Studies On Gully Erosion Assessment And Partitionin Loess Plateau Based On Shoulder Lines

Loess landform has always been the focus of Loess Plateau because of its strong fragmented, rolling surface. Gully erosion is a kind of soil erosion which causes the forming of gully through runoff erosion and incision. Different kind of gullies in the Loess Plateau, are the results of different gully erosion process. Loess shoulder lines lies in the surface where the gullies and scouring gullies is active development. The development of a channel, such as its length or area increasing, will always be been reflected through the investigation of the shoulder lines.Based on previous research, a series of gully erosion indices are extracted from DEMs. Then gully erosion processes and its spatial variation are discussed through thorough analysis of the indices. Main works and conclusions of this paper include:(1) Gully erosion indices based on should line which can properly reflect the morphology, statistical characteristics, and development of the loess surface; scale effect of the indices also discussed here;(2) Spatial distribution of gully erosion in the Loess Plateau is studied based on the indices of 166 test areas, and then the degrees of gully erosion in the Loess Plateau are classified with unsupervised classification method. The results show that quantitative indices proposed in this paper are effective to describe the features of gully erosion with significant differences in different loess landform types. Also, the degree of gully erosion from high to low is:loess hill, loess hill-ridge, loess ridge, loess tableland, loess low hill, mountain area, loess plain.(3) The temporal distribution of gully erosion in 9-stage simulated loess watersheds is also discussed through a comparative analysis between traditional indices and the proposed indices based on loess shoulder line. The results shown that erosion intensity was reducing wavelike with the erosion process. The change of erosion intensity is related to rainfall. Compared with the traditional indices of gully erosion, the proposed indices could describe more diversity features of gully erosion.This study is a beneficial investigation of digital terrain analysis of loess landform. In addition, it could also deepen our understanding of soil erosion in Loess Plateau, formation and evolution process of loess landform.