Hydrology in a Changing World: Environmental and Human Dimensions Proceedings of FRIEND-Water 2014, Montpellier, France, October 2014 (IAHS Publ. 363, 2014). 309 Study of the relationship between sediment transport and rainfall extremes in the watershed of the wadi Mina (northwest Algeria) F. HALLOUZ 1 , M. MEDDI 1 & G. MAHE 2 1 LGEE, ENSH, Blida, Algeria a-fouzette71@yahoo.fr 2 IRD, Mohamed V University, Rabat, Morocco Abstract Arid and semi-arid areas are characterized, in particular, by the great irregularity of their climate. This irregularity comes out as sporadic, sometimes very important, showers. They can be responsible for erosion and for exceptional sediment transport. The spatial variability of erosion and sediment transport phenomena in North Africa is very high, either because of the intensity of the phenomena or for their consistency. The main factor of these phenomena is the water. Langbein & Schumm (1958) showed how erosion varies according to the annual rainfall. Two factors act antagonistically on erosion: rain and vegetation. To have erosion, it is necessary to have rain. Erosion is an increasing function of the height of annual rainfall. This article aims to analyse and describe the relationships between sediment transport and rainfall extremes. The study was conducted on Mina, a sub-watershed of 6000 km 2 on the left bank of the River Cheliff. The wadi Mina feeds Dam Sidi M’hamed Ben Aouda (SMBA), for agriculture and drinking water supply in the region. This watershed is facing a serious problem of soil degradation, as reported by almost all Western Algerians. This problem causes the rapid siltation of dam Sidi M’hamed Ben Aouda, which has a capacity of 160 million m 3 . This also affects local agriculture, causing huge losses to cropland, forcing farmers to migrate to urban areas. It is interesting to note that before the 1980s, the dam was experiencing the lowest siltation rates in Algeria. Currently, sediment deposits in the reservoir of the dam are very high, and they have doubled in two years. This dam is classified among the most silted dams in Algeria. The study of the basin covers a period of 33 years (1968/69–2000/01). Key words climate; Algeria; Oued Mina watershed; sediment transport; extreme rainfall; silting INTRODUCTION Sediment transport is influenced by several parameters including: climatology, geology of the site, slope, rain and its intensity. In Algeria, physical conditions, geomorphological, hydro- and socio-economic factors are particularly favourable to the launching and acceleration of the phenomenon of erosion and sediment transport. The average amount of basin sediments discharged into the sea every year by the tributaries of the Mediterranean, is estimated at 120 million tonnes. One of the serious consequences of this phenomenon is the siltation of reservoirs. Due to silting, Algeria’s water infrastructure is decreased annually from a potential water reserve equivalent of 20 million m 3 . In semi-arid regions, characterized by erratic rainfall which is often very intense, climatic factors have a significant influence on soil loss. Negev (1967) developed a model based on the fact that the amount of soil removed by the effect of “splash” is a function of the height of hourly rainfall. Williams (1978) has developed an instant unit turbidigramme for ungauged basins, in which the suspended load varies linearly with the volume drained away. Bergaoui et al. (1998) has developed from hydropluviometric data a non-constant relationship for the micro basin of Tebaga, in central Tunisia. He concluded that 84% of the solid linear transport model is explained by the maximum flow. This work focuses on the use of parameters representing the intensity of the rain (rainfall and Pjmax) and other factors resulting in extreme runoff (maximum flood flow) to estimate the contributed suspended solids. The concentration of suspended materials depends on changes in flow. Values of concentration, actually observed, depend on the intensity of rainfall and the type of soil, the erosion forces due to topography (Benkhaled & Remini, 2003). The objective of this work is to find a relationship which allows the estimation of major contributions based on one or more hydro meteorological parameters. Copyright  2014 IAHS Press