Assessment of Impacts of Sea Level Rise on Coastal -{ase Studies in Japan and Thailand-

Yukihiro HIRAI*I, Tetsuo SATOH*2, Charlchai tANAVUnx3

Abstract

Global warming is one of the most serious environmental issues of the present day. The average temperature is predicted to rise 1.7'C to 3.8t by the end of the next centu4f. Sea level is also projected to rise 15 cm to 90 cm during the same period. In this paper the authors first present an example of the assessment of impacts of sea level rise of the lagoons in Japan. We also present the common methodology of vulnerability assessment and an original procedure to assess the impact of sea level rise on the Songkhla Lake in southern Thailand. Following this procedure we describe the natural and socioeconomic characteristics of the Songkhla Lake, and we identify major factors that control the development of each natural region. It is most important to clarify the natural and socioeconomic systems and also to identify the development factors at each natural region for the proper assessment of the impact of sea level rise.

various aspects depending on the natural and I. Introduction socioeconomic conditions at coastal area of each . Major thirty-four coastal lagoons in The study on Land-Ocean Interaction in the Japan were grouped into five types (namely from Coastal Zone (LOICZ) started in 1993 as one of Type-A to Type-E) in terms of "artificial littoral the Core Projects of IGBP (International - shoreline" and "intensive land use in littoral low- sphere Biosphere Programme). The objective of land" (Figure I ). LOICZ project is to predict the change of coastal The littoral lowland of type-A lagoon remains environment by global warming in the near almost natural without any artificial structure or future, and also to develop further sustainable land use. This type of lagoon is very valuable in ways of utilization of coastal areas. Four major Japan and important especially for the protection fields of LOICZ research are proposed as follows of wild waterfowl. The Lake Kucharo, for in- (Yonekura et al., 1998): stance, has been registered since 1989 as one of ( 1) Effects of changes in external forcing or the designated lakes of . In boundary conditions on coastal fluxes. the littoral lowlands of type-8, the rate of arti- (2) Coastal biogeomorphology and global ficial littoral shoreline is very low, but aboat 40Vo change. of the area is used for grassland. In the case (3) Carbon fluxes and trace gas emissions. of type-A and -B lagoons, few environmental (4) Economic and social impacts of global changes will be observed when sea level rises change on coastal systems. several tens of centimeters to 1 m. This study focuses on the fourth domain, i.e. to Littoral shorelines of type-C and -D lagoons forecast how the responses of coastal systems to are partly artificial and urban or industrial land global change affect the habitation and usage of use is found in the littoral lowlands. Urbaniza- coastal environments. Hirai (1998), one of the tion has been taking place rapidly for the last two authors, has discussed the impacts of sea level rise or three decades. In the process of development on the coastal lagoons in Japan and presented planning around these types of lagoons, it is nec- strategies against their responses. In that discus- essary to consider carefully the influences of lake sion, he emphasized that the impact would have level rise caused by sea level rise.

*r Department of Geography, Faculty of Education, Ehime University, Matsuyama, Japan. *2 Department of Geography, Kom azawa University, Tokyo, Japan. *3 Faculty of National Resources, Prince of Songkhla University, Hat Yai, Thailand

33 Regional Views No. 12 1999

（ Ｓ ０） 目 ∞ 〓 〓 ｏ

日 ∞ ■ 】 ｏ 〓口 ＥＯ 鉤

η“ 目 重 日 』 ｃ 』 ０ 目 Ｃ ” Ｃ 日 く 目 の ｃ ｅ ョ 』 ３ 。 ε ｏ ∽ つ ２ 。 ０ 目 “ Ｊ １ 。 」 ｏ ｏ 撼 。 “ 0 l0 m 30 .{o 50 60 70 8[) 90 100

Rate of Artificial Shoreline(%)

Figure 1. Relationship between "artificial 511on1 ghslshine" md "intensive land use in littoral lowland" of lagoons in Japan Source: Hirai (1998)

Type-E lagoons are transformed artificially to the greatest extent, and the littoral lowlands are II. Methodology of vulnerability assess- intensively utilized,. Almost all the littoral - ment of the impacts of sea level rise line is artificially embanked with shore protec- tions, and urban land use is predominant. In the 1. Common methodology of the vulnerability case of this type of lagoons, the impact of sea level assessment by IPCC rise on the littoral lowland will be immense, caus- The IPCC common methodology was devel- ing serious damage to these areas. oped by Subgroup of IPCC For the sake of appropriate assessment of the in order to promote vulnerability assessment in impacts of sea level rise on coastal lagoons, it is every country. Aiming at making assessment of most important to clarify the natural and socio- vulnerability on both physical and human aspects, economic characteristics of each lagoon and its the common methodology consists of seven steps littoral lowland. In this paper, the authors first as shown in Figure 2 (Center for Global Environ- show the common methodology of vulnerability mental Research, 1996). According to this meth- assessment developed by the IPCC Coastal Zone odology, a case study area is selected and the Management Subgroup. And an original proce- scenario for sea level rise and climatic change is dure is presented to assess the impacts of sea level presumed at the first step. Based on the data of rise on the coastal lagoons in developing coun- natural and socioeconomic systems (step-2), rele- tries. In this process, emphasis is laid on the vant development factors should be identified identification of development factors at each litto- (step-3). And the assessment of physical changes ral zone. Natural systems and socioeconomic and natural system responses will be conducted as systems in lacustrine lowlands are delineated to the forth step. identify the relevant development factors, 2s Such physical changes may be recognized as shown in the case of the Songkhla Lake in south- inundation or displacement of lowlands, coastal ern Thailand. erosion, intensification of coastal flooding, in-

