ~ere are two sou.,rces- ol- Iin;es-int ernual conc-.ef io~n~ be-t-.een the i) 1)oints anJ -oonecti un from tLhe taointI-s; to t he outside. z be c1es rabie t~o estalL' is the proportiJon of -li ne density contributed ai i4 —rnlal and external1 conneotions. T-I- ould1-,,; als b1~)( Oe desiab Le to copre,Lhe - i n -.Le t ~i ~ec<`(of ars obser'-ed ne t wor' w i t h so me stkandard network. ~T -aof raps S eaim sggest s erttain t' L''~ c-aih is defi ne.3 ~-i set of p' nt ts and lins i which e~ach line is 170

TABE 27 INTERNAL AND EXTERNAL CDONECTIONS AND ENDPOITZS AS A IERCENTAGE OF TOTAL NETWORK EVENIS Perc:ntage of total events on routes a a, ap le int eraal external area ccnnection connections endpoints code (lustrs and (boundary nuZer intersections) points) Malaya, Singapore, lowland P-7 60 13 27 Malaya, Singapore, upland M-7 58 14 27 Malaya, Kuala Luur, upland H-6 55 31 13 South VietNam, Saigon, delta D-13 54 22 25 Malaya, east coast lowland P-8 52 29 ' 19 North VietNia, Tonkin delta D-16 51 31 19 Malaya, Kuala 'Luur, lowland P-6 50 23 28 Burma, Rangoon, delta D-3 43 15 42 Malaya, east coast upland M-8 43 29 29 South VieSIam, coastal plain P-14 43 39 18 Thailand.. coastal plain P-9 42 38 21 South VieStN, delta D-12 39 28 34 Bunna, delta D-2 35 23 42 Burma, coastal plain P-4 35 33 31 South VietNam, coastal plain P-1.5 35 45 19 Thailand, Bangkok, delta D-10 31 41 29 Burnma, coastal plain P-1 30 46 24 Eastern Thailand, Csbodia, coastal plain P- l 26 41 33 North Viet:Nm, coastal upland M-16 24 55 21 South VietHem, coastal upland M-14 20 40 40 South VietNam, coastal upland M-13 18 44 38 I

defined as a segment connecting two, and only two, points. Each point, on the other hand, may have any number of lines incident to it. A planar graph is a graph with points on a plane and pairs of points joined by lines also in that plane such that no two lines intersect except at defined points. The transportation network, as we have defined it, is a model of a planar graph in which the above definitions hold as well as the corndition that every point has at least one line incident to it. The minimum connected graph is one standard to which a real network may be compared. A connected graph is one in which there is a path (a sequenc'y of points and lines) between every pair of points. The number of lines in a minimume c oncted graph is: qmin = p - 1(3) Partition the points p of a graph of the transportation network in the sanmple observations into two sets po = (set of internal points) and p = (set of boundary points). Notice that each point in pb has degree 1. If the nunber of boundary points is b, then the number of line segments connected to the outside is also b. The density of the internal connections of a network is: q-b _ 2(q-b) P 0 o p0 p * (4) The (density of' the minimum connected graph of internal connections is: 2(qomin) -(Po-l) p _ —_ --- * (5) rnPo Po An index of internal density of a network relative to the standard minimum connected graph of the network is then, Po q-b Do mi P -1 (6) Consider the set of boundary points pA as a single point, that is, if a route crosses the boundary of the observation area it is s imply considered t.o be connected to a point designated as "the outside." An index for the total n.etwork is now derived. 2q Pt = po+ ( -) 1Y2

