Coastal Barriers
Protecting people, property, and industry |
Sand Dunes, Sand Engines, and More:
Natural sand dunes and "environmental socks" have been used for years as a form of protection from storms. The challenge with them, however, is that they don't last long when confronted by a major storm system. At best they will only remain for a few hours and then be overcome or swept away by heavy rains and massive storm surges.
In the Netherlands they have used "engineered" dunes and have even built a dune with a parking garage underneath it!
"Engineered" dunes have an inner concrete core surrounded by clay or a mixture of clay and large rocks. This inner core is covered with more clay and then sand. This structure works to hold back multiple storm surges; while coastal grasses are planted to help stabilize the sand and make the dunes aesthetically pleasing to the eye.
[See the diagram below]
In September 2019 I traveled to the Netherlands to see what they had done. It has been proposed that samples of storm surge engineered dunes be constructed on Galveston Island so people can come and experience them for themselves without needing to travel to the Netherlands. I think this is a great idea; letting folks in Texas get a idea about what is being proposed.
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In the Netherlands they have reclaimed land from the North Sea by adding sand in front of their dunes. Then they built a "sand engine" on the beach that continually replenishes the beach sand naturally.
The Sand Engine:
In 2011 the Dutch conducted a pilot project to naturally replenish their beaches and to combat erosion. They place a mountain of sand on a portion if their beach where ocean currents would redistribute it along the shoreline. To date, this project has done as advertised, combatting erosion while also offering a recreational area in the process.
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Here's an Idea:
There are places on Galveston Island where it appears there isn't enough room between the homes on the beach and the Gulf to place an engineered dune. What if we took a page from the Dutch's play book, built engineered dunes near these houses, extended the beach in front of them, and then added our own version of a sand engine? I don't know whether this would work or if it would be cost prohibitive but it might provide the required storm surge protection, look esthetically pleasing, provide an additional recreational area for the public, and help counteract beach erosion.
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Here is what the beach looks like in 2019, eight years
after
the sand engine (or sand motor) was built.
A mile or so down the coast the beach has been extended and continues to be renurished by the sand engine.
[Click here to download a 360 degree video of what the beach looks like from the water's edge]
 (This may be a long download because of the size of the file)
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The Scheveningen Coastal Waterfront Defense
In a study of the Dutch coastline, the protection at Scheveningen was found to be a weak link in the Dutch coastal flood protection line. As a consequence efforts were taken to beef up its protection. They incorporated several features including a dike upon which  was built a boulevard (boardwalk) for foot traffic.
The improved coast protection was designed as a ’hybrid’ structure: a combination of a ’hard’ dike with an extended soft sandy beach. The sand volume in front of the dike reduces the wave height  and thus limits over-topping. The base of the dike is situated below the level of anticipated sand erosion sand during storms. In this way collapse of the dike due to erosion is prevented.
 Restaurants that frequent the beach in front of the dike used to be removed during the October-February storm season. In more recent times they have been allowed to remain because of the extended beach. They may still be subject to flooding but the risk has been reduced.
Click on images to see a larger view |
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