34 Assessment of Impacts of Sea Level Rise (Hirai et al.)

LERATED STE‖ 酬H皿胤 i器W認暇脚翻器獅gにξ

▼ DEttNEAT10N OF CASE ttDY STEP‐ 2 NATURAL nS¬ いl DATA ― C卜 ECONOMiC,ぼ圧M DATA

▼

STEPo3 1DE卜 1日CAl10N OF離 圧Vノ い DEVELOPME卜 FACrORS 「 「 「 ▼ STEP4 篤瞬響肌」轟 裂織菖S =甦 ▼

わ:LP‐5 FORMULAnON OF RESPONSEttRA薦 IES

▼

籠 P‐6 ASSESSING OF WLNERABIL「 Y AND lr爛 庭RPRETAnON OF RESULTS

▼

鉦 P‐7 1D側 日α¬ON OF NEEDS AND ACl10NS

Figure 2. Common methodology of vulnerability assessment by IPCC Source: IPCC (1992) crease in salinity at , salt water intrusion, area (step-3). change of tide, change of sedimentation patterns, Then the study area is divided into some homo- decrease in the amount of light reaching sea geneous zones through integration of the data on bottom, and so on. On the other hand, the natural and socioeconomic systems (step-4). responses of natural system are supposed to be After that, development factors in each zone will some impact on local ecosystems such as wet- be identified and the impacts of sea level rise will lands, tidal flats, , and coral reefs in the be estimated (step-5). Then the assessment of the coastal zones. Such physical changes and re- impact on the whole lagoon area will be made by sponses of the natural system heavily depend on the synthesis of assessment at each zone (step-6). the natural or socioeconomic conditions of each Finally this procedure is supposed to be applied to lagoon or each coastal zone. That is to s&y, it is other coastal lagoon areas (step-7). In this study, very important to identify the relevant develop- we discuss mainly step-3 and -4 of the procedure. ment factors at each lagoon or coastal zone. IfI. Natural systems in the lacustrine low- 2. Original procedure of assessment of the im- lands of the Songkhla Lake pacts of sea level rise on coastal lagoons Considering the importance of identifying rele- 1. Geomorphological conditions vant development factors, the authors show an It is very effective to know local geomorpholog- original procedure to assess the impacts of sea ical conditions not only for estimation of the area level rise on coastal lagoon (Figure 3). This subject to inundation or erosion caused by sea procedure consists of seven steps that start with level rise, but also for discussion about the rela- collecting both general and detailed data on phys- tionship between natural and socioeconomic sys- ical and human conditions at a study area (step- 1 tems. In this study we classified our study area and step-2). The data on natural system is ar- with such geomorphological units as follows; ranged from geomorphological and hydrological , erosional , swamp, , , viewpoints. In the same w&y, the data on socio- littoral lowland, delta, Holocene lacustrine ter- economic system is analyzed in relation to the race, Pleistocene marine terrace, tower karst and land use pattern and water use conditions of the hill or mountain. Two kinds of remote sensing

―- 35 -一 Regional Views No. 12 1999

Step-1

Collectingof basic data on the case study area (Remote Sensing Images such as LANDSAT, SPOT, JERS, Geomorphological Map, NavigationChart, Land Use Map, General Statistics)

Step-2

Coliectingof cietaiiedciata on the case stuciy area ndMap, Detailed Statistic,s ) I *analysis of the data,Field Survey

Natural Systems Socioeconomic Systems a,Geomorphological Conditions ( t- a. Land Use Patterns Classification of lacustrine lowland) b. Water Use Conditions b.Hy drological Conditions (Rainfa Groundwater, Lake Water ! *mregration

Classification of Lacustrine Lowland Based on both Natural Systerns and Socioeconomi

I -consrcieratrcn

Identification of Development Factors of Each Unit and Assesst'nent of impact of Level Rise

I -svnthesis

of Sealevel Rise on Whole t *Pormulation

ion of the Assessment to other coastal I

Figure 3. Original procedure of assessment of the impacts of sea level rise on coastal lagoon. data, namely LANDSAT 5-TM images and JERS Lake, which is linked to the sea through a narrow I-VNIR images, were used to classify the topog- (Figure 4). raphy in general. In addition, we measured actual Littoral lowlands of the Songkhla Lake can be topography in the field to prepare some cross divided into five zones; ( 1) Beach ridge plain, (2) sections of typical geomorphological units. Thale Noi and its vicinity, (3) Western part of The Songkhla Lake, located on the eastern Thale Luang, (a) Deltaic lowlands of Thale Sap of the Malay , is the biggest Songkhla, and (5) Holocene terraces and Pleisto- coastal lagoon in Thailand. Total area of the lake cene terraces. basin is about I 182 km2 and six or seven times as large as Lake Kasumigaura in Japan. The lake is, ( 1) Beach ridge plain however, very shallow and about only 1.1 to 1.8 A wide and long beach ridge plain is developed m deep in the mean depth. It consists of three between the basin of the Songkhla Lake and the major basins; Thale Noi, Thale Luang and Thale of Thailand. The width of the plain is 3 to Sap Songkhla. Thale Noi is a small lake north of 8 km, and its height is less than a few meters. The Thale Luang. Thale Luang is the main lake, beach ridges are separated 2W to 300 m from being separated from the Gulf of Thailand by a each other in the northern part, but they become wide and long beach ridge plain. Thale Sap closer in the south, about 50 to 100 m or in a Songkhla is the southern part of the Songkhla complex form (Pitmatr, 1985). Number of ridges

