EVALUATION OF THE EFFECTIVENESS OF FOREST RESTORATION AND CHECK-DAMS TO REDUCE CATCHMENT SEDIMENT YIELD

摘要

Reforestations and check-dams are two commonly used measures to reduce soil erosion rates and sediment export from highly eroding catchments. Here, we evaluated the impact of the construction of 94 check-dams and land use changes (caused by agricultural abandonment and reforestations) on sediment yield in the Upper Taibilla catchment (320 km(2), SE Spain) from 1956 to 2000. We combined land use change analysis, field surveys, and application of the WaTEM-SEDEM erosion and sediment yield prediction model for nine scenarios combining land use maps (1956, 1987, and 2000) and different numbers of check-dams throughout the catchment. Land use changes alone reduced sediment yield up to 14%, but in combination with check-dams, the reduction in sediment yield reached 44 +/- 6%. Sediment yield reduction was higher in smaller sub-catchments, with, on average, a higher transport capacity than larger catchments, illustrating the scale dependency of human impacts on sediment fluxes and the buffer capacity of larger catchments. From an economical perspective, the construction of check-dams was estimated to be more expensive than reforestation programs in the studied catchment, while adding more check-dams did not always result in a proportional reduction of sediment yield. This indicates that optimizing check-dam distribution relative to land use patterns is crucial to decrease catchment sediment yield. Check-dams have a large and instantaneous impact on sediment yield over a restricted time period, while reforestations have important sustained effects at a lower economic cost. These contrasting effects require a careful evaluation for optimal effective catchment management. Copyright (C) 2014 John Wiley & Sons, Ltd.