Sediment transport in a semi-arid stream: case of the wadi Boumessaoud (NWAlgeria)
The analysis of instantaneous water discharge and suspended sediment loads in the watershed of the Boumessaoud Wadi (118 km2), for the period from September 1988 to August 2004, revealed the existence of annual and seasonal variability in sediment transport in this Mediterranean semi-arid catchment and demonstrated the impact of flood events, which contribute to about 71% of the overall solid tonnage in the autumn and up to 97% in the spring. The results of this analysis indicate that the annual average specific erosion is about 518 t∙km-2∙y-1. The methodological approach adopted consists of finding a regression model capable of explaining the sediment load (QS) as a function of the discharge (QL), tested by studying this relation at various temporal scales. The produced models are a power relationship type (QS = aQLb), where water discharge explains overall more than 80% of the variance in sediment yield. The identification of periods that are sediment-productive in this dynamic erosion system was studied by analysis of the evolution of the sediment concentrations in the stream. The objective of this modeling is to overcome the shortcomings of the sediment transport data available for our studied catchment.