36 Assessment of Impacts of Sea Level Rise (Hirai et aI.)

②Thale Phヽ ① Beach ttr P血 ICluan 雅塁

囲 赳 ■ 目 mountain

hiu

③ tower karst

1だKttx31=慟 ne Pleistocene terrace LovJhnd of □ Thale L― g 因 dluvid lowland □ 圃beach 囲 ridge □ tidd flet

mengrov€, Swarnp

water surface

shrimp ｏ 201Cn

ヽG“J/。/Tttlib″ ヽ

＼

⑤ Holocene and Plttme ＼④ DelLic Lowhnd of Thale Sap騎 山 ＼ Terraces 理離 Figure 4. Geomorphological map of the Songkhla Lake Area Source: Hirai ( 1995 ) is reported at four in the north and eight in the measuring actual topography. These ridges can south (Haruyama, 1995; Ookura et al., 1996), but be grouped into 3 or 4 types by difference of their we counted eight ridges in the middle part of the shapes. The height of the top of these ridges is plain and nineteen in the southernmost part when about 2 to 3 m above sea level, being 1 to 2 m

一- 37 -一 Regional Views No. 12 1999

higher than the lowlands between the ridges. 2l0O mm. Heavy rains are observed during the northeast monsoon season from October to De- (2) Thale Noi and its vicinity cember, because the dividing mountain ranges of The area of Thale Noi itself is only 26 kmz, but the Malay Peninsula lie in the north-south direc- a swampy area called Phru Khuan Khreng ex- tion to the west of the Songkhla Lake. tends around the lake over l26km2. This huge The groundwater of this area is found mainly swamp includes covered with various in the following three types of aquifer (NESDB, kinds of aquatic plants, grassland, peat swamp 1985). Shallow but limited amount of ground- forest, and tropical evergreen forest. water is contained in the beach of the beach ridge plain east of the Songkhla Lake and also in (3) Western part of Thale Luang the alluvial deposits of the western coast of Thale Marine or lacustrine lowlands lower than 10 m Luang. On the other hand, a large quantity of above mean sea level are developed along the groundwater is contained in the deep gravel western coast of Thale Luang. These lowlands layers, which have been deposited in the bottom are flooded every year because the lake level rises of ancient river channels formed at an earlv stage up to about 1 to 2 m at the maximum in the rainy of basin development. The third type of aquifer is season. the fractures or solution cavities in the basal rocks or limestone in the west of the study area. (4) Deltaic lowland of Thale Sap Songkhla Present and former river deltas of the U-taphao (2) The lake systems River and the Phu Mi River are developed at the The Songkhla Lake consists of three main lake southern and western coast of Thale Sap Songk- basins; Thale Noi, Thale Luang and Thale Sap hla. The littoral shoreline of this zone is indented Songkhla, and it is connected to the Gulf of due to the development of natural levee along the Thailand through a deep narrow channel to the diverged river courses. The height of this deltaic east of Thale Sap Songkhla. The total lake area is zone is so low, almost the same as the mean lake 1082 km2(Lake Biwa Institute and International level, that the littoral lowland is often inundated Lake Environment Committee, 1988) to 1182 by flooding every rainy season. km2lNESDB, 1985), with about 90 km length from north to south, and 25 km width from east (5) Holocene and Pleistocene terraces to west. Total area of the drainage basin is 6999 A Holocene marine or lacustrine terrace is seen km2(Lake Biwa Institute and International Lake at the height of below 4 m above mean sea level in Environment Committee, 1988) to 8020 km2 the southern coast of Thale Sap Songkhla (Hirai, (NESDB, 1985). 1995; Haruyama, 1995). On the other hand, four Lake water level fluctuates usually from -0.3 kinds of Pleistocene marine terraces are devel- m to +0.3 m above mean sea level. The annual oped at the height of 10 to 50m to the west of the flood peak level is commonly above * I m, but Songkhla Lake. Among these marine terraces, the level rises up to about *2 m in the upper lake the second lowest terrace (T2) covers this area when extreme flooding occurs. There are almost most extensively at about z0m above mean sea no littoral banks or shore protections along the level. shoreline of the Songkhla Lake. The littoral shoreline is not defined so clearly as those of 2. Hydrological conditions Japanese lagoons, and it generally retreats land- Hydological data of the Songkhla Lake, both ward in the rainy season while it advances off- on the drainage basin and the lake systems, were shore in the dry season. collected to estimate the impacts of sea level rise, The lake systems of Thale Noi, Thale Luang especially that of the physical changes such as and Thale Sap Songkhla are described in the intensification of flooding and increase in salinity. report by NESDB (1985) as follows.

( 1) Hydrological conditions of the drainage a. Thale Noi basin Thale Noi has an area of 26km2 and mean The study area is under tropical monsoon cli- depth of the lake is 1. I m. This is the deepest part mate and the annual mean temperature of Songk- of the huge swamp of Phru Khuan Kreng. There hla City is 27.7"C with little seasonal changes. is a low ridge between Thale Noi and Thale The average annual precipitation of the basin is Luang at about 0.5 m above mean sea level, and a

