Modeling Household Flood Risk Management in the Lower Mono River Basin, Togo–Benin (West Africa)

Abstract

The catchment of Lower Mono River, shared between two West African countries, Togo and Benin, used to overflow each year, threatening the community surrounding it. This situation is likely to increase and exacerbate the damages of climate change and urbanization without suitable adaptative strategies. In this study, we used the HEC RAS model to test structural measures that are effective from the point of view of households to cope with flood risk. To this end, a survey was conducted in twenty-four (24) villages in the basin to identify: the socio-economic causes and vulnerabilities of households in the study area, the existing adaptation and mitigation strategies developed by households, identification of factors influencing households to adapt and choose a particular measure and simulate the flood risk based on household decision making. Also, historical flood data in the area and geospatial data were collected. Using the powerful tool HEC-RAS, helped model the potential flooding areas and test structural measures, hence, enabling to proposal of effective adaptive measures to cope with flood risk in the Lower Mono River basin. The results of the different analyses showed that climate change and bad management of Nangbeto dam represent the hydrological drivers to flooding and the presence of households in low land areas and close to the river, having less income and education level are the social drivers to flood. Households rather choose less costly measures such as having other commercial activities, modifying their agricultural calendar or diversifying their crops to cope with the flood-related impact on their agricultural land. The choice of the household to adapt and choose a specific adaptive measure is positively influenced by their experience of past flood events and the exposure of their agricultural plot. The results of the HEC-RAS model confirm that this model is capable of modeling potential flooding areas and also allows testing structural measures. Indeed, the effectiveness of the drainage system and the water retention basins were tested with the HEC-RAS model. The results show that these measures can reduce the risk of flooding in the basin. It can be used by decision-makers in the implementation of suitable adaptive strategies for the well-being of the population. A combination of structural measures (drainage systems and retention basins) and structural measures (capacity building, awareness raising) can significantly reduce the impact of flooding in the study area.