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

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

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

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

Georeferencing Spatial adjustment tool used to fix georeferencing problem

Georeferenced Data

Connectivity Interrupted by other feature types Interrupted by other feature types –maintenance access holes Not ConnectedConnected

Connectivity Interrupted by missing surface water feature Interrupted by missing surface water feature –Ditch –Pond

Directionality Line features not digitized with directionality Line features not digitized with directionality Not DirectionalDirectional

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

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

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

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

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

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

Storm Water Features – St. Paul

Network Tracing – St. Paul

Hydrologic Unit Redelineation Watersheds 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 Drainage network –Enhanced network with hundreds of new features

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

DEM Reconditioning “Burn-in” the storm sewer drainage “Burn-in” the storm sewer drainage Adjust elevation of the digital elevation model based on input line features Adjust elevation of the digital elevation model based on input line features

Revised Delineation

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

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

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

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

Credits 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

Questions?