Abstract:Because of the combined effects of global and coastal environmental processes and human activities, dramatic changes to coastlines have had significant effects on the environment, ecosystems, and human society in the coastal zone, and the issue has increasingly become a major socio-economic concern to countries along the coast. Consequently, coastline changes have drawn great attention in the academic community, and numerous studies on this issue have been conducted and results subsequently published. Following the definition of proxy-based coastlines and rules of coastline classification, in this paper, we review the methodologies and technologies of coastline interpretation, quality calculation, and estimation of coastlines extracted from remote sensing imageries and topographic maps, as well as analytical methodologies and technologies related to coastline change. Driving factors and the effects of coastline changes are also summarized and analyzed in this paper. Progress and directions of expected research are presented in the last part of this paper. A coastline is a wet-dry boundary or ocean-land boundary. In this paper, individual shoreline indicators generally fall into two categories: visually discernible coastlines (e.g., wet-dry line, debris line, vegetation line), or intersection lines of the coastal profile with a specific vertical elevation defined by the tidal constituents of a particular area (e.g., mean high-low water line, mean sea level line). Methodologies and data sources of coastline data extraction are reviewed in the second part, and the methodologies are classified into three categories based on whether they involve human assistance (automatic extraction, semi-automatic extraction, and visual interpretation). Calculation of quality and estimation of coastlines are discussed in the second part of this paper, and include line-based evaluation, point-based evaluation, and deduction evaluation. In the third part, methods for analysis of coastline change are reviewed and explained, from simple methods to more complicated ones, and from qualitative methods to more quantitative ones. The driving factors are reduced to three categories: global environmental processes (e.g., global warming, sea level rise), coastal environmental processes (e.g., ocean dynamic, sediment movement), and human activities (e.g., coastline hardening, sea reclamation). In the last part of this paper, we discuss research progress and expected research on coastline change around the world. We put forward the following views. Dynamic monitoring of coastline changes remains one of the highest research priorities, as our understanding of features, laws, and mechanisms of coastline change deepens, and as research based on high-accuracy data and advanced mechanistic models develops. Studies focus on causes and mechanisms of coastline changes, impacts on coastal environments and ecosystems of various coastal zones, as well as on the characteristics of interrelations and mutual influences of different coastal regions, are another major area of focus of studies on global coastline change. Furthermore, coastline changes in China have distinct characteristics and complexity; therefore, studies of the Chinese coastline should be used to set the primary goals for improving and supporting the practices of ICZM (Integrated Coastal Zone Management). These studies will increase the awareness of decision-makers and stakeholders of the risks of hazards caused by coastline change, and will provide key information for coastal scientific planning and development.