The density of the minimum connected graph with the boundary considered a single point is: (Po+l)-1 2po Ptmin - Pol Po+l * (8) 2 The index of total connectiveness is, then, Pt _ q(9) Dt = tmin Po The indices (6) and (9) are easily calculated for each observation area given a count of the points and their degrees. Table 28 is a summary of these calculations. The indices of line densities may be read as percentage comparisons with the density of the minimum connected graph with the same number of internal points. Networks with indices at 100% are just equal in line density to a graph with a single line from each point. Less than 1000/% values indicate a system is broken into component parts. An uppennr limit on the density index is suggested by the maxi'mum planar graph, that is, -he graph with not more than onre line between any pair of points and with no lines intercepting except at defined points. The maximum number of line q in a planar graph of p points is: qmax = 3(p-2) for p > 2. (10) Given this fact, it is easy to show that the index of maximum density to minimum density connected graph is: Pmax _ 3Po Dna = = p +1, ( 1) D - Pmin - Po+ These values are shown in the last column of Tab]e 28. These values are useful for gauging the extent of connectiveness in the network. The maximum planar. graph is not an absolute i-mit of density on a road network because -more than one route may connect a pair of points. Table 28 is ordered by decreasing values of internal connections. This value is correlated with size of. the network and slightly inversely related to external connections. Aain the Bangkok area is.istinguished by resembling the poorly connected uplands and narrow coastal valley areas more than the airea with the other large cities.. The former rely more on external contacts to exceed the minimumn connected density then do the later which achieve gren'ter internal completeness. 175

TABLE 28 ITMERNAL AMn) BOUNDARY P0ITS, LE SEO'-cTS AND P.EPCENTAGES OF LINE DENSITIES TO LINE DENSITY OF MINI.M CONNECTED NETWOfKS sample cl.usterx endpoints total boundary line area and internal points segments code intersections points number Po b q percentage line percentage density to minimum maximur line connected line density density to minimum internal external total line density Do Db Dr Dmax-min Malaya, Singapore Kuala Lumpur Burma, Rangoon North VietNam, Tonkin delta Thailand, coastal plain Malaya, eastern coastal plain South VietNa=", Saigon Malaya, east coastal upland South VietNam, coastal South VietNam, coastal Z-; South VietNam, coastal Burma, coastal plain South VietNam, delta Burma, coastal plain Burma, delta Thailand, Bangkok Thailand, east coastal North VietNam, upland South VietNam, upland talaya, upland P-7 M-7 P-6 D-3 D-16 P-9 P-8 D-13 M-8 P-14 M-13 P-15 P-1 D-12 P-4 D-2 D-10 P-11 M-16 M-14 M-6 233 261 196 63 180 24 106 421 12 52 30 24 15 44 18 11 17 16 7 3 49 109 342 57 494 123 16 144 299 119 380 57 536 126 15 141 299 111 307 91 477 126 29 155 299 62 125. 22 178- 126 16 142 298 66 246 108 406 122 43 165 299 12 36 22 64 120 58 178 292 38 144 58 225 117 39 156 298 192 613 174 885 116 28 144 300 8 20 8 30 116 34 150 285 22 74 47 129 112 59 174 295 21 51 24 80 112 45 157 294 13 37 31 67 100 81 181 292 12 27 23 48 96 82 178 289 38 82 31 106 93 36 129 296 16 34 17 44 82 47 129 291 13 24 7 24 74 26 100 288 16 33 23 46 72 67 139 291 20 36 25 48 67 66 133 300 6 13 16 24 67 118 185 277 6 6 il 63 59 122 267 12 1l 28 61 55 45 100 295

