A Study of the use of Morphometric variables of catchment area in the regional flood analysis (A case study: Sardabrud, Chalous, Kourkoursar catchment area)

In orther to use morphometric variables of catchment area in regional flood analysis in Sardabrud ,Chalousrud and koukoursar watersheds at first , the basic raw data of annual instantaneous peak discharges for hydrometric stations in the region was collected, then the missing data was filled in and new statistics were generated. A twenty nine-year-statistical period for this case was selected .Then a homogeneity test was conducted by the use of Run test method . The new statistics of the stations was then analysed by the use of current statistical distributions in which Pearson Type III and Log Pearson Type III distributions as the most suitable statistical distribution was selected for the region through which the mean flood discharge of stations was estimated .Moreover, the morphometric variables of basins and sub basins were measured and estimated which consisted of 13 independent variables. After that, coefficient of correlation and significance level test between flood discharge and morphometric variables was conducted. The results of the study show that five out of the thirteen morphometric variables (number of stream channel , length of stream , area of the basin , Horton form coefficient and perimeter of the basins ) are significantly and linearly correlated with flood variable under study in which the number of stream channels with higher R – square (R2) was selected as the best independent variable for the formation of the linear regression equation and also for the estimation of the mean flood discharge . Then , the other significant independent variables were removed from the formation of the regression equation for their multicolinarity .