FLOOD ESTIMATION IN MUMBAI METROPOLITAN REGION.

Abstract

A dependable estimation of flood in terms of their magnitude as well as their occurrence is very much relevant in developing countries like India. Mumbai Metropolitan Region having a large potential for future growth has been suffering from flood threats at different locations. The present. study is an attempt to estimate the design flood for the aforesaid area keeping in view the national importance of the same. In order to carryout the regional flood frequency analysis for design flood estimation, the annual peak flow data of 12 gauged sites lying in and around the target area have been used for this study. L-moments approach which is the most advanced and reliable technique in this field has been adopted for the analysis. Pearson Type-3 distribution is found to be best fit distribution for the area and growth factors are derived for different return periods after estimation of best fit distribution parameters. The design floods are directly estimated for gauged catchments as a product of growth factor and mean annual peak flood. A relationship between catchments area and mean annual peak flood has been developed for obtaining the design floods at ungauged catchments of the region. Further more design floods with 25 yrs, 50 yrs and 100 yrs return periods have been estimated for four gauged catchments of MMR with relatively short flow record by Regional Unit Hydrograph Approach, given by Central Water Commission, Govt. of India for the hydro meteorologically homogeneous sub-zone No-5(a). The results obtained from different approaches have been compared and the findings are depicted. The study has been concluded by giving the recommendations regarding the adoption of different approaches depending on various possible circumstances within the area.