38 Assessment of Impacts of Sea Level Rise (Hirai et al.) connecting river flows across it. But at the time littoral lowlands around the Songkhla Lake area of flooding, two lakes connect with each other are divided into three geomorphological zones; along this boundary for about 13 km. swampy lowland, littoral lowland and deltaic low- land. They are deeply connected with the lake b. Thale Luang systems of Thale Noi, Thale Luang and Thale Sap Thale Luang can be divided into northern and Songkhla respectively. We can find some devel- southern parts of the lake basin by the peninsula opment factors of the study area to assess the of Ko Yai, which is not a true (Ko) but a impacts of sea level rise. The factors to be noted land- connected by . are as follows; The northern part of Thale Luang has an area ( 1) Intensification of flooding at the southern of 491 km2 and its mean depth is 1.8 m. The coast of Thale Luang and the deltaic zone salinity of lake water is predominantly fresh, or of Thale Sap Songkhla. lower than L%0, but it increases above this level in (2) Increase in salinity of both northern and August, September and November. In the years southern parts of Thale Luang. of low rainfall with long dry season or with few (3) Salt water intrusion to the groundwater floods in the rainy season, its salinity is raised and at beach ridge plain, the western coast of may exceed lO%0. The waters of Thale Luang are Thale Luang and deltaic lowland of Thale usually very muddy because of fine suspended Sap Songkhla. loads carried from catchment area or derived Further investigation will be necessary on these from bottom sediments by wave action. matters. The southern part of Thale Luang has an area of 267 km2 and its mean depth is 1.2 m. The lake III. Socioeconomic systems in the lacus- water is predominantly brackish, forming the tra- trine lowlands of the Songkhla Lake nsition zone between salty and fresh systems. Although the salinity level varies from year to 1. Land use year and from season to season, it usually stays at Land use is one of the most comprehensive 5 to l1%oo and exceeds 200/oo in the dry season. In indicators to understand local socioeconomic contrast, it becomes fully fresh in the rainy conditions, and is closely related with geomorp- season. There are some rock in the south- hological and hydrological conditions. Land use ern part of Thale Luang, which suppress wave patterns around the Songkhla Lake are classified action and resuspension of bottom sediments. as shown in Table 2 according to the "Land Use Map of Songkhla Lake Basin; 1996 prepared c. Thale Sap Songkhla with GIS by the Laboratory of Land Reclamation Thale Sap Songkhla has an area of 190 km2 and at the Faculty of Natural Resources, Prince of its mean depth is 1.4 m. The water quality is Songkhla University. usually brackish or salty because this lake is con- According to the land use data on the catch- nected to the Gulf of Thailand through a deep ment area of the Songkhla Lake (Lake Biwa channel. The usual salinity level is 20-3OToo, but it Institution and International Lake Environment becomes fresh in the flood season, or in Novem- Committee, 1988), forest area occupied 24.7Vo, ber, December and January. while agricultural land covered 73.OVo, and settle- At the southern and western , the U- ment area reached only 2.3Vo in 1982. Agricul- taphao River, which is the largest tributary tural land includes paddy field (35.3Vo) and stream, and the Phu Mi River flow into this lake. rubber plantation (37 .7 Vo). Paddy fields are dis- Therefore severe flood sometimes occurs in the tributed mainly in the beach ridge plain and lacus- littoral lowlands of this area. For example, lake trine lowland of the western coast of Thale level rose up to I to 1.2 m, inundating houses and Luang, while rubber plantations are found pri- farm gardens for two weeks in a severe flood in marily on the Pleistocene terraces or hills in the 198 8. west of the Songkhla Lake. But recently, rubber plantations are rapidly spreading by clearing nat- 2. Relationship between geomorphological and ural tropical forest. Typical land use pattern in hydrological conditions each geomorphological zone is described as fol- The features of natural systems in the Songkhla lows. Lake are arranged in Table 1 from both geomor- phological and hydrological viewpoints. The ( 1) Beach ridge plain

39 Regional Views No. 12 1999

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一-40 -― Assessment of Impacts of Sea Level Rise (Hirai et al.)

Table 2. Classification of land use in the Songkhla Lake Basin

Water Surface

Swamp

Forest Natural Forest Melaleuca Forest Peat Swamp Forest Tropical Evergreen Forest

Windbreak Forest

Plantation

Paddy Field Agricultural Land Cultivated Field Orchard

Stock Farm /Shrimp Farming Pond

Urban Area Residential Zone ColmIIlercial Zone lndustrial Zone Public Zone Open Space

In this beach ridge plain, settlements and or- mainly for paddy fields, but the farmers also grow chards, especially of sugar palms, are situated on many kinds of fruit trees and raise chickens and the ridges, and the lowlands between the ridges pigs. Some farmers began fish or shrimp cultiva- are utilized for paddy fields. But many shrimp tion in recent years. They made small ponds have been developed recently mainly in the converted from paddy fields. This zone is charac- northern coastal zone of this plain about 2.5 km teristic of diversified farming, or so-called mixed width from the seacoast. These shrimp ponds farming. were converted from paddy fields or fruit gar- The Khuan Rae River flows into the northern dens. On the other hand, in the southern coastal part of Thale Luang from the west, forming a zone of the plain near Songkhla City, a consider- small delta about 500 m in width, on which Lam able area of lowlands between ridges has turned Pam Resort was opened in 1992. There is an into wasteland without cultivation for the last 5 to amusement complex with some restaurants, a 6 years. In addition to that, severe campsite, a small park and so on. But its physical is taking place in this region. According to our conditions are disadvantageous, as those facilities interview with a resident in Ranot, he had to were almost submerged in December of 1997 move his house twice in the last l0 years because when we visited. People say that lake level in the the coast line has retreated about 35 to 40 m by flooding season rises about 50 to 60 cm higher erosion. than usual. On the other hand, along the western coast of (2) Thale Noi and its vicinity the southern part,lacustrine lowlands are utilized Thale Noi (28 km2) and its vicinity (22km2) for rubber plantations as well as paddy fields and have been designated as a no-hunting area in fruit gardens. Although soil condition of such t975, and are famous for "Thale Noi Waterfowl lowland is not suitable for rubber cultivation, the Park" today. Although this zone is globally im- farmers try to grow rubber trees to earn more portant for the protection of wild birds, some part money by receiving government subsidies. of the forest in this zone has been cleared by local people for timber and fuel wood. (4) Deltaic lowland of Thale Sap Songkhla New settlements with detached urban type (3) W'estern part of Thale Luang houses, or housing estates, have appeared along In this zone, lacustrine lowland is utilized the former river course of the U-taphao River.

