ZONAGE DE L'ALEA INONDATION DANS LES AIRES AVALES DU BASSIN VERSANT DE LA N'DJILI A KINSHASA (REPUBLIQUE DEMOCRATIQUE DU CONGO)

Abstract

Floods are the most dangerous natural disasters in the world. In Kinshasa, the lower N'Djili basin, elongated and subject to recurrent flooding, covers 762.8 km2 and its perimeter is 177.4 km. With a compactness index of 1.8, this sub-catchment is in a mature state, with a lower sloping relief. The question often arises: "Why have floods become recurrent in this part of the N'Djili catchment and how far can its waters extend?" The main objective is to circumscribe and prioritize the "flood" hazard in its lower course. A probabilistic "Frequency Ratio (FR) Modeling" approach combined with geomatics tools was adopted to establish a flood hazard zoning. Eleven flood causative factors were selected based on the literature review: Slope, Land Use, etc. The analysis resulted in a map of four flood susceptibility zones with a risk of "high, medium, low, very low". It follows that the proximity, shape and density of rivers are the causal factors. The downstream part of the catchment, with its elongated shape, experiences a relatively long response time during rainy periods. On the other hand, the water stagnation mechanism becomes recurrent in lowlands. The most exposed areas are those located at altitudes ≤ 300m.