Soil erosion modes of sealing soils: a phenomenological study

Surface seal development and failure substantially affect soil erosion processes. A flume study was conducted to determine surface seal failure of a variable charge subsoil by rainfall and surface flow under different slope steepnesses. Two experiments were conducted: (1) an alternating sequence of a rainfall-surface flow for a 2.6% slope bed involving increasing rainstorm intensities and surface flows, and (2) a 2 h rainstorm of 55.4 mm · h⁻¹ intensity followed by surface flow on a soil bed with slope steepnesses of 8.9, 12.5 and 16.5%. The results indicate that seal failure on this soil is a local ‘catastrophic’ phenomenon, in which failure occurs in the form of a cavity that rapidly grows under local flow conditions. Observations suggest that seal failure was caused by a combination of surface flow hydrodynamics and several subsurface factors such as pore pressure changes, vented soil air, and return flow.