-41- Regional Views No. 12 1999

And it is remarkable that a great number of (3) In the delta of Phu Mi River on the shrimp ponds have been built on a large scale one western coast of Thale Sap Songkhla, they use after another along the littoral lowland of the two kinds of groundwater; from shallow aquifer southern coast. On the other hand, a complex of and also from deeper one about 50m in depth. government facilities, such as municipal hospital The former contains high salinity and is used only and college, was constructed recently in the low- for general purposes, while the latter can be utili- land near the new bridge across the lake through zed for drinking and irrigation. Ko Yo. The built-up area with large factories and commercial buildings is rapidly expanding around 3. Socioeconomic characteristics of the Songk- this complex. These lowlands were formerly cov- hla Lake area ered with mangrove and melaleucc forests. Typical land use patterns and water use condi- tions in the study area are examined for each (5) Holocene and Pleistocene terraces geomorphological zone (Table 3). Their socio- Rubber plantation is the most predominant economic characteristics and potential environ- land use on the Holocene and Pleistocene ter- mental problems are described as follows; races, but many "open lands" are recognized in the "Land Use Map of Songkhla Lake Basin; ( 1) Beach ridge plain 1996. In this ffi&p, the land where old rubber The area of shrimp ponds has been expanding trees, aged about 25 to 30 years, have been cle- rapidly for the last two decades from north to ared and left without vegetation is assigned to south along the coast of this beach ridge plain. In "open land". In such "open land", the red soil this area, many palm trees on ridges are dying covering terrace surface will be eroded by heavy because of the increase in salinity of groundwater. rains, and this makes more fine materials flow into On the other hand, in the double-cropping area in the Songkhla Lake in the rainy season. the northern part of this plain, the increase in salinity of the lake water will be a serious problem 2. lVater use when the sea level rises in future because the It is necessary to make a comprehensive survey irrigation system of this area depends on the fresh about actual water use conditions in the study lake water. area for assessment of impacts of sea level rise. But systematic data on water use in this area has (2) Western part of Thale Luang not been collected yet. Accordingly only a brief In this zone, rice cultivation is the most exten- note is presented here as inductive information sive and predominant land use for the moment, obtained from interviews at each location during and normal flooding does not damage it severely. 1997 /98 surveys. It is, however, necessary to pay more attention to ( I ) In the northern part of beach ridge plain, the vulnerability of new types of land use against they can crop rice twice a year owing to the inundation. Some new types of land use, such as government irrigation syst€fr, which utilizes the a resort area, fish farming ponds, grassland for water from Thale Luang. The pumping station is dairy cattle and rubber plantations, have been located on the northeastern coast of the lake. But introduced to the littoral lowland along the lake they cannot use water when its salinity level rises coast. over 1.5%0, as in the dry season of 1990. They say that such a problem arises about every ten years. (3) Deltaic lowland of Thale Sap Songkhla In the coastal area, shrimp farmers use a large Rapid development of shrimp ponds on a large amount of seawater for shrimp cultivation, and scale as well as urbanization in the suburbs of Hat polluted waste water is said to flow into irrigation Yai and Songkhla City are in progress with defor- canals or directly into the Gulf of Thailand. estation of mangrove and melaleuca forests. It is (2) In the middle to southern part of beach important to prevent water pollution caused by ridge plain, local people use more rainwater be- the waste water from shrimp farming and urban cause groundwater from shallow well is salty activities. At the same time, new urban areas except in October. The communal irrigation should be protected from severe floods or long- system, which utilizes the lake water, is also suff- term inundation. ering from salinity problem more seriously than the government system because of its lower loca- (4) Holocene and Pleistocene terraces tion of water intake. Rubber plantations have spread from the top of

一-42 -― Assessment of Impacts of Sea Level Rise (Hirai et al.)

∽ 【 ● ０

】 ０ 】 、 ヽ 、 Ｏ い 一 い 飩 】目 ・】 目 】 目Ｏ Ｃ 目 ロ 【 〓 目 ロ “ “ “ Ｏ Ｏ “ “ “ “ 一 ∽ ∽ ∽ 目 ｏ ” ” ” 目 目 饉 〓 目 口 目 Ｈ 目 〇 】 Ｏ 】 】 ０ 〇 。】 餞 ０ Ｏ ∽ Ｃ Ｏ 】 ０ 目 餞 飩 ０ ∽ “Ｏ ∽ 】 ● 】 ● Ｏ 】 ｏ ＣＯ 】● ０口 Ｏ 】 ｏ ｏ ＞ 目 一 】 ＯＯ 一 Ｏ ＯＯ 一 ＯＯ ＯＯ ゛たｒ０ 目 ゛ Ｏ ゛ 】 ≧ 【 】 ≧ｒ 】 国 』 』 』 』 【』 Ｈ Ｈ Ｆ Ｈ

０ 口 Ｏ 餞 】 饉目 ０ 】 一 】 】 目 “ ｏ “ 〇＞ 』 ０ ∽ Ｏ 〇 ゝ Ｐ ｏ 』 】 “ 】 ０ ↓ 卜 ＼ 】 ０ 一 】】 “ ｏ● “ ヽ 目 口 ０ 口”ゝ Ｐ 〕 ″ 颯 ∽ 目 り 【＼ ” ０ ａ ｏ 。】” 】 ｏ ） Ｏ 】 】 ０ 】 ｏ “ ｂ 卜 出 “ ０ 一 Ｏ ″ ０ “ 一 一 “ 卜 ´ ｐ “ 一 “ ０ ¨ ） 口 【 ¨ ゝ ″ “ ゝ Ｐ 出 目 ≧ 〓 ゝ ″ ● 】 Ｆ ¨ 一 “ 】 ０ Ｑ Ｏ Ｊ ● 目 ● 目 目 一 】 Ｏ ＞ 】 Ｏ ＞ 一 日● 』 ０ ０ “ “ ∽ 脳 ｏ 】 〓 Ｏ “ “ ゝ Ｐ Ｚ 覇 鮨 覇 餞０ ■コ 餞 ∽ 日

