Flood risk assessment by a multicriteria spatial analysis in the municipalities of Pobè and Adja-Ouèrè

Abstract

Floods are natural phenomena that give rise to a wave of interest in the management of space especially following their recurrences and intensifications. In order to prevent them, it is essential to carry out risk assessment studies.For this purpose, several methods of flood risk assessment and modeling are used. Of all, combination of Geographic Information Systems (GIS) and Multicriteria Analysis guarantees considerable accuracy in results obtained. This methodology combines risk identification and spatialization of results using the WLC algorithm to perform complex calculations on each pixel. Hazard criteria (soil types, slope, rainfall, altitude, groundwater potential and water accumulation) and vulnerability criteria (land use, degree of poverty and population density) were identified, standardized, weighted and aggregated during the analysis based on Hierarchical Analysis Process and Weighted Linear Combination algorithm.Weighted superposition of hazard and vulnerability criteria maps reveals four categories of flood risk areas. These are areas with a low risk of flooding (17.69%), areas with medium flood risk (50.28%), areas with high risk of flooding (27.39%) and areas with very high flood risk (4.64%).Thus, 32.03% of the study area presents a significant flood risk, precisely in the districts of Kpoulou, Ahoyeye, Igana, Issaba, Adja-Ouèrè and Massè. A significant portion of the 18,000 households in these boroughs are at risk of flooding, which threatens human lives and socio-economic activities.