Evolution of Port and Terrestrial Space in the Coast Zone of Bohai Bay from 1974 to 2023

In the past half - century, China’s reclamation area has exceeded 15,000 km², making it the country with the largest reclamation area in the world. Among them, 3% of the area of the Bohai Sea has been reclaimed, and the land - sea changes are very significant, making accurate and continuous monitoring and analysis of the area necessary. Starting from “dynamic monitoring - utilization analysis”, this paper studies the dynamic spatial distribution and quantitative changes of reclaimed areas in Bohai Bay based on the yearly remote sensing images from 1974 to 2023, using ENVI and GIS technologies. In the past 40 years, a total of 1379.79 km² of the sea area has been reclaimed in the study area, mainly in the inshore and tidal flats. The land - use change map shows that land - use changes are closely related to policy and economic mode changes. Under the five - year time slice, the comprehensive land - use degree of the Bohai Bay is less than 4%, showing an extremely slow chagne.