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
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 How can the extent of the problem be quantified?
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
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?