<p>Nature-based solutions (NBS) are gradually emerging as innovative methods for reducing urban flooding, consolidating the resilience of cities and promoting sustainable, In Morocco's Oriental region, the Greater Berkane area has experienced major floods throughout its history, the most destructive being those of 1968, 1986 and 2004. These floods are the result of the conjunction of several parameters, such as the aridity of the climate, with highly variable rainfall intensities; the urban development of Greater Berkane; and the characteristics of its four watersheds (Zegzel, Ouartass, Jaber and Sidi Ahmed).In this context, the assessment of flood hazards is a crucial step in guiding the choice and implementation of nature-based solutions. The main objective of the present work is to evaluate the effectiveness of retention basins based on adaptation to the natural morphology of watersheds, while at the same time being consistent with the assessment of flood hazards. The comparison through modeling is made in order to visualize the impact of retention basins on the hydraulic behavior of floods. The methodology adopted is based on 2D hydraulic modelling using Iber 3.1 software. It is based on the combination of two components: water level and flow velocity. The results obtained for flood hazards show that there are three intensities of runoff during rainfall events or river flooding: high, medium and low. Flood hazards cover most of the town of Berkane and the north-western part of Sidi Slimane Charâa. The results of the retention basins show a beneficial effect, encouraging the search for more environmentally-friendly solutions.</p>