The Influence of Scale on Runoff and Erosion

Runoff and soil loss data are presented from three scales; 0.2 ha catchment within a contour discharging through a rill, 1 ha contour catchments-discharging from a graded channel into a waterway and 250 ha catchments leading to trunk streams. Peak runoff rates decline rapidly with increased catchment size. A large reduction in sediment concentration occurs between the 0.2 ha rill outlet and the 1.0 ha contour catchment; with a lesser reduction in sediment concentration at the 250 ha. Implications of this result on the stability of valley floors is briefly discussed.