The effect of season and parent material on water erosion on highly eroded soils in eastern Spain

On highly eroded soils, where vegetation is absent or negligible, the nature of the parent material can greatly affect hydrological and erosion processes. Moreover, under Mediterranean climatic conditions, season determines soil surface morphologies via the soil water content and thus exerts a major control on runoff and erosion rates. Rainfall simulation experiments and cylinder infiltrometer measurements were carried out on degraded surfaces developed on three different parent materials (marl, clay and sand) during autumn (wet) and summer (dry conditions) in order to determine the influence of season and parent material on infiltration, runoff and erosion. For marl soils, ponding and runoff initiation were rapid, infiltration rates low, and runoff coefficient (81%) and erosion rates high. On the clay and sand soils, ponding and runoff initiation were delayed, infiltration rates greater, and runoff coefficient and erosion rates lower than on marl soils. Seasonally, infiltration rates decrease in autumn and thus runoff increases. Seasonal differences in erosion are less clear due to the increase of the runoff sediment concentration during summer, although the greatest erosion rates were found under autumn conditions. Clay soils show the greatest seasonal differences (Rc moves from 27% to 51%), which is due to crack development during summer