SUMMARY OF TRANSPORTATION NETWORK ANALYSTS The attempt has been made in this section to define and devise measures for a suf ficient number of properties of a transportation network to establish all of its important characteristics. Network-to-area relations, quality of surface, orientation and connectiveness have been considered. Although the nature of the transportation network in the Project Area has become apparent in the discussion, the value of this section is more in specifying characteristics likely to b? important in any type of transportation network analysis. Further steps are required to make the meas-res presented more iimmediately useful. One such step is to combine these various measures using factor analysis or some similar technique to establisl transportation network types. If the material presented here yielded to a grouping analysis several useful results might become available. Of course, areas could be classified by their transportation network type. We were thinking more of correlating transportation network types with other features and events, nhysical and cultural. For example, the Army is collecting detailed tactical battle histories, eventually for analysis of factors in success or failure of battles. The degree of connectiveness or orientation of the road network could possibly be an influence in such events. Or for another example:, population densities and the road density are very likely highly correlated. An investigation might be made to determine if one could be estimated from the other. The measures presented here were not particularly satisfying. Large variances in the network density. make st-i 1s.ical estimates of road-to-area relations difficult. Lack of consistent sources of data and great variation in quality of the surface and const ruction miake capacity estimates difficult. What is needed here is good information on the capacities of roads under different weather conditions. The nunmber of lanes and at least grades of surface are minimum requirements for capacity est imates. The measures of orientation and connc;t,;iveness are new. They require further development and demonstration of useful:ess. For example, some definition of a "local area" is required because both orientation and connectiveness change with the radius of observation. The Projec-i.Area. One type of transpor`taticn rcute —waterw..ays, did not receive attention. Tack of data prevented any significant comments. It is impossible to tell from the map availab-le whether a stream or can.l Is navigable or not. Nevertheless this omission Ls probably serious for all the delta ar-as i +the study. Some of the smre measures suggested here could be used to analyze a canal network if definitional problems cou.ld be resolved. 175

VIII. NATIVE ANIMALS UAD DISEASES OF IMPORTANCE TO MILITARY OPERATIONS Native Animals The larger carnivors, leopard and tiger, are present in the coastal areas of Southeast Asia particularly in the wooded, brushy, and sparcely populated parts. The estuarian Crocodile inhabits the tidewater parts of the lower rivers. Although these animals can harm men, none are serious menaces to military personnel and except for the exercise of "common sense" precautions, they may be disregarded. Poisonous snakes are common throughout the area both on the plains and in theL hill country; howevrer, the danger they present to military personnel is much less than their niumbers might indicate. Tihey do net "lie-in-wait" for passers by; most are timid, ife are aggressive, and many are nocturnal. In the tropics snakes do not bask in te-e sun as they do in colder climates. Ordinary service clothing which covers legs offers considerable protection against the Flapidae (cobras and kraits ) but less ag.tainst the Virers. Although the danger from poisonous snake.s is small, it should not be disregarded. Someone in cross-country foot parties shLuld be