Description:
An exceptional precipitation event occurred during three consecutive days (17, 18 and 19 janvier 1994) in the East of the Rifian region, Morocco. The records enregistrated in all the climatological stations of the region exceeded 150 mm. A maximum of 237 mm is reached in the Boudinar station. Despite its low occurrence, a such event gives an exceptional opportunity to observe the behaviour of terrains under cultures, bare terrains and soil and water conservation techniques. The purpose of this paper is to evaluate the role of human activities in a region having a fragile ecosystem equilibrium. The methodology adopted is based on direct observations of all kinds of phenomena acting on the previous terrains and techniques. We had also made some field mesures to evaluate the degree of degradation phenomena and its costs.