The Effect of Storage Coefficient in Flood Routing A Case Study of Kasilian Watershed, Mazandaran Province

The present study was conducted to study the effect of storage coefficient on estimating the output hydrograph in a watershed which lacks basic data, using time- area method and Clark’s model. To this end, the time area histogram was determined by ArcGIS and the topographic map of the area. Then, using rain gauge data and time-area method, the output hydrograph was estimated. In the next step, the obtained results were compared with the observed output hydrograph. The Clark instantaneous unit hydrograph was also estimated by using storage coefficient in order to simulate the hydrograph in Kasilian watershed. As for the unit hydrograph, the statistical values of root mean square of error, bias in peak discharge, coefficient of efficiency, and relative errors in peak discharge, time to peak and base time were 1.64, 0.90, 0.76, 11.38, 33.33 and 15.38%, respectively. The results showed that Clark’s model was more efficient compared to time area method which is indicative of the effect of storage coefficient on flood routing in Kasilian forest watershed. Therefore, this method can be used to accurately estimate the output hydrograph in forest watershed when there is a lack of basic data.