Multi-Return Periods, Flood Hazards, and Risk Assessment in the Congo River Basin

Flood disasters have regularly been reported in the Congo Basin with significant damage to human lives, food production systems, and infrastructure. Losses incurred by these damages are huge and represent a major challenge for economic expansion in developing nations. In the Congo River Basin, where availability of in situ data is a significant challenge, new approaches are needed to investigate flood risks and enable effective management strategies. This study uses recently developed global flood prediction data in order to produce flood risk maps for the Congo River Basin, where flood information currently does not exist. Flood hazard maps that estimate fluvial flooding at a grid cell resolution of 3 arc-seconds (~90 m), gridded population density data of 1 arc-second (~30 m) spatial resolution, and a spatial layer of infrastructure data set are used to address flood risk at the scale of the Congo Basin. The global flood data provides different return periods of exposure to flooding in the Congo Basin and identifies flood extents. The risk analysis results are presented in terms of the percentage of population and infrastructure at flood risk for six return periods (5, 10, 20, 50, 75, and 100 years). Of the 525 administrative territories, 374 are exposed to fluvial flood, and 38 (10%) of them are categorized as risk hotspots. Analysis shows that the most exposed territories represent 1% of total exposure, which is estimated at 2.65% of the basin's population. This study demonstrates the first and potentially most important stage in developing flood responses by determining the flood hazard areas and the population that would be exposed. The flood risk maps produced in this study provide information necessary to support policy decisions of flood disaster prevention, including prioritization of interventions to reduce flood risk in the CRB.