A comparative study of coastline changes at Tampa Bay and Xiangshan Harbor during the last 30 years

A large number of world's population lives within coastal areas. These environmentally sensitive zones bear both natural pressures such as erosion, accretion and natural disasters and anthropogenic impacts such as urban growth, resource exploration and pollution. The decay of coastal ecosystem has an interactive influence on surrounding residents. Monitoring the change of coastlines could help the government and coastal managers make sounds policies. This paper presents a track of coastline changes at Tampa Bay (TB) and Xiangshan Harbor (XH) during the last 30 years. There are several methods used to obtain coastlines. One popular way is waterline extraction method using normalized difference water index (NDWI). Several studies recommended on-screen digitizing technique to delineate coastline based on classified NDWI images. However, in this study, a GIS technique, converting raster to polyline, was applied to capture coastlines to reduce laboring work. The preliminary analysis results indicate that the coastlines in TB only had slight changes during these 30 years while the coastlines in XH suffered severe erosions and anthropogenic impacts. In recent decades, TB managements put lots of efforts on ecosystem protection, such as implementing the Tampa Bay Estuary Program to keep a healthy and stable coastal ecosystem. Therefore, the government of XH needs to pay more attention to ecosystem protection during the process of urbanization and to learn the advanced experience and policies of protecting TB coastlines.