It’s clear St. Augustine’s archeological zones and historic downtown are vulnerable to anticipated sea level rise along the coast, according to a report released through a state and federal pilot program.
But what isn’t clear is how fast and how high waters will ultimately swell.
Just a foot or more of sea level rise would make the historic downtown, St. Augustine’s economic lifeblood, dangerously vulnerable to regular or so-called nuisance flooding.
The vulnerability assessment was released last week. It was drafted through a pilot partnership between the Florida Department of Economic Opportunity and the National Oceanic and Atmospheric Administration. The report finds that a rather moderate sea level rise would affect 20 to 50 percent of the historic district by the 2040s at earliest, or 2100 at the latest.
Unfortunately, city public works director Martha Graham said, that’s a wide range.
“Well, I think the biggest surprise, I guess, is the fact that we really don’t know how much or how soon,” she said.
With one-and-a-half feet of sea level rise, 30 percent of the city’s road network will be affected by regular flooding, shifting between occasional to frequent road closures. That type of scenario would also see 60 percent of the city’s archeological zones affected and two feet of rising tides could leave 50 percent of the city’s bridges vulnerable to nuisance flooding.
Even more disconcerting is the impact sea level rise would have on the city’s outlying water plants and wastewater treatment facilities.
Although the report concluded that the St. Augustine Water Plant is “not vulnerable to any flood hazard or [sea level rise] combination examined,” it did find St. Augustine Wastewater Treatment “would have increasing vulnerability to nuisance flooding with sea level increases between two and four feet.”
Graham said the city is already working through a strategic plan to harden its defenses against flooding using the vulnerability assessment, but the uncertainty that still exists presents a particular problem for St. Augustine’s engineers.
“Because as an engineer we design to a design condition, you have a design year, you know what capacity or what you’re designing for,” she said “And we really don't know.”
St. Augustine is one of three communities selected for the Community Resiliency Initiative Pilot Project administered through FL DEO and funded by NOAA. The other two communities include Escambia County and Clearwater, Florida. St. Augustine’s study began in 2016.
The next step in the program is to identify federal, state and local programs or funding that the three areas can leverage to further plan for anticipated sea level changes.