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Bull Creek Watershed

Bull Creek Watershed. Elaine B. Darby GIS – Fall 2005. Direction Provided by Dan Yates, Lower Colorado River Authority (LCRA). Lake Travis. Bull Creek Watershed. ERSI Imagery with NHD Streams. ArcGIS generated Hillshade Layer. Data Gathering & Processing. 10 m & 30 m DEM’s

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Bull Creek Watershed

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  1. Bull Creek Watershed Elaine B. Darby GIS – Fall 2005 Direction Provided by Dan Yates, Lower Colorado River Authority (LCRA)

  2. Lake Travis Bull Creek Watershed ERSI Imagery with NHD Streams

  3. ArcGIS generated Hillshade Layer

  4. Data Gathering & Processing • 10 m & 30 m DEM’s • Downloaded from USGS Seamless server • 10 m DEM clipped for Bull Creek Watershed • 30 m DEM extent masked to 10 m DEM • NHD Streams & Waterbodies (1:24,000) • LCRA Hydromet Gauging Stations • NEXRAD Data – Nov, 2004

  5. Bull Creek WatershedAgree DEM based on 10 m DEM & NHD Streams LCRA Hydromet Gauges

  6. Watershed Delineation Area = 4.553 km^2 Area = 4.475 km^2 30 m DEM 51 Catchments 10 m DEM 52 Catchments

  7. Area Analysis by DEM 1.7% Difference

  8. Drainlines vs NHD StreamlinesNHD Streamlines - Blue Default Threshold = 0.81 km2 Threshold = 0.3 km2 Threshold = 0.2 km2

  9. Rainfall Event in November, 2004

  10. NEXRAD DataProvided by Dan Yates, LCRA • Data Source – National Weather Service – West Gulf River Forecast Center • NWS archive – http://dipper.nws.noaa.gov/hdsb/data/nexrad/wgrfc_stageiii.php • NCDC Java NEXRAD Tools – http://www.ncdc.noaa.gov/oa/radar/jnx

  11. NEXRAD Data in GIS Old Spicewood Springs Road Photos from Bull Creek Foundation - www.bullcreek.net

  12. Nexrad Grid – Nov. 14 – 17, 2004 Bull Creek Watershed 0 – 0.37 0.37 – 1.02 1.02-1.70 1.70 – 2.35 5.7 inches 2.35 – 2.94 2.94 – 3.53 3.53 – 4.12 4.12 – 4.70 4.70 – 5.29 5.29 – 5.99 5.99 – 6.84 6.84 – 7.91 7.91 – 9.14 9.14 – 10.6 10.6 – 13.6 6.0 inches

  13. LCRA Hydromet Gauges Jollyville SW2 Bull Creek at 360 November 14 – 17 ,2005 Jollyville SW 2 5.80 inches Bull Creek at 360 6.12 inches

  14. NEXRAD Stage III Data • Stage III – based on reflectivity measurements merged with surface rain gauge observations • Hourly precipitation – mm/hr – 4 km2 • Grid based data • Hydrologic Rainfall Analysis Project (HRAP) projection

  15. NEXRAD Projections • Polar Stereographic map projection • Spherical Earth vs. Ellipsoidal • East-West distances distorted relative to North-South distances Ref.CRWR Online Report 95-3 A GIS Procedure for Merging NEXRAD Precipitation Data and Digital Elevation Models to Determine Rainfall-Runoff Modeling Parameters (1995) By Seann M Reed and David R. Maidment

  16. Reed, Maidment (1999) & Xie, Zhou, et. al. (2005) Algorithms to perform coordinate transformations to mesh NEXRAD and DEM NCDC Java NEXRAD Tools Vector and Raster Grid Export Options NEXRAD  GIS Large data sets – use algorithms

  17. CONCLUSIONS • 10 m vs 30 m DEM – Catchment Areas • Very small difference for Bull Creek Watershed • No substantial difference in drainage area using 1% default threshold and ¼ % threshold • NEXRAD data • Integration into GIS can be done using transformation programs

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