Abstract

The aim of this study is to analyze rainfall dynamics and stormwater management in the Djiri watershed, northeast of the city of Brazzaville. The methodological approach used is based on documentary analysis, data collection from the local SRTM-DM, rainfall statistics covering the period 1990-2023, field observations and socio-anthropological perceptions of SWM. These data were processed using Excel, ENVI and QGIS. The results show that the watershed, which has a KG=1.8, is elongated, rainfall is highly variable, with an upward trend, particularly in 2020, when the index reached its highest value of 0.35 since 1990, i.e. an average of 163.7 mm, and finally, the rainwater management is deficient. Under these conditions, rainwater that escapes infiltration is not domesticated by households, and uncontrolled by the lack of drainage systems, exploits the bare or waterproofed slopes of the hydrosystem, whose gradients sometimes reach 22% on a bedrock of almost 90% sand, to erode the soil. This phenomenon, whose direct consequences are 21 gullying and sedimentation, affects the environment, mankind, its activities and developments. The solution is treating gullies using biomechanical methods (gabion baskets and vetiver grass), install a weather station in the watershed to better monitor rainfall, raise awareness among the rainwater management population and, lastly, lobby the Congolese government to build an effective rainwater drainage system.

Keywords: Watershed, Rainfall, RWM, Water erosion, Djiri