Remote Sensing Monitoring of Shenzhen Coastline Changes over the Past 40 Years

Since the reform and opening-up, the ecological environment of the coastline of Shenzhen has been under pressure from high-intensity human exploitation activities. Additionally, the structure, type, and length of the coastline has undergone significant changes. Studying the changes of the Shenzhen coastline over the past 40 years is helpful to reveal its spatial and temporal evolutionary processes and driving mechanisms to provide a reference for the protection and utilization of coastline resources. This study screened 16 scenes of the Shenzhen regional Landsat remote sensing images from 1979 to 2019, and performed a coastline extraction using Remote Sensing (RS) and Geographic Information System (GIS) methods to ensure alignment, accuracy, and extraction precision to meet the research requirements. Based on four coastline evaluation indexes (End Point Rates, Linear Regression Rates, Coastline-type Diversity Index, and Comprehensive Index of Coastline Utilization), the spatiotemporal characteristics of the coastline length, structure, types, and rate of change were analyzed to explore the factors driving the spatio-temporal evolution of the Shenzhen coastline. The results found that over the past 40 years, (1) the length of the Shenzhen coastline has experienced a continuously increasing trend, with a total increase of 41.52 km, and an average annual growth of 1.04 km. All the natural coastlines within the coastal area of Shenzhen decreased significantly to varying degrees, with a total decrease of 56.61%, while the proportion of artificial coastlines increased rapidly. (2) The change in coastline type in Shenzhen is mainly from the early muddy and sandy coastline to the farming reclamation and engineering construction coastline, i.e., the transition from natural to artificial shore. Among them, coastline length increased the most from 1979 to 1988. The most drastic coastline change was observed from 1979 to 1994, and the peak period of land reclamation was from 1994 to 2008. After 2008, Shenzhen coastline development gradually entered a sustainable and rational stage. (3) The spatial vicissitudes of the Shenzhen coastline have progressed through the stages of initiation, acceleration, and rational restriction. Areas with significant coastline expansion were located in Bao'an International Airport, Qianhai Cooperation Zone, Shenzhen Bay of Houhai, Yantian District, and near Longqi Bay. The change in the west coast of Shenzhen is more drastic than that of the east coast. The maximum rate of change (EPR) on the west coast reaches 422.19 m/a, which occurred during the Shekou Peninsula seaward extension period from 2004 to 2008. The EPR on the east coast reached the highest level of 449.65 m/a during the development and construction of Yantian Port from 1994 to 1998; and (4) the Shenzhen coastline change is a dynamic and a continuous process of change. Human activities, special zone policies, and natural factors were the main driving forces of the coastline changes. The special zone policy is the core driving force for Shenzhen's population expansion, urban sprawl, and the fundamental reason for the reduction in natural coastlines and the growth of artificial coastlines. This study provides important guidance for future sustainable urban development in Shenzhen.