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

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.