Building a 2-D model for the floods in the inner delta of Niger River

The inner delta of Niger River, a large floodplain of about 30,000 km(2), is flooded every year. Building a hydraulic model is essential to analyze the possible evolutions of the flooded areas, which should be affected by large projects or climate change. The main challenge is to get a DEM accurate enough for hydraulic modelling. The DEM obtained from SRTM provides the ground elevation on a grid 90m * 90 m. In order to describe the channel geometry, this DEM must be combined with cross-sections coming from ground topographical survey. This main network is essentially described by its capacity to evacuate the flood. In the floodplain, the mesh is built to respect the main network. Applying a 1 kilometer side cell in average limits the number of cells and the calculation time. A first test was carried out on the South Eastern part of the Niger delta. Calculation shows a right pattern during the 2000-2001 hydrological events, showing a correct location of overflows and a right propagation in the flood plain.