Topographic characteristics and threshold of gully erosion in the red soil hilly region of Southern China

摘要

Gully erosion causes and intensifies a tensed man-land relationship, buries land and raises the stream bed in the red soil region of Southern China. Various people, governments and social sectors have paid attention to gully erosion and its damages and prevention. Thus. it is important to study the characteristics. evolution, and impact factors of gully erosion for predicting and controlling gully erosion. In this study, an area of 862.7 km2, which is located in Yudu County, Jiangxi province, was selected as a case study to explore geomorphical characteristics and spatial distribution of gully erosion. Location, slope gradient and aspect, slope position and distance from gully head to slope top of all gullies was measured for further analysis. The results indicate that gully erosion density of 16954t/km2.a is much greater than the loss tolerance of 500t/km2.a. Gullies are distributed from northeast to southwest. Generally, gullies are stacked and single gullies occur rarely. Most gully erosion appears in slope gradients of 8-33°. Gully quantity in the south slopes was found to be more than in the north due to the fact that rainfall is accompanied with southern winds. There are different percentages of gullies in the different slope positions: upper slope (5.9%), middle slope (26.5%), downslope (43.2%), footslope (18.2%) and stream or canal (6.25%). This is because concentrated runoff has a strong effect on gully erosion. 44.4% of all gullies are located in the waterways. In addition, gully erosion is located on both sides of other gullies or streams because runoff from both slope and road or stream embankments causes gully erosion. Thus, it is concluded that it is an effective way to prevent gully erosion to some extent if the runoff is diffused by proper soil and water conservation measures such as grassways.