Geotubes on Galveston Island Laura Mullaney Mars 485 Spring 2003

Galveston’s 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?

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]

Tropical Storm Frances and 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]

Funding Fiscal year 2002, congress appropriated $10 million, of which Texas will receive $387,957 [7] Geotubes = $125/foot [8] [4]

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]

Geotube Installation

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

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

Locations on Galveston Island

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

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]

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

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]

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

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 = feet –30 miles SW of the Galveston geotube projects –[2]

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

Decreased Beaches Beaches in front of the tubes are 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]

Beach Widths July 17, 2001 [2]

References 1. –Aggie-Hotline, April 16, 2001/A&M Galveston Studies Beach Erosion, by Jane Maxwell ( ) 2. –Geotubes along the gulf Shoreline of the upper Texas coast: Observation During 2001 ( ) 3. tloc=49662&p_ploc=24777&pg=3&p_tac=&ti=31&pt=16&ch=501&rl=14 tloc=49662&p_ploc=24777&pg=3&p_tac=&ti=31&pt=16&ch=501&rl=14 –Title 31. Natural Resources and Conservation. Part 16. Coastal coordination Council. Chapter 501, subchapter B (3-5-03) 4. –Memorandum of Project Understandin (MOU) – West Galveston Island Beaches – CERPA II Project ( ) 5. –CEPRA II – GOALS AND CONCERNS November 13, 2002 (4-6-03) 6. –Chronology of Events set in motion by the PPOA and the WGIPOA ( ) 7. –The Beach Act, by Coastal Coordination Council, ( ) 8. –Annual meeting: October 12, 2002 ( )