Sediment yield and transport in badlands located in the Inner Depression (Araguás Basin, Central Pyrenees)

Abstract

This study shows the analyses of suspended sediment transport from badland areas developed in the Inner Depression (Central Pyrenees). The importance of these morphologies is related to its frequency, and to the high impact that they produce on the drainage net, because of their intense geomorphological dynamics. The occurrence and development of these morphologies is associated to two main factors: the geological characteristics of the substratum constituted by marls, and the strong climatic seasonality of the submediterranean climate. The area has been studied since 2004, through the selection of a small basin, which was monitored with sensors and plots for observation of weathering and erosion processes (between January 2004 and December 2006). This instrumentation was completed with a gauging station (October 2005) on the main drainage (Rebullesa ravine) that facilitates the record of hydrological response and suspended sediment transport. This paper shows an analysis, based on 79 recorded events between October 2005 and April 2007. The results, that correspond to a short period of time, have allowed pointing out some general characteristics of hydro-sedimentological responses in these morphologies: very high hydrological response, even during the driest period; great capacity of sediment yield and exportation, with punctual concentrations than can reach more than 1000 g·l-1, and the strong sensibility against climatic seasonality. Likewise, it was observed that precipitation intensity is well correlated with sediment concentration, especially during the driest periods, which demonstrates that the main runoff generation process is associated to infiltration excess mechanisms (Hortonian flow).