Fluvial geomorphology of Indian rivers: an overview

The rivers of India reveal certain special characteristics because they undergo large seasonal fluctuations in flow and sediment load. The rivers are adjusted to an array of discharges, and most rivers exhibit morphologies that are related to high-magnitude floods. In the last 100 years primarily hydraulic engineers have contributed to the understanding of the fluvial forms and processes. Though this trend has continued even today, in recent decades some interesting fluvial research has also been carried out by earth scientists. Four large rivers, namely Brahmaputra, Kosi, Indus and Narmada, have received greater attention from fluvial geomorphologists.The major themes in Indian fluvial geomorphology include the hydrology of monsoonal rivers; forms and processes in alluvial channels; causes of avulsion, channel migration; and anomalous variations in channel patterns; dynamics of suspended sediment; and the geomorphic impacts of floods. Studies of bedrock channels are far less than similar studies in alluvial channels. Only a few rivers have been investigated in this respect.Studies indicate that the Himalayan rivers are different in many respects from those of the Indian Peninsula. The former occupy a highly dynamic environment with extreme variability in discharge and sediment load. Earthquakes and landslides also have a great impact on these rivers from time to time. Consequently, the rivers are characterized by frequent changes in shape, size, position and planform. In comparison, the adjustments in Peninsular rivers are less frequent and of a much smaller magnitude.An inescapable conclusion is that in the tropical monsoonal environment, large floods are important geomorphic agents that temporarily affect the forms and behavioural characteristics of some rivers, but leave a lasting effect on others. In magnitude-frequency terms, large floods are major formative events in many rivers of the Indian region in general and the Indian Peninsula in particular.