Flows variability in a forest watershed undergoing accelerated urbanization: the case of Mefou (South Cameroon)

The objective of this study is to understand the impact of rainfall variability and anthropization on the flows of the Mefou watershed over a recent period. For this, the hydropluviometric data of the catchment concerned were analyzed using the Pettitt test. Likewise, the dynamics of the main land-use patterns have been assessed, using supervised classifications carried out from the processing of Landsat satellite images of the basin studied at two dates. The results of this study show that the average and extreme flows of this basin have been increased since 1985-86, unlike the rainfall, which generally decreases for all seasons from the 1970s, apart from the summer, where the reverse is observed. Land-use changes (increase in impervious areas and a decrease in forest and water bodies) seem to be the main cause of the observed increase in runoff. The rainfall changes observed in this basin have just contributed to amplifying this increase in runoff in some cases and attenuating it in others. The summer and the spring for which the rainfall recorded respectively an increasing break and no break are also the seasons for which the increases in runoff are the most important. Conversely, autumn and winter, which saw significant decreases in rainfall, experienced the smallest increases. These results could be useful for long-term planning of water demand and use in this basin, as well as for improving future simulations of main collector flow and preventing socio-environmental disasters like flooding.

Keywords: Mefou, variability, precipitation, runoff, land use patterns