建闸河口整治工程与河床演变特征

Study on Effect of Regulation Engineering Project on Morphological Evolution Downstream of Tidal Barrage

建闸河口整治工程引起的河床演变调整十分复杂.基于验证好的潮流、泥沙输运及河床演变模型分析了双龙河口整治一期工程和二期工程后水动力和河床演变的响应特征.结果表明,闸下河道水动力变化和河道冲淤分布与局部浚深拓宽及纳潮量增加有密切联系.若仅对河道上段局部河道进行整治,浚深拓宽段的涨落潮不对称现象加剧,局部产生回流区.若以固定坡降对整条河道进行整治,则涨落潮流速显著增加且不对称性减小.纳潮量增加在工程初期会引起口门段冲刷,而局部拓宽段会因流速相对减小而产生淤积,特别是在回流区淤积严重.因此为延长工程寿命,尚需辅以定期开闸放水和局部清淤等措施.

Morphological evolution downstream of tidal barrage is sensitive to regulation engineering project. A set of methodology integrating verified tidal current model, sediment transport model and morphological evolution model was set up to quantify the influences of different stages of regulation engineering project in the Shuanglong Estuary on currents and morphological evolution. Results indicate that the changes of currents and morphological evolution are closely associated with partially deepened-widened channel and increased tidal influx. In general, increased wetted area in the upper estuary has intensified the asymmetry of flood-ebb current velocity and even induces recirculating flow. While fully regulation over the estuary with a fixed slope will increase tidal current velocity significantly and relieve the asymmetry of flood-ebb current velocity as well. Though increased tidal influx at the estuary acts a positive factor washing out the sediment in lower channel, sediment deposition occurs in widened section of the estuary due to the decr.easing tidal current velocity, especially in recirculating flow region. Therefore, for enhancing the function of regulation project, releasing water from upper barriers and dredging regularly are also needed.