Comparison of Soil Conservation Service Model SCS and the Bennett Soil Moisture Accounting Model (SMA-B) in theFlood Estimation Zard River Basin

This study aims to compare Soil Conservation Service and Bennett Soil Moisture Accounting models in the rainfall-runoff process simulation. To do this، rainfall-runoff data obtained from the Zard River watershed، the East Khuzestan province and the HEC-HMS hydrological model were used. First، the physiographic parameters of the study area were collected and studied. Recorded rainfall data and their corresponding flood events collected from the Mashine station were utilized. Of the data collected، 3 rainfall-runoff events were considered for model calibration and 3 events were chosen to compare the models. The results showed that the SCS model is not capable to estimate losses due to evapotranspiration and surface maintenance. This leads to significant errors in estimating the peak and volume of floods with a long time-base Statistical tests including mean residual error، the remaining mass index، relative error and root mean square residual error as well as the compliance index were used to compare simulated and observed hydrographs. The statistical analyses showed that the hydrograph resulting from the soil moisture model (SMA-B) has a better ranking compared to other models. In estimating the flood peak and volume، the SMA-B model was associated with least differences between the simulated and observed values produced.