Analysis of Regional Floods on the Common Base Time (963-2003) In Hydrometeric Stations A Case Study of Southern Sistan & Bluchestan Province, Iran

The regional flood analysis was used for estimating magnitude of flood in ungagged watersheds or on watersheds withless than 0 to 20 years of flood data. The study area is located in the south of Sistan and Baluchestan province and its area is 27,654 square kilometers. In this paper, maximum instantaneous discharge of five hydrometric stations has been studied over the 963-2003 period and after testing data homogeneity by using the log Pearson type distribution that has been detected as the most appropriate distribution, maximum instantaneous discharge for various return periods was obtained. It also, 20 physiological characteristics of watersheds in the upstream stations was calculated by Arc GIS software and using cluster analysis, watersheds was classified into three homogeneous groups. By using multiple regressions, physiographical models were specified for all return periods. In this models, equivalent rectangle width, maximum height of river, concentration's time and curve number are more effective factors to estimate maximum instantaneous discharge with various return periods and by increasing maximum instantaneous discharge the effect of three parameters including equivalent rectangle width, maximum height of river and concentration's time are increased whereas the effect of curve number parameter is decreased.