Flood mapping in lower Zambezi river sub-basin, Mozambique

Most of Zambezi Basin in Mozambique is prone to flooding with negative impacts to its economic development. Those impacts are worsened by the lack of hydraulic infrastructures associated with inefficient Decision Support System such as Global Information System (GIS) and Hydraulic/Hydrologic model that could be useful in attenuete the impacts of floods. This study was conducted to simulate flood for return period of Q25, Q50 and Q100 years for the Lower Zambezi catchment through combine GIS/Global Mapper techniques and HEC-RAS hydraulic model also in the future can be used as basic decision material, when building public infrastructures, in order to avoid their rupture or destrution due to water velocity the Zambezi River and its tributaries, during floods. Remote sensing Moderate-Resolution Imaging Spetroradiometer (MODIS) images were used to validate the flood inundation maps. The study area covers area around 75,256 km2. With return period of Q25 years the inundated area is around 20,626 km2 (27%), for return period of Q50 years inundated area is around 25,864 km2 (34%) and the return period of Q100 years the inundated area is around 31,220 km2 (41%). The Q25 year return period flood affects the Mutarara, Caia, Marromeu, Mopeia and Chinde districts. MODIS image is estimated around 13.1% of the area flooded compared with results from the model. The 50 years return period affects the Dôa and Tambara districts up to downstream. The results of MODIS image cover area of 14.2% the total area. The 100 years return period flood affects almost all the Administratives posts a long the Zambezi River with several impacts to riverine population. The use of LIDAR imagery 1 meter resolution will improve the quality of results of the HEC-RAS model.