able to recognize the difference between the t wo groups m entioned above, because the first-aid measures required are different, Invertebhrate pests are present and may cause annoyance but not casualties. Large spiders, scorpions, and centipedes can give painful bites but are not at all common.. The worst pes t are land leeches which arc found almost everywhere in jungle, forest, or long grass situations, especially durirg the rainy periods. T,eech-bites are painless but continue to bleed after the animal is removed because of the anticoagulent injectedc The bite is not poisonous but readily becomes infected. Clothing const-:ructed to prevent entrance and impregnated with leech repellant greatly re duces the incide nce of attachment,, Diseases The native- population of s-uthe ast Asia, particularly in the rural areas is in poor hea.lt condition by. Un ted States standards. This condition is a result of many factor c.ef amo.g whi'ch ar. poor die-ts, lack of hygienic k<nowledge ond practices, ina- deueate san ta. ticn, lack of' and indifference to medical treat iment, a-nd const at. ex p osure to food and watfer contamination. Although Ln it.ed States,,litary rsonnel would be with-in the samre environment. they wouli not be subject o any o f t'he above factors. In addition, 1T17

they would have innoculative immunity to some of the common diseases and would come into the environment in excellent health condition. The medical problem in relation to disease, therefore, would be preventive rather than curative in the main. The infectious diseases of southeast Asia are spread by three methods: (1) By insects: malaria, typhus, fil.iarisi, plague, dysentery, dengue fever, relapsing fever, and encephalitis. (2) By contaminated food, water or soil: bacillary cuyeentery, armebiasis, typhoid, schistosomiasis, cholera, Aneylostomiasis, Taenia Solum or Saginata, and Ascariasis (infection with hookwor, -tapeworm, and roundworm, respectively). (5) By social contact: tuberculosis, smallpox, syphilis, yaws, leprosy, trachoma, and diphtheria. Under disciplined conditions of field service it should be possible to protect personnel to a large degree from disease bearing insects, contaminated water and food, and contact with natives. No measures will absolutely be certain and no very effective ones exist against the enteric diseases but experience in this and similar envircnments in World. War II do not indicate that health problems will incapacitate military forces that contain modern medical facilities. Sources: Native Animals and Diseases Simnmons, J., Global Epidemiology, Vol. 1., London (1945). Schwardt, H., List of Arthropods of Medical Importance. Ithaca, N. Y., (1957?). Harrison, Audy, and Traub, "Further Tests of Repellants and Poisons Against,eeches." Med. Journ. of Malaya, 9:1 (1954) pp. 61-71. Walton, Traub, and Newson, "Efficacy of Clot1,ng Tnpregnants NT-2065 and N2066 against Terrestrial Leeches in North Borneo." A-mer. Journ. of Trop. Medicine and Hygiene, 5:1 (1956) pp. 190-196,. U.S. Army, Walter Reed Army Institute of Research, 11-Health Data Publications, Washington. No. 2a Cambodia.o..5 Re.ic of VietNa ' (South VietNam) No. 6 Thailand No. 9 Kingdom of Laos. 178

