Comportement hydrologique et dynamique d´un bassin versant en milieu semi-aride: Exemple du Bassin versant du Ksob (Haut Atlas Occidental, Maroc)

Abstract

Located at the Western extremity of the High Atlas range in a semi-arid zone, the Ksob watershed area presents an elongated shape with steeps slopes at the tributaries. The outcrops, rather impermeable in their majority, are composed by Jurassic and Cretaceous carbonated rocks and marls. All these characteristics induce an increase of the river discharge and the development of important floods. The Ksob River is affected by frequent floods, which are violent and short in duration. Transported solid loads deposited in Essaouira bay, play a fundamental role in the maintenance of morphodynamic and sedimentary equilibrium in the river mouth and in the Essaouira beach. The construction of Zerrar dam, upstream of the Ksob River, would involve an important sedimentary deficit, which would drive in a very intense coastal erosion of the Essaouira Bay.