不同植被类型对堆积体坡面径流特性的影响

针对植被防护堆积体侵蚀动力机制的问题,通过野外模拟降雨试验,分析直根系和须根系植被对堆积体径流流速、水力和水动力参数的影响。结果表明:植被削减堆积体平均侵蚀速率达88.34%~92.88%,直根系消减平均流速效益为50.51%,须根系为21.32%~35.61%;裸坡和植被堆积体径流流型均属于层流(雷诺数<40),裸坡径流在降雨强度≤1.2 mm/min时处于急流态,直根系堆积体均处于缓流态,须根系堆积体在急流态和缓流态间变化。直根系对坡面径流的阻滞作用大于须根系;植被防护下堆积体侵蚀速率、水力和水动力参数与裸坡呈显著性差异(P<0.05),径流剪切力和径流功率可用于较好地刻画坡面侵蚀动态过程,呈显著线性关系(R²为0.63~0.96)。研究成果可为生产建设项目工程堆积体水土流失量预测模型的植被因子修订提供科学依据。

Impact of Different Vegetation Types on Runoff Characteristics of Spoil Heaps

To obtain the erosion dynamic mechanism of spoil heaps, we examined the effects of taproot system (Artemisia gmelinii) and fibrous root system (Medicago sativa and Cynodon dactylon) vegetation on the runoff velocity, hydraulic parameters, and hydrodynamic parameters of the spoil heaps through artificial rainfall simulation experiment. Results demonstrated that vegetation reduced the average soil loss rate of spoil heaps by 88.34%-92.88%, as compared with bare spoil heaps. Average runoff velocity decreased by 50.51% under taproot system vegetation, and 21.32%-35.61% under fibrous root system vegetation. Both the runoff patterns of bare and vegetated spoil heaps were laminar (Reynolds Number <40). Runoff flow of bare spoil heaps was rapid when rainfall intensity was not greater than 1.2 mm/min; however, under the protection of taproot system vegetation, the runoff flow was slow, while under fibrous root system vegetation, the runoff flow pattern varied between rapid and slow regimes. Taproot system vegetation had a greater retardation effect on runoff resistance coefficient than fibrous root system. The flow shear stress and stream power could better describe the dynamic process of erosion on the spoil heaps under vegetation protection, showing a significant linear relationship (R² was 0.63-0.96). Our findings offer scientific basis for revising the vegetation factors in the establishment of soil and water prediction model suitable for production and construction projects.