Conclu!:ion

There are considerable differences in the geo-environment of the Chao Phraya delta, and the effects of sea-Ievel rise will cause these areas to react differently. If the prompt measure is not taken for the sea-Ievel rise, the following effects may happen in each region.

ln the region of tidallowland along the present coast, vulnerability is characterized by coastal erosion and submergence of low-Iying tidal land. Low elevation of the tidal delta caused by land subsidence may easily be affected by f100dings and the condition will accelerate in response to the sea-Ievel rise.

ln areas of further inland on the deltaic floodplain, the contrast of geo-environment can be recognized in eastern and western flanks in terms of land consolidation. If the drainage function is not enough against the sea-Ievel rise, the eastern flank might become a broad poor drainage area. On the other hand, most natural levees are free from floodings in the western flank of the deltaic floodplain. Serious problems may occur in the part of flood basin surrounded by natural levees..

Further examination should be undertaken using estimation of sea-Ievel effects based on the combination of geo-environmental and socio-economic conditions.

The Chao Phraya Delta: Historical Development, Dynamics and Challenges of Thailand's Rice Bowl

156

Masatomo Umitsu

Acknowledgement

Effect of sea-IevelTiseon the Chao Phraya delta ...

The authors would like to express our sincere gratitude to Mr. Sin Sinsakul, Mr. Suwat Tiyapairach and Dr.Niran Chaimanee for their kind support to my fieldwork in the Central plain. JER8-1 data are used under the permission of RESTEC.

References

Bird,~.C. ~.ltnd Sehwlttfz edl:.(19<l5) The Wotld Coltl:t!ine. Vltn~ol:h1tnd ReinholdCorn~ltny, ~ewYotk, 1071 ~~.

Mllllrnltn, J. D. ltnd !-lltq, B. U. ed. (1996) Selt-Ievel Ri!:!! ltnd Colt!:flll Subl:ldenee. K1uwet Aeqdernie PubJll:he~,

g69M>.

~uhllltylt, P., Young, R. ~., Churnnltnkit, T. ltnd Bult~eng, S. (1996) Lltnd l:ubl:ldenee ln Bltngkok duting

197<l-19~.In Mllllrnltn, J. D. ltnd !-lltq, B. U(ed!:.) Selt-Level RI!:!! ltnd Coltl:tltISub!:idenee, 105-1gO.

Sltbhlt!:tl, S. ltnd SUWlttflltlitt, K. {1996} in Mlllirnltn, J. D. ltnd J-lltq, B. U (edl:.) Selt-Level RI!:!! ltnd Coltl:tltl -S:ubl:idenee, g4g-g56.

Sornboon, J.R.P. (1990)Georno~hologyof the Chlto Phl1tYlt deltlt, Thltilltnd. Ph.D. The!:ll:, Kyofo Unive~'ty, <l6~.

Sornboon, J. R. P. ltnd Thllitrnong,kol, ~. (199g) ~ffeetof !:!!lt-Ieve! tI!:!! on the notth eoltl:t ofthe blght of Bitngkok, Thltllltnd. MltlltYl:lltn Joutflltl ofTf(jf)leql Geo"hy, 24,g-12.

U~CRD/CIRDAP (1992)Develo~rnentof Module!: fot Tlitlnlng on /nfeYJ1ltedAt>~tOlteh fo Df!:lll:fet Mltnltgernent ltnd Reglonltl /Rulitl Develo~rnent Plltnning.U~CRD-C/RDAP wotk!:ho~ ltnd !:!!rnlnltt, Phlt!:!! III, vol. Il, gg4~.

Vongvl~rnllti,S. et ltl, (1996) Coltl:tltl ero!:lon ln the Gulf of Thltilltnd. In Mllllrnltn, J. D. ltnd !-lltq, B. U(ed!:.)

SeQ-Leve! Ri!:e ltnd Coltl:tltl Sub!:ldenee, 1gl-150.

Wltttfek, R. A. ltnd Ahrnlld,Q.K.ed. (1996) The /rn~lIeqt1oh!: of C!irnltfe ltnd~-Ievel Chltnge fot Bltnglltde!:h. K1UWl!t Aeqde.rnle PubJll:~, 415~~.

Photo 1

Land subsidence in the suburbs of Bangkok

Photo 2 Poor drainage area of the deltaic t100dplain in the Chao Phraya delta

The Chao Phraya Delta: HistoricalDeve/opment, Dynamics and Challenges of Thailand's Rice Bowl

MaS8tomo Umitsu

Figures

Effectof soo-1eve! rise on theChao Phraya delta ...

FIG. 1 lANDFORM ClASSIFICATION MAP OF THE CHAO PHRAYA DELTA

CJ ^Mounlamsand~

0 ^PIei.IOC_Surfac.

0 ~F""

0

FloodP\$n llettaic

~ Denaic

tidaIpl.in

8 ^Uppet_~

l<l'lVe' tidaIpIm Nat..aile"""

Ri_sancl -X N'au"a1lev8'eS

Fig. 2

JERS1 satellite image of the eastem f1ank of deltaic flood plain in the Chao Phraya delta.

Fig. 3 JERS 1 satellite image of the western f1ank of deltaic f100dplain in the Chao Phraya delta

TheChao PhrayaDelta: Historiea! DeveJopment. Dynamics anQ-Chafenges of Thailand's Rice Bowl

158

B. Szuster and M. Flaherty Inland low-salinity shrimp farming ...

Inland low-salinity shrimp farming in the central plains region of Thailand

Brian W. Szuster¹ and Mark Flahert/

AB5TRACT: Thailand is the world's largest producer of farmed black tiger shrimp which eamed approximately $2 billion US in export revenues during 1999. The need for large volumes of brackish water to fill pond enclosures has traditionally limited the cultivation of tiger shrimp (a marine species) to a relatively narrow band of coastal land. Thai farmers have discovered, however, that it is both feasible and profitable to grow tiger shrimp in areas far removed from the coast by trucking hyper-sa/ine water inland and mixing it with freshwater drawn from irrigation canals or natural streams.

Small-scale tiger shrimp farms are now common in traditional rice growing areas such as Chachoengsao, Prachinburi, Supanburi and Nakhon Pathom. The development of low sa/inity culture techniques has been a major (actor which facilitated the spread of tiger shrimp farming into freshwater areas. Other contributing factors include the substantial economic profits that shrimp culture provide as compared to rice cultivation, govemment policies that promote shrimp farming as a means of rural economic development, and the be/ief that inland freshwater areas are free from virulent shrimp pathogens.

The rapid development of inland shrimp farm in the Central Plains region has, however, been accompanied by growing concems over the potential environmental impacts associated with this activity. Specific impacts include soil sa/inization, water quality degradation as a result of effluent disposaI, and water use conflicts with competing activities such as rice farming. Although many inland low sa/inity shrimp farms are small (Jess than 1 hectare in size) over 22,000 hectares of pond area were identified in a recent national inventory of this activity. This magnitude of development suggests that inland shrimp farming may have the potential to effect both local and regional soil and water resources.