NHDGeoConflationTool: Conflation Lessons in Iowa Using NHD

1. U.S. Department of the Interior U.S. Geological Survey National Geospatial Technical Operations Center Conflation Lessons In Iowa Using the NHDGeoConflationTool Tim Hines 04.15.2009

2. History • Iowa has LiDAR derived DEMs for most of the state • Iowa has created Local Resolution NHD and are using the NHDGeoConflationTool to conflate the local data to the 24k NHD • Currently completed line work for 27 Subwatersheds • Want to submit the revisions/updates to the NHDGeodatabase • This can be accomplished using the NHDGeoConflationTool • Presently 2 Subwatersheds have been successfully conflated and 2 datasets have loaded into the NHDGeodatabase High Resolution • This is a first using the NHDGeoConflationTool

3. Properly structured Source and Target Data is crucial to the success of the NHDGeoConflationTool Process • What is required for the NHDGeoConflationTool?

4. What is required for the NHDGeoConflationTool Two Data Inputs are required Target Data = “Your Revised Data” In Geodatabase format using Schema Template v1.06 Source Data = Extracted NHD Data

5. Target Data Preparation Input Naming Convention NHDGeoConflationTool requires the typical NHD Geodatabase feature naming convention and associated tables as per Schema v1.06 Target Data can be projected/extracted into a Empty Schema Template using the ArcGIS “Distributed Geodatabase/Extract Data Tool” to create the necessary schema feature classes and tables to start conflation Schema Templates can be downloaded from the NHD Stewardship page “Download NHD Software” link at http://webhosts.cr.usgs.gov/steward/scripts/st2_software.pl

6. Target Data Preparation Input Naming Convention Schema 1.06 Feature Class & Table Naming Convention Hydrography: NHDFlowline NHDLine NHDWaterbody NHDArea NHDPoint NHDAreaEventFC NHDLineEventFC NHDPointEventFC • Hydrologic Units: • Regions • Subregions • Basin • Watershed • Subbasin • Subwatershed • Tables: • NHDFCode • NHDFeatureToMetadata • NHDFlow • NHDFlowlineVAA • NHDMetadata • NHDProcessingParameters • NHDReachCode_ComID • NHDReachCrossReference • NHDSourceCitation • NHDStatus • NHDVerticalRelationship

7. Target Data Preparation 1D and 2D Line work All features must have FCodes as per NHDFCode table

8. Target Data Preparation 1D and 2D Line work 1D and 2D Line work should have correct features in correct feature class layers. Correct FCodes are required.

9. Tool Sets Used • NHDGeoConflationTool • NHD Subset by Poly Tool • NHD Flowcheck Tool • NHDUtilities • XMLExtract • XML2GDB • NHD Tools Toolbox • 3 Python Scripts

10. Target Data Preparation Line work 1D • Flowlines should have Connectivity, Flow Direction, With digitized (Unless you don’t want Flow), and split at Flowline confluences • Use the “NHD Flowcheck Tool” to check for Connectivity, Flow Direction, and legitimate Network Ends

11. Target Data Preparation Line work 1D • NHDFlowline should not have GNIS ID gaps - Use the NHD Tools “Gap or Branched Attribute Check” script to check for this type of error

12. Target Data Preparation Line work 1D and 2D • 1D and 2D features must register • Use the NHD Tools “Find Artificial Paths Out of Area Features” script to check for this type of error Lake/Pond

13. Target Data Preparation Line work 1D and 2D • And the reverse as well • Use the NHD Tools “Extract Improper Stream/River Flowlines” script to check for this type of error Lake/Pond

14. Target Data Preparation Line work 1D and 2D • What Features Conflate • NHDWaterbody • NHDFlowline • What Features DoNot Conflate • NHDArea • NHDLine • NHDPoint

15. Typical ConflationSituation in Iowa

16. 12 Digit SubwatershedEx. 1 Total NHD Flowlines = 123 Total Iowa Flowlines = 1014

17. 12 Digit SubwatershedEx. 2 Total NHD Flowlines = 234 Total Iowa Flowlines = 2559

18. Questions?

19. Link to Iowa Conflation Process v1.doc

20. You are now ready to start using the NHDGeoConflationTool • Run Prep on NHDSource dataset as well