Abhatoo - Centre Nationale de Documentation

In Morocco, for some reservoirs average annual loss of capacity reaches 1.6%. Assessments of erosion rates suggest sediment yields from drainage basins may be almost 5000 t km^-2 year-¹ in the Rif Mountains with mean rates of between 300-500 t km^-2 year-1 in the High Atlas Mountains. In a study of the Aoulouz basin in the High Atlas Mountains factorial scoring methods founded on a GIS approach estimated that 46% of the sediment was produced by less than 25% of the 4446 km² catchment. The potential erosion rate of the most erosion susceptible sub-basin was estimated as 1592 t km^-2 year^-1. Field monitoring of actual erosion in the highest yielding sub-basin showed that gully sediment yields were in excess of 1000 t km^-2 year-1 for individual storm events and exceeded rill erosion by two orders of magnitude. The study also emphasized the need to target soil conservation management strategies on gullied areas in the catchment.