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FFMP Basin Customization Webinar #3 - Merging and Subdividing Basins and Manual Editing

Join us for a webinar on merging and subdividing basins, as well as manual editing techniques in FFMP basin customization. Learn how to correct basin delineation errors, define smaller basins, and improve FF detection.

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FFMP Basin Customization Webinar #3 - Merging and Subdividing Basins and Manual Editing

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  1. FFMP Basin Customization Webinar #3Merging and Subdividing Basinsand Manual EditingThursday, December 3, 2009 2:00 PM – 3:30 PM EST

  2. Agenda • Merging Basins • DEMO • Subdividing Basins • DEMO • Manual Editing • DEMO • DEMO – Example Basin Boundary Correction Procedure

  3. **Reminder about access to the repository websites** • Access to the FFMP Basin Repository and the FFMP Basin Customization Repository is restricted by IP address. • You can still access these sites from the same IP address you used during the Tier I processing. • If you need to access these sites from a new IP address, please send it to: Ami.Arthur@noaa.gov • Original basin repository: http://nmqxrt-29.nssl.noaa.gov/Website/ffmp_nbr • Customization repository: http://nmqxrt-29.nssl.noaa.gov/Website/ffmp_cust

  4. Three-Tiered FFMPA Shapefile Processing • Tier I (completed) • All WFOs completed this prior to OB8.3 • Involved download and basic processing of shapefiles • Completed for your FFMPA domain (your CWA plus the CWA(s) for which you have flash flood backup responsibility, plus a 25-km buffer) • The result of Tier I processing was an AWIPS/FFMPA-ready set of basin and stream shapefiles • Tier II • This tier is OPTIONAL • Must be completed if you plan to use the basin names in WarnGen • Involves verifying and adding stream names to the post-processed shapefiles resulting from Tier I • Stream names should be modified only for basins within your CWA • The customized shapefile should be submitted for inclusion in the Basin Customization Repository • Tier III • This Tier is OPTIONAL • Involves more extensive customization tasks such as editing basin boundaries, subdividing basins, clipping out lakes, etc. • Tier III customization should only be done for basins within your CWA • The customized shapefile should be submitted for inclusion in the Basin Customization Repository

  5. Why Edit the Basin Features? • Correct minor delineation errors • Redelineation is recommended for significant errors • Define smaller basins or include tributary basins that were left out • Often helpful in urban areas • Segment basins for improved FF detection • Often helpful in elongated basins • Merge to eliminate very small basins • Judgment call

  6. Review of FFMP Basin Dataset Hydrologic-Connectivity Attributes • Basin_id • A unique integer basin ID (different from the Pfaf_id) • Parent_id • The Basin_id of the immediate downstream basin • A Parent_id value of 0 indicates that this is an outlet basin • Flow_acc • Upstream contributing drainage area in square miles • Upstream* • The Basin_id of the immediate upstream basin(s) • An Upstream1 value of 0 indicates that this is a headwater basin

  7. Review of FFMP Basin Dataset Hydrologic-Connectivity Attributes

  8. Merging Basins • Always use the Merge Basin Tools in the FFMPA Toolbox • The Merge Basin Tools automatically update all attributes including basin area, hydrologic-connectivity, and flow accumulation • There is one exception when you can use ArcMap Editor Merge instead of the FFMPA Toolbox Merge Basin Tools—will be discussed later • Basins to be merged must be hydrologically-connected • An upstream/downstream pair—a basin and its immediate downstream (parent) basin or • An upstream/downstream trio—two adjacent (sibling) basins with a third basin that is their immediate downstream (parent) basin • Multiple selections can be merged during a single run of the Merge Selected script • Multiple selections MUST be isolated from each other (not hydrologically connected)

  9. Merging BasinsAcceptable Upstream/Downstream Merge Selections

  10. Merging BasinsUnacceptable Upstream/Downstream Merge Selections This pair cannot be merged with the Merge Selected script because the basins are adjacent (sibling relationship) rather than upstream/downstream (basin/parent relationship). These three basins are all in upstream/ downstream order—a trio should consist of two adjacent upstream basins and their immediate downstream basin.

