SEDIMENT BUDGET FOCUSED IN SOLID MATERIAL TRANSPORT IN A SUBHUMID MEDITERRANEAN DRAINAGE-BASIN

A sediment budget for a subhumid Mediterranean granitic drainage basin is compiled. Emphasis is placed on the assessment of the contribution of the solid material transport to the sediment yield. Sediment budge t of the Arbucies drainage basin is based on the description and quant ification of several geomorphological processes: a) sediment yield, b) soil transfer from the hillslopes, c) secondary sediment sources whic h includes dissolved salts contained into the precipitation and human- induced contributions and, d) residence time of sandy-gravel sediment in the main channel. Solid material transport is responsible for 75% o f the annual sediment yield, and the drainage network is the main sedi ment source of the drainage basin, being the estimated contribution of about 12 tonnes ha(-1) yr(-1). Average residence time of sand and gra vel stored in the main channel is approximately 28 years. The estimate d rates of soil contribution from the hillslopes (by creep and surface wash) and the average sediment load are nor in balance. This non-equi librium situation may induce to a progressive incision processes of th e drainage network, hipochetically reinforced by the tectonic activity in the study region.