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Bureau of Economic Geology John A. and Katherine G. Jackson School of Geosciences The University of Texas at Austin
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GEOTUBES ALONG THE UPPER COAST Initial Analysis James Gibeaut Tiffany Hepner, Rachel Waldinger, John Andrews Coastal Coordination Council Executive Committee Special Meeting January 29, 2002 A report of the Texas Coastal Coordination Council pursuant to National Oceanic and Atmospheric Administration award number NA97OZ0179
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Geotube Schematic Approx. 30 ft Approx. 7 ft
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InstallationCovered and vegetated ExposedMaintenance
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Treasure Island July 19, 2001 (section destroyed in November 2001) QAd496Gibeaut_CCC_Jan31_2002
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Long-term Average Annual Rate of Shoreline Change QAd496Gibeaut_CCC_Jan31_2002
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The Problems Problem 1: Long-term shoreline retreat has placed many structures in danger of failing during the next storm or being gradually undermined as retreat continues in the absence of adequate beach nourishment. Problem 2: In the absence of adequate beach nourishment, geotubes may form an unacceptable landward boundary or barrier to the public beach because of shoreline retreat. They may also cause adjacent shorelines to retreat at a higher rate. QAd496Gibeaut_CCC_Jan31_2002
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Geotube Monitoring Goals Determine how geotubes affect the beach/dune system –How they serve as storm protection structures erosion control structures –How they affect the beach/dune system where they are located beach/dune system adjacent to them Provide data for designing future erosion mitigation projects QAd496Gibeaut_CCC_Jan31_2002
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Field Methods 3 ground surveys per year –Beach profiles (topographic transects) –Shoreline survey –Geotube visual inspection: damage, sand cover, vegetation cover 1 airborne topographic lidar survey per year Wave and water-level analysis QAd496Gibeaut_CCC_Jan31_2002
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Geotube Locations November 2001 Rollover Pass San Luis Pass Gilchrist East11,300 feet Gilchrist East Total = 7.28 miles Gilchrist West Gilchrist West14,400 Dellanera Dellanera 1,590 Pocket Park 2 Pocket Park 2 380 Riviera Riviera 590 Pirates Beach Pirates Beach 8,540 Treasure Island, North, Middle, South Treasure Island 1,650 QAd496Gibeaut_CCC_Jan31_2002
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2001 July 1997 Nov 1998 Pre- Frances 1998 Post- Frances 2000 May Lidar Topographic Images Gilchrist East Geotube Area Rollover Pass Gulf of Mexico 1,000 ft QAd496Gibeaut_CCC_Jan31_2002
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Beach Profile Gilchrist West (GLO-021) QAd496Gibeaut_CCC_Jan31_2002
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GLO-021 Profile Location Gilchrist West Sept. 23, 1999 QAd496Gibeaut_CCC_Jan31_2002
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June 13, 2001 GLO-21 Profile Location Gilchrist West Geotube July 18, 2001 November 14, 2001 QAd496Gibeaut_CCC_Jan31_2002
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GLO-021 Profile Location Gilchrist West Sept. 23, 1999 QAd496Gibeaut_CCC_Jan31_2002
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Gilchrist East Geotube November 15, 2001 ( example of “fully” exposed face) QAd496Gibeaut_CCC_Jan31_2002
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Exposed Geotubes June 2001July 2001November 2001 ProjectExposed (ft) Exposed % Exposed (ft) Exposed % Exposed (ft) Exposed % Gilchrist, East 1,67027007026 Gilchrist, West 10,630746,142433,96728 Dellanera413265453620714 Pocket Park 2 000000 Riviera000000 Pirates Beach 85010791101081 Treasure Isl. 960589255084666 Total14,523 ft43%8,403 ft24%5,830 ft15% QAd496Gibeaut_CCC_Jan31_2002QAd496Gibeaut_CCC_Jan31_2002
