Field studies on the slope length effect of grass cover and rainfall
intensity on erosion on typical watersheds of the Loess Plateau, China
Abstract
Slope length is an important topographic factor for controlling soil
erosion and pivotal parameters in the soil erosion model. The impact of
slope length on soil erosion was studied under different grassland and
different rainfall intensity through simulated rainfall experiments. The
experiment included five rainfall intensity treatments (1, 1.5, 2, 2.5
and 3 mm h−1), four grass cover treatments (0, 30%, 60% and 90%) and
five slope length treatments (2, 4, 6, 8 and 10 m). The results show
that the rate of soil loss increased exponentially with increasing slope
length under 0 and 30% grass cover. Under high grass covers (60% and
90%), the slope length increased sedimentation from runoff and reduced
slope erosion.The increase of slope length led to enhancement of soil
loss as rainfall intensity increased. At 1 mm min−1 rainfall intensity,
natural grass slopes (60%) controlled soil loss very well and were not
affected by slope length. At 1.5–2 mm min−1rainfall intensity, the soil
erosion increased with slope length, but the overall soil erosion amount
was small. This indicates that grass cover at 10 m slope length had a
good impact on soil erosion. When the rainfall intensity exceeded 2 mm
min−1, soil loss increased with slope length. Regression analysis showed
that soil erosion was more strongly related to grass cover and rainfall
intensity than to slope length.