Erosión y desertificación.-Soil erosion processes and sediment fluxes in a Mediterranean landscape of marls, Campiña de Cádiz, SW Spain

Abstract

ABSTRACT Marl landscapes, especially in the Mediterranean, show evident traces of high present-day and past soil erosion rates. The tendency to develop hillslope channels leads even at moderate rainstorm magnitudes to a significant increase of slope-to-slope connectivity, resulting in high amounts of mass transfer from upper parts of the hillslopes towards footslopes and valleyfloors. To analyse the intensity of this transfer a study was conducted focussing on late Holocene sediments correlative to modern-time soil erosion in the marl landscape of SW Spain. Based on field observations and sediment analysis several landscape positions within a medium-scale catchment were explored. Depending on landscape constellation, the sediment characteristics reflect either hillslope processes or alluvial processes or an interchange of them. For a temporal context a method to trace young sediments by analysing nutrients originating from modern-time application of mineral fertiliser was applied. Results show high rates of sedimentation (>1 cm/year) for this young period in several profiles. By identifying the predominant geomorphic components and processes in the study area a conceptual model of the studied system was developed.