MA_Islands_ST.shp - Digital Shoreline Analysis System version 4.1 Transects with Short-Term Rate Calculations for the Massachusetts Islands Region including Martha's Vineyard and Nantucket

Sandy ocean beaches are a popular recreational destination, often surrounded by communities containing valuable real estate. Development is on the rise despite the fact that coastal infrastructure is subjected to flooding and erosion. As a result, there is an increased demand for accurate information regarding past and present shoreline changes. To meet these national needs, the Coastal and Marine Geology Program of the U.S. Geological Survey (USGS) is compiling existing reliable historical shoreline data along open-ocean sandy shores of the conterminous United States and parts of Alaska and Hawaii under the National Assessment of Shoreline Change project.

There is no widely accepted standard for analyzing shoreline change. Existing shoreline data measurements and rate calculation methods vary from study to study and prevent combining results into state-wide or regional assessments. The impetus behind the National Assessment project was to develop a standardized method of measuring changes in shoreline position that is consistent from coast to coast. The goal was to facilitate the process of periodically and systematically updating the results in an internally consistent manner.

滨海沙质海滩是热门的休闲度假胜地，周边往往坐落着坐拥高价值不动产的居民区。尽管海岸基础设施面临洪涝与侵蚀威胁，沿岸开发活动仍呈上升态势。因此，社会对精准掌握历史与当前海岸线变化情况的需求与日俱增。为满足此类国家层面的需求，美国地质调查局（U.S. Geological Survey, USGS）下属的海岸与海洋地质项目组，正通过《海岸线变化国家评估》项目，汇编美国本土（48州）、阿拉斯加部分区域及夏威夷的开放洋域沙质海岸沿线的现有可靠历史海岸线数据。
目前尚无被广泛认可的海岸线变化分析标准。现有海岸线数据测量方式与岸线变化速率计算方法因研究而异，导致无法将不同研究的结果整合为全州或区域级的综合评估成果。本《海岸线变化国家评估》项目的初衷，便是研发一套适用于全美所有海岸、统一规范的海岸线位置变化测量方法。其目标是实现以内部统一的标准，定期且系统性地更新相关评估成果的流程化运作。