TABLE 29 A SELECTED LIST OF IN EECTS AND OTHER ANIALS OF L.-PORTANCE IN THE TRANSMISSION OF DISEASE OR AS PESTS IN THE COUNTRIES OF SOUTHEAST ASIA Distribution within country is not regionalized because of lack of necessary iiors:atiopn. Principall" r'-.. Simmons, J., Global Epidemiology, Vol. 1, London, 1945,, and Schwardt, H., Li portance, Ithaca, N.Y., 1957. Distribu.tional symbols taken from references but lack of symbol does not mes presencf: (?) from logical assumption of other dist; l'1,tions. Distritutional Legend: R} rare VC very common or abundant C common 7 probably present Burm Cambodia Malaya Thailand VietNam Mosquitos (1) Culex species * Anopheles minimus (3) A. IMaculatus (5) A. fluviatilis (6) A. hyrcanus sinensis (7) A. sundaicus: (8) Lice Pedliculus capitJ s f'. corporis Phthiris pubis Cr.;e:-a,.!a -ivessia Musca doestesilca Flies of fCurily Tabinidae Cultcoides various species Gnats Siptl-.p.,culina funi cola signata Ticks Typlhus tick Rhipicephalus sanguineus Mites Triombicula Fleas.Xe nopsylla checpis X. ~;^tla Ctenocephalis canis Rodents Mus museUl- us Rattus concolor R. norvegicus R. rattus Th I zomys Snakes dangerous Fit Vipers (22) Kraits (23) NaJa naja (24) N. hannah (25) Vipcra russellii (26) Hyl ophi:ne (2 7) non-malarial malarial malarial malarial malarial r.alarial on natives on natives on natives blowf ly housefl'y horsefl.ies & deer flies Midge flies VC C C C VC VC vc VC C(2) C C C VC C VC C(4) c C C 7? C C C C c C VC(9) C C C(9) C C C C C C? vc C(15) VC(12) VC(15) C C C c( o10) C(lO) C(14) C( 15) 1 (,,s6) c C C C c( 18) C VC C c C(15)? 7 C C(17) C(19) VC C dog tick 0(17) rat flea rtt flea dog flea domestic rat bu own l'st black rat "bamboo rat" to man several species several species co.-on cobra king cobra Russell's viper sea (marine) snakPs c( 18) C(20) VC C VO C C C C C C C c(18) C C C vc c c R R C( 17) c(19) C VC 7?? C C 7? C C C l,'i) C C; 7 C VC VC VC C C C C C C C C C R R R C R R C C C Pests Haemadipsa zeylanica Leeches (28) land leeches Cockroaches (29) Scorpions (o0) FeIl:no osmiSA hairy spider Centlpedev (31) Cther An.mals of Significance (not distributed) Tigers, Leopards, Estuaraer. Crocodile, Sharks, C. C C C VCl VC VC 'C C C C C 7? C C 7 R7. R R Poisoncus Frsh, Retlculated Pythcn. 179

TABPIE 2) (ContinuE1d) NOT CS Mosqluitos (1) Culex species are non-malarial but transmit other disease. There are fifty or more species of Anopheles a few of w!hih carry m.a'riar between persons. All breed in water but of differir.g characteristics so that the species an.e distribut"d in terms of the breeding conditions required. However there are malarial Anopheles in all envioron.en.t;;;nd protection is requi,'d,"vcr.ywhere. (2) Culex fa'.hjnas is the vt-ctor for filariasis. (5) Anopheles m'.irnus live tn fresh rtaning water, seldom in rice paddles or ponds; also found in clear ulpo,] l.ted pits and tank.;, Pre'nu.ed to be the most important vector of ialraria in aititutcs of 1,5O feet and under. Very common in footh-ills. (4) Found below altitude:; of.1.500 feet. (5) Found in water, pool:; of fast stream.s. Mo.;Lly nocturnal but will bite il. daytime if disturbed. (6.) Biabtat and htabit.; about the samune as (5). (7) Fcund in still or s;low vater, oca-..ioially in brackish or in rice paddies. Enters houses by day; most active at night. (8) Usually ne-ar coa:;t isn mny kind of water; bites iday an. night. (0) Particularly abiindir:t.n-ri;c dy season. Lice The three for0.;,; hadl ic?, boly liee, ind crab lice, are comm-on amorg rnat.ives in crowded and filthy conditions, especially in citi,_.. T-'hu':s is tr-.nsm-ittd from: person to person by hume.ra.1ice which do not live on other apmlrs. Flies are found everw'hert tTd,1 tnn '..::;it di.;ease by carrying; filth borne liseases::'echali:ally. 