三维水沙模型在永定河河势分析中的应用

Apptication of three-dimensional flow-sediment model in flood control planning of Yongding River

为了检验永定河现状治导工程能否有效控制河势,采用CREST三维水沙数值模拟系统模拟分析河势走向、水沙浓度以及河床变形。根据永定河卢梁段河流泥沙和河床变化特征,引入合理床面悬移质平衡输沙浓度、推移质平衡输沙率以及平面分配系数,建立永定河卢梁段三维水沙模型并进行河床变形验证;模拟分析了河道流速场分布、悬沙浓度分布及河床变形规律,以及现状治导工程在控导河势方面发挥的作用,得到了河道环流、丁坝头绕流等复杂水流规律,并对游荡型河道流势、流向和顶冲点位置以及洪水主槽冲刷、边滩丁坝保护区淤积情况进行了预测。分析结果表明,河道治导工程在控制河势方面依然起到主导作用,部分丁坝坝顶受漫流冲刷破坏,局部河道需要添加少量短丁坝以巩固堤防安全。

In order to examine whether the training structures could effectively control the river regime or not, a three-dimensional （3D） model CREST is applied to analyze the river regime trend, sediment transportation, and river bed deformation of Yongding River. According to the characteristics of sediment and riverbed variation of Lu-Liang section of Yongding River, a 3D numerical model is set up with a proper equilibrium concentration of suspended load, the bedload transport rate, and plane partition coefficient. The model is calibrated by bed deformation. Then, the rule of training structures played in controlling the river regime is studied by simulating the velocity field, the sediment concentration distribution and bed deformation. As a result, complex flow laws of the vortex and the spur dike flow are obtained. Additionally, the flow tendency, flow direction, scouring point location, erosion in main channel due to flood, and deposition owing to spur dike protection are predicted. The 3D numerical model is applied to simulate the river regime variation, sediment transport, and bed deformation of Yongding River. The results show that long spur dikes control the river regime, and some of them are suffered from overflow and local scour on the head. For levee safety, short groins need to be added to some local river banks where the erosion often happened.