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Enhancing Texas Hydrography: Geodatabase Connectivity and Data Completeness Efforts

This project presents the status of the National Hydrography Dataset High Resolution (NHDH) for Texas, which has identified several challenges. Key issues include missing data in certain subregions, unconnected flowlines, and improperly initialized flowlines affecting water tracing capabilities. The methodology employed flags key locations to trace upstream and identify disconnected areas. Results suggest that with targeted fixes, 91% of the network could be interconnected, addressing substantial data completeness gaps. Future efforts will focus on filling data voids and enhancing the geodatabase's overall connectivity.

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Enhancing Texas Hydrography: Geodatabase Connectivity and Data Completeness Efforts

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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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