在河口水动力模式的基础上，耦合泥沙模块和底部冲淤方程，建立了崇明东滩鸟类保护区海堤外侧引水渠冲淤三维数值模式. 模式上游闸门水通量由堰流公式计算，内侧水位由随塘河水动力模式计算，模式下游水位、盐度、泥沙浓度由长江河口大区域数值模式计算. 利用2018年7月28—30日优化工程区水闸开闸冲淤前后实测引水渠底部高程进行验证，模式计算的高程与实测值吻合良好，表明模式能较好地模拟引水渠冲淤变化. 冲淤计算结果表明，闸下引水渠在自然状态下，涵闸关闭60 d后基本淤平，闸口淤积量最大，淤积程度自闸口向外海逐渐减小. 引水渠自然淤积2个月后，随塘河蓄水至3.0 m开闸放水，引水渠平均冲淤量为96 mm；随塘河蓄水至3.8 m开闸放水，引水渠平均冲淤量为133 mm；纳潮冲淤一天，引水渠平均冲淤量为625 mm. 纳潮冲淤是最为有效的冲淤方式. 研究成果可为崇明东滩国家级自然保护区生态修复工程区的保护与管理、引水渠冲淤方案提供科技指导.
A three-dimensional numerical model for erosion and deposition at the water intake channel of the outer seawall of Chongming Dongtan Bird Sanctuary was established based on the hydrodynamic model of the estuary coupled with the sediment module and the bottom erosion and sedimentation equation. The model’s upstream boundary condition at the sluice was specified with water flux calculated by the Weir formula, where the inner water level was calculated by the hydrodynamic model of the Suitang River. The model’s downstream boundary condition of the water level, salinity and sediment concentration were calculated by the large domain numerical model of the Changjiang Estuary. We measured bottom elevations at the water intake channel before and after the sluice opening from July 28 to July 30, 2018 and found that the calculated model elevations were in general agreement with the measured values, indicating that the model can accurately simulate erosion and sedimentation changes. The calculation results for scouring and siltation show that under natural conditions, the water intake channel becomes level after 60 days of sluice closure because of sediment deposit. Siltation is largest near the sluice and gradually decreases with distance from the sluice to the sea. After the water intake channel was naturally silted for two months, the mean erosion thickness at the water intake channel was 96 mm in the case where Suitang River accumulated up to 3.0 m of water and discharged thereafter, 133 mm in the case where Suitang River accumulated up to 3.8 m of water and discharged thereafter, and 625 mm in the case where Suitang River accumulated up to 3.0 m of water and the sluice was opened to receive tidal water. Leaving the sluice open to receive tidal water is the most effective way for scouring sediment in the water intake channel. The research results provide scientific and technical guidance for the protection and management of the ecological restoration project area in Chongming Dongtan National Nature Reserve and the scouring sediment scheme of the water intake channel.
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