Response of Soil Pipe Collapse Features to Land Management and Soil Hydropedology.

Flow through macropores can be sufficiently rapid to cause internal erosion and, thereby, creation of soil pipes. Soil pedology and hydrology interact to determine the location of soil pipes, flow rates through soil pipes and rates of internal erosion. Soil pipes tend to develop in duplex soil in that water restricting horizons cause a proliferation of biopores at the interface and foster lateral subsurface flow by perching water. Internal erosion can enlarge these preferential flow paths to the extent that pipe's collapse, thereby forming flute holes, sinkholes and ephemeral gullies at the surface. The soil hydropedologic properties determine the erodibility of the pipe surfaces and shear forces acting on pipe walls.  Little is known about the impact of past land management practices on soil pipe formation. This paper will review the connections between hydrologic and pedologic soil properties with soil pipeflow processes using observations of soil pipes in Goodwin Creek Experimental Watershed. Three adjacent catchments, all classified as the same soil series, were surveyed for pipe collapse features. One contained no pipe collapse features, while the other two exhibited 32.6 and 15.7 collapse feature ha^-1. Soils in these catchments contain a fragipan that perches water and fosters lateral flows. Subsurface layers exhibit vulnerability to internal erosion. However, it appears that past land management practices control to a large degree the location of soil pipes and hydrologic response of the catchment. This paper will use field observations to highlight gaps in our understanding of the hydropedologic processes associated with soil piping and their interaction with and/or response to land management practices.