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Creating Local Resolution NHD: Similarities and Differences in Three State Projects

Creating Local Resolution NHD: Similarities and Differences in Three State Projects. Susan Phelps, CFM, GISP. March 29, 2012. Local Resolution NHD in Mississippi. 2010 – Ongoing Managed by Mississippi Department of Environmental Quality (MDEQ)

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Creating Local Resolution NHD: Similarities and Differences in Three State Projects

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  1. Creating Local Resolution NHD: Similarities and Differences in Three State Projects Susan Phelps, CFM, GISP March 29, 2012

  2. Local Resolution NHD in Mississippi • 2010 – Ongoing • Managed by Mississippi Department of Environmental Quality (MDEQ) • Work conducted by Mississippi Geographic Information (MGI), of which AECOM is a member • Stewards: • MDEQ: Steve Champlain • Mississippi Automated Resource Information System (MARIS): Jim Steil • USGS POC Region 4: Elizabeth McCartney • USGS Geospatial Liaison: George Heleine

  3. Background Overview • Purpose and Goal • 1 of 7 statewide framework data layers identified as priority by MDEQ • Increase accuracy, content of hydrography layer in Mississippi Digital Earth Model (MDEM) • Pilot local-resolution NHD project to define accuracy, specifications for collection of hydrography statewide • Coordination with Arkansas, Tennessee NHD stewards regarding edge-matching

  4. Project Scope Digitization • Source Data Used: • Statewide 2 ft orthos • Supplemented by NAIP • Terrain • USACE LIDAR • Statewide 5 ft contours and DTMs • 18 acre guide streams • Breaklines from terrain processing • 24K NHD • FEMA National Flood Hazard Layer (NFHL) for dams and levees • MDEQ Safe Dams database • FEMA Mid-Term Levee Inventory (MLI) • USACE Vicksburg district levee database

  5. Project Scope Digitization • Horizontal Alignment • Streams up to 18-acre drainage area upstream limit collected • if 24K extended further upstream and visible in imagery, it was maintained • Water bodies draining 1 acre or greater collected • if less than that but included in 24K NHD and visible in imagery, it was kept • All 24K NHD Area, Lines and Points collected • New dams and levees also digitized

  6. Project Scope Conflation and Attribution • Pre-conflation steps completed using combination of USGS scripts and ArcGIS 9.3 tools • Following were checked: • Topology • Flow direction • Artificial paths • All within Area or WB features • Stream/rivers • All outside of Area or WB features • Conflated 24K NHD attributes to local-resolution hydrography, attributes populated for new features • USGS NHD toolset utilized • Reach codes, ComIDs, GNIS info conflated • Feature level, FGDC compliant metadata generated for each sub-basin deliverable

  7. Project Scope Status • Conflation complete in Lower Mississippi, Upper Big Black sub-basins • Now available on The National Map • Conflation in progress for remaining two sub-basins, Coldwater and Upper Pearl • Using .NET version of conflation tools

  8. Similarities with Local Resolution NHD Projects in Indiana, Mississippi and North Carolina

  9. Similarities • All 3 projects included some form of pilot study • Upstream drainage limit used to determine scale of mapping • Guide streams generated from terrain sources, used for general stream location • Streams and water bodies digitized from combination of imagery and terrain • Intermittent/Perennial designations –conflating over 24K attributes, but not attributing for new features • Urban areas most challenging • No stormwater data to incorporate as of yet • None included coastal component as of yet

  10. Differences with Local Resolution NHD Projects in Indiana, Mississippi and North Carolina

  11. Differences

  12. Value-Added Attributes included with Local Resolution NHD Projects in Indiana, Mississippi and North Carolina

  13. Value-Added Attributes / Data • Catchment areas (IN) • Metadata shapefile tracking source data (IN) • Flow accumulation and flow direction grids (IN) • Collection of new dams, levees (MS) • Drainage areas (NC) • Point events (NC)

  14. Conclusions

  15. Conclusions • Differing upstream limits b/w states not necessarily a bad thing • Topography different in every state; can have different needs w/in same state • Pilot study can help determine best path forward • Clear guidance and documentation on Ftypes and procedures a must • Can’t always rely on what’s in 24K • Certain info such as perennial vs intermittent vs ephemeral or canal/ditch versus stream/river very difficult to discern without field visits or additional local data • Urban areas very difficult to digitize w/out local stormwater data (surface vs subsurface?) • Never too early to start thinking about maintenance • If phased approach is used, should it start prior to completion of local res NHD statewide? • Consider priorities when budgeting

  16. Conclusions • Support from Workgroup and/or Advisory Council is helpful • Ensures that local res NHD product is useful to greater number of end users • Can provide local knowledge and resources • Support from USGS POCs, NHD Stewards a must!!! • NHD tools and training • Guides and standards • Funding opportunities • Coordination with surrounding states recommended • Potential cost-sharing opportunities

  17. Questions? susan.phelps@aecom.com March 29, 2012

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