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About The National Hydrography Dataset
 

The NHD is a comprehensive set of digital spatial data that represents the surface water of the United States using common features such as lakes, ponds, streams, rivers, canals, stream gages and dams. Polygons are used to represent areal features such as lakes, ponds, and rivers; lines are used to represent linear features such as streams, canals and smaller rivers; while points are used to represent point features such as stream gages and dams.

The NHD dataset is distributed in an ESRI geodatabase format that consists of several feature classes including Points, Lines, Areas, Flowline, and Waterbody. The Flowline feature class allows the lines to be used to show how water flows through areal features. The combination of lines in the Flowline feature class are used to create a geographic network of water flow and allows users of the data to trace upstream and/or downstream directions from any particular point along the network using tools already embedded in the ESRI ArcGIS application.

The NHD has several features that make it unique to use as a hydrographic layer:

  1. The development of the geographic network for tracing flows.
  2. Each individual feature has a unique reference identifier called the common identifier (ComID within the dataset).
  3. Individual features also include a link to feature level metadata. Metadata, being the data about the data, allows for the user to find out the who, what, when, why, and how a feature has been changed.
  4. Reaches (the length between a stream confluence and divergence) are identified using an EPA assigned reachcodes.
  5. Change management is employed in the dataset so that the history of a feature can be identified, in example: previously assigned reachcodes can be identified or the metadata history of a feature.
  6. The dataset includes a reference boundary dataset for the areas nominally drained by specific waterbodies also know as watershed boundaries.
  7. Inclusion of officially recognized geographic names from the Domestic Geographic Names Information Service.

Both the National Hydrography Dataset and Watershed Boundary Dataset were created through joint coordination efforts among federal, state, and local agencies. The NHD started as a combination of the USGS Digital Line Graph (DLG) data for the 7.5-minute quarter quadrangles (1:24,000 or 1:25,000 map scale) combined with the information contained in the Environmental Protection Agency’s Reach File 3 (RF-3). These datasets combined gave the initial NHD its start. In Florida, the effort to get the WBD up to the 5th and 6th levels was a combination of reviews and approvals at the federal, state, regional, and local agency level. These datasets are dynamic and change is inevitable for some areas with urban development, after-effects of hurricanes and other instabilities in the natural order therefore these datasets represent a snapshot in time of the conditions during that time. Because of the dynamic nature of these datasets, federal agencies are now pursuing a program of data stewardship among interested stakeholders, such as the Florida Department of Environmental Protection.

The Bureau of Watershed Restoration recognized the need for better spatial information on surface waters and in an agreement with the U.S. Geological Survey has assumed the data stewardship for this data in Florida. The Maintenance and Update phase of this project is designed to update all surface water features in the NHD that fall within the boundaries of Florida with primary concentration being applied to streams, rivers, lakes, pond and reservoirs. This effort is now underway with an estimated completion date of late-2012 to mid-2013.

The Watershed Boundary Dataset

The Watershed Boundary Dataset (WBD) is a companion dataset to the NHD. It defines the perimeter of drainage areas formed by the terrain and other landscape characteristics. The drainage areas are nested within each other such that a very large drainage area such as the Upper Mississippi River will be composed of multiple smaller drainage areas. Each of these smaller areas can further be subdivided into smaller and smaller drainage areas. The WBD uses six different levels in this hierarchy with the smallest averaging about 30,000 acres in size. Each boundary consists of unique identifiers of a series of two digits known as a Hydrologic Unit Codes (HUC).

The WBD is made up of polygons nested into six levels of data:

Level WBD Name Other Common Names Example HUC
1 Region   03
2 Subregion   0308
3 Basin Accounting Unit 030802
4 Subbasin Cataloging Unit 03080201
5 Watershed   0308020105
6 Subwatershed   030802010509

Using the Data

These data are designed to be used in general mapping and in the analysis of surface water systems using geographic information system (GIS) technology. In mapping, the NHD is used with other themes of data such as elevation, boundaries, and transportation to produce general reference maps. These maps can also be customized to meet the specific needs of the user by emphasizing certain aspects of the data such as the WBD.

In the analysis of surface water, scientists use the NHD and WBD by applying GIS technology. This takes advantage of a rich set of embedded attributes that can be processed by a computer system to generate specialized information. This information can then be portrayed in specialized maps to better understand the results. These analyses of hydrography are largely possible because the NHD contains the flow direction network. It also uses an addressing system to provide specific information about the water such as water discharge, water quality, and fish population. Using the basic water features, flow network, linked information, and other characteristics, it is possible to study cause and affect relationships, such as how a source of poor water quality upstream might affect a fish population downstream. The WBD plays an important role in this analysis by outlining the area on the landscape that drains into the flow network defined by the NHD.

Data Availability

The NHD is available nationwide in two seamless datasets, one based on 1:24,000-scale topographic mapping, known as the high-resolution NHD, and the other based on 1:100,000-scale topographic mapping, known as the medium-resolution NHD. It is also becoming available in select areas based on larger scales such as 1:5,000-scale mapping. The WBD is also available in a nationwide seamless dataset. Typically users download the WBD polygons using either the fourth or sixth levels of the drainage hierarchy. The NHD and WBD will be available as part of the same database in 2009.

The NHD can be viewed in The National Map and also downloaded for use in a GIS. The NHD can also be downloaded from a specialized portal to address the specific needs of scientists. For data management purposes, the NHD is organized into units of area defined by the second or fourth levels of the WBD.

Data Stewardship

The NHD and WBD program of data stewardship is designed to improve upon the existing NHD and WBD to keep it continuously up-to-date by available means. At the Florida DEP project, we use the most current available aerial imagery that has been ortho-rectified, local GIS layers concerning water and water distribution (as available), and information from local hydrologists and experts in the water systems. This will assure that the data are accurate, current, and meet the objectives of users.

Project Contacts

Administrative, Technical Evaluation and Coordination Efforts

Florida NHD Principle Coordinator/Steward –  Edwin Abbey - Edwin.Abbey@dep.state.fl.us, (850) 245-8550,  Environmental Manager

Quality Assurance & Control:

Jeneane Carter - Jeneane.A.Carter@dep.state.fl.us

Editors:

Jon Labie - Jonathan.Labie@dep.state.fl.us

Maria Rivera - Maria.Rivera@dep.state.fl.us

Param Maharaj - Param.Maharaj@dep.state.fl.us

Additional Links

Last updated: October 08, 2013

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