Résumé : With a geographic holistic and multi-scales approach of physical and human factors combining Very High Resolution satellite imagery interpretation, a survey on the ground (observation, interview, DGPS measurement) and a Geographic informatic system (GIS), this study helped to explain by a set of physical and especially human factors that intra-urban gully erosion is a complex phenomenon with multiple causalities. Those are the orthogonality of roads on the slopes, the tracks traced in the direction of (the highest point of) the slope, housing construction techniques on weeded and loosened terraces offering no resistance to concentrated water runoff, soil sealing residential towns upstream of spontaneous settlements, sewerage that fail at the outlet and erosion control devices poorly maintained or not, the non-appropriation of public spaces and the late intervention in the management. This intervention in the erosion control is asymmetrical from a temporal point of view. This delay not only worsens the living conditions in poor neighborhoods, but also it allows the gully erosion to accelerate, to branch out and take dramatic dimensions.