Evolution of loess gullies and geohazard chains in the Dongzhi tableland, China

Abstract

The Dongzhi tableland suffers from land degradation due to severe gully erosion. To determine the relationship between the gullies development and the evolutionary of geohazards chains in the gullies, a small watershed of the Dongzhi tableland was chosen as the study area. Subsequently, the morphometric characteristics and development process of loess gullies were systematically examined through statistical methods, including field investigations, unmanned aerial vehicle (UAV) photogrammetry, and geographic information system (GIS) spatial analysis. Results revealed that (1) The study area comprised 914 small incised gullies (SIGs), 57 incised gullies (IGs), and 5 dry gullies (DGs) based on the length, width, and depth of loess gullies. (2) SIGs were clustered and distributed at the bottom of the loess gully or on the edge of the loess tableland, and the SIG length exhibited a good power exponential relation with elevation difference, average gradient, area, and perimeter. (3) Based on the type of gully head and the degree of surface complexity, the SIGs were further divided into 27 profile types. And the most and least common profile combinations in the upper-middle-lower profiles were flat-flat-flat in 160 locations and concave-flat-stepped in one location. The corresponding results revealed loess collapse as the most dominant form of disaster during the evolution of SIGs. (4) Overall, SIG evolution was divided into four stages: initial, development, expansion, and stabilization stages. These stages mainly evolved in the form of geohazard chains and caused development of the SIGs. The results of this study will provide a scientific basis for the selection of preventive and control measures to manage gully erosion of the Dongzhi tableland.