22-09-2014, 02:38 PM
Abstracts: Flood occurs at Surat city frequently due to sudden release of water from Ukai dam in river Tapi. At the time of floods in river Tapi, Surat city and surrounding regions are most affected. The city has faced many floods since long back. Major flood event occurred in the year 1883, 1884, 1942,1944,1945,1949, 1959, 1968, 1994, 1998, 2002, 2006, 2007 and 2012. The carrying capacity of river is approximately about 4.5 lacs cusecs (12753 cumecs) at present. The effective waterway of river Tapi is reducing day by day with respect to width and depth due to silting and encroachment due to urbanization which also affect the carrying capacity of the river. In this, stability of a segment of lower reach approximately 6 km length of Tapi river between Weir cum causeway and Sardar bridge is evaluated for its carrying capacity in response to discharge and slopes using HEC-RAS software for past flood data. The study reach consists of 24 cross-sections. The study reach consist of residential area with more than fifteen lacs people. The design sections are compared with existing sections and classified as highly critical, moderately critical and critical. The hydraulics model, HEC-RAS is employed to evaluate flood conveyance performance. The uniform flow computation are carried out using HEC-RAS for flood discharges of 1944, 1945, 1959, 1968, 2006, 2007 and 2012. In the present study existing storm drains are not only marked but based on the HEC-RAS water surface elevation computation for various flood discharges, need of flood gates on the storm drains are also assessed. The recommendations will be done based on this study either to increase height of bank or construct a retaining wall at certain sections along the study reach. The present study also recommends installations of flood gates on all the storm drain outlets which are without flood gates. The width of river in no case is encroached as sections are sensitive high floods.