The Benefits of Barrier Islands

Jason Lauritsen, chief conservation officer for the Florida Wildlife Corridor, had some good news in the wake of Hurricane Ian, the Category Four hurricane that impacted the island on September 28. Lauritsen says that Marco Island actually has some built-in protection from the devastation of hurricanes that many other barrier islands don't have.

Marco Island was affected by Ian’s storm surge that made landfall on Captiva Island. Surveys have shown a storm surge of more than seven feet on Marco Island, according to data compiled by the U.S. Geological Survey.

Lauritsen says it is not a question of whether Marco Island will be hit by a major storm, but when.

"We know enough watching these storms,” Lauritsen said, "that it’s not a matter of will a storm hit, it’s a matter of when will it hit.”

Lauritsen said one needs to look at Marco Island, a barrier island, with an historical perspective.

"When you look at the coastal communities,” Lauritsen said, “you think about the barrier islands and the coastal mangroves. And you think about 100 years ago, where those mangroves were and what those barrier islands looked like. And if you look back over time and look at the shifting and the accretion, the erosion, the deposition of sands over time how those barrier islands change shape and move over time. Those islands are rather dynamic.”

Accretion is the process of coastal sediment returning, which makes the beach wider, while erosion does the opposite.

"You have two forces at work,” Lauritsen said. "You’ve got the wind and you’ve got the storm surge. The interior of the state hurricane codes are often looking at CAT Five winds. An 18-foot storm surge. Boy, isn’t that tough to engineer against. I don’t know what an 18-foot storm surge might do to Marco. What would 12-feet do on Marco? I know a lot of folks in Northern Collier and Southern Lee County had 8-feet in their parking garage or the lower level of their home. Second stories were all okay, at least in terms of flooding and storm surge. I don’t know anybody who had a second story impacted by the surge and flooding. So I don’t know what a direct hit on the dirty side of the storm would have done to Marco. I’m sure we could engineer against that by putting all the parking on the bottom floors of buildings.

Lauritsen says Marco Island benefits from the mangrove barrier islands to its north and south, and also from the Big Cypress National Preserve and the Everglades National Park to its east.

"Mangroves, as an example,” Lauritsen said, "when you have a storm coming in, those mangroves slow the storm down and reduce the wind speeds for the path behind them. It’s absorbing the impact of the storm.”

Lauritsen said Marco’s beach berm, created during the beach renourishment of the 1990s, certainly helps to protect the island during a major hurricane.

"Those coastal berms definitely help to ameliorate some of the storm effects and the vegetation on them,” Lauritsen said. "Our building codes, and the drainage in our communities, you have these certain standards to engineer against. Your one in 10-year flood event, your one in 25-year flood event, your one in 100-year flood (event). And I think some people think that if you have that one in 500-year event, you’re good for another 499 years. That isn’t the way it works."  

Lauritsen says the Fruit Farm Creek Mangrove Restoration Project, currently being completed on the east side of the island, shows how things can get out of hand by a lack of maintenance. 

Tidal flow to the mangrove forests south of San Marco Road was cut off when the road was initially built circa 1940. The section of road’s lone culvert was badly overgrown. The Fruit Farm Creek Restoration Project adds an additional five-feet diameter culverts to restore tidal flow, and eventually regrow the mangrove forests on both sides of San Marco Road. Arteries from Marco River are also being reopened as part of the project.

"That’s a great example where we can engineer something where it has the volume and just the natural growth of vegetation, trees dropping in, debris getting piled up in places,” Lauritsen said. "It can make it look like we didn’t design this with enough flow. It might just be that you didn’t maintain it. Spend a whole lot of tax dollars, and dredging costs, when maybe all you needed to do is clean and snag."

"The Marco area is really interesting,” he said, "It’s startling to see how much the Cape Romano shoreline has shifted over time. That area certainly has seen some impacts.”

Cape Romano, south of Marco Island, is where the famous Dome Homes once stood. Constructed in the early 1980s, the Dome Homes were once built on day land. Over the years, beach erosion caused the homes, built on concrete “stilts,” to end up surrounded by water.

Lauritsen said there is modeling available that would show how Marco Island might fare against a direct hit for a major hurricane.

"Think about just what angle would be catastrophic for a community and how might that impact us,” Lauritsen said. "I know there’s modeling available. All kinds of projections. If the storm came in at this angle and this velocity. I don’t know how customizable that could be. I don’t know that’s it’s interactive. I know that you can do those projections in locations.”

Lauritsen said Marco benefitted from the mangroves islands during Hurricane Irma. 

"When Irma was coming in,” he said, "we thought that Marco was going to get blasted. My guess is the fallout from that is the barrier islands to the south must have really saved Marco some damage. If the dirty side of Irma had hit Marco, instead of being further to the east, the storm surge projections would have likely been different.”

Lauritsen said Marco’s natural location saves it from a lot of potential peril.

"Rookery Bay, the 10,000 Islands,” Lauritsen said, "all the mangroves that are around Marco Island, definitely help. The Marco community benefits from the presence of those natural systems around it. And that’s a good thing. I would suggest any effort to clear the mangroves in any of those nearby islands and put structures in there would have a negative impact on Marco. Right now, Marco is in that green footprint.”

Lauritsen said the density of the island works in its favor when it comes to weathering a hurricane.

"Marco is densely developed,” Lauritsen said. "When it comes to smart growth in Florida, you would like communities to have high population densities rather than sprawl. It’s better to build up than out. There’s less impact, there is opportunity for biking to work, biking to the grocery store. Mass transit and things like that. Rather than have everybody sitting on a five-acre lot, there’s an advantage to being more compact. Less of a cost to the surrounding environment. When you spread people out in an estate-style growth, everyone has a five-acre lot, then you’re adding a lot more concrete and asphalt for roads, a lot more feet of electrical line and water and sewer. So there’s a spread-out effect. By having a community configured more densely you have a more efficient infrastructure.

Lauritsen said Marco also benefits from efficient draining. He said that drainage is helpful after the storm.

"I would say when you look at Marco from the air,” Lauritsen said, "it’s a network of canals. There’s water connections to the Gulf everywhere. You certainly would expect it to drain quickly. The question would be how high are people's foundations off of that high tide line. The quick drainage certainly makes it easier to come in and do cleanup and get power lines back up and make it much more hospitable. But I don’t know if that is any kind of security or safeguard against the surge. I think Marco is certainly a very well drained island.”

Lauritsen is one of the leaders of the Florida Wildlife Corridor, the statewide ecological corridor. Some consider the Florida Wildlife Corridor one of the most ambitious landscape conservation plans of any U.S. state. The corridor integrates protected land with strategic tracts of land throughout the state, from the panhandle to the Florida Keys. Currently the core focus of the Florida Wildlife Corridor is to fill in the missing links in the corridor. Quite often this involves working with developers to develop corridor-friendly communities.

"I always look for what big message comes out of a storm like this,” Lauritsen reflects. "For me, one of the things that happens when a storm occurs, questions surface and you learn things and you’re surprised by things you hadn’t considered before."