'A.1 fresh provis'ions need protection. (10) plowfliels c ';' t inYi'.;1: of n'.kidn wo..s and carry yaws;, intestinal <ii. eases, and eye i, "t'f t-ion:s. (11) 5.a-e s: (1o) a bov-s.. (12) 1'artic uarly pl.tlfl:l lid 1annoylnEc' i-r. rapiny.;e'a;cn. (.1,) 're il-s n. t!::le cover' ^.r,:ecial 1.y ii r1 iny '.:a.-o,:. Bites ar e tpa nful and e;cough of t!:,n rn.ay c..,;:e itcaeIc t tI, tIon, (l4) uVery S.hI a;id rr.-tiary Fcr',- tnhroung orr.ettin/;. They hbito' vir:cioul:;ty. A.:tino'ying, t niig t wheo t.l';r;, t[- littlh- wind. (1H.') Are;:.ec..'i.n cil vector;1:: 0 5 of d o the eyes., also pcE'.Iibhly of yaw.-;, (16) Tick: are knrown to b, lpre:;"'ntl. in t'he coun.tr'ie'.of:et?.:a:;;t. A';iat A bit rio.ick-borne d1i:;ea:;-e have beern report-d. ()t Trs s: l —p s. ly1 i (t.) Pat lr.-t is. th}e v.'cot.u or' fp.1.gU ( Ci) qt. iri ir" n tit's.' cc, uttrlc' I '.o [:a'. vs.'ctc.r of tr:'opical ty^hu';;. ('C) Fo':.i 1; tno;'t of t:e F o irt c'it.':;. o.,-nt:::-.:' -- o:;::r.on t o':,;~::,i t,':,' '>.:'L:.:l -1;,:,t rr,::, flyingr r. irl;, a:;r.i ric will e. ncotnt re yw;..e: o:tn [:.'1:.F:'t:::;t::! [,; o:t ' 7.ri '' th-,: F.:,::.-;, t: of:!',dit k.l. p. e '.:; C:!c. 1 r,:Si ne paart.. (1) Fo:':. 'cuw 'ort:..::;'te ':t ' i:lot cot.i,':','i,L, g:" o:' tO..!{u, V,:.., ',r'...~ _:O'.''o{J;:;.:, '..::,-.:.':' i o t.t'f:, c',"t ir,.:' '-I t ':: C;:;t.., t, ' '.,r:o:. T. e r.,,: 1.:;: Ir,',I" f. i:o:'::;::"... t,.r r!'.:!'., A C;:, r., C'.t:, ',..:'. '!'.,;'-,' ' ' l 1 -!'' t. i..' ' i: '.'r:':, C * S; 1 *,:.a.fX t l,-lv.. -.:;oh..:.,:..,: I,.: ':...: ' t.. i f t.. it. vii':: '.';. C. ' V.,.-:. ':; z. l:,.:? i'f;::, J t.: k:';.it.;,r I,-::'k,.' ~ ':',':'. -.:,s,:-;. t:.. '.- ~:. c'~:..'.;:"'Ct;:l b;te-. '.., t,,tt',c~: it.:-.,:; t.C.. wI,'.: T:.,-:., k:-.',t...-> <. t-.:;- '.t ' ';:. t.:;c;,.t. )...c,:: ' f._., T;-. 18o

TABLE 29 (Concluded) Deaths from snake bite are sm-r.ll in proportion to those bitten. T.he Pastuer Institute in Bangkok treated 221 persons for snake bite in 1952 whereas the deaths from bites of venomous animals for the entire country averaged 200 between 194'6 and 19-O. if military personnel ]Lave available intelligcat first aid and antivenons, the mortality from; snakes should be infinitesimal. Th: Pastuer Institute in Bangkok produces antivenins for specific snakes anA also polyvalent antivenin for the poisonous species of Thailand. Antivenon should be available quickly to military parties in the field. (P?2) Mainly in the coastal districts or on sandy soils. Some are aborccl. heart-shaped heac.. Usuallyv not aggressive; venom causes pair and swelling but is not fatp.l to men. (25) Smooth-headed snakes, commonly banded or striped. Very poisonous but caue few death; because of:'noffensive disposition and reluctance to strike even when abused. Readily come into houses or tents, even into sleeping bangs. (24) Smooth dark-colored snakes whih flatten neck into a "hood" when annoyed. Some types spit venoma which is injurious to the eyes. The nelurotoxic venom is deadly but statistics show that 40, of those bitten recover without any trtasment, piobably because the snake did not get in a good bite. (25) The king cobra, world's largest poisonous snake, may be 10 to 14 feet long. Lives mostly in open Jungle and is rplatively rare. To str.ike will rear up so that head is six feet or so above the ground. Large a~rount of neurotoxic venom makes this sn?.ke probably the world's most deadly; has been known to attack without provocation. Best defense-a shotgun. (26) V'ry common in Burma and probably also in the inland parts of the other countries. Hemolytic venom is very dangerous. It is said without statistical evidence that Russell's Viper bites