Geomorphological Processes and Human Impacts in River Basins (Proceedings of the International Conference held at Solsona, Catalonia, Spain, May 2004). IAHS Publ. 299, 2005., 131-138.

Patterns of suspended sediment transport in two forested Mediterranean mountainous basins (Ribera Salada, Catalan Pre-Pyrenees, NE Spain)

J. CARLES BALASCH1, RAMON J. BATALLA1,2, ROSA M. POCH1,2 & DAMIA VERICAT1

1 Department of Environment and Soil Science, University of Lleida, Rovira Roure 191 E-25198, Lleida, Catalonia, Spain

cbalasch@macs.udl.es

2 Forestry Institute of Catalonia, Pujada del Seminari s/n, E-25280, Solsona, Catalonia, Spain

Abstract Suspended sediment dynamics and trends are analysed in two Mediterranean mountainous basins in the southern Pyrenees. Rainfall, discharge and suspended sediment are monitored in order to establish the long-term water and sediment budgets of the basins and to determine sediment transport dynamics. A nested basins research scheme (2.6 km2 and 65 km2) allows determination of the conveyance and routing of sediment through headwaters, tributaries and main channel during flood response. Hysteretic loops show seasonal complex relationships between water response and sediment availability. Clockwise and anticlockwise hysteretic patterns and exhaustion effects are recognized and explained in terms of temporal runoff generation, sediment sources distribution and stream channel sinks, demonstrating the different seasonal patterns of processes involved. Mean sediment yield of the two basins was in the order of 1–3 Mg km-2 year-1, well below the regional values.

Key words forested mountainous basin; hysteresis; Mediterranean rivers; sediment transport