Soil erosion and sediment delivery in a mountain catchment under scenarios of land use change using a spatially distributed numerical model

摘要

Soil erosion and sediment yield are strongly affected by land use/land cover(LULC). Spatially distributed erosion models are of great interest to assessthe expected effect of LULC changes on soil erosion and sediment yield.However, they can only be applied if spatially distributed data is availablefor their calibration. In this study the soil erosion and sediment deliverymodel WATEM/SEDEM was applied to a small (2.84 km2) experimentalcatchment in the Central Spanish Pyrenees. Model calibration was performedbased on a dataset of soil redistribution rates derived from point 137Csinventories, allowing capture differences per land use in the main modelparameters. Model calibration showed a good convergence to a global optimumin the parameter space, which was not possible to attain if only external(not spatially distributed) sediment yield data were available. Validation ofthe model results against seven years of recorded sediment yield at thecatchment outlet was satisfactory. Two LULC scenarios were then modeled toreproduce land use at the beginning of the twentieth century and ahypothetic future scenario, and to compare the simulation results to thecurrent LULC situation. The results show a reduction of about one order ofmagnitude in gross erosion (3180 to 350 Mg yr?1) and sediment delivery(11.2 to 1.2 Mg yr?1 ha?1) during the last decades as a resultof the abandonment of traditional land uses (mostly agriculture) andsubsequent vegetation recolonization. The simulation also allowed assessingdifferences in the sediment sources and sinks within the catchment.