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Bureau of Economic Geology John A. and Katherine G. Jackson School of Geosciences The University of Texas at Austin. GEOTUBES ALONG THE UPPER COAST. James Gibeaut Tiffany Hepner, Rachel Waldinger, John Andrews. Initial Analysis. Coastal Coordination Council - PowerPoint PPT Presentation
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Bureau of Economic GeologyJohn A. and Katherine G. Jackson School of Geosciences
The University of Texas at Austin
GEOTUBES ALONG THE UPPER COAST
Initial Analysis
James GibeautTiffany Hepner, Rachel Waldinger, John Andrews
Coastal Coordination CouncilExecutive Committee Special Meeting
January 29, 2002
A report of the Texas Coastal CoordinationCouncil pursuant to National Oceanic and Atmospheric Administration award number
NA97OZ0179
Geotube Schematic
Approx. 30 ft
Approx.7 ft
Installation Covered and vegetated
Exposed Maintenance
Treasure IslandJuly 19, 2001
(section destroyed in November 2001)
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0 20 40 60 80 100 120 140 160 180
kilometers alongshore
-10
0
10
-5
5
re
tre
at
m/y
r
ad
va
nc
e
Freeportjetties
Brazos River
San LuisPass end of
seawall
GalvestonSeawall
East Beach
W est Beach
BolivarRoads
Rollover Pass
HighIsland
Follets Island Galveston Island Bolivar Peninsula
Sabine Pass
Long-term Average Annual Rate of Shoreline Change
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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.
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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
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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
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Geotube LocationsNovember 2001
Rollover Pass
San Luis Pass
Gilchrist East 11,300 feet
Gilchrist East
Total = 7.28 miles
Gilchrist West
Gilchrist West 14,400
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 1,650QAd496Gibeaut_CCC_Jan31_2002
2001July
1997Nov
1998Pre-Frances
1998Post-Frances
2000May
Lidar Topographic ImagesGilchrist East Geotube Area
Rollover Pass Gulf of Mexico
1,000 ft
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Beach ProfileGilchrist West (GLO-021)
0 20 40 60 80 100 120
D istance (m )
-1
0
1
2
3
4
5
Hei
ght R
elat
ive
to M
SL
(m)
GLO21Bolivar Peninsula
vertica l exaggeration = 10:1
datum
geotubeSeptem ber 23, 1999June 13, 2001Ju ly 18, 2001N ovem ber 14, 2001Vegetation line2 nd Vegeta tion line
M H H W+0.6 m
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GLO-021 Profile LocationGilchrist West
Sept. 23, 1999
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June 13, 2001
GLO-21 Profile LocationGilchrist West Geotube
July 18, 2001 November 14, 2001
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GLO-021 Profile LocationGilchrist West
Sept. 23, 1999
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Gilchrist East Geotube November 15, 2001
(example of “fully” exposed face)
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Exposed Geotubes
June 2001 July 2001 November 2001Project Exposed
(ft)Exposed
%Exposed
(ft)Exposed
%Exposed
(ft)Exposed
%
Gilchrist, East
1,670 27 0 0 702 6
Gilchrist, West
10,630 74 6,142 43 3,967 28
Dellanera 413 26 545 36 207 14
Pocket Park 2
0 0 0 0 0 0
Riviera 0 0 0 0 0 0
Pirates Beach
850 10 791 10 108 1
Treasure Isl.
960 58 925 50 846 66
Total 14,523 ft 43% 8,403 ft 24% 5,830 ft 15%
QAd496Gibeaut_CCC_Jan31_2002 QAd496Gibeaut_CCC_Jan31_2002
Gilchrist East Geotube November 14, 2001
(typical - some sections less vegetation)
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Exposed Geotubes
June 2001 July 2001 November 2001Project Exposed
(ft)Exposed
%Exposed
(ft)Exposed
%Exposed
(ft)Exposed
%
Gilchrist, East
1,670 27 0 0 702 6
Gilchrist, West
10,630 74 6,142 43 3,967 28
Dellanera 413 26 545 36 207 14
Pocket Park 2
0 0 0 0 0 0
Riviera 0 0 0 0 0 0
Pirates Beach
850 10 791 10 108 1
Treasure Isl.
960 58 925 50 846 66
Total 14,523 ft 43% 8,403 ft 24% 5,830 ft 15%
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Gilchrist West GeotubeNovember 15, 2001
(fully exposed face)
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Gilchrist West GeotubeNovember 15, 2001
(one of several small holes)
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Gilchrist West GeotubeNovember 15, 2001
(covered but steep and little vegetation)
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Exposed Geotubes
June 2001 July 2001 November 2001Project Exposed
(ft)Exposed
%Exposed
(ft)Exposed
%Exposed
(ft)Exposed
%
Gilchrist, East
1,670 27 0 0 702 6
Gilchrist, West
10,630 74 6,142 43 3,967 28
Dellanera 413 26 545 36 207 14
Pocket Park 2
0 0 0 0 0 0
Riviera 0 0 0 0 0 0
Pirates Beach
850 10 791 10 108 1
Treasure Isl.
960 58 925 50 846 66
Total 14,523 ft 43% 8,403 ft 24% 5,830 ft 15%
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Pirates Beach on Galveston IslandNovember 15, 2001(only exposed section)
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Pirates Beach on Galveston IslandNovember 15, 2001
(covered and vegetated, typical for project)
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Comparing Beach Widths(SW End Pirates Beach)
MHHW +0.6 m msl Geotube
Landward boundaryBEG-02
Beach profile
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Beach Profile (BEG-02)SW of Pirates Beach Geotube
0 20 40 60 80 100 120 140
D istance (m )
-2
-1
0
1
2
3
Hei
ght R
elat
ive
to M
SL
(m) BEG02
Galveston Island State Park
vertica l exaggeration = 10:1
datum
June 14, 2001Ju ly 19, 2001N ovem ber 13, 2001Vegetation line2 nd Vegeta tion line
+0.6 mM H H W
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Beach Profile (BEG-02)SW of Pirates Beach Geotube
June 14, 2001
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Beach Profile (BEG-02)SW of Pirates Beach Geotube
July 19, 2001
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Beach Profile (BEG-02)SW of Pirates Beach Geotube
November 13, 2001
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-20 0 20 40 60 80 100 120 140 160 180
D istance (m )
-2
-1
0
1
2
3
4
He
igh
t Re
lativ
e to
MS
L (m
)
GAL01Galveston Island
vertica l exaggeration = 10:1
datum geotube
June 14, 2001Ju ly 19, 2001N ovem ber 13, 2001Vegetation line
M HH W+0.6 m
Beach Profile (GAL-02)Near SW end of Pirates Beach Geotube
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Beach Profile (GAL-02)Near SW end of Pirates Beach Geotube
November 13, 2001
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Beach Profile (GAL-02)Near SW end of Pirates Beach Geotube
July 19, 2001
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Comparing Beach Widths(SW End Pirates Beach)
MHHW +0.6 m msl Geotube
Landward boundaryBEG-02
Beach profile
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Beach Width at Pirates Beach
0 20 40 60 80 100 120 140 160 180W idth (ft)
0
0.2
0.4
0.6
0.8
Rel
ativ
e F
req
uen
cy
In front of geotubeAdjacent to geotube
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Water Level and Waves Combined(data from Pleasure Pier tide gauge)
TS Allison
TS FrancesTS Josephine
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Conclusions as of 2001
1. Improvement in keeping geotubes coveredbut 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
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Website
www.beg.utexas.edu/coastal/coastal01.htm
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