含盐风暴潮溃堤洪水数值模拟及风险分析

为了研究三角洲河口风暴潮溃堤时的盐水运动规律,建立一、二维耦合的盐度数学模型对风暴潮溃堤时的盐水运动进行模拟。模型考虑洪泛区建筑物对盐水运动的影响以及溃口的渐变发展过程。用2008年多个测站的实测数据对河网模型的潮位和盐度计算结果进行了验证。将模型应用于珠江三角洲河网某近海溃口风暴潮溃堤的盐水运动模拟,并绘制了最大盐度等值面图。计算结果表明,该溃口大部分区域的溃堤积水盐度超过了4psu,因此,溃堤洪水的高盐度积水影响不容忽视。通过比较“溃堤”和“不溃堤”两种情况下的河网盐度计算结果,发现上游河道的溃堤分流增大了河道的纳潮量,促使涨潮量增大,增大了下游河网的咸潮上溯风险,减弱了上游来流对咸潮的压制效果。

Saline storm surge levee-breach flood numerical simulation and risk analysis

In order to study the motion law of salt water when the levees break with storm surge in the delta estuary, one-dimensional and two-dimensional coupled salinity numerical models are developed to simulate the salt water movement when the levees break with storm surge. The impact of buildings in flood plains on the salt water movement and the gradient development process of the dyke breach are considered. The water levels and salinity calculated by the river networks model are tested with the measured data of multiple survey stations in 2008. The model is applied to simulate the salt water movement of an offshore dyke on the Pearl River Delta when the levees break with storm surge, and the maximum salinity isosurface diagram is mapped. The results show that the salinity of levee-breach flood in most of the breaches is over 4psu. Therefore, the impact of the high salinity ponding of levee breaches flood cannot be ignored. By comparing the drainage salinity calculated in the cases of "levee breaches" and "non-levee breaches", it is found that the levee breaches shunt of upstream enhances the storage capacity of tidal water, increases the flood tidal volume, raises the trace-back risk of salt water intrusion of downstream river network and weakens the suppressing effect of the upstream flow on salt water intrusion.