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This paper aims to apply the MERCEDES distributed hydrological model with an event-based mode to simulate flood generation in the Wadi Mekerra basin situated northwest of Algeria. This catchment is characterized by a semi-arid climate, convective thunderstorms, and ephemeral flow. The input data are mainly the daily rainfall-runoff and numerical maps such as slope, flow direction, and land use. The comparison between calculated and measured runoff revealed that the MERCEDES performance to simulate flood generation in Wadi Mekerra basin is encouraging and satisfying which is justified by the Nash-Sutcliffe and observations standard deviation ratio criteria. However, the proposed model tends to underestimate peak runoff due to convective rainfall that may be much localized in space. Furthermore, the sensitivity analysis shows that the hydrological response in the Wadi Mekerra catchment depends strongly on the potential maximum retention parameter which is related to the land use type and varies significantly between seasons according to the vegetation cover dynamics, rainfall intensity, and drought.