The use of computational models of varied complexity helps to understand the hydrological dynamics studying different scenarios of urban flood. In this perspective, a hydrological model of the Macaé river basin (RH-VIII) was built using the MOHID Land platform to simulate the implementation of a hypothetical attenuation reservoir for flood mitigation in the Macaé urban region. The results indicate that the maximum flows obtained with the simulation from project rainfalls were compatible with values observed in the literature, in the region of interest. The analysis of the flood hydrograms (m3/s) indicates a high efficiency in flood mitigation near the reservoir region, higher than 50%, while at the lower part of the basin, more urbanized region, the attenuation was of the order of 10%.The use of computational models of varied complexity helps to understand the hydrological dynamics studying different scenarios of urban flood. In this perspective, a hydrological model of the Macaé river basin (RH-VIII) was built using the MOHID Land platform to simulate the implementation of a hypothetical attenuation reservoir for flood mitigation in the Macaé urban region. The results indicate that the maximum flows obtained with the simulation from project rainfalls were compatible with values observed in the literature, in the region of interest. The analysis of the flood hydrograms (m3/s) indicates a high efficiency in flood mitigation near the reservoir region, higher than 50%, while at the lower part of the basin, more urbanized region, the attenuation was of the order of 10%.