TITLE:
Contribution of Hydrological Modelling to the Quantification of Surface Runoff in the Ungauged Watershed of the City of Bambey (Senegal)
AUTHORS:
El Hadji Ousmane Ndiaye, Saly Sambou, Honore Dacosta, Joseph Sarr, Boubou Aldiouma Sy
KEYWORDS:
Watershed, Rainfall, Bambey, Modelling, Flow
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.13 No.10,
October
24,
2025
ABSTRACT: In recent years, recurring floods in the city of Bambey have caused catastrophic consequences for the lives of the population. Bambey’s vulnerability to flooding is exacerbated by a lack of measurement data, which makes it difficult to understand the hydrological phenomena of its watershed. The objective of this study is to use the HEC-HMS distributed model, which subdivides the watershed into several sub-basins, to quantify surface runoff from the ungauged watershed area of the city of Bambey. The method chosen in the Hec-Hms model is based on defining a production function and a function for converting rainfall into flow after creating the model watershed. The Green and Ampt infiltration model was used for the production function, and for transformation, the Snyder unit hydrograph model was chosen. Next, the meteorological model was created by selecting the SCS method to specify the hundred-year rainfall event at the Bambey weather station as the input rainfall for the simulation. Finally, before running the simulation, the model was carefully calibrated over a control period to ensure that the total flow reached the outlet of the watershed. This rigorous methodology made it possible to determine the water balance and the shape of the hydrograph for the watershed and its sub-watershed. The peak flow rate for the large watershed is 128.3 m3/s, and the runoff coefficient is 27.26% over an area of 94.9 km2. However, the water level is higher in the sub-watershed with hydromorphic soils and gravel beds on marl-limestone. The simulated unit hydrographs show a fairly short rise phase, a flood peak, and a longer fall phase.