This study involves geological material, topographic phenomena and the river system in a cause-and-effect relationship in the Mayo-Kebbi watershed. This river connects South - West Chad to Northern Cameroon via the Benoué River, which connects with the Niger river basin. The main objective of this work is to understand the influence of geological material and topographic factors on the Mayo-Kebbi hydrographic system. For this purpose, the description of the rocks in place and their structure was made on the basis of a state of the art of the acquired knowledge. Characterization of the river system was done by mapping watersheds. In addition, to understand the organization of the hydrographic network, we described rocks and tectonics and determined the hypsometric variables. The analysis of the data shows, on the one hand, the tectonic-assisted geological right-of-way on the main watercourse route because their profiles follow the axes of break and are marked by right-angle elbows and their sinuosity index close to 1 (0.90, 0.84, 0.97). On the other hand, the secondary drainage beam is linked to the influence of the topography characterized by low slopes (0.67, 0.073, ...). This study made it possible to characterize the water network of the Chadian basin of Mayo - Kebbi and to understand its surface organization. The results obtained show a dualism of factors between tectonics and topographic parameters.
