23-Dam Break Flood Simulation in Natural Floodplain Topography with 1D and 2D Numerical Models.

Abstract

Floods due to failure of dams induce widespread damages to life and property owing to its high magnitude and unpredictable sudden occurrence. The response time for such flood is quite small compared to natural floods. Simulation models are most useful approach for prior assess of the impacts of the dam break floods. It is required to be simulated to determine the inundated area, flood depth and travel time of the flood waves so that adequate safety measures can be provided. In this study, dam break flood analysis has been carried out through its' application in natural floodplain topography. A hypothetical situation of failure of the proposed dam on the river Dibang, a Himalayan tributary of the river Brahmaputra has been considered. Two different approaches for selecting the 1D computational natural channel have been adopted here. In one approach, the predictions are made by adopting a computational channel, which considers the floodplain downstream of the dam when River Dibang enters the plain (1D-FP). The other approach considers the river channel of Dibang (1 D-CH). A 2D model has also been developed and simulation results of 1D models are compared with it. Comparable maximum probable fl ood depths are predicted by the 2D and the 1 D-FP models. The peak depth found to arrive earlier in 1D-FP model i.e., time of peak arrivals are estimated smaller compared to the 2D results. In case of the 1D-CH model, flood parameters are highly overestimated compared to the results of the 2D model. 1D model is computationally highly efficient. The runtime in case of the 20 model is 6413% of that of 1D-FP model.