FLOODS TYPOLOGY IN SEMIARID ENVIRONMENT: CASE OF AIN SEFRA WATERSHED (KSOUR MOUNTAINS, SAHARIAN ATLAS, SW OF ALGERIA)

Abstract

The watershed of Ain Sefra covers an area of 1957 km2, which is located in the southwestern of Algerian territory in an area called Ksour Mountains. It is moderately elongated and characterized by a fairly widespread network, steep slopes and relatively impermeable terrains with variety lithology, providing a favorable environment for the development of flashfloods. The surface flow regime in this semi-arid region is consistent with the rainfall. Floods are highly variable and irregular, short and stormy, with very high peak flows if compared to the average modules, they are characterized by a very fast rise, leading severe damages in Ain Sefra city, and a slow decline followed by a prolonged dry period. Autumn is reported as risky season. The flow in dry periods demonstrates a groundwater potential, which is produced by the Atlas relief that shows a fairly strong hydrological relationship between surface water and groundwater