Estimation of Surface Runoff Hydrograph in Ungauged Basin without Land Cover and Land Use Data

The SCS model is one of most important proposed models for estimation of flood hydrograph in ungauged basins and need to land cover¡ land use¡ physiographical properties and antecedent moisture data but using this model is limited for basins with no access to these data. In this study¡ the lag time based on proposed relation between lag time and time of concentration and estimation of time of concentration based on velocity of flood peak is investigated to overcome to this limitation. The results of proposed model are compared with traditional SCS model in four rainfall-runoff events in Amameh basin using percentage error in volume (PEV)¡ percentage error in peak (PEP)¡ percentage error in time to peak (PETP)¡ and root mean square error (RMSE). The results show the mean of PEV¡ PEP¡ PETP and RMSE for SCS-Proposed models are (-6.35)-(-6.45)¡ (0.97)-(-48.31)¡ (27.38)-(56.08) and (1.4)-(2.55) respectively. Both models tend to overestimation of runoff volume and underestimation of time to peak while conventional SCS tend to underestimate and proposed model tend to overestimate flood peak. Also¡ comparisons of RMSE beside other criteria indicate that with lack of required data for SCS model¡ the proposed model can present relatively estimation of runoff hydrograph acceptable.