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) –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

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

Project Scope 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 Digitization

Project Scope 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 Digitization

Project Scope 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 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

Project Scope 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 Status

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

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

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

Differences IndianaMississippiNorth Carolina USGS NHD Tools Used? XX Customized Geodatabase? X HUC 8-Based Submittals? XX 6 Acre Upstream Limit? XX ¼ Acre Water Body Size Limit? XX Differing Applications of Ftypes? XXX

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

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)

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

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

Questions? March 29, 2012