  11. Merging BasinsMultiple Merge Selections The two selected pairs are isolated from each other (not hydrologically connected). Acceptable Unacceptable These multiple selections are not isolated from each other. NOTE: The Merge Selected tool will attempt to merge some of the selected basins, but the hydrologic-connectivity will not be updated correctly. • DEMO

  12. Subdividing Basins • Define smaller basins (e.g., in urban areas) • Define or separate a tributary basin • Segment elongated basins

  13. Subdividing BasinsBasic Procedure • Use ArcMap Editor tools to split a basin feature • Resulting features will have identical attributes • Attributes MUST be updated • FFMPA will not function correctly with duplicate Pfaf_id values • Area, hydrologic-connectivity, and flow accumulation must be updated • Other attributes (county name, stream name, etc.) should be updated as necessary • Requires a good understanding of the hydrologic-connectivity attributes

  14. Subdividing BasinsUpdating Pfaf_id • To ensure a unique Pfaf_id for the new subdivided basins: • Start with the original Pfaf_id • Change the first zero-digit to an odd number • “1” indicates the furthest downstream segment • “9” indicates the furthest upstream segment • Fill in values between as needed • Examples: For two segments, add a “1” and “9” For three segments, add a “1”, “3”, and “9” For four segments, add a “1”, “3”, “5”, and “9” For five segments, add a “1”, “3”, “5”, “7”, and “9” Original Pfaf_id = 1606243700000 New Pfaf_ids = 1606243710000 1606243730000 1606243790000

  15. Subdividing BasinsUpdating Hydrologic Connectivity • To update Basin_id values for new segments: • Set their Basin_id values to 0 • Run the Initialize Basin_id script in the FFMPA Toolbox • To update basin/parent links: • Select new segments and all of their immediate upstream basins Immediate Upstream Basins

  16. Subdividing BasinsUpdating Hydrologic Connectivity • Unselect the furthest downstream segment Unselect the furthest downstream subdivision segment (do not want to set this Parent_id to 0 because it will break the link with its downstream basin) • For the selected basins, set their Parent_id values to 0

  17. Subdividing BasinsUpdating Hydrologic Connectivity • Select basins to be linked and run Link Selected Basins—recall that Link Selected Basins must be run once for each link that needs updating Linking order is important • Begin by selecting the furthest downstream subdivision segment and its immediate upstream basin(s) • Run Link Selected Basins U U U U Furthest downstream subdivision segment

  18. Subdividing BasinsUpdating Hydrologic Connectivity • Continue working upstream making basin selections and running Link Selected Basins until all links have been updated Linking order is important • Continue by selecting the next upstream subdivision segment and its immediate upstream basin(s) • Run Link Selected Basins U Next upstream subdivision segment • Can check basin/parent links at any time by running Check Basin/Parent Links in the FFMPA Toolbox

  19. Subdividing BasinsUpdating Hydrologic Connectivity • After updating all links, run Add Upstream Links • Verify that hydrologic-connectivity has been restored by running Validate Basins • Run Compute Flow Accumulation script • Initialize flow accumulation values prior to running script • Original Flow_acc values for basins receiving flow from outside the area • 0 for all other basins • Run Reorder Fields if necessary • DEMO

  20. Manual Editing • For modifying basin boundaries and stream lines • Use ArcMap Editor and Topology tools • Reshape edge • Make a sketch to modify the feature • Modify edge • Add, delete, or move individual vertices • IMPORTANT: Be sure to enable snapping • Split Tool or Modify Feature for editing stream lines • The amount of attribute updating necessary after manual editing depends on whether the hydrologic connectivity was modified • At a minimum, update the area and flow accumulation and make sure the attribute fields are in the expected order for FFMPA • DEMO

  21. DEMOExample Basin Boundary Correction Procedure

  22. Summary • Basin Merging • Use FFMPA Toolbox scripts • Attributes and hydrologic-connectivity are automatically updated • Basin Subdivision • Use ArcMap Editor tools • MUST update Pfaf_id and initialize Basin_id (both must be unique) • MUST update Area_sq_mi • MUST update hydrologic-connectivity and Flow_acc • Should update other necessary attributes (stream name, etc.) • Manual Editing • Use ArcMap Editor and Topology tools • MUST update Area_sq_mi and Flow_acc • If a new basin is created or hydrologic-connectivity is changed, the Pfaf_id and hydrologic-connectivity attributes must also be updated.

  23. Wrap-up/Q&A Final Webinar Clipping Lakes/Reservoirs and Wide River Polygons **Date/Time TBD If you have any problems or questions, please contact me: Ami.Arthur@noaa.gov 405-325-6457 Questions?

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