Ocean-friendly Oyster “Sea Walls” May Provide Cost-Effective Hurricane Defense

Kristen Rodman, Staff Writer
May 24, 2014; 5:12 AM
See larger image below.

With sea levels consistently on the rise and recent hurricanes ravaging coastlines, seaside communities are on the lookout for cost-effective ways to protect their homes from the ocean’s fury. After more than a decade of research, one coastal geology professor and his colleagues may have found a dynamic solution that also benefits the well-being of oceans.

The construction of sea walls for protection against storm surges and climbing sea levels is no new concept to the modern world. However, a team of researchers alongside of Coastal Geology Professor at the University of North Carolina at Chapel Hill Antonio Rodriguez have discovered an innovative alternative to the usual granite and limestone bulkhead: oyster reefs.

“We can build reefs instead to serve the same protection against erosive waves but keep a more natural habitat,” Rodriguez said.

Oyster reefs are constructed by spreading shell out thinly over the desired location then placing oyster larvae on top of the shell base. As water flows over the shells, the larvae settle on top of the shells and with time, grow into oysters. These oysters then become settling sites for the next year’s larvae and the process persists as oysters grow one on top of the other, year after year.

“When it grows, it’s a big cemented structure so it’s really hard, unlike the natural shoreline which is very soft,” Rodriguez said. “The reef will take the blunt of the waves and dampen them so that when they reach the shoreline, they have less of an invasive effect.”

A North Carolina professor and his team recently published a research study in favor of using oyster reefs instead of seawalls, after spending years growing an oyster reef in Back Sound, N.C. (Photo/Rodriguez Laboratory University of North Carolina Institute of Marine Sciences)

In Back Sound, North Carolina, where Rodriguez and his colleagues experimented with oyster reefs, the team uncovered perhaps the largest potential benefit that these kinds of reefs can offer.

“The reefs grow so quickly because they grow on top of each other and each one is growing a few centimeters each year,” Rodriguez said.
During their trials, the team found research showing oyster reef growth at half a centimeter a year, but their findings were of a much greater magnitude with the group discovering the reef growth at approximately 11 centimeters per year.
“The reef will keep up with sea level rise and maintain the same elevation through time, relative to the sea level,” he said. “This could help along all the estuary shorelines at least on the East Coast.”

While Rodriguez admitted that oyster reefs will never grow like sea walls, these reefs also generate numerous environmental benefits.

“It’s a living structure that creates a new habitat so more fish will come in and the oysters also clean the water because they are filter feeders,” he said.
Aside from aiding marine life, oyster reefs bear a minimal financial burden in comparison to the construction of a sea wall, which can cost an upwards of $10 million. The oyster shells required cost approximately $5 a bushel but recycled oyster shells can be used too. In total cost, Rodriguez estimated that an entire reef would cost only a few hundred dollars.

A team of researchers at North Carolina University at Chapel Hill grow an oyster reef in Back Sound, N.C., discovering the rapid growth of these reefs. (Photo/Rodriguez Laboratory University of North Carolina Institute of Marine Sciences)

While oyster reefs may provide a cost-effective, eco-friendly and more natural solution for waterfront towns looking for protection, the reefs do have some setbacks.

After parts of Alabama attempted to build oyster reefs for shoreline defense after the Deepwater Horizon, or BP, oil spill in April 2010, no oysters settled in the area.

“It can be tricky to build by the shoreline, oysters have to be at the right depth,” Rodriguez said. “They have to be exposed to air at least 40 percent of the time.”

In addition to oxygen necessities, oysters can be prone to diseases which can wipe out entire reefs.
Despite the threats to oyster reef construction, numerous non-profit organizations as well as the North Carolina Coastal Federation in the Chesapeake Bay are currently in the building process.
Looking ahead, Rodriguez and his team hope to see less bulkhead building as this movement catches fire and spreads.
Special thanks to Richard Charter

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