Suspended sediment and typology of floods in Wadi Saïda (Highlands of Algeria)
The Wadi Saïda lies within the Mediterranean basins of northwestern Algeria and is characterized by a semi-arid climate. Rainfall is very irregular in time and space and occurs in the form of intensive showers that lead to important erosion and solid transport. This work focuses on the study of the relationship between the concentration of suspended sediment, C, and flow rate, Ql, for hydrological events such as floods. The analysis of graphs representing C as a function of Ql for 11 floods in the Wadi Saïda revealed three types of hysteresis curves: clockwise, counterclockwise and figure-eight. The sediment discharge Qs for each flood is related to flow by the power relation Ql= aQlb. The floods studied with a clockwise hysteresis curve have maximum concentrations and generally high flow. Loops in the counterclockwise and figure-eight configurations for the relationship (C-Ql) are characteristic of winter and spring floods, which present the lowest concentrations of suspended solids; soil conditions and vegetation cover are such that erosive action is reduced.