Spatial Distributions and Interactions of Different Erosion Processes

This chapter first describes the spatial distributions of mass movements, gullies, and tunnels within the Wangjiagou (WJG) watershed; then, the spatial relations between gully development and mass movement, tunnel formation and gully development, and mass movement and tunnel formation are analyzed. Furthermore, the effect of runoff generation from the intergully area on sediment production in the gully area is evaluated. The upper intergully area is dominated by sheet and rill erosions, and the lower gully area is active in mass movement, tunnel erosion, and gully erosion. Runoff generated from the intergully areas not only causes erosion there but also causes significant erosion in the gully area. In the gully area, tunnel formation is closely associated with gully development in the headwater and hillside gullies but is largely absent in the valleyside gullies and ephemeral stream channels. Mass movement is also active in gully development and is dominated by earth falls in headwater gullies, slides and falls in hillside gullies, and soil creeps in ephemeral stream channels. The spatial interactions of erosion processes should be taken into consideration in erosion control and planning in the watershed.