Calibration of HEC-RAS Model for One Dimensional Steady Flow Analysis—A Case of Senegal River Estuary Downstream Diama Dam

Document pages: 20 pages

Abstract: The Sahelian regions have experienced a drought thathas made them vulnerable to hydro-climatic conditions. Strategies have beendeveloped to reduce this vulnerability. Thegovernments of Senegal, Mauritania, Mali and Guinea have created theOrganization for the development of the Senegal River (OMVS in french) with theaim of realizing large hydraulic installations. This resulted in theconstruction of the Diama and Manantali dams in the Senegal River Basin. Thefirst aims to stop the saline intrusion, the second to regulate the flow of theriver, to allow the irrigation of agricultural perimeters, and to produceelectrical energy. The impoundment of the Diama dam has modified the hydraulicbehavior of the estuary. The purpose of this study is to carry out the hydraulic modeling of the estuary of Senegalriver downstream of the Diama Dam in transient mode by the HEC-RAS software.Two geometric models were constructed on the basis of a digital terrainmodel (DTM) using the Arc-GIS and HEC GeoRAS soft wares after processing thecollected topographic data. The first geometric model, of which the areas ofSenegal river downstream Diama Dam have been represented by cross-section, isone-dimensional. The second one is also onedimensional; in this model, the area of the Senegal River estuarydownstream Diama Dam is introduced as water storage zones. The components ofthese models are the stream sections, lateral links, and storage areas. Theflood hydrograph downstream Diama Dam is introduced as conditions at theupstream limits of the models while the tidal is introduced as a downstreamcondition. After the stability and calibration, the results given by HEC-RAS simulationsare the variations of the water levels, the temporal variations of the flowrates for each section, the maximum flow velocities and the propagation timesof the flood waves. The analysis and comparisons of these results stronglysuggest using HEC-RAS issues as a decision-making tool helping to manage floodsduring times of crisis.