Runoff and soil erosion in badlands : modelling an agrosystem in the Pyrenees (Huesca)

Erosive dynamic of gullies in Mediterranean environments represents one the main causes of land degradation and sediment yield in productive agrosystems. In this work the semi-physics enhanced RMMF model is applied into a GIS to elaborate spatially distributed maps of potential and effective cumulative runoff and soil erosion at the La Coloma Gully catchment (Spanish Central Pre-Pyrenees). The gully reaches a maximum length of 523 m and is divided into four different sectors according to its physiographic properties. The map of soil detachment by splash highlights the key role of vegetation properties to explain the different estimated rates. Processes of runoff accumulation and infiltration and slope values mainly control the estimated values of soil detachment by runoff. The average value of soil erosion at catchment scale is 33.9 Mg ha(-1) yr(-1) being runoff transport capacity the limiting factor in 88% of the surface and total soil loss adds up to 411.4 Mg yr(-1). The average value of estimated soil erosion in the gully is 176.5 Mg ha(-1) yr(-1) with values that range between 0.1 and 502.6 Mg ha(-1) yr(-1) for the different sectors and the total volume of runoff is 779 mm yr(-1). Crops, paths and areas with low vegetation cover and high slope are the main source areas of sediment to the main channel of the gully and present high values of soil erosion (higher than 30 Mg ha(-1) yr(-1)). Information gained with the enhanced RMMF model is of interest to implement soil and water conservation practices and develop sustainable economic and environmental strategies.