黄土区草地坡面片流阻力系数试验研究

阻力系数是坡面流水动力学参数之一,是反映坡面流水力学特性的重要特征值。通过室内人工模拟降雨试验,研究了不同雨强(0.7,1.0,1.5,2.0,2.5mm/min)和坡度(7°,10°,15°,20°,25°)下,黄土区草地坡面片流阻力系数随雨强和坡度的变化特征。结果表明:(1)不同雨强和坡度下,草地坡面片流阻力系数随降雨历时的变化均呈先波动减小,后逐渐趋于稳定的趋势,且变化过程均可用二次多项式进行描述,相关性显著,决定系数0.5以上。(2)草地坡面片流阻力系数随雨强的增加而逐渐增大,可用指数方程描述,决定系数0.8以上;而片流阻力系数随坡度的增加而减小,可用对数方程描述,决定系数0.6以上。(3)草地坡面次降雨平均片流阻力系数对雨强及坡度的综合响应关系可用二元指数函数描述,决定系数0.923,且雨强对草地坡面片流平均阻力系数的影响大于坡度对阻力系数的影响。研究结果为草地坡面水流动力学特性及草地植被的阻流机制提供参考和理论基础,对于深刻认识黄土区草地坡面侵蚀动力和生态建设具有重要意义。

Experimental Study on Sheet Flow Resistance Coefficient of Grassland in Loess Area

The resistance coefficient is one of the hydrodynamic parameters of the slope surface and also is an important eigenvalue that reflects the hydraulic characteristics of the slope surface. In order to explore the variations of surface runoff resistance coefficient of grassland in loess region with different rainfall intensities (0.7, 1.0, 1.5, 2.0, 2.5 mm/min) and slope gradients (7°, 10°, 15°, 20°, 25°), indoor artificial rainfall simulation was adopted in this study. The results showed that:(1) The sheet flow resistance coefficient of grassland slopes decrease firstly, and then gradually stabilized with the rainfall duration under different rainfall intensities and slope gradients. The relationship between resistance coefficient and rainfall duration could be described by a quadratic polynomial equation, and the correlation was significant, also the coefficient of determination was above 0.5. (2) The sheet flow resistance coefficient of grassland slope increased gradually with rainfall intensity, and the relationship could be described by a exponential equation with the coefficient of determination was above 0.8; while the sheet flow resistance coefficient of grassland slope decreased with the increase of slope gradient, and the relationship could be described by a logarithmic equation with the coefficient of determination was above 0.6. (3) The integrated response of the average flow resistance coefficient of the grassland slope could be described by a binary exponential function with the coefficient of determination was 0.923. Through comparative analysis, it was found that the influence of rainfall intensity to average sheet flow resistance coefficient was greater than that of slope gradient. This study provides a theoretical basis for the reference of grassland flow hydrodynamics and the flow control mechanism of grassland vegetation. It is of great significance for us to deeply understanding the erosion dynamics of grass slope and ecological construction in the loess area.