Flooding Estimation of Karkhe's Watershed by Using Dicken and Creager Formula

It’s not possible to estimate flooding intense of sub-basin only by using existence data of hydrometric stations because of lack of hydrometric stations on sub-basin and also lack of recorded flood data. To estimate flooding intense, Karakhe’s watershed with 43 thousand km2 was selected. This watershed is located at Lorestan province, west southern part of Iran. Data from 11 hydrometric stations was used to investigate the reaction of sub-basin without recorded data. By using homogenous test, correcting errors or lacks and determining 57 years as common time base on SMADA software, the best statistic distribution model was log Pearson type 3. This distribution model was used to determine flooding coefficient and to calculate planed discharge values in the return periods. Results indicated that planed discharge values was equal to flooding coefficient (kt). Additionally, experiment formula of Dicken and Creager was used to estimate flooding coefficient and then the results was evaluated by calculated results derived from hydrometric stations. The results indicated that Dicken’s formula is more applicable. Values derived from Dicken’s formula are approximately to values with return periods of 2, 5, 10, 20, 25 and 50 years and differences was not significance. Coefficients of experimental formula was also calibrated for the study area and then it is possible to calculate maximum momentous discharge on the sub-basin and used on the ongoing projects.