柔性植被倒伏对地表径流水力特性及侵蚀的影响

[目的] 为探讨柔性植被倒伏后形成的近地表覆盖减少径流和侵蚀量及调节地表径流水力特性的影响。[方法] 以流体力学和水力学基本理论为依据,通过5个覆盖度、5个坡度和3个流量组合的条件下进行室内放水试验,系统研究柔性植被倒伏下的侵蚀规律以及水动力学特征。[结果] (1)侵蚀量分布随坡度增加呈先上升后下降趋势,流量在高坡度下对侵蚀过程的影响更为显著;(2)随着柔性植被覆盖度增加,以50%覆盖度为分界线,侵蚀量基本呈先降低后增加趋势;(3)平均流速v随覆盖度增加而减小,下降趋势随覆盖度增加由急变缓,Fr变化趋势与平均流速相似;阻力系数f与覆盖度呈线性正相关,随坡度升高,阻力系数值逐渐降低;而雷诺数Re对土壤侵蚀的影响比Fr、v和f更敏感。(4)随着植被覆盖度增加,形态剪切力增大(颗粒剪切力减小),形态剪切力在总剪切力的变化中起决定性作用,总剪切力与植被覆盖度呈正相关。[结论] 柔性植被倒伏后形成的近地表覆盖可减少土壤侵蚀,研究可为坡面流植被侵蚀规律奠定一定的理论基础,促进明渠水力学理论在坡面水流方面的扩展。

The Impact of Flexible Vegetation Lodging on the Hydraulic Characteristics of Surface Runoff and Erosion

[Objective] This study was aimed at exploring the influence of nearsurface coverage formed by the collapse of flexible vegetation in reducing runoff and erosion yield, and in modulating the hydraulic properties of surface runoff. [Methods] Based on fundamental principles of fluid mechanics and hydraulics, the erosion patterns and hydrodynamic characteristics under lodged flexible vegetation were systemically investigated through indoor hydrodynamic experiments across five levels of coverage, five slope gradients, and three flow rates. [Results] (1) The distribution of erosion volume demonstrated an initial increase followed by a decrease with the increment of slope angle, with the influence of flow rate on the erosion process being more pronounced at steeper slopes. (2) Corresponding to an increase in the coverage of flexible vegetation, and taking 50% coverage as a threshold, the erosion volume generally exhibited a trend of initial reduction followed by an increase. (3) The average flow velocity (v) decreased with increasing vegetative coverage, with the rate of decline becoming gradual as coverage intensified. The variation in Froude number (Fr) mirrored the trend in average flow velocity. The friction coefficient (f) was positively linear correlated with coverage and decreased with an increase in slope gradient; the Reynolds number (Re) demonstrated a higher sensitivity to soil erosion compared to Fr, v, and f. (4) With the increase in vegetation coverage, morphological shear stress intensified (while particle shear stress diminished), playing a pivotal role in the changes in total shear stress, which was positively correlated with vegetation coverage. [Conclusion] The study establishes a solid theoretical foundation for the erosion patterns of slope flow vegetation and facilitates the expansion of open channel hydraulic theories in the realm of slope flows.