不同覆盖度下坡面流植被阻力特性研究

Characteristics of Vegetation Resistance in Overland Flow under Different Coverages

为深入研究植被覆盖下坡面流阻力规律,以植被覆盖下明渠水流植被阻力公式为基础,通过5个覆盖度、6个坡度和7个流量组合条件下的室内放水试验,结合理论分析,建立适应于坡面流的植被阻力模型。结果表明,植被阻力随等效覆盖度和等效水力半径的增加而增大,等效覆盖度对植被阻力的贡献率(0.106)小于明渠水流(0.167),而等效水力半径(0.5)和拖曳力系数(0.5)的贡献率与明渠水流(均为0.48)基本一致。植被阻力模型的NSE值高达0.84,为坡面流植被阻力计算奠定了一定的理论基础,可促进明渠水力学理论在坡面水流方面的扩展。

For further researching the laws of flow resistance, based on the vegetation resistance model under open channel flow, vegetation resistance models were established under six slopes （2°-12°）, seven flow discharges （3.65 L/rain, 4. 92 L/min, 8. 13 L/min, 11.78 L/min, 15.47 L/min, 19. 12 L/min and 27.26 L/min） and five vegetation coverage degrees （9. 300% ,6. 975% ,4. 650% ,2. 325% and 0） by combined experiment with theory which was adapted to overland flow. Equivalent coverage and equivalent hydraulic radius were defined in the model based on the definition of vegetation coverage and the hydraulic radius in the open channel flow. The results showed that when the other hydraulic conditions were identical, vegetation resistance was increased with the increase of equivalent coverage and equivalent hydraulic radius, the contribution rate of equivalent coverage （0. 106） was less than that （0. 167） of the open channel flow; however, the contribution rates of equivalent hydraulic radius （0.5） and the drag force coefficient （0.5） were approximately identical with those of the open channel flow （both of values were 0.48） , the Nse value of the model was 0. 84. This article distinguished vegetation resistance and comprehensive vegetation resistance, which may provide the theoretical basis for calculation of vegetation resistance of overland flow, so as to promote the expansion hydraulics theory of the open channel in the aspect of overland flow.