An Encyclopaedia of Indian Archaeology v1.c14.s10.t1.1

v1.c14.s10.t1.1

River valleys are the most common and important land-forms in every country. They come into existence as soon as the water on the land begins to flow over the uneven natural surface. Further developments in river valleys take place by the erosion of the bed-rock and the deposition of the sediments thus formed. As each stream carves its own valley several streams in the drainage network form several valleys which coalesce with each other and the resulting landscape presents a topography of hills and valleys. Normally each river valley passes through three stages—young, mature and old—from the source of the river to its end in the sea, lake-basin or some other river. The valleys are deep, gorge-like in the mountainous tract, V-shaped at the lower altitudes, broad and shallow on the plains and deltaic near the sea coasts. Depending on climate, underlying geological foundation and differential erosion of rocks, the stage in the cycle of river life, etc., they develop straight, braided or meandering courses.