No abstract

Gullies characterized by frequent material exchange have profoundly affected the loess landforms evolution in the Loess Plateau of China. Accompanying gully development, various types of gullies have shaped the distinctive loess landforms. Thus, the spatial variations of gully morphology map the regional differences of gully development and loess landforms. Based on 6 key test areas with 5 m resolution DEM and 156 evenly distributed test areas with 25 m resolution DEM, a comprehensive gullyshape index system of topographic feature points, lines, and surfaces was constructed to describe spatial differences of the gully development. After comparing gully-shape indexes in the key test areas, an obvious correlation existed between these indexes and loess landform types. The gully development degree was low in Shenmu and Chunhua, high in Suide, Yanchuan, and Ganquan, while Yijun lay in-between. Using the method of Universal Kriging interpolation, a series of spatial interpolation maps of the gully-shape indexes were obtained, which revealed gully development degree in the whole Loess Plateau. Overall, The active areas of gully development were basically distributed along loess hilly ridges, loess hills, loess ridges, and in a few medium mountain areas, while the inactive areas were basically distributed in the thin loess coverage areas, including plains, river terraces, aeolian dunes, and a few loess platforms. Finally, the gully development regionalization was realized, which contained 6 subzones. These results provided significant references for loess landform research and soil erosion management in the Loess Plateau.

Gully development is an important topic in the evolution of modern geomorphology. The study of the development process of gullies is key to understanding the genesis, mechanism and spatial differentiation of loess geomorphology. This study explored the mechanism of the development process of gullies whilst taking into account the erosion characteristics of the gully head area, gully slope area and gully bed area. Based on geographic cellular automata (Geo‐CA), the transition rules were interacted with the fundamental hydraulic principles for gully evolution simulation. Different sediment transfer rules apply to the gully slope area and gully bed area. A simulation model of the loess gully evolution was constructed and implemented based on the loess simulation small watershed. The superior performance of the model was demonstrated by the accuracy evaluation of the model structure and the comparative analysis of the modelling results. Moreover, the model was validated by natural watershed data, and the analytical results indicated the feasibility of the model.