Topographical Analysis of the Southern Basin of the Central Plain, Thailand

Abstract

The Central plain, which develops along the middle and lower reaches of the Chao Phraya, is a strip of land 500km long, north to south, and 100km wide. It is topographically divided into three parts; the Northern basin, the Nakhon Sawan area, and the Southern basin. The Northern basin coincides with the drainage basin of the three big tributaries into the Chao Phraya; the Ping, the Yom and the Nan, and has an elevation ranging approximately from 25 to 100m. In the Nakhon Sawan area three big tributaries join together to form the trunk river of the Chao Phraya, which passes through a narrow valley to the point where the first distributary splits this trunk river. The Southern basin is ocassionally called the deltaic plain and is characterized by flat low lying land less than 15m above sea level and well developed distributaries of the Chao Phraya, such as the Suphan Buri and the Noi. In this paper topographic characteristics and the geohistory of the Southern basin are discussed.