USGS Map service: National Shoreline Change - Short-Term Shoreline Change Rates

Beach erosion is a chronic problem along most open-ocean shores of the United States. As coastal populations continue to grow, and community infrastructures are threatened by erosion, there is increased demand for accurate information regarding past and present shoreline changes. There is also need for a comprehensive analysis of shoreline movement that is regionally consistent. To meet these national needs, the USGS National Assessment of Shoreline Change Project has collected and analyzed a comprehensive database of digital vector shorelines by compiling shoreline positions from pre-existing historical shoreline databases and by generating historical and modern shoreline data. This dataset consists of short-term (~30 years) shoreline change rates. Rate calculations were computed using the Digital Shoreline Analysis System (DSAS), an ArcGIS extension developed by the U.S. Geological Survey. Short-term rates of shoreline change were calculated using an end-point rate method based on available shorelines to provide an approximately 30-yr short-term rate. A reference baseline was used as the originating point for the orthogonal transects cast by the DSAS software. The transects intersect each shoreline establishing measurement points, which are then used to calculate short-term rates. To make these results more accessible to the public and other agencies, the USGS created this web service. This web service was created utilizing ESRI ArcServer. This service meets open geospatial consortium standards. The data compilation used to derive the shoreline change rates is available in a service with the title USGS Map service: National Shoreline Change - Historic Shorelines by State. The reference baseline used to derive the shoreline change rates is available in a service with the title USGS Map service: National Shoreline Change - Offshore Baseline. The locations of the transects used in the change rate calculation are available in a service with the title USGS Map service: National Shoreline Change - Intersection Points. The geographic information system (GIS) data layers from this web service are cataloged by state for ease of access.海滩侵蚀是美国绝大多数开阔洋岸长期存在的共性问题。随着沿海人口持续增长，社区基础设施日益受到侵蚀威胁，社会对能够准确反映过去与当前海岸线变化的信息需求日益攀升，同时也亟需开展区域一致性的海岸线移动综合分析。 为满足这些国家层面的需求，美国地质调查局（U.S. Geological Survey, USGS）国家海岸线变化评估项目通过整合已有历史海岸线数据库中的海岸线位置，并生成历史与现代海岸线数据，收集并分析了一套完整的数字矢量海岸线数据库。 本数据集包含短期（约30年）海岸线变化速率数据。速率计算借助美国地质调查局开发的ArcGIS扩展模块——数字海岸线分析系统（Digital Shoreline Analysis System, DSAS）完成。本次短期海岸线变化速率采用端点速率法，基于现有海岸线数据计算得出，旨在得到约30年尺度的短期变化速率。DSAS软件生成的正交断面以参考基线为起始点，这些断面与每条海岸线相交以获取测量点，随后利用这些测量点计算短期变化速率。 为便于公众与其他机构获取相关成果，美国地质调查局开发了本网络服务。该网络服务基于环境系统研究所（Environmental Systems Research Institute, ESRI）ArcServer搭建，符合开放地理空间联盟（Open Geospatial Consortium, OGC）的标准规范。 用于推导海岸线变化速率的原始整合数据，可通过标题为「USGS地图服务：国家海岸线变化——各州历史海岸线」的服务获取。用于计算变化速率的参考基线数据，可通过标题为「USGS地图服务：国家海岸线变化——近海基线」的服务获取。而变化速率计算所用断面的位置数据，则可通过标题为「USGS地图服务：国家海岸线变化——相交点」的服务获取。 本网络服务提供的地理信息系统（Geographic Information System, GIS）数据图层按州分类编目，以提升访问便捷性。