Ephemeral gully erosion by preferential flow through a discontinuous soil-pipe

Subsurface flow through soil-pipes can contribute to ephemeral gully erosion but these soil-pipes are cut-off when tillage fills in the gully. The objective was to determine the effect of flow through discontinuous soil-pipes on ephemeral gully erosion. Experiments were conducted on 150 cm long by 100 cm wide soil beds with an artificial soil-pipe at the upper end that extended 50 cm into the soil immediately above a water-restricting horizon. The combination of rainfall with pipe flow produced extensive (63 kg) soil losses by mass wasting. The mode of mass wasting appeared to be sudden, cataclysmic pop-out failures. Total soil loss by sheet erosion with rainfall and pipe flow combined (13.6 kg) was four times higher than by rainfall alone (3.4 kg). Under rainfall with pipe flow, soil loss by mass wasting was nearly 20 times higher than sheet erosion from rainfall alone. Soil conservation practices that treat surface runoff process alone may be ineffective if subsurface flow is contributing.