A sea wall won’t save Miami, but these innovations just might

Miami is all about the water and the outdoors. Walking paths and parks line large swathes of the downtown waterfront with a breathtaking view of the bay.

This downtown area is where the Army Corps of Engineers plans to build a $ 6 billion seawall, 20 feet high in places, through downtown neighborhoods and right between the Brickell neighborhood skyscrapers and the bay.

There is no doubt that the city is at an increased risk of flooding as sea levels rise and storms intensify with climate change. A hurricane as powerful as André from 1992 or Irma 2017 make a direct hit on Miami would devastate the city.

But the dike the army corps proposes– protecting only 10 miles of downtown and the financial district from a storm surge – cannot save Miami and Dade County. Most of the city will be outside the wall, unprotected; the wall will always trap water inside; and the Corps has not closely studied what building a a high dike would affect the quality of the water. At the same time, it would block the views of the water on which the city’s economy thrives.

Much of Miami is built right up to the water’s edge. On average, it is six feet above sea level. [Photo: Ryan Parker/Unsplash]

To protect more of the region without losing Miami’s vibrant character, there are ways to combine the strength of less intrusive enhanced infrastructure with “green” nature-based solutions. With our colleagues from Miami University Rosenstiel School of Marine and Atmospheric Sciences and the College of Engineering, we have been design and test innovative hybrid solutions.

Natural storm management

Living with water today is not what it was 50 years ago, even 20 years ago. Parts of Miami now experience regular “sunny days” flooding during high tides. Salt water is seeping into basements and high-rise parking garages, and flooding caused by tides is expected occur more frequently when sea level rises. When storms hit, the storm surge adds to this already high water.

Hurricanes are less frequent than tidal floods, but their the destructive potential is greater, and that’s what the Corps is focusing on with its dike plan.

If Miami Beach were an undeveloped barrier island, and if thick mangrove forests were still common along the South Florida coastline, the Miami area would have more natural protection against storm surges and weather strikes. waves. But most of these living tampons are long gone.

However, there are still ways in which nature can help preserve the beauty of Miami’s marine playground.

Coral reefs like those in Biscayne National Park have struggled with warming waters. [Photo: NPS/Flickr]

For example, healthy coral reefs break the waves, dissipate their energy before the waves reach the shore. Dense mangrove forests also dissipate wave energy with their complex root systems that rise above the waterline, considerably reducing the impact of waves. In areas where coastal flooding is a growing problem, low-lying communities may be moved to higher ground and vacant land converted into wetlands, canals or parks designed to handle flooding caused by storm surges.

Each zone of the coast is unique and requires different protection measures depending on the dynamics of entry and exit of the water. Given Miami’s limited space, only the living shores will not be enough against a major hurricane, but there are powerful ways to pair them with a strong “gray” infrastructure that is more successful than either alone.

Hybrid solutions mix green and gray

No one wants to look at a cement breakwater offshore. But if you look at a breakwater covered in corals and welcoming to marine life – and you can go out and swim on it – it’s different.

Corals help the structure to better dissipate wave energy and at the same time they improve water quality, habitat, recreation, tourism and quality of life. For many people, these are some of Miami’s biggest selling points.

By pairing corals and mangroves with a more sustainable and environmentally friendly hard infrastructure, hybrid solutions can be much less invasive than a large sea wall.

For example, a cement-based breakwater structure submerged offshore with coral grafts could provide habitat for entire ecosystems while provide protection. We work with the city of Miami Beach through the University of Miami Integrative Knowledge Lab To implement three hybrid coral reefs just offshore that we will monitor for their technical and ecological performance.

Closer to shore, we experiment with a new marine and estuarine modular system we call “Seahive”. Below the waterline, water flows through hollow hexagonal concrete channels, losing energy. The summit can be filled with soil to grow coastal vegetation such as mangroves, providing even more protection as well as an ecosystem that benefits the bay.

We are currently working to test Seahive as a green engineering alternative for North Bay Village, an inhabited island in the bay, and as an infrastructure for a newly developed marine park where these models of “green-gray” reefs and mangroves will be presented.

What about the rest of Miami?

The Corps of Engineers of the Army draft plan—A final version is expected in the fall — would leave little room for nature-based solutions beyond a small mangrove and seagrass restoration project South. The Corps determined that natural solutions alone would require too much space and would not be as efficient as physical infrastructure in the worst case.

Instead, the corps plan focuses on the six-mile levee, flood gates, and raising or strengthening buildings. It basically protects the infrastructure of the city center, but leaves everyone alone.

Dikes and flood gates can also affect water flow and adversely affect water quality. The body documents warn that dikes and gates will affect wildlife and ecosystems, including the permanent loss of protective corals, mangroves and seagrass beds.

Mangrove roots rising above the water help to break the energy of the waves on the shore. [Photo: Unsplash]

We would like to see a plan for all of Miami-Dade County that takes into account the value that green and hybrid solutions bring to marine life, tourism, fishing and the quality of life in general, in addition to their coastal protection services.

Both types – green and gray – would take time to develop, especially if the dike plan was challenged in court. And both are at risk of failure. Corals can die in a heat wave, and a storm can damage mangroves; but storms can also undermine technical solutions, such as New Orleans’ dike system during Hurricane Katrina. To help build resilience, our colleagues at the University of Miami have been coral farming to be more resistant to climate change, by studying new cementitious materials and non-corrosive reinforcements and by developing new designs for coastal structures.

Miami in the future

Miami will be different in the decades to come, and the changes are already starting.

Heights are everything, and this manifests in real estate decisions that push low-income residents to less secure areas. Anyone looking back to Miami is likely to think the region should have handled growth better and maybe even manage some form of retirement endangered areas.

We don’t want to see Miami become Venice or a city isolated from the water. We believe Miami can thrive using the local ecosystem with new green engineering solutions and architecture that adapts.

Landolf Rhode-Barbarigos is assistant professor of civil, architectural and environmental engineering at the Miami University, and Brian Haus is professor of ocean science at the Miami University.

This article is republished from The conversation under a Creative Commons license. Read it original article.


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