人类重大工程改变河口潮波传播方向引发的灾害与恢复

珠江河口网河密布,地貌形态极其复杂.人类为改变环境而进行许多重大工程,但有时因为对工程引发的复杂河口水动力特性的变化认识不足,导致工程带来严重的负面灾害性影响.有些影响通过长时间自然演变得以恢复,有些则不可逆转.五十年前珠江河口白藤堵海工程造成当地严重的内涝灾害,却又在十年后自然恢复,其动力变化原因始终不明,值得研究.采用河口整体数值模拟对白藤堵海工程及其水动力特征进行了计算.通过河口整体大区域计算的流动过程分析发现,堵海工程后鸡啼门水道因通潮能力不够,造成了潮波由竹银经泥湾门水道至上而下的逆向传播,引起了工程前后泥湾门区域水动力特征的极大变化,引发严重的内涝灾害.十年后鸡啼门水道自然冲刷,通潮能力的增强,使潮波逆向传播现象消失,该区域水位过程基本恢复到工程前状态,洪涝灾害自然消除.

Tide reverse transmitted resulted in flood by human project in estuary

A numerical simulation with model ccost-2d was carried out for studying the variations of surrounding hydrodynamic characteristics, which was induced by Baiteng sea-closure project 50 years ago. The sea-closure project induced that the tidal range decreased, the low water level ran up more than 0.5 m and the tide time delayed more than 2 hours at Baijiao station in Niwan waterway, which all caused serious flood problem. Through the analysis of the entire process of river networks flow by numerical simulation, the dynamical reasons for previous problem were found that, after sea-closure project, the tidal wave in the Niwan waterway came from Zhuying in the Modaomen waterway and reverse transmitted from upstream to downstream, because the tidal transmit capacity was not enough in Jitimen waterway due to too small cross section, which resulted in enormous change of dynamic characteristics. The hydrodynamic situation was simulated by numerical method when the waterway depth was increased by natural erosion 10 years later. With the increase of tidal transmit capacity in Jitimen waterway, the reverse transmit tidal wave in Niwan waterway disappeared, and water level process came back almost to the origin state before Baiteng sea-closure project.