High plateaus and forested mountains are located to the west of the province, while there are low basins in the center and along the eastern coast. This topography has created 14 river basins including Tapee, Pum Duang, Tha Thong, Tha Krajai, Chaiya, Tha Chang which are the most important basins. All rivers in Surat Thani flow east of the province to the Gulf of Thailand.