The floods of the Lahdar river cause repeated inundations and damage to road infrastructures, particularly crossing structures in the territorial center of Had Msila. Our study involved the application of various methods to estimate flood flows for different return periods along the Lahdar river. The selected flows were chosen after a comparative analysis of values calculated by the different methods used. These results served as the basis for hydraulic modeling aimed at assessing water levels to establish risk zone mapping. This step is crucial in flood risk assessment. Two main approaches were distinguished: hydrometeorological methods, based on regional parameters derived from rainfall data, and empirical methods, used in the absence or with limited data on flood flows in a given region. Hydraulic modeling was carried out using two software programs: a Geographic Information System (GIS) such as Arc-GIS, and a specific river modeling software like Hec-Ras, allowing for the numerical representation of the natural state of the territory. The results obtained serve as the foundation for all river hydraulic modeling, thereby facilitating flood prediction and hydrological risk management in floodplains. Modeling Lahdar river floods in the studied sections enables the prediction of flood risk and its impacts on constructions and infrastructure in the Had Msila Center.