GLACIAL LAKE OUTBURST FLOOD MODELING FOR SELECTED LAKE IN UTTARAKHAND

Abstract

Indian Himalayas stretches for almost 2,400 kms and has a width of around 400 kms. This stretch has approx. 10,000 glaciers in Indian Himalayan boundary which houses few thousands glacial lakes which are growing in terms of area and volume. The recent Kedarnath disaster in Uttarakhand Himalaya in the year 2012 which led to massive loss to both human life and livelihood in surrounding areas is an alarm to the ever increasing threat from those store house of water. This has further increased the importance of GLOF studies in potentially dangerous areas including Indian Himalayas. With this motivation the present study was done for Basudhara Tal located in Dhauliganga Basin in Uttarakhand Himalaya. This basin houses 4 working hydropower projects, apart from many villages downstream. In the present study Glacial Lake Outburst Flood (GLOF) was simulated using 1D moraine-dam breach model. The reason for choosing 1D model over 2D is due to the fact that 1D model produces substantially better results in shallow water conditions and the Basudhara Tal is a shallow lake with average depth of 18 m. The GLOF Hydrograph selected after several combinations of manning’s n value, breach width and failure time is validated through several empirical relations established in the past. Also, the hydrograph has been routed along the course of river in correlation with 100 yr return period flood of 1700 cumec. The peak discharge obtained through the model can well accommodate both the average conditions and worst case scenario as obtained from empirical relations. The current study has produced competitive results as compared to other commercial software like Mike 11.