Effect of cultivation in upstream catchment on gully headcut erosion process in dry-hot valley

Abstract：The development of gully erosion has seriously threatened the local ecological environment and social and economic development in dry-hot valley region of Jinsha River. In order to explore the influence of catchment cultivation on the headstream erosion process in the dry-hot valley, an active gully head was selected to construct four in-situ experimental plots, which is located in the Gully Erosion and Collapse Experimental Station in Yuanmou Dry-Hot Valley. Along the vertical section from the gully catchment area to the gully bed, the gully was divided into 4 test plots, each of which was divided into three parts: the gully catchment area, the gully wall and the gully bed. A series of in-situ scouring experiments were carried out. The flow rates were set at 30, 60, 90 and 120 L/min based on local rainfall intensity. The runoff and erosion characteristics of different parts of gully head under bare land and cultivated land in the upstream catchment area were researched. For the bare land in the upstream catchment area, it was considered as bare land gully. For the cultivated land in the upstream catchment area, it was considered as cultivated land gully. The results showed that: The soil erosion rate of upstream catchment area of cultivated land was higher than that of bare land, while no significant difference in soil erosion rate could be found at gully wall between bare land gully and cultivated land gully. Meanwhile, no significant difference in soil erosion rate could be found at gully bed between bare land gully and cultivated land gully. As the experiment progressed, temporal variation in soil erosion rates of bare land gully was similar with that of cultivated land gully. Compared to the bare land, the resistance coefficient of runoff (f) was higher in the cultivated land in upstream catchment of bank gully. Compared to bare land gully, the resistance coefficients of upstream catchment area and gully bed in cultivated land gully increased by 6.96 times and 2 times, respectively. For bare land gully, a gradually increasing trend in f was observed in the upstream catchment areas and downstream gully beds. However, a decreasing trend in f was observed in the cultivated land gully over time. For different parts of the gully, cultivation had no significant effect on the energy consumption of runoff, but it had a significant effect on the energy consumption of runoff per unit soil loss. Runoff energy consumption per unit soil loss in upstream catchment area of cultivated land gully decreased by about 50% compared with that of bare land gully. As a result, cultivation could increase soil resistance coefficient and soil erosion rate, while decrease energy consumption of runoff per unit soil loss in the upstream catchment area of gully. It should be noted that no significant differences in soil erosion rate and the energy consumption of runoff in the gully wall and gully bed could be found between cultivated land gully and bare land gully.