![]() ![]() Streamgages, which are point features, can be displayed and identified in the network through linear referencing with a network address. NHDPointEventFC, NHDLineEventFC, and NHDAreaEventFC represent point, line, and area data events that behave as map features and linearly referenced events. NHDPoint contains hydrography related point features. Artificial path carries the critical attributes of the stream/river, whereas NHDArea represents the geometric extent. These polygons typically encompass NHDFlowline artificial paths that represent the stream network. It represents the areal extent of the water in a wide stream/river with a basic set of attributes. One of the more important is the stream/river feature. NHDArea contains many additional water-polygon features. Other NHDWaterbody features are swamp/marsh, reservoir, playa, estuary, and ice mass. These water polygons may have NHDFlowline artificial paths drawn through them to allow the representation of water flow direction. They portray the spatial geometry and the attributes of the feature. Waterbodies such as lake/pond features are represented in NHDWaterbody. ![]() NHDLine contains linear features not core to the network. Additional NHDFlowline features are canal/ditch, pipeline, connector, underground conduit, and coastline. It represents the spatial geometry, carries the attributes, and contains linear referencing measures for locating features or “events” on the network. NHDFlowline is the fundamental flow network consisting predominantly of stream/river and artificial path vector features. It is also available as a shapefile download, which simplifies this structure by containing all of the feature classes as separate shapefiles and tables as separate data files.įor information about NHD specifications, please see the Hydrography Standards and Specifications page. It also includes the WBD in a second feature dataset. ![]() The NHD file geodatabase download contains NHD data in the Hydrography feature dataset. The NHD is available as a file geodatabase download, which maintains the richness of the complex NHD database model, including multiple feature datasets, feature classes, event feature classes, attribute tables, relationship classes, domains, and feature-level metadata. The NHD, Watershed Boundary Dataset (WBD), and 3D Elevation Program (3DEP) data are used to create the NHDPlus High Resolution. These data are updated and maintained through Stewardship partnerships with states and other collaborative bodies. For more information on using the data in Google Earth™, please see Using the National Flood Hazard Layer Web Map Service (WMS) in Google Earth™.The National Hydrography Dataset (NHD) is mapped at 1:24,000 or larger scale (1:63,360 or larger scale in Alaska). To do so, you will need GIS or mapping software that can read data in shapefile format.įEMA also offers a download of a KMZ (keyhole markup file zipped) file, which overlays the data in Google Earth™. This data can be used in most GIS applications to perform spatial analyses and for integration into custom maps and reports. Using the “Search All Products” on the MSC, you can download the NFHL data for a County or State in a GIS file format. You can also use the address search on the FEMA Flood Map Service Center (MSC) to view the NFHL data or download a FIRMette. For more information on available services, go to the NFHL GIS Services User Guide. Technical GIS users can also utilize a series of dedicated GIS web services that allow the NFHL database to be incorporated into websites and GIS applications. In the NFHL Viewer, you can use the address search or map navigation to locate an area of interest and the NFHL Print Tool to download and print a full Flood Insurance Rate Map (FIRM) or FIRMette (a smaller, printable version of a FIRM) where modernized data exists. Or you you may view, download, and print current local digital effective flood hazard data in an ArcGIS map. ![]()
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