Development of a time-varying MODIS/ 2D hydrodynamic model relationship between water levels and flooded areas in the Inner Niger Delta, Mali, West Africa

Abstract

Study region: The Inner Niger Delta (IND), Mali, West Africa, is a vast floodplain with abundant natural resources that supports the livelihood of about two million people. Ecosystem services in the IND are strongly affected by flood dynamics. Study focus: An accessible yet accurate flood extent estimation method is crucial for the management of natural resources in the IND. The relationships between water levels and inundation extents are examined for both the rising and receding flood periods, using the outputs of a 2D hydrodynamic model. Inundation extents derived from MODIS images were used to validate the result. New hydrological insight for the region: The relationship between water levels and flooded areas in the IND changes from year to year due to the amplitude of the incoming flood. Equations were developed to capture that dynamic relationship and estimate flood extent in real-time from September to the end of flood using water levels at Mopti. The relationship is dependent on the maximum water level at Mopti and maximum flooded area which was forecasted using streamflow and precipitation in the Upper Niger Basin. Results show that in addition to forecasting the maximum inundation ahead of time, the inundation predicted with the method shows improvement over the existing formulas by Mahé et al. (2011), Zwart et al. (2005), and Mariko (2003).

Keywords

• Inundation extent
• Forecasting
• Hydrodynamic model
• Inner Niger Delta
• Mali