基于水流功率的坡面流挟沙力模拟

Study on sediment transport capacity of overland flow based on stream power

基于WEPP(Water Erosion Prediction Project)模型挟沙力方程,用两组水槽试验数据评价了水流功率对陡坡坡面流挟沙力的模拟能力。研究结果表明,坡面流挟沙力随着水流功率的增大而增大,可以用水流功率1.25次方的幂函数较好地模拟挟沙力(NSE=0.97),计算得到的泥沙输移系数独立于自变量水流功率,且趋向于常数。分析不同泥沙粒径的试验数据发现,泥沙输移系数随着泥沙粒径的增大呈幂函数递减(R2=0.99),从而构建了基于泥沙中值粒径、水流功率以及某一粒级泥沙在侵蚀泥沙中所占百分比的坡面流挟沙力方程,用独立的试验数据对方程进行检验发现,纳什效率系数高达0.97,检验结果表明模拟值与实测值间无显著差异,说明基于水流功率构建的坡面流挟沙力方程具有较好的实用性,可以实现陡坡坡面流挟沙力的有效模拟。

This study was conducted to assess the performance of stream power to predict sediment transport capacity of overland flow based on the concept of WEPP model using datasets obtained from two separately experiments performed in hydraulic flume with fixed bed on steep slopes. Results showed that Tc increased with stream power. The power function with an exponent of 1.25 for stream power simulated the measured Tc very well （NSE = 0.97 ） and the calculated transport coefficient K, was independent with stream power. K~ decreased with sediment median diameter as a power function （R2 = 0.99）. Sediment transport capacity could be well predicted （NSE = 0.97） using two independence terms： sediment median diameter power function and flow stream power. The modified equation was improved greatly and NSE increased by 40.6% when shear stress was replaced by stream power in WEPP model. No significant difference was detected between the meas- ured Tc and those calculated by new equation.