Abstract
The capital city of Niger, Niamey, is frequently affected by floods resulting from the overflow of the Niger River. In recent years, Niamey has been affected by flash flooding in small watersheds caused by high runoff from expanding urban areas. This study aims at mapping the floodprone areas in Gounti Yena watershed drained by a large ravine (kori). The watershed characteristics were derived from the ASTER DEM data, and the land use/land cover evolution was characterized from Landsat data (1986 and 2018). Statistical analysis of rainfall data and empirical methods have been applied to estimate resulting peak discharges for different return periods. The flow propagation in the kori was simulated with the HEC-RAS 4.1 model. The simulations reveal a risk of overflow caused by rainfall events with a return period of 10 years. These results reveal the relevancy of the combination of different methods for flood risk evaluation and the design of flood management strategies.