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Gilchrist East Geotube November 14, 2001 (typical - some sections less vegetation) QAd496Gibeaut_CCC_Jan31_2002
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Exposed Geotubes June 2001July 2001November 2001 ProjectExposed (ft) Exposed % Exposed (ft) Exposed % Exposed (ft) Exposed % Gilchrist, East 1,67027007026 Gilchrist, West 10,630746,142433,96728 Dellanera413265453620714 Pocket Park 2 000000 Riviera000000 Pirates Beach 85010791101081 Treasure Isl. 960589255084666 Total14,523 ft43%8,403 ft24%5,830 ft15% QAd496Gibeaut_CCC_Jan31_2002
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Gilchrist West Geotube November 15, 2001 (fully exposed face) QAd496Gibeaut_CCC_Jan31_2002
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Gilchrist West Geotube November 15, 2001 (one of several small holes) QAd496Gibeaut_CCC_Jan31_2002
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Gilchrist West Geotube November 15, 2001 (covered but steep and little vegetation) QAd496Gibeaut_CCC_Jan31_2002
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Exposed Geotubes June 2001July 2001November 2001 ProjectExposed (ft) Exposed % Exposed (ft) Exposed % Exposed (ft) Exposed % Gilchrist, East 1,67027007026 Gilchrist, West 10,630746,142433,96728 Dellanera413265453620714 Pocket Park 2 000000 Riviera000000 Pirates Beach 85010791101081 Treasure Isl. 960589255084666 Total14,523 ft43%8,403 ft24%5,830 ft15% QAd496Gibeaut_CCC_Jan31_2002
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Pirates Beach on Galveston Island November 15, 2001 (only exposed section) QAd496Gibeaut_CCC_Jan31_2002
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Pirates Beach on Galveston Island November 15, 2001 (covered and vegetated, typical for project) QAd496Gibeaut_CCC_Jan31_2002
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Comparing Beach Widths (SW End Pirates Beach) MHHW+0.6 m msl Geotube Landward boundary BEG-02 Beach profile QAd496Gibeaut_CCC_Jan31_2002
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Beach Profile (BEG-02) SW of Pirates Beach Geotube QAd496Gibeaut_CCC_Jan31_2002
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Beach Profile (BEG-02) SW of Pirates Beach Geotube June 14, 2001 QAd496Gibeaut_CCC_Jan31_2002
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Beach Profile (BEG-02) SW of Pirates Beach Geotube July 19, 2001 QAd496Gibeaut_CCC_Jan31_2002
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Beach Profile (BEG-02) SW of Pirates Beach Geotube November 13, 2001 QAd496Gibeaut_CCC_Jan31_2002
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Beach Profile (GAL-02) Near SW end of Pirates Beach Geotube QAd496Gibeaut_CCC_Jan31_2002
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Beach Profile (GAL-02) Near SW end of Pirates Beach Geotube November 13, 2001 QAd496Gibeaut_CCC_Jan31_2002
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Beach Profile (GAL-02) Near SW end of Pirates Beach Geotube July 19, 2001 QAd496Gibeaut_CCC_Jan31_2002
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Comparing Beach Widths (SW End Pirates Beach) MHHW+0.6 m msl Geotube Landward boundary BEG-02 Beach profile QAd496Gibeaut_CCC_Jan31_2002
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Beach Width at Pirates Beach QAd496Gibeaut_CCC_Jan31_2002
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Water Level and Waves Combined (data from Pleasure Pier tide gauge) TS Allison TS Frances TS Josephine QAd496Gibeaut_CCC_Jan31_2002
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Conclusions as of 2001 1.Improvement in keeping geotubes covered but keeping covered is significant effort 2.Beach width is generally narrower in front of the geotubes 3.Adjacent shoreline not affected 4.Storm-protection function not yet tested QAd496Gibeaut_CCC_Jan31_2002
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Website www.beg.utexas.edu/coastal/coastal01.htm QAd496Gibeaut_CCC_Jan31_2002
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