荆江河段河床冲淤计算滞后响应模型改进

Improvement of river evolution delay response model in the Jingjiang Reach

针对河床演变滞后响应模型在荆江河段的应用进行了三方面的改进：一是对于特征变量平衡值的计算表达式进行了调整,更为全面地考虑了非汛期来水量、泥沙级配和水位等水力要素对于河道冲淤变化的影响;二是考虑年际间来水来沙过程的变化,对河道调整速率参数β的计算方法进行了修正;三是引入水面比降J作为折减系数,在模型计算中减弱洞庭湖出流对于下荆江干流的顶托效应影响。选取2003-2014年荆江河段枯水河槽对应的单位河长累计冲刷量作为模型的特征变量,结合枝城、沙市、监利和城陵矶4个水文站的实测资料对改进后的模型进行验证。结果表明,改进后的模型更为准确地反映了特征变量随水沙等条件变化的调整规律,计算精度R^2达到0.85-0.97之间,在进行有关荆江河段河道冲淤计算时有较好的适应性。

The channel evolution delayed response model is applied in the Jingjiang Reach. The modified model is improved in three aspects ： 1 ） Adjusting the calculation formula of the balance value of the characteristic variable, which includes the influence of non-flood season water volume, sediment gradation and water lever on the scour and silt changes of the channel. 2） Modifying the channel regulation rate parameterβ by the change of interannual incoming water and sediment process. 3） Reducing the influence of the outflow of Dongting Lake on the backwater effect of Lower Jingjiang Reach by introducing water surface slope J as a re- duction coefficient in the model. Selecting unit accumulated volume of sediment degradation under lower water level in the Jingjiang Reach from 2003 to 2014 as the characteristic variables. The improved model is tested by observed data at Zhicheng, Shashi, Jianli and Chenglingji stations. Result indicates that the improved model has a higher accuracy with a determinant coefficient R^2 as 0.85 - 0.97.