Scientists Wary of Fort Lauderdale’s Proposed Seawall Plan
Sea level rise experts think the city's plan to raise seawalls won't be enough.
Photo by Dave via Flickr Creative Commons
Update: Nancy Gassman, an assistant public works director with a doctorate in coastal ecosystems, tells New Times that the proposed minimum height for the sea wall is based on the level of the ocean. The proposed minimum seawall height is about eight inches higher than the current allowable maximum. The maximum height proposed in the new ordinance is based on a property's base flood elevation meaning that it depends on the property. For example, if a property's base flood elevation is 7 feet, then the sea wall can be raised to 7 feet. The maximum height is imposed to prevent storm water run off from flooding homes. Gassman explains that if the sea walls were higher than the base flood elevation, water would run off towards the properties and potentially flood homes. The idea is to have storm water run off away from the home.
"We're trying to keep ocean water off the property but also trying to keep storm water away from the homes too," Gassman explains. "There are multiple concerns when dealing with sea level rise. There is not a single answer to a single problem. We're trying to take a comprehensive approach and recognize that sea walls have multiple functions on the individual property."
Fort Lauderdale has over 200 miles of seawalls. During high tides and storms, seawalls protect properties from coastal flooding. Currently, a city ordinance dictates that seawalls be no higher than five and a half feet. But during King Tides, the really high tides in September, the seawalls are not cutting it. In coastal communities like Las Olas Isles, water is already washing over them and nearly flooding homes. Experts fear this flooding will get worse as sea level is predicted to rise.
So, earlier this month, city officials introduced a new ordinance that would require every seawall in the city to be raised at least eight inches — but no more than 12 inches. This has some sea-level-rise experts scratching their heads, because raising the walls just inches will not protect properties for long: By 2045, sea level is anticipated to rise at least a foot, a
Earlier in April, Miami Beach commissioners approved a plan to increase the minimum seawall height to five feet six inches above mean sea level for private seawalls and seven feet three inches for public seawalls. They did not dictate a maximum height.
“The Miami Beach proposed freeboard ordinance appears to give each property owner more leeway in deciding how high to elevate above the new minimum, under their particular circumstances,” says Albert Slap, co-founder of Coastal Risk Consulting.
Coastal Risk Consulting launched in 2014, advising how to prepare for sea-level rise. They have also digitized their data so that any person can look up any address in Miami-Dade, Broward, Palm Beach, and Monroe counties and determine its risk of flooding from sea-level rise over the next 30 years. Their data reveals that Fort Lauderdale’s vulnerability to sea-level rise is not uniform or standard. Each parcel of land is located at a certain point above sea level and therefore has its own risk. Bolter, Slap, and other sea-level-rise experts fear the consequences of cookie-cutter mandates, like this ordinance.
“The vulnerability of each property is different. We need something that gets down to the
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Bolter guesses that the city is placing a mandatory maximum height for two reasons: to not obstruct the ocean view and to create a uniform code so that one property and its neighbors will look similar.
It is estimated to cost a property owner anywhere from $10,000 to $125,000 to raise an existing seawall or completely replace a 100-foot seawall. With four miles of public seawalls, it can cost the city as much as $26 million to replace its seawalls. Slap worries about spending all that money on plans that might not last more than 20 years. “If the legal maximum seawall elevation height is too low,” Slap warns, “then the improvements won't last long enough and the costs to renovate yet again may be unaffordable.”
Commissioners are expected to discuss the ordinance next month and vote on it in June.
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