Pantnagar Journal of Research

Abstract

Dams have been built for many reasons such as irrigation, hydropower, flood mitigation and water supply to support the sustainability of humanity since the golden age. However, if huge amounts of water are released during the dam breach unexpectedly, it may adversely impact the downstream population and ecosystem. The prediction of the dam’s breach geometry is crucial in studies of dam breaking. The hydrograph characteristics of the flood resulting from breaching of the dam mainly depend on the geometry of the breach and the formation time of the breach. The sensitivity analysis was performed on the Ramganga dam which is located in Pauri Garhwal district of Uttarakhand, its latitude and longitude are 29031’10"N, 78045’31"E to assess the effect of breach width on the resulting flood hydrograph. HEC-RAS model was used to calculate the effect of breach width on flood hydrograph. In the present study the breach width (Bavg.) was increased and decreased by 25%, 50% and 75%, respectively. Flood hydrograph was estimated at five different locations: Kalagarh, Harewali, Afzalgarh, Dilari and Moradabad, located at 2.5 km, 25.4 km, 16.9 km, 61.2 km and 94.5 km downstream of Ramganga dam, respectively. Sensitivity analysis was performed with Froehlich method with the mode of overtopping failure and maximum operating level at 365.3 meters above sea level. It has been observed from the results of sensitivity analysis that the percent change in peak discharge is high corresponding to breach width i.e., peak discharge is directly proportional to breach width.