NHD Flowline

This dataset includes flowline data that are contained by a subbasin that overlaps the 16-county NCTCOG region. The data are extracted from the NHD. The NHD is a digital vector dataset that contains features such as lakes, ponds, streams, rivers, canals, dams and stream gages. NHD Flowlines dataset consists of routes that make up a linear surface water drainage network. Flowlines have a reach code and a measure, allowing for the establishment of upstream/downstream relationships. This network allows for powerful analysis and modeling capabilities. Each Feature type is attributed with descriptive information by an Fcode. For more information about NHD features, see the Feature Catalog at http://nhd.usgs.gov/FeatureDirectory.swf. The NHD is a combination of USGS hydrologic digital line graph files (DLG) and EPA reach files, version 3.0 (RF3). The USGS files were used for spatial accuracy and the EPA files were used for attribute information. This dataset was downloaded from http://nhd.usgs.gov/data.html and processed but otherwise unaltered. This file is for reference use only. NCTCOG and its members are not responsible for errors or inaccuracies in the file.本数据集涵盖与16县北德克萨斯中部区域委员会（North Central Texas Council of Governments，NCTCOG）辖区存在重叠的子流域内的河道流线（flowline）数据。 本数据集提取自全国水文数据集（National Hydrography Dataset，NHD）。NHD为一套数字矢量数据集，涵盖湖泊、池塘、溪流、河流、运河、水坝及河道测站等水文要素。 NHD河道流线数据集由构成线性地表排水网络的路径组成。河道流线均带有河段编码（reach code）与度量值，可用于构建上下游关联关系。该网络可支持强大的分析与建模能力。 每种要素类型均通过Fcode附带描述性属性信息。如需了解更多NHD要素相关详情，请访问要素目录：http://nhd.usgs.gov/FeatureDirectory.swf。 NHD由美国地质调查局（USGS）水文数字线划图（Digital Line Graph，DLG）文件与美国环境保护署（EPA）3.0版河段文件（RF3）整合而成。其中USGS文件用于保障数据集的空间精度，EPA文件用于提供属性信息。 本数据集从http://nhd.usgs.gov/data.html下载并经处理，未进行其他修改。本文件仅作参考用途，北德克萨斯中部区域委员会（NCTCOG）及其成员不对本文件中的错误或不准确之处承担责任。