Hydrography - NHD Flowlines

The WA State National Hydrography Dataset (NHD) is the standard hydrography for Washington. NHD Flowline contains linear watercourses representing streams, rivers, canals, ditches, coastline, pipelines, and artificial paths (centerlines through water polygon features such as lakes, estuaries, or double-banked streams). Flowline data for Washington are developed at a resolution of 1:4,800 to 1:24,000. This dataset was extracted and projected into WA State Plane Coordinates South. The coastline in the Puget Sound was updated in 2022 and references the Mean High Water (MHW) datum. Strahler Stream Order has been calculated and added using Esri ArcGIS Pro tools. A trace network was created from simplified flowlines and has also been added. The National Hydrography Dataset (NHD) is a feature-based database that interconnects and uniquely identifies the stream segments or reaches that make up the nation's surface water drainage system. This high-resolution NHD, generally is developed at 1:24,000/1:12,000 scale, but many areas of Washington State have been improved to 1:4800 scale. NHD data was originally developed at 1:100,000-scale and exists at that scale for the whole country. Local resolution NHD is being developed where partners and data exist. The NHD contains reach codes for networked features, flow direction, names, and centerline representations for areal water bodies. Reaches are also defined on waterbodies and the approximate shorelines of the Great Lakes, the Atlantic and Pacific Oceans and the Gulf of Mexico. The NHD also incorporates the National Spatial Data Infrastructure framework criteria established by the Federal Geographic Data Committee. Stream Orders in Washington State range from 1 to 10. The smallest headwater streams are a 1, and the Columbia River is a 10. A detailed data dictionary is available at https://nhd.usgs.gov/userguide.html?url=NHD_User_Guide/Feature_Catalog/NHD_Feature_Catalog.htm华盛顿州国家水文数据集（National Hydrography Dataset, NHD）是华盛顿州的标准水文测绘数据。NHD流线（Flowline）要素包含代表溪流、河流、运河、沟渠、海岸线、管道以及人工水道的线性水系要素，此类要素即穿过湖泊、河口或双岸溪流等水面多边形要素的中心线。华盛顿州的流线数据分辨率区间为1:4800至1:24000。本数据集已完成提取并投影至华盛顿州平面坐标系南带（WA State Plane Coordinates South）。普吉特湾（Puget Sound）的海岸线已于2022年完成更新，其高程参考基准为平均高潮面（Mean High Water, MHW）。已使用Esri ArcGIS Pro工具计算并添加了斯特拉勒河流分级（Strahler Stream Order）字段，同时基于简化流线创建了追踪网络并纳入本数据集。 国家水文数据集（NHD）是一款基于要素的数据库，可实现美国地表排水系统内各溪流片段或河段的互联与唯一标识。该高分辨率NHD通常以1:24000/1:12000比例尺生产，但华盛顿州的多数区域已将数据精度优化至1:4800比例尺。NHD数据最初以1:100000比例尺开发，目前全美全域均保有该比例尺的数据集。在具备合作方与可用数据支持的区域，正推进本地化高分辨率NHD的建设工作。 NHD包含网络化要素的河段编码、流向、名称以及面状水体的中心线表达形式。河段同时也定义于各类水体以及五大湖、大西洋、太平洋与墨西哥湾的近似岸线之上。NHD还符合由联邦地理数据委员会（Federal Geographic Data Committee, FGDC）制定的国家空间数据基础设施框架标准。华盛顿州的河流分级范围为1至10级，其中最小的源头溪流为1级，哥伦比亚河则为10级。详细的数据字典可通过以下链接获取：https://nhd.usgs.gov/userguide.html?url=NHD_User_Guide/Feature_Catalog/NHD_Feature_Catalog.htm