MauiW_baseline - Offshore baseline used to cast shore-perpendicular transects for measurement of historical shoreline positions along the West Coast of Maui, Hawaii (Ukumehame to Honolua)

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胜地，周边多分布着坐拥高价值不动产的聚居社区。尽管沿海基础设施始终面临洪涝与海岸侵蚀的威胁，沿岸开发热度仍持续攀升。为此，社会对精准获取历史与当前海岸线变化信息的需求与日俱增。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，在全国海岸线变化评估项目（National Assessment of Shoreline Change project）框架下，正针对美国本土48州、阿拉斯加部分区域及夏威夷的开放洋域沙质海岸，整合沿线现有可靠的历史海岸线数据。

当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手段与变化速率计算方法因研究项目各不相同，致使各研究结果无法整合为州级或区域级的统一评估成果。全国海岸线变化评估项目正是以此为核心动因，旨在研发一套跨海岸保持统一的标准化海岸线位置变化测量方法，其目标在于以内部一致的方式，定期且系统性地更新评估结果，便于该流程的高效开展。