Flood forecasting with a dam watershed event-based hydrological model in a semi-arid context: case study in Morocco

Event-based rainfall-runoff mechanism modeling is a very useful process for flood forecasting, in particular at the level of the dam watersheds in semi-arid regions. In this regard, this paper presents a flood modeling application in the Sidi Mohammed Ben Abdellah (SMBA) dam watershed in Morocco, using the HEC-HMS model. The Soil Conservation Service (SCS) Curve Number (CN), the SCS Unit hydrograph, and the Recession were chosen as loss, transform, and baseflow methods respectively. The various frequency floods entering the SMBA dam were simulated using the elaborated model. The results show that it is possible to estimate the volumes of water generated during floods satisfactorily with errors of 6–11%, while the error in peak flow is around 20%. The median NSE, during validation, is 0.58 and the R2 is about 0.67. Sensitivity analysis shows that the runoff volume, the peak flow, and the NSE were found to be more sensitive to lag time and CN parameters. The developed event-based model will make it possible to carry out several simulations allowing the assessment of the North to South Water Transfer Project operation, in particular, the SMBA dam reservoir management during the flood periods.