FLOOD ESTIMATION IN MAHANDI BASIN

Abstract

Mahanadi is one of the major east-flowing peninsular rivers draining into Bay of Bengal. It ranks second to the Godavari amongst the peninsular rivers. Mahanadi is known for its large water potential as well as devastations due to floods. Its 99% catchment lies on two states i.e Chhatisgarh and Orissa. The coast line of this river is highly developed as far as urbanization and industrial growth is concerned. The river steps down to flat land as it reaches Hirakud and passes through mostly populated area where flooding causes great loss to mankind and infrastructures. The information on flood magnitudes and their frequencies are needed for the design of hydraulic structures such as dams, spillways, road, railway bridges and culverts etc. When river flow records are not available at or near the site of interest, it is difficult for hydrologists or engineers to derive reliable flood estimates directly. In such a situation the use of flood formulae developed for the regions is the only alternative method. When the available flow data of a catchment is too short to conduct frequency analysis, a regional analysis is adopted. Our aim remains to form hydrologically homogeneous region / regions from the statistical point of view is considering flow data alongwith available catchment characteristics. The observed values of annual maximum flow data (AFS) is collected for these stations for different length of periods. Available long time data from neighboring catchments are tested for homogeneity and a group of stations satisfying the test are identified. For deciding the homogeneity, the L-moment approach of Hosking and Wallis has been used. This group of station constitutes a region and all the station data of this iv region are pooled and analysed as a group to find the frequency characteristics of the region.