KauaiW_baseline - Offshore baseline used to cast shore-perpendicular transects for measurement of historical shoreline positions along West Kauai, Hawaii (Oomano to Polihale)

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休闲度假目的地，周边往往分布着拥有高价值不动产的社区。尽管沿海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。由此，社会对准确掌握过去与当前海岸线变化信息的需求日益增长。为满足这一国家层面的需求，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，依托《海岸线变化国家评估》项目，正在汇集美国本土48州、阿拉斯加部分区域及夏威夷的开放海域沙质海岸沿线已有的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。现有海岸线数据的测量方式与岸线变化速率计算方法因研究而异，导致无法将各研究结果整合至州级或区域级评估中。启动《海岸线变化国家评估》项目的初衷，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，以实现以内部统一的标准定期、系统地更新评估结果。