Total sediment load in a Mediterranean mountainous catchment (the Ribera Salada River, Catalan Pre-Pyrenees, NE Spain)

摘要

The total sediment yield of the Ribera Salada River basin, a representative forested catchment in the Catalan Pre-Pyrenecs (NE Spain), is assessed based on sediment transport measurements between 1998 and 2002. Mean annual suspended sediment yield is 13,600 t/y (210 t/km(2) y), while mean annual bedload yield is 2,175 t/y (20 t/km(2) y). Bedload thus provides 9% and suspended load 91% of the total load. Sediment dynamics are mainly controlled by the availability of fine sediment in the channel in the case of suspended sediment, and by the threshold of entrainment of riverbed materials in the case of bedload. The major part of the annual load (> 90%) is transported by discharges equalled or exceeded less than 10% of the time. The few flood events (equivalent to discharges equalled or exceeded 0.5% of the time) are responsible for the transport of around 50% of the total sediment load of the river. Thus, the results emphasize thus the role of floods in the long-term transport of sediment in mountainous Mediterranean river basins. The residence time of riverbed sediments is around 100 years. The denudation rate of the catchment has been established at 0.14 mm/y (140 mm/10(3) years), a value that is higher compared with other forested catchments, a fact that can be related to recent land use changes in the area that still affect the sediment yield of the basin.