2. Rivers-Structure and Functions

Rivers are the corridors connecting the terrestrial environment to the ocean realm. They play an important role in the sustenance of life systems of nature. As a geological agent, rivers carve out distinct suite of geomorphic features on the surface of the Earth. But human interventions consequent to economic developments in the past few decades have imposed tremendous pressure on rivers. As a result, most of the rivers in the world, especially the small rivers, have been altered to levels, often beyond their natural resilience capability. The present chapter gives a brief presentation of the river environment with special reference to its ecological and geological functions. River sediment characteristics, channel processes, classifications of rivers, and some of the classic concepts in riverine studies are also given in the chapter.