南方风化花岗岩坡地产流过程与侵蚀率模拟研究

采用室内人工降雨模拟方法研究了不同坡度(5°,8°,15°,25°)和降雨强度(1.0,1.5,2.0,2.5 mm/min)对南方风化花岗岩坡地土壤侵蚀特征的影响。结果表明,径流量和径流率均随降雨强度的增大而增大,但随坡度的增大而减小。径流入渗率与坡度呈极显著正相关(r=0.660,p<0.01),而随着降雨时间的延长呈现出3个不同阶段的变化:初始全渗阶段、快速下降阶段和相对稳定阶段。降雨强度对径流量的影响比坡度更明显。平均产沙浓度与坡度呈极显著正相关(r=0.694,p<0.01),而其与降雨强度之间的关系取决于坡度条件。土壤侵蚀率随降雨延长呈先增后减趋势,整体上与坡度和降雨强度呈正相关(r>0.580,p<0.05)。土壤侵蚀率和径流率在陡坡上呈线性关系(R^2>0.861),在缓坡上呈幂函数关系(R^2>0.966)。最后采用修正的典型土壤流失方程模型来预测土壤侵蚀率,发现模拟值的变化趋势与实际测量值接近,表明该修正模型在研究区具有一定的适用性。研究结果可以为风化花岗岩地区的土壤侵蚀率研究提供数据支撑,对进一步理解土壤侵蚀过程有着重要的意义。

Simulation Study on Runoff Processes and Erosion Rate on the Weathered Granite Slope in Southern China

The method of artificial rainfall simulation was applied to study the effects of different slope gradients (5°, 8°, 15° and 25°) and rainfall intensities (1.0, 1.5, 2.0 and 2.5 mm/min) on the characteristics of soil erosion on the weathered granite slope land of South China. The results showed that both the runoff volume and runoff rate increased with the increasing rainfall intensity, but decreased with the increasing slope gradient. The runoff infiltration rate was significantly positively related to slope gradient (r=0.660, p<0.01)and exhibited three different stages with rainfall duration, including the initial all-infiltrated stage, rapid decreasing stage and the relatively stable stage. However, the effect of rainfall intensity on runoff yield was more obvious than that of slope gradient. There was a significantly positive correlation between the average sediment concentration and slope gradient(r=0.694, p<0.01). The relationship between rainfall intensity and average sediment concentration depended on the conditions of slope gradient. The soil erosion rate, which overall was positively related to slope gradient and rainfall intensity(r>0.580, p<0.05), showed a trend of increasing first and then decreasing with the prolongation of rainfall duration. The soil erosion rate and runoff rate showed a positive linear correlation (R²>0.861) on the steep slopes and a power function relationship (R²>0.966) on the gentle slopes. A revised typical soil loss equation model was used to predict the erosion rate, and it was found that the change trend of the simulated values was close to the actual measured values, which indicated that the revised model had certain applicability in the study area. These results could provide data support for the study of soil erosion rate in the weathered granite area, and had important significances for further understanding of soil erosion process.