Geotubes on Galveston Island

1
Geotubes on Galveston Island

• Laura Mullaney
• Mars 485
• Spring 2003

2
Galvestons Problem

• Losing up 10 feet of shoreline a year for the
  last 50 years 1
• Causes
• Global water levels are rising
• Sinking due to pumping out of ground water, oil,
  and gas
• Natural weather events
• These events are happening everywhere so why such
  detrimental effects to Galveston Island?

3

• Rivers are being damned off cut off the fresh
  sand source
• Flat beaches allow for minute sea level rises to
  have significant effects
• 1 meter of water rise means Galveston looses 100
  meters of beach to the Gulf 2

4
Tropical Storm Francesand the Aftermath

• September 7-11, 1998
• Estimated 250 million dollars worth of damage
• Approximately 100 homes now on public beach
  (seaward of the natural vegetation line)
• 6

5
Funding

• Fiscal year 2002, congress appropriated 10
  million, of which Texas will receive 387,957 7
• Geotubes 125/foot 8
• 4

6
The Geotube

• Sediment filled sleeve of geotexile fabric with a
  cross section of 12 feet
• Rests on a fabric scour apron with
  sediment-filled anchor tubes along each edge
• Placed in a trench running parallel to the shore
• 2 feet of sand and vegetative cover
• 2

7
Geotube Installation
8

• Intended to be a temporary storm-surge protection
  and erosion control
• The tubes will fail when exposed to a direct wave
  attack

9
Locations

• Cover 7.3 miles of shoreline from Follets Island
  to High Island
• With Pirates Beach being the largest on Galveston
  Island measuring 1.553 miles

10
Locations on Galveston Island
11
Guidelines for Locations

• Guidelines set forth by the Coastal Coordination
  Council
• If foredune is present, then will be placed
  landward
• No fordune, then landward of the line of
  vegetation
• Project shall only be placed seaward of the line
  of vegetation as long as beach width is
  maintained through nourishment

12
Mistakes

• Galveston island projects particularly Pirates
  Beach placed the geotubes seaward of the line of
  vegetation, have not yet started their beach
  nourishment
• Leading to a decrease in the width of the beach
• Communities are not providing adequate parking to
  allow visitors to use the public beach, forming a
  de facto private beach
• 3

13
Maintenance

• Tubes stay covered with sand and vegetation
• Beach nourishment
• Repair holes as soon as possible

14

• The quantity of sand placed on the beach of each
  participant is directly related to their monetary
  contribution 5
• Impossible as of date to keep even a sparse
  vegetative cover on at least half of the project
  lengths 2

15

• Primary source of beach and dune sand is that
  which is eroded from the beaches that are up
  drift of any given location
• The prevention of erosion and release of landward
  sand to adjacent beaches, will cause higher rate
  of erosion to neighboring beaches
• This can be stopped by nourishing the geotube
  beaches allowing the sand to migrate to the
  surrounding areas

16
Experimental

• The geotubes have not been tested with a full
  storm impact
• 44 of the total length of the project was
  totally exposed and most areas suffered erosion
  of sand cover following TS Allison
• Peak water level 3.12 feet
• Peak wave height 13.94 feet
• 30 miles SW of the Galveston geotube projects
• 2

17

• Pirates Beach faired well with respect to keeping
  its vegetative cover
• Only 10 of the Pirates Beach project was exposed
• Due to Sand fence and lack of coppice mound sub
  environment

18
Decreased Beaches

• Beaches in front of the tubes are 21-83 feet
  narrower then those without
• Due to the tubes being placed seaward of houses
  overlapping the natural vegetation line
• Making some parts impassible when water is only 2
  feet above normal sea-level
• This is most visible at the Pirates Beach project
• 2

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Beach Widths July 17, 2001

• 2

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References

• 1. http//twri.tamu.edu/watertalk/archive/2001-Apr
  /Apr-17.1.html
• Aggie-Hotline, April 16, 2001/AM Galveston
  Studies Beach Erosion, by Jane Maxwell (3-28-03)
• 2. http//www.beg.utexas.edu/coastal/200120final
  20report.pdf
• Geotubes along the gulf Shoreline of the upper
  Texas coast Observation During 2001 (2-19-03)
• 3. http//info.sos.state.tx.us/pub/plsql/readtace
  xt.TacPage?slTapp9p_dirFp_rloc95556p_tloc
  49662p_ploc24777pg3p_tacti31pt16ch501
  rl14
• Title 31. Natural Resources and Conservation.
  Part 16. Coastal coordination Council. Chapter
  501, subchapter B (3-5-03)
• 4. http//www.cityofgalveston.org/whatsnew/mou.pdf
  
• Memorandum of Project Understandin (MOU) West
  Galveston Island Beaches CERPA II Project
  (3-28-03)
• 5. http//www.cityofgalveston.org/whatsnew/mou.pdf
  
• CEPRA II GOALS AND CONCERNS November 13, 2002
  (4-6-03)
• 6. http//www.texasopenbeaches.org/WGIPOAchronolog
  y.doc
• Chronology of Events set in motion by the PPOA
  and the WGIPOA (3-28-03)
• 7. http//www.glo.state.tx.us/coastal/beachwatch/i
  ndex.html
• The Beach Act, by Coastal Coordination Council ,
  (2-10-03)
• 8. http//www.bermudabeach.org/2002minutes.htm
• Annual meeting October 12, 2002 (2-10-03)