Gully erosion associated with peri-urbanization: focus on the catchments in the south of Kinshasa

The catchments draining the small plateau of Kimwenza in Kinshasa's south (DR Congo) are undergoing rapid and extensive peri-urbanization with limited planning. In this research, we study gully erosion processes that are associated with several infrastructure. The goal is to identify and characterize the primary erosion sites, to understand the factors of gully erosion, as well as to develop appropriate and effective methods for reducing gully erosion. To achieve this, we proceeded as follows: characterize the morphometry of the catchments, describe the surface water flow network, assess the runoff rates and propose an adequate drainage to collect runoff. Following the proliferation of street-gullies and the absence of water retention devices, it appears that these basins have a high drainage density ranging from approximately 1800 to more than 11000 m/km², with a general average of approximately 6570 m/km² following the field and laboratory investigations. Furthermore, all of the basins in this area have a somewhat rounded shape and a modest extension. This means they're more likely to have a quick rainwater concentration-time and, as a result, a quick response time. As a result, runoff flows can only be torrential, especially since the majority of this sector (80 percent) has slopes of more than 8%. The peak flow rate of surface flows can surpass 650 l/s/ha, according to an analysis of active showers and their intensities. Due to the soil's incoherent structure, which primarily consists of sands, 30 gullies were mapped, with an average length of 560 meters, a width of 27 meters, and a depth of 10 meters. Under these conditions, attenuating the gully phenomenon necessitates a significant reduction in runoff flows.