Seasonal patterns of runoff and erosion responses to simulated rainfall in a badland area in Mediterranean mountain conditions (Vallcebre, southeastern Pyrenees)

Abstract

Regolith surface characteristics and response were examined over a three-year period in a badland area in a Mediterranean middle-mountain zone near Vallcebre (Eastern Pyrenees). Preliminary work carried out in this area indicated clear seasonal patterns of regolith properties driven by frost heaving in winter and crusting and erosion in the rest of the year. Rainfall simulations were performed with a small portable nozzle simulator in order to study seasonal changes in runoff generation, erosion rates and raindrop effect on bulk density changes. The results showed large seasonal variations in runoff and erosion responses. Infiltration rates after runoff start were correlated with precipitation depth before runoff start; runoff generation was therefore related to regolith saturation only to a very limited extent. Erosion rates were more controlled by runoff rates than by the weakness of regolith against raindrop splash, and sediment grain size increased with concentration. The combined role of antecedent regolith moisture and bulk density explained most of the seasonal variability in infiltration, bulk density changes during rainfall and erosion rates, but some seasonal differences in sediment detachability were not explained by these variables and may be attributed to changes in roughness. Overall, runoff and erosion responses were relatively stable during spring and autumn, whereas wide variations in infiltration rates and sediment detachment occurred in winter and summer respectively. Experiments conducted in a single season would have produced poorly representative, if not erroneous, results.

Modelling soil detachment rates in rainfed agrosystems in the south-central Pyrenees

“…Temporal patterns observed in the current study were similar to that reported by Regüés and Gallart (2004) at Vallcebre, southeast Pyrenees. In that study, sediment concentrations in runoff samples were higher in spring and autumn than in winter and summer, and sediment detachability by splash was higher in spring and autumn than in winter and summer.…”

Analysing the effect of land use and vegetation cover on soil infiltration in three contrasting environments in northeast Spain

“…Low infiltration rates are recorded in bare soil due to the typical surface sealing in badlands (Regüés and Gallart, 2004;Nadal-Romero and Regüés, 2009), which agreed with the properties of soils developed on marls (Badía et al, 2015). Slope aspect has often been identified as a factor that determines soil degradation, vegetation cover and infiltration rates (Seeger et al, 2006;Regüés et al, 2012;Robertson and Sharp, 2015), especially in areas affected by farmland abandonment (Lana-Renault, 2009).…”

The application of terrestrial laser scanner and SfM photogrammetry in measuring erosion and deposition processes in two opposite slopes in a humid badlands area (central Spanish Pyrenees)

“…Nadal- , based on field evidence and laboratory work, suggested that in these badland morphologies shallow landslides and small mudflows commonly occur during prolonged rainfall events. These erosion processes produced the development of fans at the base of slopes and near the main channels, processes also observed in different badland morphologies (Balasch, 1998;Regüés and Gallart, 2004;Desir and Marín, 2007). It is also remarkable that during summer, convective storms of high intensity and short duration overcome infiltration capacity and generate intense concentrated runoff.…”