more people and causes tore deaths than any other snake.in Asia. (27) Are abundant along the coasts, in inlets and bays. May be disregarded as a hazard. (28) Leeches are perhaps the worst pest and most feared annoyance of the Jungles and forests. They are especially prevalent during the rainy season along trails on the ground or vegetation, awaiting opportunity to attach themselves to passing animals. The bite is painless but bleeds profusely and amy become infected. Leeches can reach the body through difficult passages such as shoelace eyelets, trouser flaps, under beltn. Some work has been done on leech repellents for i.npregr.ting clothirg; if effective it would be very useful to troops in the area. (29) Common everyhwere. Supplies need to be protected. (70) Common and may be found in large. groups. Stings painful but not deadly. (51) Often found in warehouses in ports. May be four or five inches long. Bites are painful but not serious. ll8

TABLE 50 PRINCIPAL CONTAGIOUS DISEASES OF SOUTHEAST ASIA,arp-cterS: Unknovn or not reported Rare - Rather common C - Common VC - Very cornaon WS - Wet season Wb - Wet season beginning We. - Wet season ending Db - Dry season beginning De - Dry season end Cs - Cold season VL - Varies greatly with lo-cality Ep -.:pidemic form End - Endeinic form Burma Cambodia Malaya Thailand VietNm Enteric Diseases TDiseases spread chiefly through the intestinal tract) Dysentery and Diarrhea Amebic Dysentery Bacillary Dysentary Tphoid Fever Cholera HeLminthic Diseases (all diseases due to worms - in intestinal tract, blood, or internal organs) Aneylostomiasis (infection with hookworm) Ascarlasis (infection with common roundworm) Enterobiasis (infection with pinworm) Strongyloidiasis (infection with the remtode Strongyloides Stercoralis - Thread worm) Tainiasis saginata (infection with beef tapeworm Tainiasis solium (infection with pork tapewornm) Trichuriasis (infection with whipworm) Fluke Diseases Optis thorchias is Schistosomilasis Diseases Spread Chiefly Through the Respiratory Tract Influenza Bronchi tis Pneumonia Smallpox Tuberculosis Viral Infections VC VC C VC VC VC C,.WS WS End, De, Wb VC.VC VC RC, VL C, End C R RC, XL RC RC RC, VC Ep, CS VC C, VL VC, AV-L C vc C, US C VL, WS R, Ep VC VC VC VC, VL C RC R VC, VL RC C R Ep VC, Cs End, RC VC RC C vc c C, ws C VL, WS C DS R C, Ep VC VC VC RC, VL C, End R R RC, VL R RC R VC VC, VL VC, VL EC, VL C, VL VC C VC, VL C End, VL, C R VC WS R, Ep, WS VC VC VC RC, VL VC, VL RC C VC, VL EC RC U Ep RC, Ds Ep, RC VC SPC C Ep, Cs VC VC R PC, Ep VC VC, VL R C Di.eases Spread Chiefly by Contact Diseases of the skin Scabies Fungli; Infections Tropical Ulcers C: i tho; to i ss i s l,eproey L.eptosplrosis (Wei.'s Disease, or infectious hepatitis) ab i e s Tetanus Trachoma Venere. l Di seFas-es Char.croid Gonorrhea Gr-anoloma Inguin:ar'le LT'.phog-;.uloma Vernereum S ihilis Dise a:':s..Spread by A\ throro'd S e e:^u I le ev e t F l1 l'l2' i S i' [..equel: 'eh~'-.tl t 5;s)ti VC VC VC C RC C, VL C C RC C, VL VC C ' C RC C RC, VL VC C C C.C R C RC End, VC C C RC C C VC VC VC C VC C C C C C VC, VL, End C C, VL RC RC, End, WS C VC RC C VC C, VL C VC C C C C C RC C RC C C SC, VI, RC, VL VC VC VC VC P.C RC R RC VC, X%. C RC;C 'I. c laps ig ver T,,hu,, Fever -~'F ie:",ic (lou-.e-borne) rm..e ( endemic?c-ub (ai te-borne) C, VL RC, VL V, VL, (Dec), WS RC, End R R R R vc R VC, V,, Wh, 'e R, 'Vi, R Ep C, VL C C,;.nd, VL C VC, VL R V U R C, VL 5, 'L VC, VL. W:': B, VL R.:, (-nU R U R. R R R R (un- R R. Ep (with.diagnosed) ou't corfi r:ation) U U U Yellow Fev-er U 182