King tides are serving as an early warning system for communities along the Intracoastal Waterway, providing seasonal examples of flooding that — in future decades — will become more frequent and more intense as sea levels rise.
The main barriers keeping salt water from flooding even more waterfront property and streets during the king tides are the existing sea walls, but most of those structures probably aren’t high or strong enough to protect against the rising sea levels to come.
In January, Delray Beach became the first city in southern Palm Beach County to shore up its sea wall regulations to address climate change. City commissioners at their Jan. 11 meeting set a minimum height for sea walls and approved other policies for when new or replacement sea walls will be needed.
The new regulations won’t force all property owners whose sea walls are lower than the minimum height to come into compliance. They will apply only to new sea walls, those on properties undergoing major renovations, those in need of major repair and those that fail to stop water from washing over them and flooding neighboring properties or streets.
If cited by the city, owners will have a year to make repairs and meet the new height requirements.
“It’s not just about water coming through your sea wall or over your sea wall and affecting your neighbors, it’s also if your sea wall is damaged to the point where you’re losing material through the sea wall and into the Intracoastal Waterway,” Delray Beach Public Works Director Missie Barletto told waterfront property owners at a December forum about the changes.
Other coastal communities are still considering what to do.
In South Palm Beach, Town Manager Robert Kellogg is looking to see if the state approves new building inspection requirements in response to the collapse of Champlain Towers South in Surfside in June.
“We are waiting to see if the state does anything with requiring inspections to high-rises,” Kellogg said of legislators. “If they do, we would then incorporate sea wall standards into any changes we would make to the code.”
Other communities know it’s only a matter of time before they will have to act. Many belong to the Coastal Resilience Partnership of Southeast Palm Beach County, which developed a climate change vulnerability assessment for its partners last year.
“We are still working together as a group to update the vulnerability assessment, and have started discussing sea walls as an action area,” Ocean Ridge Town Manager Tracey Stevens said in an email to The Coastal Star.
Besides Ocean Ridge, the other partners are Boca Raton, Delray Beach, Boynton Beach, Highland Beach, Lantana, Lake Worth and Palm Beach County.
Highland Beach has had a minimum sea wall height for new construction on its books for years, but Mayor Doug Hillman said the town needs to take a closer look at how it will adapt its regulations to the growing threats from global warming.
“It’s a very big subject and a very costly one for our residents, so it’s not just something we can ignore,” Hillman said. “You don’t want water flowing over the land and then getting into the homes. And you can’t make a decision when it’s too late.”
The Delray Beach regulations require someone selling property in an affected area to disclose in the sale contract — in all caps — that the property is “in a tidally influenced area.” The notice says the buyer may have to meet minimum standards “during construction or substantial repair to the property or the sea walls,” or when needed “to abate nuisance flooding.”
How high to build
One of the most confusing aspects of sea walls is how their heights are measured. If the height is based on an old surveying system, known as NGVD 29, the recorded height is about 1.5 feet lower than if measured on the newer system, called NAVD 88. Some cities, such as Highland Beach, may use another Federal Emergency Management Agency standard called “base flood elevation.”
NAVD 88 is “a surveyed elevation, which is a benchmark point in space,” said Cynthia Buisson, assistant public works director in Delray Beach. “Sometimes when we think of elevation, we think well that’s just the water level, but the water level changes with the tide, with the season, and what I’m referring to is a surveyed elevation.”
Highland Beach last year began using base flood elevation because its previous 6 feet NAVD 88 minimum requirement was getting confused with that height using NGVD 29, which is lower, said Jeff Remas, the town’s floodplain administrator. The change also makes the town proactive as sea levels rise, he said.
“This way, as the flood maps raise the base flood elevation, the sea wall height requirement also increases without the need for legislative intervention,” Remas said in an email to The Coastal Star.
Delray Beach’s new requirements are lower than what’s already on the books for new construction in Highland Beach. In fact, what Highland Beach has as the minimum allowed for new sea walls — the base floor elevation — is the maximum height for Delray Beach.
In Delray Beach, using the NAVD 88 measurements, the city is requiring sea walls be built to a minimum height of 4.2 feet and that the structure be able to accommodate a cap that reaches a height of 5 feet if needed in the future.
“We’re going to continue to monitor sea level rise. There may be changes that come forward. Instead of having to replace your entire sea wall, you can just add a cap for that additional level of protection,” Buisson said.
Delray’s 4.2 feet minimum compares to minimum sea wall heights of 3.9 feet in Fort Lauderdale, 5.7 feet in Miami Beach and 5 feet for Broward County.
Delray’s maximum height of 5 feet or the base flood elevation, depending on location, compares with maximum heights of 4 feet in Lighthouse Point and 5 feet 10 inches in Pompano Beach. Fort Lauderdale also uses base flood elevation as a maximum.
About 70% of current sea walls in Delray Beach are below its new minimum and only about a quarter are in good or satisfactory condition, a 2018 city survey showed. The survey covered about 20 miles of privately owned sea walls and 1 mile of public sea walls.
Buisson said a sea wall has a life expectancy of about 30 years, so Delray Beach officials don’t want to make them be higher than needed during that time.
“Some folks think that we’re not going high enough,” Buisson said. “The whole idea is to still allow you to live on the water, enjoy why you bought the house on the water, while still protecting yourself and your community.”