Bull Creek Watershed

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Bull Creek Watershed

• Elaine B. Darby
• GIS Fall 2005

Direction Provided by Dan Yates, Lower Colorado
River Authority (LCRA)
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Lake Travis
Bull Creek Watershed
ERSI Imagery with NHD Streams
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ArcGIS generated Hillshade Layer
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Data Gathering Processing

• 10 m 30 m DEMs
• 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 (124,000)
• LCRA Hydromet Gauging Stations
• NEXRAD Data Nov, 2004

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Bull Creek WatershedAgree DEM based on 10 m DEM
NHD Streams
LCRA Hydromet Gauges
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Watershed Delineation
Area 4.553 km2
Area 4.475 km2
30 m DEM 51 Catchments
10 m DEM 52 Catchments
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Area Analysis by DEM
1.7 Difference
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Drainlines vs NHD StreamlinesNHD Streamlines -
Blue
Default Threshold 0.81 km2
Threshold 0.3 km2
Threshold 0.2 km2
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(No Transcript)
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Rainfall Event in November, 2004
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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

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

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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
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NEXRAD ? GIS

• 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

Large data sets use algorithms
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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