LAUSR

Ongoing demands for irrigation, drinking water supplies and hydropower generation encourage human beings to construct dams and reservoirs on rivers. Such engineering structures together with embankments may protect downstream areas from flooding, can give short-term benefits but may degrade the natural or pristine condition of a river by altering the longitudinal and lateral connectivity of water and sediments. This study analyses the human-induced changes in the channel belt and floodplain morphology of the Yamuna River between Wazirabad and new Okhla barrages using topographic maps and satellite image. In the pre-dam condition (1867–1868), the Yamuna River had a highly braided channel pattern compared to the post-dam situation. After construction of the Tajewala, Hathnikund and Wazirabad barrages, the longitudinal connectivity of sediments and discharge were disturbed so that bar areas were reduced and values of the braided index declined. Dam-induced moderation of peak discharges, rapidly growing population, increasing length of embankments and roads in the floodplain are the major reasons behind the urbanization of Yamuna floodplain in Delhi. This study also shows that the increasing length of engineering structure caused a reduction in channel belt area and its width. Results of the present study are useful for the environmentalists, policy makers and earth scientists working on the restoration and management of floodplain between Wazirabad and new Okhla barrage.