「 目● （ ∽ “ （ 目 ０ ０ （ 月 目 “ ■ 】ロ ロ“ 一 日 ● 目 」 嘱 ｏ （ 』 一 出 』 ０● ∽ 】“ ｏ 目０ ゛≧ 〓 増』 ● 目 ● ０ 餞 〓 】“Ｆ 】“ ｏ ｏ Ｏ （ 口 』 ０ 口 】 （ 〇 、 お ● 」 、 Ｃ 〇 由）〓【 魚 Ｆ Ｏ ↓ 餞 〓 ２ 【０ 事 目 口 目 ０】一 Ｓ “ “ ヒδ 一 【 】 】“ 』 一 卜 “ “ ∽ 一】 ｏ 卜 』 】 〇 ０ 目 ” 餞 ０ ρ「 εＯ 餞 〓 “ 】一 】一 の 日 一 一 】Ｏ一 “ 口 “ ● 「 ■Ｌ ） ご 、 ） “ “ 目 】 ｏ● ● 目ｏ 目ｏ 一 】 一 一 目 ● Ｌ ●０ 】 饉“ 目】 ０ 目 “ 饉 ε 餞 』“ ＼ Ｆ Ｏ ● ● ０“ 目目 ● ● 【 “０● 【 一 ∽ 】 Ｏ 】 ● 】 “ Ｏ 一 ｏ “ ０ ● ０ Ｆ声“ ｏ ｏ 【 “ 一 】 ｏ 【 ｏ ｏ Ｌ 口ｏ口】】 ｏ 、 魚 つ ０ 】 ゛ 】 ゛餞 』〔 Ｑ 目０口】 ０“ 餞 餞 ∩ ´口 ・』 】」目“ メ 】 ∽ 】』 】 】〓 「 』 ∽ ｏ 』脳 』 Ｑ 、 、 ０〓 ０ 】 Ｑ 〓 】 ｏ 】 ｏ、 目 ヽ 、 】 一 、 ｏ 口】 】 “ 、 「 】 ∽ ∽ “い 】 口 ０ ０ 、 【 、 ０ ● ● “ 飩 「 一 ● Ｏ∽ ●● 〓 ００ 目ρ Ｏ つ ●● Ｏ 一 ● 】 】 言 』“】“ 綱 【 一 ｏ ●】 』“● 口“ 】 一 一 【 ● ” ● 一 一 ｏ“ つ ● 目Ｃ ｏ ） ● 』 ” ” 吾 ０ “ ヽ “ 餞 餞 “ 】 ０ “ 】 〓 ” ０ “ 飩 “ 日 ∽ ∽ 餞 “ 飩 餞 ０） 』 “ 魚 』 “ 魚 』 ト “ 餞 ぼ 餞 日 ） ） ∽ ∽ ）

。 ０ “ ０ 目 【 ´ “ ↓ ∽ Ｏ ● ∽ “ ０ 目 】Ｏ “ ト “ 一 ●】 ｏ Ｌ 】 】 ０ “ ０ “ （【 ∽ 目 一 “ 目 〓 ●Ｏ Ｏ ００ “ 】 ｏ 目● ∽ ０ 】 【 〓 ∽ “ 口Ｏ Ｏ ぉ“ 卜 】 ０ 一 ００“】 脳 ∽ Ｃ０ 【 】 】 】 ０ 餞 卜 」 Ｏ 餞 一 ＞ ゛ 哺 ∩０ ｏ Ｌ “ ∽ “ ｏ 覇 麟 ∽ ｏ 】 ｏ ＞ “ 目Ｏ 】 Ｏ ＞ 】 一 日 目 ０ ） 卜 】Ｏ ｏ い 一 ａ ０ ｏ 〇 “ ｏ ∽ “ Ｏ ０ “ ∽ ２ 餞 目“● Ｏ● ｏ ｃ 日 国 ０ 目 覇 隠 の 目 一 ↓ ０ ） 幅 ０ “ ヽ 層 ０ 【 “ぉ 己【 Ｑ Ｏ ∽ 〇 目“ ● 口】 Ｏ “ Ｏ● Ｈ 「 【 】 ｏ 〓 ｏｏｏ ｍ ＼ 目“ Ｑ “ ∽ 〇“ 】 一 一 【 ∽ ｏ 目“ ● ゛ Σ ０００ 〓 〓 ∽ ●ｏ∽ “ 日“お∽ ∽ “卜 〓 ” 、 】 】 〓 Ｏ Ｑ 一 ０ “ｏ Ｏ “ぉ ｏ ↓ Ｑ 〓 一 【 Ｏ 一 ∽ ｏ 国 “ “ ” 【】 “ｏ Ｏ 〓 ● ∽ ゛ 】 【 ∽ 目Ｏ ０ 】 ｏ 〓 〓 餞 〇 Ｏ “ Ｚ 】 〇 己 【 ｍ一 ｍ 日 日 ∽ ０） 餞 ト ∽ ト Ｄ 飩 〓 ＞ ・ 】↓ 】 ● Ｃ ０ ｏ 口 ０ 「 ） ↓ 【“ ０ ∽ ● ｏ “ “ 口 Ｑ 】 〓 脳 】 ・】“ “ 日に 〇 【 餞 日 “ 】 お 目 ０ Ｏ ｏ “ 〓 “ ∽ 口 “ ● ∽ Ｑ ●り臓 ● 』 目 “ ａ ０ “ ∽ ０ ０ “ 】 日 目 】 ∽ “ Z ぉ 一 ０ 〓 ｏ ｏ 】 ｏ 【 ｏ Ｏ ９ “ｏ “ 日 【“ （Ｈ 門） 〓 〓 ト 】 ０ ｍ ト ト ト

