A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand

Thesis (M.Eng.) - Asian Institute of Technology, 1977

The Central Plain of Thailand is located within latitudes 13° 30'N and 16°00'N and longitudes 99°30'E and 101°30'E. It is bounded on the west by the Tanaosri Range, on the north by the Nakhon Sawan Depression, on the east by the Khorat Plateau and on the south by the Gulf of Thailand. Trend surface modelling study reveals that the landform features of the Central Plain consists of 17 terraces, 2 bahadas, 5 alluvial fans and 2 swells. The landform units were classified into five catergories namely: the Tanaosri Piedmont, the Khorat Apron, the Chao Phraya Plain, the Marine Landforms, and the Structural Troughs and Swells. The Tanaosri Piedmont consists of two pediplains, and two big alluvial fans bridged by smaller ones. The Khorat Apron consists of two bahadas, three alluvial fans, the apron was dissected by the terraces of the Pa Sak and the Hanuman Rivers. The Chao Phraya Plain consists of four terraces and a deltaic plain. The marine landforms consist of four terraces and the Gulf Coastal Plain. The Bang Sai Swell and Bangkok Swell, the Suphan Buri Trough, the Ban Phreak Embayment, the Mae Kong Trough, the Krok Phra Ridge, and the Nakhon Sawan depression are the structurally controlled landforms. On the average corre lation coefficient and goodness of fit values obtained are 0.84 and 70.00% respectively. In the sediment distribution characteristics study it was found that the sands of the Central Plain of Thailand were derived from the mountains of the Tanaosri Range and the Khorat Plateau.