The role of vegetation in the retardation of rill erosion

Large rills with catchment areas measuring tens to hundreds of square metres pose serious soil erosion problems to South China, after deforestation has exposed the deeply weathered granitic slopes to the impacts of tropical rainstorms. Runoff and sediment discharges of rills respond rapidly to rainfall, but compared with bare rills, vegetated rills show considerably lower amounts of flow and sediment yield from unit rainfall input. Rainfall interception is one main reason for reduced runoff, and enhanced infiltration also lowers surface flow from vegetated areas. Potential sediment yield from unit runoff is greatly reduced when the rills are grown with fern, and this provides a far more effective mechanism for soil erosion control than the more temporary measures of installing sediment traps along the rills.