-43- Regional Views No. 12 1999

目 ０ 】 一 “ 】 ｏ 、 ● 言 ｏ 一 口●目 に お ■ ｏ ∽ 目 ● ｏ Ｏ ０ 〓 Ｈ 己 【 目 ” ｏ 】 】∽ Ｏ “ ∽ ＾ 目Ｏ ∽＾ 員 目 】 四】 目ｏ 】 】 】∽ 〇 ・Ｏ ０ ） ∽ ０ ∽ “ ０ 】】 ０ 目 ＞ 』 ｏ 】 “ 一 員四 」 〇 一 “日“ Ｏ 一 ∽ “０ ∽ ０ “ 【 ０ 、 “ 己 【 一 目 目 Ｌ 一 ０ 】 一 】 〇 ｏ ｏ ∽ Ｃ０ 目 】 〇 ） Ｈ 、 〓 ・一 “ 一 ＾ ● 目Ｑ日【 目 へ “一 口 つ “ ” 』 ０ ０ ） 目 〇 〇 一 日∽ δ 〓 ＾ 】 〇 】一 一 ● 一 目 魚 ０ ● “ ” ＾ 餞 Ｑ ゝ Ｐ 目“ 、 目０ 】 Ｏ 目 口Ｏ 目 一 一 】 ｏ パ ∽ ０ 】 ｏ 【 ０ 嘔 Ｏ 】 、 ∽ “ ０ 事 ） 一 ∽ 一 ＞ｏ 餞 Ｏ ヒ ロ“餞 “＞】 ０∽ Ｏ 】 “ 一 脳 “ ＞ 】 ｏ ∽ ｏ 】 Ｏ “ “ ＣＯ 』 ゝ Ｐ 〔 】 ｏ “ 】 ０ 【 〓脳 ゝ Ｐ 口 【 Ｌ﹇ ０ ● 【 一 一 】 “ “ 一 ●へ ＾ 、 ０ ゝ Ｐ ｍ “ Ｈ ● ゝ ″ 一 〇〇 ０ ∽ 目 餞 “ へ ＯＯ 餞 “ ０ 】 Ｃ 一 日０ 】】 Ｏ Ｆ “＾ ゝ Ｐ “へ ∽ へ Ｆ 出 Ｈ 】 出 目 、へ 目 」 一 陶 い 】“ “ へ ■ ∽ 】 “ ●。 「 ｏ ¨へ ０ “ 。 目』 “、 目 口 餞 目〇 “ ｏ 】 目 目 口 ∽ ０ 』“ “ 】 ｏ 】 】 ■ ∽ 】 一 ≧ ヒ 】 ● ↓ 』一 目 Ｏ 目““Ｎ Ｌ 一 餞 “Ｎ Ｏ Ｃ ス ロ “ ０ Ｑ “ 】 ａ 、 囁 】 ０ 甲 【 】 ∽● 目“ 目“ 』〔 目“ 口 “ 口 】 ｏ ０ ０ 綱 串 ≧ “ ０■コ ρ 一 Ｘ ＯＪＤ 】 】 】 】 ヽ ′ 〓 】 餞 〓 きＤ 〓 ● ０ 目 〓円 たｒ ヌ “ ７ 嘱 ∽ Ｈ ∽ 【 【 り “ 一 一 一 “【

● “ “ 〓 【 〓〓 】 目 ヽ 脳 日【 “ “ 目 目 “ Ｏ “ Ｏ “ “ 】 〓 【 目出 目“● ∽ ∽ 目“ 〓 ａ “ ａ ｍ ” “ 目〇 】 ０ ＞“ 目ｏ 日 目 ∽ ∽ ｏ ｏ ｏ ∽ 覇 ｏ ∽ 【 】 餞 】 “ 】“ “ Ｑ “ 〓 〓 ｏ 〓 〓 “ 】 ∽ 卜』 卜 餞 ∽ 『“ 餞 ■ ↓ 」 ヽ ｈ・ ↓ 】 口 』 』 Ｏ 』 Ｏ ＞】 ｏ 〇 【 ● 〇 目 ｂ ｏ “ 〓 ｒ 〓 嘱 ● ● ● ０ ０ 』 一●● ” Ｏ＞ 口“ 目“ 』 目 “ 目“ り 』 ● 目“ 」 口 ∽０ 】 』 “ 一 ● 【 ● 更 【 目“ 更 ０目 口“ ぉ 】 ０ 、 ぉ て 一 一 卜 目“ Ｆ 〓 ＦＯ Ｆ 】 ０ Ｏ Ｏ 一 ｏ Ｏ ∽ ● 】 】 ０ ０ 口 』 ‐ 目 一 ぉ 日 日 】ぉ 口 ﹇ 】 日 ａ 一 ０ ＞ 口 【 Ч ∽ 】一 Ｏ ０ 賢 ｏ ｏ ０ ● ● Ｆ ｏ 目 ０ 目 ゛ 口 ０ ● ０ 目 ０ 饉 覇 目０ロ 口】 日 ∩ ） ″ Ｍ 】“ 】 ０ 目０ 電 ■ 電 ■ 】 ∽ 】 “ 一 】 】 Ｆ ｏ 一 一 】 Ｏ 一【 一 “ 一 ∽ ロ 一 ∽ ∽ 一 ∽ 〓 】０ ∽ ∽ Ｃ ｎ ∽ “０● ● ∽ ● 一 ● ● ａ ●０ “ ｏ “ ｏ “ Ｏ ｏ “ ０ “ ０ 目“ ｏ “ Ｃ “ ０ 一 【 “ 一 日 一 ● ０ 日 ロ ０ Ｊ一 日 Ｊ〔 ■ ∽ ＞ 〓 ・】 口 】 目】 ｏ【 薇】 Ｏ一 〇 【 目 ０ 目】 Ｏ Ｃ ｏ 目ｏ ロ】 ｏ●】 ｏ ” フ 口 】 ０ 〕 ６【 Ｏ 【 ｏ“ Ｏ 〓 〓 〓 〓 Ｊ ∽ ０ 〓 〓 〓 Ｊ 〓 〓 一 】 言 言 一 一 一 】Ｏ ゛ “ 一 一 Ｏ ⊇Ｚ ●０ ” 】 ⊇ Ｚ ョ 】 Ｏ ０ ． Ｏ Ｑ 調 〇 Ｏ 寸 Ｚ一 Ｚ ト （【 Ｚ 一 ∽ ∽ ∽ ∽ “ ０ 饉 【 ´ 】 ● “ 】 ト “ ０ 【 〓 ０ ０ “ 喜 “ ＣＯ む ｏ Ｏ口 ∽ 一 ａ 目ｏ ＞目 Ｏ “ Ｎ一 目 “ “ ∽ 【 “０ ｈ ● ｏ 】 ↓ 】 】 口 “ Ｏ ＞ 】 目 〓 “ 】 ｏ 】 Ｏ Ｏ 【 餞 一 “ 」 “ 】 Ｆ ０ Ｏ ″ 〓 」 目０ 〓 目 卜 〇 ∽ Ｑ 】 ● 一 ， “ 〓０ 』 】 口 “ ０ 餞 ｏ “∽ 日 目“ 一 ｏ 】“ て 】 ｏ ｍ ＦＯ ｏ ∽ ● 】 餞 】 轟 ０ り 〇 ａ 一 餞 】 ワ 口』 ０ 角 ０ ヽ 】 〓 Ｏ “ ¨ ｏ “ ｏ 【 一 一 ０ “ ∽ 】 一 〓 ｐ Ｏ Ｏ ｍ ト ≧ （【 Ｚ Ｆ

