Erosión y desertificación.-Influencia de los procesos de sofusión (Piping) en la evolución del modelado. Bardenas Reales (Navarra)

Abstract

ABSTRACT Piping processes are controlled by many interacting factors, such as the index of dispersion and the sodium content, SAR and ESP. To it is necessary to join the density of cracking and the slope of the hillsides on which it develops. In the study area climatic characteristics together with soil structure and chemical and mineralogical composition of the substrate has a key role in Piping's formation. Cracking is linked to the presence of dispersive clays with high contents in SAR and ESP, which give the rates of swelling until 12%. The process presence of piping is linked to two concrete situations: the massive intermediate levels of the intermediate Holocene filling sediments and the sediments deposited by the gullies; whereas in the tertiary materials it does not manage to develop. The size and scale of the pipes studied show a clear relationship among the level thickness, slope and hydraulic gradient. In the Holocene landfills the principal bounding factor is the levels thickness since the lower laminated levels do not facilitate the continuity in depth of the process due to the high number of discontinuities, generating centimeter-scale conduits that are always on duty to the drainage network.