CS(AR)-1/2000-2001 : Dam break study of Myntdu Leska dam using DAMBRK model

Abstract

The safety of downstream area of dam against its possible failure is one of the most important aspects to be considered during the planning, design, construction and operation of the dam. Flood wave due to a failure always assumes large magnitudes and inundates large area in the downstream portion.

The DAMBRK model developed by U. S. National Weather Services (NWS) attempts to represent the current state-of-art in understanding of dam failures and the utilization of hydrodynamic theory to predict the dam break wave formation and downstream progression. The model has wide applicability; it can function with various levels of input data ranging from rough estimates to complete data specification, the required data is readily accessible and it is economically feasible to use, i.e. it requires a minimal computation effort on large computing facilities.

This report presents a study of hypothetical failure of Myntdu Leska dam in southern part of the Meghalaya near the international Indo-Bangladesh border. The maximum water level attained by the dam break flood in the river downstream of dam has been calculated and ascertained for extent of submergence of the area. Also the dam break flood wave characteristics at four different sections downstream of dam is presented for different failure characteristics. The sensitivity studies of the various parameters have also been done to know their effect over the movement o dam break flood wave.

It has been concluded after the study that the spillway capacity is sufficient enough to pass the PMF even when the reservoir is at FRL and therefore the dam will not fail by overtopping. The dam may fail by breaching, for which the study has been done. The reservoir storage is very low while the carrying capacity of the river is very high in general