一- 44 -一 Assessment of Impacts of Sea Level Rise (Hirai et al.) the terrace to both hilly areas and lacustrine Agency of Japan (Grant No. B-12, Project Man- lowlands. Soil erosion may become more severe ager; Hiroyuki Kawaguchi of Geographical on the slopes and greater amounts of fine materi- Survey Institute of Japan). als will flow into the lake and deposit there in the rainy season. References fV. Concluding Remarks Center for Global Environmental Research. 1996. Data Book of SEA-LEVEL R/,SE. 88p. Envi- The final goal of this study is to make an ronment Agency of Japan. assessment of the impacts of sea level rise on the Haruyama, S. 1995. Geomorphological features coastal lagoons in developing countries. For the of the of the Songkhla Lake. Scr. first step of this study, the authors presented an & Tech. (Journal of JIMSTE\, 8(3), 2l-29. original procedure of assessment. And as a case (in Japanese). study following that procedure, the data on both Hirai, Y. 1995. Geomorphological Features and natural and socioeconomic systems in the lacus- Environmental Problems Around Songkhla trine lowlands of the Songkhla Lake are collected Lake in South Thailand. Mem. Fac. Ed. Ehime and analyzed. According to our study, the lacus- Univ., Natural Science, 15(2), 1-16. (in Japa- trine lowlands can be divided into eleven distinc- nese with English summary). tive geographical units, and the development fac- Hirai, Y. 1998. Koshyo no kaihatu-riyou to kan- tors of each unit are identified tentatively as kyou-hozen (Development and environmental shown in Table 4. preservation of coastal lagoons). In Mizube- Lacustrine lowlands of the Songkhla Lake are kankyou no hozenn to tikeigaku (Preservation classified into four zones from geomorphological of environment of waterside and geomorphol- and hydrological viewpoints; Beach ridge plain, ogy), €d. Geomorphological Union of Japan, Thale Noi and its vicinity, Western part of Thale 86-111. Tokyo: Kokon-shoin Ltd. (itr Japa- Luang, and Deltaic lowland of Thale Sap Songk- nese). hla. Each zone except Thale Noi and its vicinity Lake Biwa Institute and International Lake Envi- consists of some distinctive sub-units with differ- ronment Committee. 1988. Lake Songkhla. In ent land use patters and water use conditions. Sur-vey of the State of World Lakes Interim And development factors were reasoned from Report I ASI-2, l-I4. natural and socioeconomic features of each unit. NESDB (National Economic and Social Devel- In order to carry forward this study for more opment Board), and National Environment precise assessment, it is necessary to identify the Board in Thailand. 1985. Physical Natural and development factors more precisely with the help Human Resource of the Basin. In Songkhla of more systematic data on both natural and Lake basin planning study, Final Report, vol. socioeconomic systems. More detailed compari- 2, Annex A. son with the case of lagoons in Japan as well as Ohkura H., S. Haruyama, S. Vibulsresth, and more intensive use of GIS data with discussions in T. Simking. 1996. Geomorphological Land the field survey would be helpful to elaborate the Classtfication Map of the Songkhla Lake and procedure of the assessment. Its Vicinity. Natural Research Laboratory for Earth Science and Disaster Prevention Acknowledgements (Japan). Pitman, J. I. 1985. Thailand. In The World's The authors wish to thank the staff of the Coastline.ed. E. C. Bird and M. L. Schwartz, Laboratory of Land Reclamation, Faculty of 771-787. Van Nostrand Reinhold Company Natural Resources, Prince of Songkhla Universi- Inc. ty, for their helpful advice and kind cooperation Yonekura N., H. Kayane, N. Mimura, and T. to our field survey around the Songkhla Lake. Yanagi. 1998. Recent Japanese Activities Re- This study was financially supported by Global lated to the IGBP-LOICZ Project. Global En- Environment Research Fund from Environment vironment Research, vol. 1, no. I &2, I-9.

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