ACJV NWI Coastal Zone focus

This data set represents the extent, approximate location and type of wetlands and deepwater habitats in the United States and its Territories. These data delineate the areal extent of wetlands and surface waters as defined by Cowardin et al. (1979). The National Wetlands Inventory - Version 2, Surface Waters and Wetlands Inventory was derived by retaining the wetland and deepwater polygons that compose the NWI digital wetlands spatial data layer and reintroducing any linear wetland or surface water features that were orphaned from the original NWI hard copy maps by converting them to narrow polygonal features. Additionally, the data are supplemented with hydrography data, buffered to become polygonal features, as a secondary source for any single-line stream features not mapped by the NWI and to complete segmented connections. Wetland mapping conducted in WA, OR, CA, NV and ID after 2012 and most other projects mapped after 2015 were mapped to include all surface water features and are not derived data. The linear hydrography dataset used to derive Version 2 was the U.S. Geological Survey's National Hydrography Dataset (NHD). Specific information on the NHD version used to derive Version 2 and where Version 2 was mapped can be found in the 'comments' field of the Wetlands_Project_Metadata feature class. Certain wetland habitats are excluded from the National mapping program because of the limitations of aerial imagery as the primary data source used to detect wetlands. These habitats include seagrasses or submerged aquatic vegetation that are found in the intertidal and subtidal zones of estuaries and near shore coastal waters. Some deepwater reef communities (coral or tuberficid worm reefs) have also been excluded from the inventory. These habitats, because of their depth, go undetected by aerial imagery. By policy, the Service also excludes certain types of "farmed wetlands" as may be defined by the Food Security Act or that do not coincide with the Cowardin et al. definition. Contact the Service's Regional Wetland Coordinator for additional information on what types of farmed wetlands are included on wetland maps. This dataset should be used in conjunction with the Wetlands_Project_Metadata layer, which contains project specific wetlands mapping procedures and information on dates, scales and emulsion of imagery used to map the wetlands within specific project boundaries.本数据集涵盖美国及其领地内湿地与深水栖息地的分布范围、大致位置及类型。此类数据依据考尔丁等人（Cowardin et al., 1979）提出的定义，勾勒出湿地与地表水体的面积范围。国家湿地清查第二版（National Wetlands Inventory - Version 2）地表水体与湿地清查数据集的构建方式为：保留构成国家湿地清查（National Wetlands Inventory, NWI）数字湿地空间数据图层的湿地与深水多边形要素，并将原始NWI纸质地图中未被纳入早期数字图层的线性湿地或地表水体要素转换为窄幅多边形要素，重新纳入数据集。此外，本数据集还补充了经缓冲处理转为多边形要素的水文数据，作为NWI未测绘的单线河流要素的补充数据源，并完善分段水系连接。2012年后在华盛顿州、俄勒冈州、加利福尼亚州、内华达州及爱达荷州开展的湿地测绘工作，以及2015年后多数其他测绘项目的成果，均完整包含所有地表水体要素，并非衍生数据集。用于构建第二版数据集的线性水文数据集为美国地质调查局（U.S. Geological Survey）的国家水文数据集（National Hydrography Dataset, NHD）。有关第二版数据集所依托的NHD版本，以及第二版数据集的测绘范围的详细信息，可查阅`Wetlands_Project_Metadata`要素类的"comments"字段。由于航空影像作为湿地探测的核心数据源存在局限性，部分湿地栖息地未纳入国家测绘项目。此类栖息地包括分布在河口潮间带、潮下带及近岸海域的海草与沉水水生植被。部分深水礁群落（珊瑚礁或管栖蠕虫礁）也未被纳入本次清查——这类栖息地因所处水深较大，无法通过航空影像探测识别。根据本机构政策，部分由《食品安全法案》定义，或不符合考尔丁等人湿地定义的"农田湿地"也将被排除在外。如需了解湿地地图中包含的农田湿地类型的更多信息，请联系本机构的区域湿地协调员。本数据集需与`Wetlands_Project_Metadata`图层配合使用，该图层包含特定项目边界内的湿地测绘专项流程、测绘日期、比例尺及影像感光类型等相关信息。