Increased rainfall erosivity and its effects on soil loss estimation: A comparison between two watersheds in southern Spain

Abstract

Recent studies have highlighted increments in rainfall erosivity along the Cordilleras Béticas Litorales. Thus, it is recommended to move forward the soil loss estimation caused by water erosion, which is the main geomorphic agent in that region. This study deals with the application of RUSLE equation in two-watershed characterised by different rainfall regimes (one semiarid/dry and other subhumid) from 1997-2018. Both watersheds present ecogeomorphic features typical from Mediterranean mountains under those rainfall regimes. The application of RUSLE was made introducing some methodological modifications in the calculation of soil loss: (a) 10 minutes periods (I10) to calculate rainfall erosivity (Factor R); (b) vegetation cover (factor C) estimated from NDVI; (c) soil loss evaluation from soil surface components inventory. The results indicated significant differences between both watersheds due to difference in ecogeomorphology and rainfall erosivity. The use of I10 contributed to a better approach to the soil loss estimation and its spatial and temporal variability. The mean soil loss was of 244.4 t h-1 year-1 and 547.0 t h-1 year-1 in the rainier watershed and the drier one, respectively. The inventory and analysis of soil surface component was better related to higher soil losses in the more humid watershed, where the biotic components of soil surface were dominant (moss, annual plants, and litter). These results may contribute to detect more appropriately critical areas to increase vegetation cover and reduce soil loss by water erosion in the framework of future reforestation.