OahuN_shorelines - Shorelines of the northern coastal region of Oahu, Hawaii, from Camp Erdman to Kahuku, used in shoreline change analysis.

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. Shoreline vectors derived from historic and modern sources represent the low water mark (beach toe).

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.

砂质滨海沙滩是热门休闲度假胜地，周边往往分布着坐拥高价值不动产的社区。尽管海岸基础设施长期受洪涝与侵蚀威胁，沿岸开发热度仍持续攀升。由此，社会对精准掌握历史与当前海岸线变化情况的需求日益高涨。为满足这一国家层面的需求，美国地质调查局（U.S. Geological Survey，USGS）海岸与海洋地质项目组正依托《海岸线变化国家评估（National Assessment of Shoreline Change）》项目，收集美国本土以及阿拉斯加、夏威夷部分区域的开放洋面砂质海岸沿线现存的可靠历史海岸线数据。从历史与现代数据源提取的海岸线矢量数据，代表的是低潮线（滩脚，beach toe）。
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为州级或区域级的统一评估。该项目的核心动因，便是开发一套跨海岸统一的海岸线位置变化标准化测量方法，目标是以内部一致的方式，实现对评估结果的定期、系统更新。