A study of twodimensional flow propagating from an opening in the river dike

Abstract

The North Eastern part of India being situated in a region of heavy rain fall, gets affected by flood almost every year. Frequent occurrence of flood due to failure of river dike has long been a serious problem for this region. However, it will be possible to mitigate the flood disaster if prior information regarding flood movement can be made available. This is possible only through mathematical simulation. Therefore, a two-dimensional numerical model for simulating flood propagation in the said situation has been developed in this study. Two-dimensional continuity and momentum equations of shallow water wave, in conservation form, have been used as the governing equations. Solution for these equations has been achieved by using two-step predictor-corrector explicit finite difference scheme. Though Shock Capturing scheme has been used, numerical computation has been started from an analytically computed initial profile as flow domain lies only on the downstream side of the separating barrier. For obtaining the initial flow surface, a new characteristic based analytical solution has been developed. This new analytical solution gives more realistic results in the concerned situation than the other existing analytical solutions of classical dam break problem. A simple lumped model has been used for obtaining a logical breach width for river dike of Assam. This has been done on the basis of probability analysis carried out on 326 breach record, collected from various places of Brahmaputra and Barak valley. As acquiring real data of flood propagation for this situation appears to be almost an impossible task, experimental data have been generated for verification of the proposed mathematical model. A laboratory setup has therefore been developed for simulating flood movement on the downstream side of the river dike, due to its sudden failure. To investigate the effect of bed resistance on flood propagation, three different bed roughness have been used for the flood plain lying downstream of the separating barrier,...