Hurricane Irma brought to light a precarious position for Floridians in flood zones.
Irma has shown that natural barriers, as opposed to artificial, engineered ones, are the best defense Florida’s coastal communities have against floods and rising waters. Coral reefs, mangrove forests, dunes, and wetlands are all examples of natural barriers that, for too long, have been degraded to make way for development. However, it is now all too clear that these dwindling natural barriers protect us from rising sea levels and storm surges.
Worldwide, natural dunes, mangroves, wetlands, and other “green infrastructure” have given way to seawalls, streets, and buildings. Florida is no exception.
To make way for the rapidly expanding populations that flocked here in the early half of the twentieth century and in the name of growth, Florida has always been a place for “fixing”. “Draining the swamp” to make way for infrastructure and progress was seen as necessity, and the Army Corps of Engineers set out to make it a reality. A few hundred drainage canals later, the communities of South Florida rose from the damp ground. Half of the historical Everglades “river of grass” no longer exist, resulting in an almost-unrecognizable Florida with over-engineered landscape and water in all the wrong places at all the wrong times.
Wetlands like the Everglades act as sponges during floods and storm surges, accepting extra water and swelling harmlessly and clean the slow-moving water. Paved landscapes, however, simply allow water to collect dirty pollution before quickly moving down streets to storm drains, canals, and to the bay. This runoff quickly overwhelms our infrastructure like municipal sewers. Unlike concrete and asphalt, green space like parks and wetlands create permeable surfaces and reduce the impacts of flooding by absorbing water. It’s been reported that, “During Hurricane Sandy in 2012, marshes prevented $625 million in direct flood damages across the Northeast Untied States.” In a more general sense, coastal wetlands across the U.S. provide an estimated $23.3 billion in storm protection annually, making them a highly cost-effective way to protect coastal communities.
Like marshes, coastal wetlands prevent damage even in places where they have been degraded to relatively small bands. Scientific research on the subject shows that 2.7 miles of wetlands will reduce potential storm surge by a foot. Additionally, one acre of wetlands can hold as much as 1.5 million gallons of floodwater.
Mangroves similarly perform many beneficial functions, including protection from storm surge, sea level rise, and erosion; habitat for juveniles fish; and carbon sequestration. Of the various types of natural solutions for coastal protection, mangroves offer the best protection from wave action. In the Philippines, for example, a country known for its typhoons, mangroves reduce annual flood damage by 25%. In Florida, roughly 469,000 acres of mangrove forests serve as the ultimate multitaskers. In addition to protecting coastal areas of Florida from waves by as much as 20 percent, mangroves also aid in nutrient cycling, carbon sequestration, sediment retention, and provide valuable habitats for marine life. Luckily, in the state of Florida, there are laws protecting mangroves. The law states that mangroves cannot be trimmed below a certain height, effectively protecting them from being cut down completely.
Coral reefs are another natural coastal defense that provides multiple benefits. The Florida Reef Tract is the only nearshore coral reef in the continental United States and the third largest barrier reef in the world. It spans from Martin County down to the southern tip of Monroe County. Between wetlands, mangroves, and coral reefs, coral reefs have the highest potential for coastal protection due to their ability to reduce wave heights. On average, coral reefs reduce wave height and wave energy by 70%, which, without them, would hit coastlines with large amounts of energy and potentially cause extreme damage. It can pay off to focus on restoring coral reefs for the purposes of flood defense. Coral reef restoration has proven to be highly cost effective when compared to the cost of typical engineered flood solutions such as breakwaters.
All in all, natural barriers like wetlands, mangroves, and coral reefs are free flood and storm protection that nature provides, making them our most cost-effective solution. All we have to do is not mess them up. During Hurricane Irma, storm surges recorded in Biscayne Bay were about four feet above the normal tide. It could have been even worse if it had been a direct hit as was previously forecasted. Restoring what has been lost would only add to future resiliency against rising waters and storm surges that South Florida will no doubt continue to experience in the years to come.