Key processes influencing erosion and sediment transport in a semi-arid Mediterranean area: the Upper Tafna catchment, Algeria

The Maghreb is a mountainous region subjected to a contrasting climate with wind storms in summer and unpredictable rainfall fluctuation both throughout the year and from year-to-year. Rainfall in the area is often intense on dry soils with poor vegetation. Intense rainfall events rapidly generate strong surface runoff that removes large quantities of soil. However, few Studies have examined the processes controlling soil erosion in the Maghreb area and it is in this context that this Study was done. The research presented is based on a detailed analysis Of Suspended sediment loads and water flow at the outlet of the Upper Tafna basin (256 km(2)) in northwest Algeria, based on a monitoring programme from September 1988 to August 1993. The results show that the increased aridity leads to an increase in the erosive potential. Marked hysteresis is observed between suspended sediment loads arid water flow. The nature of the hysteresis is variable arid the various types of hysteresis are used to characterise the various mechanisms of erosion and transport that operate in the area and show the importance of the storage of previous sediment deposits in the river.