Geomorphological dynamics of subhumid mountain badland areas — weathering, hydrological and suspended sediment transport processes: A case study in the Araguás catchment (Central Pyrenees) and implications for altered hydroclimatic regimes

28 páginas, 11 figuras, 4 tablas.This study investigates the geomorphological dynamics of badland areas in the Araguás catchment (0.45 km2) in the Central Pyrenees. The genesis and development of badlands in the Central Pyrenees is favoured by the presence of Eocene marls and a markedly seasonal climate. The Araguás catchment has been monitored since 2004. Analysis of weathering processes and regolith dynamics showed that alternating freeze-thaw and wetting-drying cycles are the main causes of regolith development and weathering, and effectiveness and intensity of these processes is maximum in winter and summer. Evolution of the badland surfaces is related to regolith moisture level and temperature, closely associated with the season and slope exposure, which cause cyclical variations in regolith physical conditions. The most important effect associated with regolith dynamics is the temporal delay between maximum rainfall erosivity and variation in maximum surface runoff generation, reflected in seasonal differences in sediment transport. The dynamics of weathering and erosion processes affecting badland areas are the principal factors controlling geomorphological development, and the extreme hydrological and sedimentological responses of badlands are the main effects of such morphologies. From a hydrological point of view, badlands increase water production, and flood frequency relative to neighbouring areas; from a sedimentological point of view, suspended sediment transport from badland areas can reach amounts two or three orders of magnitude higher than other nearby environments. Given these results, possible responses of badland dynamics to altered hydroclimatic regime are briefly discussed.This research was financially supported by projects CGL2006–11619/HID (Processes and sediment balances at different spatial scales in Mediterranean environments: effects of climate fluctuations and land use changes) and CGL2007-66644-C04-01 (Space-temporary behaviour and models of the sediment transfer on different land uses), funded by the CICYT, Spanish Ministry of Education and Science; and PI032/08, financed by the Aragon Government. Monitoring of the badland catchment was also funded by a consortium of the CSIC and the Spanish Ministry of Environment (RESEL Project). The first author benefited from a research contract (Human resources mobility, National Programme I-DþI 2008-2011) funded by the Spanish Ministry of Education and Science.Peer reviewe