Assessment and Simulation of Glacial Lake Outburst Floods for Dhauliganga Basin in Northwestern Himalayan Region

Abstract

Glacial lake outburst flood (GLOF) is created when water dammed by a glacier or a moraine is released. Some of the glacial lakes are unstable and most of them are potentially susceptible to sudden discharge of large volumes of water and debris which causes floods downstream i.e., GLOF. Many glacial lakes are known to have formed in the Himalaya in the last half century, and a number of GLOF events have been reported in the region in the last few decades. Due to extreme hazard potential of GLOF events, it is necessary to take into account GLOF while planning, designing and constructing any infrastructure, especially water resources projects, as they are located on the path of glacial lake outburst flood wave and would be the prime target in case of GLOF. GLOF modeling may be carried out by either scaled physical hydraulic models or mathematical simulation using computer. A modern tool to deal with this problem is the mathematical model, which is most cost effective and reasonably solves the governing flow equations of continuity and momentum by computer simulation. Mathematical modeling of dam breach floods can be carried out by either one dimensional analysis or two dimensional analysis. In one dimensional analysis, the information about the magnitude of flood, i.e., discharge and water levels, variation of these with time and velocity of flow through breach can be obtained in the direction of flow. In the case of two dimensional analyses, the additional information about the inundated area, variation of surface elevation and velocities in two dimensions can also be assessed. In the present paper, methodology for simulation of glacier lake outburst floods has been discussed. Further, the discussed methodology has been demonstrated in Dhauliganga basin located in Northwestern Himalayan region. For the present case, MIKE-11 model of Danish Hydraulic Institute has been selected in this study because of its modeling accuracy for the slopes steeper than 0.01 and wide acceptability in more than 40 countries.