HEC-RAS simulation of the India Dam Break

Abstract

The February 2021 India dam break in Uttarakhand took away hundreds of lives and destroyed the Tapovan dam in construction. It's hypothesized that the melting of the Kagbhusandi glacial lake north east near the Nanda Devi national park induced flooding along the Dhauliganga river. Debris and mud flow carried by the flood caused significant damage to the downstream Tapovan dam. Using HEC-RAS simulation, we are able to estimate the time at which the flooding arrived at Tapovan dam from the meltdown of the glacial lake at about 31 hours from the onset of the glacial meltdown. Along the flooding path, there are several populated residential areas that could give advanced warning of the flood. In particular flooding arrived at the NPTC Tapovan power station after 18 hours which means at least 13 hours of warning time available for the downstream Tapovan dam. Various magnitudes of glacial lake meltdown are modelled to examine their effect on the flooding pattern down stream of the Dhauliganga river. Water flow arrives at the Tapovan dam at about the same time for the various magnitudes of the meltdown simulated. Global warming is considered as the main cause of the meltdown of the glacial lake. Increased global and local atmospheric temperature has increased the temperature of the glacial ice resulting in higher risk of glacial avalanche and downstream flooding.