双导堤工程下潮汐汊道与海岸潟湖地貌稳定性

Geomorphological Stabilities of Tidal Inlet and Coastal Lagoon Under Influence of a Double-guide-dike Project

摘要:

以渤海湾沿岸具有双导堤工程的单一潮汐汊道的华北最大海岸潟湖—七里海潟湖为原型建立理想模型，通过设置包括临界侵蚀应力、临界淤积应力、泥沙沉速、初始床面高程和径流量等影响潟湖地貌演变的相关参数，得到理想模型达到稳定状态后的纳潮量P和潮汐汊道断面最大流量Q_m。分别建立其与潮汐汊道断面面积A的相关关系式以表征潮汐汊道稳定性。比较分析发现在表征潮汐汊道稳定性方面，Q_m?A关系较P?A关系的拟合效果更佳。分别利用Q_m?A关系以及泥沙净冲淤量计算得到潮汐汊道和潟湖稳定所需时长，对比结果表明潟湖明显滞后于潮汐汊道达到稳定状态，临界侵蚀应力对潮汐汊道稳定性影响更大，而临界淤积应力、泥沙沉速和初始床面高程对潟湖稳定性影响尤为显著，径流量对潟湖和潮汐汊道稳定性的影响相当。

关键词:海岸潟湖;潮汐汊道;地貌稳定性;Q_m‒A关系;P-A关系;平衡状态

Abstract:

To investigate the stability of a coastal lagoon system with a single tidal inlet under the influence of a double-guide-dike project， an ideal model was established based on the largest costal lagoon with a single tidal inlet in North China， Qilihai Lagoon. Scenarios were set with different variables， including critical erosion shear stress， critical deposition shear stress， sediment settling velocity， initial bed elevation and runoff. The tidal prism P， the maximum discharge Q_m， and the cross-section area A of the tidal inlet were collected when the ideal model attains the equilibrium state in each case， and then equations about Q_m-A relationship and P-A relationship are established to indicate the stability of the tidal inlet. It illustrates that the Q_m-A relationship is more effective than the P-A relationship to show the stability of the tidal inlet. Then， both Q_m-A relationship and net erosion or deposition amount are utilized to calculate the time costs for the tidal inlet and the lagoon to attain the equilibrium state in each case. It indicates that the lagoon costs more time to attain the stability than the tidal inlet； critical erosion shear stress causes more effect on the tidal inlet； the lagoon is more sensitive to critical deposition shear stress， sediment settling velocity and initial bed elevation； runoff brings about the similar influence on the stability of the lagoon and the tidal inlet.

Key words:coastal lagoon;tidal inlet;morphological stability;Q_m-A relationship;P-A relationship;equilibrium state