Hydrological variability and flood risk in a forest watershed undergoing accelerated urbanization: the case of Mefou (South Cameroon)

This article has as objectives to investigate the impact of precipitation variability and land use change on the hydrological dynamics of the Mefou river over the recent period (1963–2018), and draw up a basin flooding risk areas map. To achieve these goals, hydrometeorological data of this basin were analyzed using the Pettitt and Mann Kendall tests. Likewise, flooding risk areas were produced from Frequency Ratio (FR) model. Average and extreme flows of Mefou river have increased since 1985–86, unlike the rainfall, which generally decreased for all seasons from the 1970s, apart from summer, where the reverse was observed. Changes in land use (increase impervious areas (+530%) and a decrease in forest (−52.9%) and water bodies (−80.4%)) seem to be the main cause of the increase in flows observed. Floods are often recurrent in basins with such hydrological behaviour. To enable policymakers to reduce the vulnerability of populations to this disaster, the proposed flood map shows that 2.67, 7.22, 22.5, 35.25 and 32.36% of the catchment area are respectively delineated into very low, low, medium, high and very high flood vulnerability classes. These results could be useful for the management of water resources and associated hydrological risks in the basin investigated.