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A Geodatabase Infrastructure for Texas

A Geodatabase Infrastructure for Texas. Project Status. Presented by: Tyler Jantzen GIS in Water Resources CE394K.3 November 29, 2005. Background Information. National Hydrography Dataset High Resolution (NHDH) is being compiled for U.S.

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A Geodatabase Infrastructure for Texas

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  1. A Geodatabase Infrastructure for Texas Project Status Presented by: Tyler Jantzen GIS in Water Resources CE394K.3 November 29, 2005

  2. Background Information • National Hydrography Dataset High Resolution (NHDH) is being compiled for U.S. • NHDH is listed as complete for the state of Texas • 24 Subregions lie within Texas • These 24 Subregions contain 1.8 million flowlines, and over 688,000 miles of streamlength. • Ultimate Goal: To trace a drop of water from source to sink

  3. Medium Resolution vs. High Resolution Medium Resolution: 1:100,000 1.38 GB High Resolution: 1: 24,000 20x number of lines 3x length of lines 7.33 GB 24 Subregions

  4. NHD Subregions in Texas

  5. Problem Definition • Some subregions are missing data

  6. Problem Definition • Flowlines are not physically connected These are duplicates, and should be connected

  7. Problem Definition • Some flowlines are not initialized properly • Uninitialized flow direction makes flow tracing impossible

  8. Problem Definition • Cannot “trace” from top to bottom of basin • How can the extent of the problem be quantified? Trace should reach entire subregion Trace Upstream Trace Downstream

  9. Data Requirements • 24 NHD Subregion Personal Geodatabases • Information at http://nhd.usgs.gov • Download at ftp://nhdftp.cr.usgs.gov/NHD_HUC and ftp://nhdftp.usgs.gov/SubRegions • Texas Natural Resource Information System (TNRIS)

  10. Methodology Developed • Place flag at subregion outlet • Trace upstream or Find disconnected • Place additional flags where trace ends Simulates “fixing” a disconnect • Continue until majority of subregion is traced

  11. Results • Measure data completeness: Drainage Density • DD<1 → Likely incomplete • DD>1 → Likely complete

  12. Results • Using Trace Upstream function

  13. Results • Using Find Disconnected function

  14. Conclusions • If 55 fixes were made, 91% of the network would be connected • 12 of the 24 regions are still missing data

  15. Future Work • Fill in missing data • Create single geodatabase for entire state • Measure connectivity for single large geodatabase

  16. Recommendations • With minimal fixes (55) over the entire state, a majority (91%) of the streams will be connected to the network • These fixes, if made, will significantly increase the utility of the NHD

  17. Questions?

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