Vol18 No.4: 907-922
【Title】Impacts of native vegetation on the hydraulic properties of the concentrated flows in bank gullies
【Author】SU Zheng-an1*, HE Zhou-yao1,2, ZHOU Tao1,3, WANG Jun-jie1,3, WANG Xiao-yi1,4, WANG Li-juan1,3, FANG Hai-dong5, SHI Liang-tao5, LIU Yi-han1,6, WU Zuo1,4
【Addresses】1 Key Laboratory of Mountain Environment Evolution and Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China; 2 Forestry College, Sichuan Agricultural University, Chengdu 611130, China; 3 University of Chinese Academy of Science, Beijing 100049, China; 4 College of Water Conservancy and Hydropower Engineering, Sichuan Agricultural University, Ya'an 625014, China; 5 Institute of Tropical Eco-agricultural Sciences, Yunnan Academy of Agricultural Sciences, Yuanmou 651300, China; 6 College of Geography and Resources Science, Sichuan Normal University, Chengdu 610101, China
【Corresponding author】SU Zheng-an
【Citation】Su ZA, He ZY, Zhou T, et al. (2020) Impacts of native vegetation on the hydraulic properties of the concentrated flows in bank gullies. Journal of Mountain Science 18(4). https://doi.org/10.1007/s11629-020-6287-9
【Abstract】To quantify the impacts of native vegetation on the spatial and temporal variations in hydraulic properties of bank gully concentrated flows, a series of in situflume experiments in the bank gully were performed at the Yuanmou Gully Erosion and Collapse Experimental Station in thedry-hot valley region of theJinsha River, Southwest China.This experiment involved upstream catchment areas with one- and two-yearnative grass (Heteropogon contortus) and bare land drained to bare gully headcuts, i.e., Gullies 1, 2 and 3. In Gully 4, Heteropogon contortus and Agave sisalana were planted in the upstream catchment area and gully bed, respectively.Among these experiments, the sediment concentration in runoff in Gully 3 was the highest andthat inGully 2 was the lowest, clearly indicating that the sediment concentration in runoff obviously decreased and the deposition of sediment obviously increased as the vegetation cover increased.The concentrated flows were turbulent in response to the flow discharge. The concentrated flows in the gully zones with native grass and bare land were sub- and supercritical, respectively. The flow rate and shear stressin Gully 3 upstream catchment area were highest amongthe four upstream catchment areas, while the flow rate and shear stress in the gully bed of Gully 4 were lowest amongthe four gully beds, indicating that native grass notably decreased thebank gully flow rate and shear stress.TheDarcy–Weisbach friction factor (resistance f) andflow energy consumption in the gully bed of Gully 4 were notably higher thanthose in theother three gully beds, clearly indicating that native grass increased the bank gully surface resistance and flow energy consumption. The Reynolds number(Re), flow rate, shear stress, resistance f, and flow energy consumption in the gully beds and upstream areas increased over time, while the sediment concentration in runoff and Froude number (Fr) decreased. Overall, increasing vegetation cover in upstream catchment areas and downstream gully beds of the bank gully isessential for gully erosion mitigation.
【Keywords】Soil erosion; Indigenous grass species; Bank gully; Concentrated flows; Flow energy consumption;Dryand hot valley.