Assessment of Flood Hazard Areas in the Congo River Basin in the Democratic Republic of Congo: a case study of the N’djili River Sub-basin.

Abstract

The issue of natural hazard in general and flood in particular is a topical problem that marks a memorable action in the world and specifically in Democratic Republic of Congo, especially with regard to the latest catastrophic floods. In January 2017, the city of Kinshasa was flooded by a six-meter water-rise (a secular event) that left 48 dead and nearly 500 families displaced for about two weeks. This research aimed to locate the areas that are exposed to inundation within the city of Kinshasa. Indeed, the management of this risk is becoming more and more a necessity which must include all the actors. In this report, the mapping of flood hazard areas has been exposed by a hydrological modelling approach through the example of the N'djili river which currently inundate the city of Kinshasa. The basin of the N’djili River is an area that by its topography and anthropogenic activities have caused it to be exposed to the hazard of flood. This research project was carried out by a supporting contribution of geographic information system (ArcSWAT, ArcScene and ArcMap). ArcSWAT helped us to analyse the various factors such soils, land use and landcover, that influence flooding in the N’djili River catchment. The change in land use along the river is a triggering factor for the flooding process within the city. ArcScene allowed us to do a 3D simulation based on a secular and a quinquennial flood. By this we calibrated our simulations on these two different water levers corresponding to the floods taken into account, which gave us two risk zones (high and low risk). ArcMap is a component of ArcGIS that allowed us to represent our research findings in terms of maps. This mapping appears to be one of the most effective ways to understand the link between the change on land-use/landcover and the hazards of flooding. It can serve as a basic document for the public authorities to define rules that can contribute to a better management of the city (for instance, the delineation of riverbeds can give an idea on the floodplains, the areas at high risk of inundation, these kinds of information can be useful for urban planners). The mapping of flood hazard zones is a way of alerting the population on the risks of inundation and areas likely to be flooded. It is also a planning tool for decision makers who are not necessarily technicians, and to whom come the final decision on the flood risk strategies.