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NHD Stewardship Conference Lakewood, Colorado April 15, 2009

Updating the National Hydrography Data for the Twin Cities with Local Subsurface Drainage Information. NHD Stewardship Conference Lakewood, Colorado April 15, 2009. What is NHD?.

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NHD Stewardship Conference Lakewood, Colorado April 15, 2009

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  1. Updating the National Hydrography Data for the Twin Cities with Local Subsurface Drainage Information NHD Stewardship Conference Lakewood, Colorado April 15, 2009

  2. What is NHD? NHD is a digital spatial dataset that describes the location, extent, and relationships of surface water features for the entire nation Uses Mapping water resources Sharing/reporting of monitoring data (reach ID) Incorporated into watershed models

  3. The Problem NHD primarily includes streams and ditches Lacks feature density in urban areas NHD for ex-urban area NHD for urban area (with storm sewers)

  4. Twin Cities Storm Water Pilot Project Phases • Phase I: Acquire and Assemble Subsurface Drainage Data from Local Governments • Phase II: Extract Significant Features and Integrate into NHD

  5. Phase I: Acquiring and Assembling Local Data Acquire local data Mostly CAD format Import into GIS Georeference Integrate into a single database There were many challenges!

  6. Georeferencing Spatial adjustment tool used to fix georeferencing problem

  7. Georeferenced Data

  8. Interrupted by other feature types maintenance access holes Connectivity Not Connected Connected

  9. Interrupted by missing surface water feature Ditch Pond Connectivity

  10. Line features not digitized with directionality Directionality Not Directional Directional

  11. Inconsistent attributes between sources Typically limited attributes Attributes may be as graphical annotation Attributes

  12. Phase I: Summary of Challenges • Unknown coordinate systems • Overlapping jurisdictions • Lack of directionality • Lack of connectivity • Inconsistent and sparse attributes • Lack of metadata

  13. Intermediate Storm Sewer Layer Results • It was possible to assemble an intermediate storm sewer layer. • Geo-referenced storm sewer data for 38 communities (> 200,000 pipes) • Only a tiny fraction will be incorporated into the NHD drainage network • Could be the beginning of regional storm sewer GIS • Several significant issues

  14. Phase II: Incorporate into NHD • Select major storm water features to add to NHD (Feature Thinning Analysis) • Complete directionality • Create feature subset • Use NHDGeoEdit Tools to update NHD

  15. Feature Thinning Analysis Factors Area drained Pipe Size > 30-in Path length Connectivity to currently mapped NHD features

  16. Area Covered – New Features • Added 1078 linear drainage features (588 km) • Features were pipelines, ditches, connectors, artificial paths • Represent 6000 individual pipe features • Connected 363 NHD waterbodies to drainage network

  17. Storm Water Features – St. Paul

  18. Network Tracing – St. Paul

  19. Hydrologic Unit Redelineation • Watersheds • Updated major and minor watershed boundaries for the Twin Cities (Mississippi) major watershed • Lake watershed boundaries for 113 lakes • Added attribute code to define upstream and downstream relationships • Drainage network • Enhanced network with hundreds of new features

  20. Example: Boundary Disagreement Local hydrologic modifications may cut across the height of land boundary

  21. DEM Reconditioning “Burn-in” the storm sewer drainage Adjust elevation of the digital elevation model based on input line features 100 Original Surface 90 Modified Surface 80 70 Elevation (m) 60 50 40 30 0 20 40 60 80 100 120 140 160 180 200 220 240 260 Lateral Distance (m)

  22. Revised Delineation

  23. Conclusions • It is possible (and useful) to use local subsurface drainage data for update the NHD • NHD is a good surface water model for the Twin Cities Metropolitan Area • NHD update capability was a key feature • NHD update tools complex to learn; docs need improvement • There were many difficulties with the base data (multiple sources); improving base data would improve NHD • Questionable data were not added.

  24. Challenges of Base Data • Multiple jurisdictions • Unknown coordinate systems • Overlapping jurisdictions • Lack of directionality • Lack of connectivity • Inconsistent and sparse attributes • Lack of metadata

  25. Solution • Develop CAD and GIS data standards for storm sewers • Collaborative effort • Publish and promote the standards • Guidance • Template • Training • Block grants

  26. Minnesota Storm Water Standards Working Group • Develop Exchange Standard for Digital Storm water System Data • MPCA: MS4 Reporting & Emergency Response • Work through Governor’s Council on Geographic Information • Submit to Standards Committee • Hydrography Committee Review • How does storm water guideline interact with surface water features? • Reference Existing Surface Water Data Sets

  27. Project Credits: Metropolitan Council: Steve Kloiber Jennifer Hinz with assistance from: USGS: Paul Kimsey Ron Wencl LMIC: Sandi Kuitunen Jim Krumrie Susanne Maeder Presentation Credits: Steve Kloiber – MN Department of Natural Resources (formerly Metropolitan Council) Susanne Maeder – MN Land Management Information Center (LMIC) Project Funding: United States Geological Survey Credits http://www.metrocouncil.org/planning/environment/NHDUpdateTCMA.pdf

  28. Questions?

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