CS(AR)-15/99-2000 : Dam break analysis of Ghodahoda project, Orissa

Abstract

The past failure study is a needed exercise to be made for assessing the flood magnitude and their behavior downstream of the river valley so as to make a preparatory plan to safe guard the lives and properties on the flood plains of the river downstream of the dam structure. To estimate the amount of flood discharge reaching at different sections along downstream channel, a large number of mathematical models are reported in the literature. One of these models, `DAMBRK' developed at the National Weather Service, USA is the most widely accepted model for it's various capabilities and advantages. The model could be employed in different levels of data availability and is reported to be efficient in computing the flood hydrograph after the breach.

The present study reports a hypothetical dam-failure study using DAMBRK model, which was carried out for simulation of flood wave in downstream of the Ghodahoda project, Orissa. Ghodahoda project is rock-filled earthen dam located in one of the tributaries of the Rishikulya River basin of Orissa State. The data used for the analysis included elevation details of the spillway and dam, spillway-rating table, elevation capacity table for the reservoir, design hydrograph for dam and cross sectional details of various downstream reaches. From the simulation, it is observed that the outflow peak over the spillway is 1776.4 cumec. The dam break flood reaches a peak discharge of 4402.9 cumec at the dam site in half an hour and the propagated flood downstream of the dam travels 28.43 km in 4 hours with a peak discharge of 3359 1 cumec. A sensitivity analysis was also carried out to study the effect of most influencing parameters such as breach length, time of breach and bed roughness, on the flood wave propagation. The analysis resulted that effect of the parameters has mere effect on the dam break flood characteristics.