GEOTUBES ALONG THE UPPER COAST

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)

QAd496Gibeaut_CCC_Jan31_2002

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


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.


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


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


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


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


GLO-021 Profile LocationGilchrist West

Sept. 23, 1999


June 13, 2001

GLO-21 Profile LocationGilchrist West Geotube

July 18, 2001 November 14, 2001


GLO-021 Profile LocationGilchrist West

Sept. 23, 1999


Gilchrist East Geotube November 15, 2001

(example of “fully” exposed face)


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)


Exposed Geotubes


(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%


Gilchrist West GeotubeNovember 15, 2001

(fully exposed face)



(one of several small holes)



(covered but steep and little vegetation)


Exposed Geotubes


(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%


Pirates Beach on Galveston IslandNovember 15, 2001(only exposed section)


Pirates Beach on Galveston IslandNovember 15, 2001

(covered and vegetated, typical for project)


Comparing Beach Widths(SW End Pirates Beach)

MHHW +0.6 m msl Geotube

Landward boundaryBEG-02

Beach profile


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


datum

June 14, 2001Ju ly 19, 2001N ovem ber 13, 2001Vegetation line2 nd Vegeta tion line

+0.6 mM H H W



June 14, 2001



July 19, 2001



November 13, 2001


-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


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



November 13, 2001



July 19, 2001


Comparing Beach Widths(SW End Pirates Beach)

MHHW +0.6 m msl Geotube

Landward boundaryBEG-02

Beach profile


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


Water Level and Waves Combined(data from Pleasure Pier tide gauge)

TS Allison

TS FrancesTS Josephine


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


Website

www.beg.utexas.edu/coastal/coastal01.htm


GEOTUBES ALONG THE UPPER COAST

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