Evaluation of Synthetic Unit Hydrograph (SCS) and Rational Methods in Peak Flow Estimation (Case Study: Khoshehaye Zarrin Watershed, Iran)

The leakage of statistic and data of hydrometry gages is the one of basic difficulties in peak flow estimation with different return periods, because of this estimation of peak flow in these gages are more importance. Khoshehaye Zarrin watershed did not have any hydrometry gages So, the present research is conducted with goal of determining amount of peak flow with two methods that mentioned in the title, firstly we calculated the run-off coefficient and rainfall intensity in each sub basin with Rational method, then with calculating of run-off height by curve number, peak flow was calculated for each sub basin and according to this, the dimensionless unit hydrograph was drawn. For assessment of accuracy of these two methods, we compared their results with nearest gage. The results showed that SCS method has accurate estimation than Rational method and it can be used for peak flow estimation in the similar condition watersheds.