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:
- The development of the geographic network for tracing flows.
- Each individual feature has a unique reference identifier
called the common identifier (ComID within the dataset).
- 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.
- Reaches (the length between a stream confluence and
divergence) are identified using an EPA assigned reachcodes.
- 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.
- The dataset includes a reference boundary dataset for the
areas nominally drained by specific waterbodies also know as
watershed boundaries.
- 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:
Andrew Morris (Andrew.Morris@dep.state.fl.us,
(850) 245-5031)
Editors:
Nathan (Andy) Woeber –
Nathan.Woeber@dep.state.fl.us
Marie Burnham -
Marie.Burnham@dep.state.fl.us
Chris Gudeman –
Chris.Gudeman@dep.state.fl.us
Additional Links
2012 State of Florida