Erosión y desertificación.-Characteristics and distribution of soil piping erosion in loess-derived soils of Belgium

Abstract

ABSTRACT Subsurface erosion (piping, tunnel erosion) in non-karstic landscapes has been considered of little importance compared to sheet and gully erosion for a long time. Although the basic factors responsible for piping in certain environments are well understood, there is still uncertainty about the topographic and soil properties inducing subsurface pipe development in loess-derived soils under temperate climate. Therefore, this research aims at understanding the factors controlling the occurrence of piping erosion in the loess-derived soils of the Flemish Ardennes (Belgium). Analysis of orthophotos as well as field surveys were conducted to detect the sites with piping in the study area. Enquiries among farmers and technical services were carried out. In total, 114 sites (parcels) with 301 collapsed soil pipes were found in a 179 km² study area. For each site with piping, data was collected on possible controlling factors: topographic parameters, land use, lithology and soil type. Land use plays an important role as 94% of the sites with piping are found under pasture. Furthermore, the probability of piping increases rapidly on slopes with gradients exceeding 8%. The areas with the Aalbeke Member, a relatively thin layer of homogenous blue massive clays, under the shallow loess cover are most prone to piping. Over 28% of the sites with piping are located on this lithologic layer, while this layer covers only 8% of the study area. The rest of the sites with piping are located on two lithologic layers containing clay as well as silt and sand.