Shorelines of the Cape Cod coastal region from Provincetown to the southern end of Monomoy Island, Massachusetts, used in shoreline change analysis (CapeCod_shorelines.shp)

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目的地，周边往往环绕着蕴含高价值不动产的社区。尽管沿海基础设施面临洪涝与海岸侵蚀的威胁，沿海开发热度仍持续攀升。因此，社会对能够精准反映历史与当前海岸线变化状况的相关信息需求日益高涨。为满足此类国家层面的需求，美国地质调查局（U.S. Geological Survey, USGS）旗下的海岸与海洋地质项目组，正依托《海岸线变化国家评估》项目，对美国本土、阿拉斯加部分区域及夏威夷的开放洋域沙质岸线沿线的现有可靠历史海岸线数据进行汇编。当前尚未形成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法与岸线变化速率计算方法因研究而异，导致相关成果无法整合至州级或区域级评估工作中。本次国家海岸线变化评估项目的核心动因，便是研发一套跨海岸统一的标准化海岸线位置变化测量方法。该项目的目标在于，以内部逻辑一致的方式，实现海岸线变化评估成果的定期、系统化更新。