North Ganga plain

North Ganga plain is a major physiographic unit of the Indian landmass. It extends from the Himalayan terrain in the north to the river Ganga in the south covering about 56980 sq km. It is roughly quadrilateral in shape and is bounded by a northern piedmont belt where water oozes to the surface, followed by a broad belt of swampy lands, depressions and lakes, and finally an aggregation of alluvial fans as all these northern streams bend to form confluence points with the Ganga.

This area is generally recognized as "a water-surplus area". Its surface is characterized by palaeo levees, swamps or flood basins locally called "Chaurs", relict palaeo channels aggraded in varying degrees, meander belts, ox-bow lakes and cut-of loops. Its fluvial geomorphology is dominated from west to east by the Ghagra-Gandak Interfluves, the Gandak-Kosi Interfluves and the western Kosi Fan Belt. Some of these rivers frequently change their channels. Their channels are called by different names in different parts of their courses.