Autumn 2016

Grand Isle, an island in the Gulf of Mexico off the coast of the American state of Louisiana, periodically has to contend with severe storms. In 2008 the southern coastline was badly affected by Hurricanes Gustav and Ike.  

The series of dunes (burritos) constructed by the US Army Corps of Engineers lost out to the implacable elements. The deterioration and breaches in the existing dune structure left the island and properties vulnerable to future storm events. The engineering corps set resolutely to work on rehabilitating and rebuilding the damaged beaches. TenCate Geotube® technology was selected as core for a new vegetated dune structure.

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TenCate Geotube® containers as the core of dunes

The USACE Grand Isle and Vicinity Hurricane Protection Project included reconstruction of 31,000 feet of dune and renourish the beach with approximately 1 million cubic yards of sand dredged from a designated offshore borrow area. TenCate Geotube® GT500 units, each 65 metres long and with a sand-coloured coating applied to the top half of the units, were filled with locally sourced drained sand mixed with seawater. The 30-ft. circumference containers were manufactured by the facility of TenCate Geosynthetics in Commerce, GA.

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TenCate Geotube® GT500 units with a sand-coloured coating

The result was a row of tubes, 9.4 kilometre (31,000 linear feet) long with a 10-metre circumference, which serves as the core of a new line of dunes more than 4 metres high. Geotextile scour aprons were installed to prevent erosion at the base both front and back. The flat ends design created tight joints and maintained a uniform elevation, while the flexible nature of the containers allowed them to conform to the shape of the shoreline.

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The filled containers fit together perfectly and conform to the shape of the shoreline

After installation, the dune core was covered with a million cubic metres of sand and beach grass. The reinforced dune structure behind the restored beach has since helped to control erosion and forms a barrier against storm and wave action. A few weeks after the installation had been completed, Tropical Storm Ida arrived on the scene. The core structure suffered no damage at all. Inspections of the dune structure afterwards showed excellent establishment of the vegetation; the structure was performing as designed.

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Established vegetation on the dune two years later

Blue fabric (Tecawork Blue 65287)