Research on the Limit Values of Reclamation Based on Ecological Security: A Case Study of Tongzhou Bay in Rudong, Jiangsu Province

Due to the growing demand for land resources, many coastal reclamation projects have been implemented around the world in recent decades. Although coastal zone reclamation provides economic benefits, it produces a series of threats to coastal environments and ecosystems. Hence, the ecological costs and economic benefits of reclamation projects must be balanced. In this study, we select Tongzhou Bay, a key development area of the marine industry in the Jiangsu Province, as the research region to study the limits of reclamation control of the port operation area based on regional ecological security. First, we determine the standard limit values of the tidal catchment water line and the water dividing line, the change rate of the tidal flux ±5%, and water area of sandbars above the 0 m line based on key factors and evaluation indices for the ecological impact of reclamation in this region. Then, eight reclamation cases are investigated in Tongzhou Bay, which include the undeveloped natural state, development status, construction projects to be built, and possible construction scale based on the results of tidal current numerical simulation calculations. Although case 3 has impacts on Section 2 (DM2) tidal flux of less than 5% and on Section 1 (DM1) tidal flux of less than 10%, it causes a northward shift of the flood catchment water line in the middle of Yaosha. Finally, case 8 meets the requirements of the standard limit values of evaluation indicators, e.g., 1455 hectares of reclamation is the limit value to maintain the natural state of the Sanshahong channel and the stability of the tidal creek system and Yaosha. Therefore, the results suggest optimizing the structure and layout of breakwaters, controlling the restriction of reclamation, and further maintaining and protecting the ecological function of Tongzhou Bay.