Collapsible loess-derived soils are prone to soil piping erosion, where enlargement of macropores may leadto a subsurface pipe network and eventually to soil collapse and gully development. This study aims atunderstanding the main factors controlling spatial patterns of piping in loess-derived soils under a temperateclimate. To map the spatial distribution of piping and identify the environmental controls on its distribution,a regional survey was carried out in a 236 km² study area in the Flemish Ardennes (Belgium). Orthophotostaken at optimal field conditions (winter) were analyzed to detect piping in open landscapes and groundthruthing was systematically done through field surveys. In total, 137 parcels having 560 collapsed pipeswere mapped. Dimensions of the sinkholes and local slope gradient were measured in the field andtopographical variables were derived from LiDAR data. Land use plays an important role as 97% of the siteswith piping are found under pasture. The probability of piping increases rapidly on hillslopes with gradientsexceeding 8% and with a concave profile and plan curvature, enhancing subsurface flow concentration. Thezones with soil profiles on shallow loess over a relatively thin layer of homogeneous blue massive clays(Aalbeke Member) are most prone to piping. Soil characteristics are of less importance to explain pipingoccurrence. Furthermore, the topographical threshold line indicating the critical slope gradient for a givencontributing drainage area was determined. This threshold line (negative power relation) is similar to thethreshold line for shallow gully initiation.
展开▼
