Soil erosion modeling in terraced landscapes-examples from the Three-Gorges-Area, China

摘要

The construction and impoundment of the Three-Gorges-Dam in China fosters an extremely high land-use dynamic. Soil erosion is expected to increase dramatically. In the mountainous landscape farming is mainly practiced on terraced land. Thus, the conceptual TerraCE model (Terrace-Condition-Erosion) was developed to assess the spatial variability of terrace condition and the resulting soil erosion risk potential. Our investigations in the Xiangxi catchment confirm the model assumptions. The conditionsof terraces were found as a key factor to determine soil erosion. They can be classified in 4 clusters, (a) well maintained (20 %), (b) badly maintained (48%), (c) partially collapsed (15%), and (d) completely collapsed (6%). Further, our investigationsshow that the distance to the inundated area and to the road network are significant covariates to predict the spatial distribution of soil erosion risk. The mean distances to the new shoreline vary between 614 m (well maintained) and 128 m (completely collapsed). The mean distances to the main roads are 588 m and 148 m respectively. A first spatial prediction of the terrace condition of the TerraCE model combined with a random forests multi-regression approach show promising results with a spatial accuracy of 70%.