Change in River Basin Morphology due to Climate Change Led Extreme Flood Event

A flood event in June’2013 in India's higher Himalayas, mainly due to excessive rainfall concentrated in a small catchment area caused a very large transport/deposition of sediments into downstream areas. The region is characterized by a fragile nature of terrain formed by a continuous deposition of sediments caused by glacial retreat due to the impact of climate change. The receding glaciers have left behind large amounts of unconsolidated loose material of rock debris and sediment. Excessive rains/lake burst have caused large quantities of sediments to be mobilized resulting in significant causalities amongst humans and animals. The sediment movement along the Khirao Ganga (tributary of Alaknanda), was temporarily blocked at a number of places. The risk of breaching this feature is anticipated to lead to amplified flood surges down the valley over very short time intervals. large boulders can be lifted and transported down valley and cause clogging of the gates of downstream spillway structures. The paper provides the assessment of the risks of these large deposits being mobilized along the Khirao Ganga at high altitude, and presents possible solutions for safe passage of such large sediment flow through hydro projects. Furthermore, the paper proposes that a comprehensive study of the entire basin be undertaken in order to make an estimate of sediments to mitigate future reoccurrences.