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Map Layer Info

1:1,000,000-Scale Hydrographic Geodatabase of the United States

What this map layer shows:

Networked hydrography of the United States as of 2014. This map layer contains coastlines, streams, waterbodies and wetlands, and streamflow gaging stations in file geodatabase format. The streams are incorporated into a geometric network.

In addition to a national dataset, there are four regional file geodatabases covering the conterminous United States, Alaska, Hawaii, and Puerto Rico and the U.S. Virgin Islands.
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Background Information
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In 1997, the U.S. Geological Survey (USGS) and the Environmental Protection Agency (EPA) began to build the National Hydrography Dataset (NHD) by combining EPA's Reach File Version 3 (RF3) with the USGS digital line graph hydrography data at 1:100,000-scale. The RF3 was a national hydrographic database that interconnected and identified over three million stream segments (called "reaches") in the United States. In the RF3 database, a unique code was assigned to each stream segment contained in the USGS digital cartographic data. Upstream and downstream relationships of each stream segment were also identified. This formed a national hydrographic transport network at an intermediate scale (1:100,000). A year after this dataset was finished in 2001, the USGS, EPA, and other government agencies began to produce the higher resolution (1:24,000-scale) NHD dataset that's also available today.

This National Atlas map layer was produced primarily from the NHDFLowline feature classes in these intermediate- and large-scale NHD databases. The data were carefully generalized to one million-scale while preserving the hydrographic transport network inherent in the sources. Like the NHD, this map layer includes a flow network that allows for tracing water downstream or upstream. It also uses an addressing system based on reach codes and linear referencing that can be used to link specific information such as discharge rates and water quality. Each geodatabase in this map layer includes streams, waterbodies, streamflow gaging stations, and coastlines to form a network at a scale that is useful for national and regional assessments. This hydrography data has been vertically aligned with selected transportation and boundary features at 1:1,000,000-scale.

The 1:1,000,000-Scale Hydrographic Geodatabase of the United States map layers were prepared by the National Atlas of the United States. These are part of our collection of fundamental digital cartographic data known as 1. This collection includes base map data in vector format at 1:1,000,000-scale and in image format at 100-meter ground resolution. Read more about the 1.

This dataset also fuels Streamer - the popular online mapping program that lets anyone trace up and down the Nation's streams and produce reports about the people and places found along each trace.


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