Local Resolution NHD Photo-Based Revision for West Virginia
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Transcript of Local Resolution NHD Photo-Based Revision for West Virginia
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Local Resolution NHD Local Resolution NHD
Photo-Based Revision Photo-Based Revision
for West Virginiafor West VirginiaJackie Strager
Kurt DonaldsonKevin Kuhn
April 24, 2007Denver, CO
West Virginia GIS Technical CenterNatural Resource Analysis Center
West Virginia University
WV State GIS Coordinator’s Office
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Introduction
• Status of NHD in West Virginia– 33 sub-basins– Medium, high resolution
NHD complete– Pilot projects underway
for Local Resolution (LR) NHD creation
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Local Resolution Pilot Project
• Objectives– Meet with potential data users – Develop methods and standards – Assemble 1:4800 source data statewide– Assemble final LR-NHD for two pilot
watersheds– Show benefits of LR-NHD for water resource
applications
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LR NHD Process Steps
1. Capture local hydro features1. Capture local hydro features
2. Data prep and revision2. Data prep and revision
3. Pre-conflation steps3. Pre-conflation steps
4. Conflation/QAQC steps4. Conflation/QAQC steps
5. Ensure data stewardship5. Ensure data stewardship
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1. Capture local hydro features
• Statewide aerial photography, 2003
• Contractor digitized hydro features from stereo pairs
Local scale hydro featuresfrom SAMB photos
Sutton Lake, WV
1:4800 streams
1:4800 polygons
• Features with visible water only• Single-lined up to 50ft wide• Double-lined over 50ft wide• Lakes/ponds (min. 100ft wide)• Swamps/marshes• No name or code attributes• Correct flow direction• Edge-matched
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2. Data prep/revision
• Systematically examine contractor’s hydro data for incomplete and missing features
• Close double-lined streams
• Add DLG codes
Approximately 15-20% of streams were not adequately captured in source local datasets.
1:4800 streams in source
Additional 24K streams added
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3-4. Pre-conflation, conflation
For pilot watersheds:
• USGS routines and NHD Geo-Conflation Toolkit (NHDGCT) – Pre-conflation– Conflation– QAQC
• Load into national dataset
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5. Long term maintenance
• Involve interested cooperators
• Encourage NHD stewardship process
• Project communications
• Show benefits of LR-NHD data
Website: http://wvgis.wvu.edu/stateactivities/LRNHD.html
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Benefits of LR NHD
• Common data framework among NHD scales
1:100,000 scale NHDMedium resolution
1:24,000 scale NHDHigh resolution
1:4800 scale streamsLocal resolution
(approximated from SAMB stream data)
Sutton Lake
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Benefits
• Provides more highly detailed cartographic base
24K NHD streams
LR NHD streams
Flatwoods WV
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Benefits
• More accurate source data
Source for 24K NHD:Big Chimney quad Last revised: 1976
Source for LR NHD:2003 Aerial photoRevised LR NHD streams shown in yellow
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Benefits
• Quantifies recent changes in stream drainage
24K NHD streams
LR NHD streams
Active mine permit, Lockwood quad
Valley fill area
EPA:Up to 1,200 miles of streams lost in multi-state mountaintop-removal mining region
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Benefits
• Supports modeling of flow and hydrology at detailed local scale
• More accurate stream mileage for stream mitigation projects, riparian buffers
• Aids in floodplain mapping and emergency planning
• More detailed dataset for resource management and planning, permitting, cumulative impact analysis
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Benefits
• Supports WV legislative requirement– WV Water Resources Protection Act– Quantify nature and extent of water
resources
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Future Considerations
• Completion of LR NHD
• Cartographic issues
• Edge-matching
• Encouraging partnerships
• Data stewardship– Updates, maintenance
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Thank you!