Dynamique sédimentaire actuelle d'un système fluvial méditerranéen: l'Agly (France): Present sediment yield from a Mediterranean fluvial system: the Agly river (France)

Abstract

The purpose of this study is to investigate the mechanical and chemical erosion rates in the Agly catchment (1 045 km 2) in order to estimate the whole sediment budget of a Mediterranean fluvial system. The climate of the catchment is characterized by a marked contrast between dry and humid conditions, with the occurrence of heavy downpours during only a few days of the year. As a consequence, the bedload charge and nearly all the suspended sediment load are transported during these events. Bedload charge is in deficit according to the fluvial geomorphology showing inner channels in bedrock. Dissolved solids, on the other hand, are transported much more uniformly over the year and reveal a dominance of carbonate weathering in the overall chemical erosion rates. On the basis of daily discharge data for the last thirty years, and taking all three transport pathways together (bedload, total suspended solids, total dissolved solids), the estimated mean annual sediment yield is 192 t·km −2·yr −1 and total denudation rate in the basin of 0.77 mm·yr −1, which is rather low for the Mediterranean area.