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Gully erosion is one of the major contributors to severe land degradation in the Yuanmou Dry-hot valley region of Southwest China. Planting vegetation in gully beds has proven to be an effective measure in controlling the development of gullies. However, the inner mechanism for this process remains unclear. In this paper, in situ scouring experiments were performed to reveal the influence of grass belt position on the hydraulic properties of runoff in gully beds. The results demonstrate that (1) grass belt position can have a significant effect on reducing runoff erosivity (runoff shear stress, stream power) and sediment content in gully beds, and that the reduction may be strengthened as the distance between the gully headwall and grass belt (DHG) decreases; (2) grass belts could play a positive role in enhancing the surface resistance and increasing flow energy consumption, as resistance and flow energy consumption increase as DHG increases; and (3) there were similar trends in the temporal variations within the hydraulic properties, which changed sharply in the early stage of the experiment and then tended to stabilize, with their time to stability continuously increasing as DHG decreased. [ABSTRACT FROM AUTHOR]

Gully initiation has been a subject of much discussion in the field of gully erosion. Gully initiation could be examined by the S-A relationship (S = aA-b) between the critical slope of the gully head (5) and the upstream drainage area (A). Gully erosion plays an important role in sediment yield and land degradation in the Dry-hot Valley region of Southwest China; however, little research has focused on gully development in this region. This study investigated gully morphology and the critical topographic threshold of permanent gullies in Yuanmou Dry-hot Valley. Data for 36 gully heads were derived from the gully digital elevation model created by high-precision real-time kinematic GPS (RTK GPS). A significant relationship between gully length and volume (r²= 0.77, p <0.01) was found to exist, indicating that gully length can be used to estimate the gully erosion rate. Additionally, as vegetation coverage inside the gully increases, the gully morphology tends to be stable. The S-A relationship was S=0.5195A-0.0899, while AS² values ranged between 4.2 and 758.5 m². The low value of constant b (0.0899) indicates that collapse of the gully wall is the dominant process of gully erosion in Yuanmou Dry-hot Valley. [ABSTRACT FROM AUTHOR]