Toxicology Research Support ServicesMoving from 1:100K NHD to 1:24K Resolution: Case Studies
Paul Andrews (presenter), Peter Ilieve,
Ken Gilland, Bill Cooter (RTI International)
Bill Kramer, and Thomas Dewald (U.S. EPA)
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Acknowledgements
• Thomas Dewald (U.S. EPA/AWPD)
• Bill Kramer (U.S EPA/OST)
• Thomas Dabolt (U.S. EPA/AWPD)
• Michael Plastino (U.S. EPA/IO)
Prepared by RTI International under contract with EPA Office of Water
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Introduction
• Background Information
• Comparison of 1:100K NHD to 1:24K NHD
• Case Studies of 303(d), 305(b), and WQS Reach Indexing to 1:24K NHD
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Indexing Tools and Resources
• National Hydrography Dataset (NHD)
• NHD Reach Indexing Tool (NHD-RIT)
• Automated Georeferencing Processes (e.g., for Adding General Use Waters)
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National Hydrography Dataset (NHD) Set of spatial data that contains
information about surface water features.
Surface water features are represented by "reaches," which are assigned unique identifiers
Contains 52 feature types including: streams, lakes, reservoirs, canals and dams.
Based upon the USGS Digital Line Graph (DLG) hydrography and the EPA Reach File Version 3 (RF3).
1:100,000-scale NHD (hi res IP)
NHD is available online at http://nhd.usgs.gov/
Toxicology Research Support Services Georeferencing (reach indexing): The
process of describing (or locating) entities in a GIS coverage; assigning an NHD reach code to the waterbody feature.
Reach Indexing Tool (RIT): ArcView 3.x extension; Tool for georeferencing surface water features to reaches in NHD.
Georeferencing and RIT are available online at: www.epa.gov/owow/monitoring/georef/
RIT was 1st and 2nd prize winner at the ESRI International User Conferences in San Diego, CA
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EPA Program Database Link to GISDatabase
Event Table Indexed to NHD
NHD Coverage
GIS Map
MO1009MO1008
MO101010300102003685
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1:100K
1,129
2,342
37.43
1:24K
3,482
1,279
16.92
Comparison of 1:100K and 1:24K NHD Subbasins: Linear Reaches
Average Number
Average Length (m)
Percent Named
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1:100K
100
0.222
23.45
1:24K
1,291
0.026
2.54
Comparison of 1:100K and 1:24K NHD Subbasins: Waterbody Reaches
Average Number
Average Area (km2)
Percent Named
Toxicology Research Support ServicesNameChattahoochee River, GA
White River, VT
Green River, WY
Teagle Wash, CA
Mississippi River, MN
Change19%
2%
<1%
-9%
-14%
Change in Reach Length for Specific Rivers
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NameCrooked Creek
Brush Creek
Wood Creek
Increase1%
2%
27%
Increase in 303(d) Reach Length for Kentucky Rivers: Subbasin 05130102
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NameMonongahela River
Owl Creek
Laurel Run
Increase1%
3%
4%
Increase in 303(d) Reach Length for West Virginia Rivers: Subbasin 05020003
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NameWood Creek Lake, KY
Deckers Creek Reservoirs, WV
Laurel Run Reservoirs, WV
Los Gatos Creek Reservoirs, CA
Coyote Creek Reservoirs, CA
Change-15%
-2%
-25%
5%
12%
Change in 303(d) Reach Areas for Lakes
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1:24K General Use Waters
WV Subbasin 05020003
WV Subbasin 05020003
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Attribute
Total Reach Length
Total Waterbody Area
Increase
39%
53%
Increase in Total Reach Length and Area for KY Subbasin 05130102
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Conclusions
• 1:24K NHD significantly increases the number of waterbodies that can be mapped
• Greater detail changes the shapes and lengths of NHD features
• Changes will impact mapping activities for all programs – tools will minimize impact
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More Information & TrainingNHD web site:
http://nhd.usgs.gov/
NHD-RIT and Reach Indexing Web Site:www.epa.gov/owow/monitoring/georef/
EPA Watershed Assessment, Tracking & Environmental Results (WATERS)http://www.epa.gov/waters/
EPA Office of Water EnviroMapperhttp://www.epa.gov/waters/enviromapper