30. Dam Break Analysis for Ukai Dam in Lower Tapi Basin, India

Dam break analysis provides important input on infrastructure development in any area. Surat city having a population of about 50 lakhs is situated in the lower Tapi basin. Further, important industries such as ONGC, Reliance and Kakrapar Atomic Power Station are situated in the said basin. The effect of the Ukai dam break flow in the lower Tapi basin along with Surat city has been carried out in the present study. The inflow hydrograph coming into the said reservoir has been considered as the upstream boundary, while tidal level at the Arabian Sea has taken downstream boundary conditions to carry out the dam break analysis. Total 190 cross sections are used to model 128 km long Lower Tapi River in the 1D hydrodynamic model (MIKE 11). The developed model has been calibrated for the flood of the year 1998 and validated for 2003 and 2006. The dam break flood hydrograph having peak discharge 2,57,885.9 m³/s is obtained and stage-discharge relationship at different locations is derived. The stage-discharge curve shows the water level 36.3 m above mean sea level at Surat for aforesaid peak flow. The derived stage-discharge curve, flow velocity, arrival time of flood and its duration were obtained from dam break analysis which can be utilized to prepare flood hazard and risk map of Surat city and the surrounding area.