Living breakwaters

 

- Ottawa, Ontario

A perfect storm of innovative barriers defuses hurricane power

Physical model testing of the living breakwaters at the NRC coastal wave basin research facility.

Futuristic breakwaters shield shorelines and ecosystems from superstorms.

In 2012, Hurricane Sandy hit New York City (NYC) and the barrier islands along the New Jersey shore. The cost of damage to the state was $32 billion, with $19 billion of that in NYC alone. More than 200 people died along its path from the Caribbean to the northern states. And the effect on the environment was immeasurable.

Furious superstorms lashing shorelines around the world are 3 times as frequent as they were 100 years ago. As climate change continues, their regularity and rage are expected to increase.

According to Andrew Cornett, principal researcher at the National Research Council of Canada's (NRC) Ocean, Coastal, and River Engineering Research Centre, this new environmental reality calls for increasingly creative storm defence systems that serve more than one purpose. "We have to change the way we think about coastal protection and resiliency," he says. "Our recent testing of new barrier concepts indicates that they are strong contenders for defusing the dangers."

In the wake of the Hurricane Sandy disaster, the U.S. Department of Housing and Urban Development (HUD) launched the Rebuild by Design program to shore up protection against future storms. The target area for a proposed mile-long system of "living" breakwaters was in Raritan Bay, off Staten Island. The design of these reef-like barriers not only provides protection from waves and flooding, but also creates a welcoming habitat for marine life, particularly oysters for which Raritan Bay was once famous. As oysters reproduce and repopulate by latching onto discarded shells, the breakwaters will grow larger on their own. Oyster reefs also help clean the water: a single large oyster can filter up to 50 gallons (190 litres) of water a day, cleaning it of pollutants and undesirable nutrients.

Testing innovative breakwater concepts

Before breakwater construction and operation could begin, designs submitted to HUD by various firms had to be tested. Initial computer-based analysis using numerical modelling to explore waves, currents and sediment transport was conducted by Arcadis, a global consulting firm. According to Joe Marrone, Arcadis' Area Leader for Coastal and Urban Resiliency, the proposed breakwater system, designed by SCAPE, had a number of new features that were not well understood. "At this point, we knew we had to test it in a physical model."

After requesting proposals from several research groups, Arcadis chose the NRC for their impressive responsiveness and superior facilities, especially the Coastal Wave Basin. "NRC researchers built 3D scale models of the breakwater designs to evaluate their performance," says Marrone. This included replicating quarried stone materials and concrete blocks shaped to form tide pools, and assessing their effectiveness in turbulent aquatic conditions.

In some cases, the research confirmed the effectiveness of the designs. In other cases, when the physical modelling showed the designs were not performing as expected, Arcadis was able to adjust them in the NRC lab. "The physical modelling that the NRC did for us gave us a lot of confidence in the proposed design," he adds. The information from these investigations was used to optimize and support the final design and obtain the necessary permits required for construction.

A sea change in storm defence systems

Many communities in Canada and around the world face the same challenges as New York State. In fact, Hurricane Sandy brought heavy rain, high winds—even snow—to Ontario, Quebec and the Maritimes.

What the research and design teams learned from the living breakwaters project can be applied anywhere, and comes with far-reaching benefits. By combating wave action from superstorms, the structures can protect waterfront communities and restore valuable habitat. A safer waterfront also creates recreational and educational opportunities for locals.

"Our multidisciplinary teams of scientists, engineers and technologists are constantly working on solutions that improve the resilience of Canada's coasts," concludes Cornett. "These will help manage the risks of erosion and flooding to both the environment and residents." And that could mean more calm within the storm.

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