Florida: Tide Check Valves: A Remedy For St. Augustine's Flooding Woes?
St. Augustine has begun installing what are known as tide check valves. These valves allow stormwater to drain out under low tide conditions, just like the city’s current drainage system, but during high tide these valves prevent ocean water from backing up into the stormwater pipe network.
When Hurricane Dorian skirted the east coast of Florida earlier this month, there was flooding throughout St. Augustine.
But the South Davis Shores neighborhood was hit harder than anywhere else in the city.
“We have 32 residential structures that had some type of flooding damage,” City Manager John Regan told City Commissioners during Monday night’s meeting.
The majority of those were in South Davis Shores.
The brave souls who live in this part of St. Augustine are no strangers to flooding.
“South Davis Shores is a low lying area,” explained Public Works Director Mike Cullum. “It historically floods probably once a month during the high tide.”
Tidal flooding, otherwise known as “sunny day” or “nuisance” flooding, is when, during extremely high tides, the ocean literally spills onto land, inundating low-lying areas with seawater. It’s becoming increasingly common in coastal communities across the country, especially along the East Coast.
On the First Coast, St. Augustine is ground zero for the phenomenon, which is becoming more frequent and more intense as sea levels rise, and the city’s aging drainage system offers little protection.
With the city’s existing system, stormwater is collected in the streets through a drainage swale or inlet when it rains. Under low tide conditions, gravity pulls that stormwater through drainage pipes and out into the Matanzas River or Salt Run.
But during high tide events, ocean water can make its way up the pipes and into the streets, causing the “sunny day” floods.
If adverse weather conditions occur at the same time as one of these tidal flooding events, the street flooding conditions are made significantly worse.
During Nor’easters, winds push tide water farther up into the storm water collection system, which leads to more extensive road flooding. If it rains, stormwater can’t gravity drain until the tide falls, so it becomes trapped in the streets, worsening flood conditions.
To address these issues, the City has begun installing what are known as tide check valves. These valves allow stormwater to drain out under low tide conditions, just like the city’s current drainage system, but during high tide these valves prevent ocean water from backing up into the stormwater pipe network.
“We've instituted, citywide, 31 of those,” Cullum said. “Davis Shores was the first place that we instituted these tide check valves.”
According to the City, tidal flooding has essentially been eliminated in areas where these valves have been installed. They even offered some flood protection during Hurricane Dorian.
“The 31 tide check valves that we installed city wide, most performed as designed. We had a couple that did not, and they'll be inspected,” Regan told City Commissioners. “For a low storm like this [Dorian], they do what they're designed for… The North Davis Shores valves that we installed worked very well.”
Given this success, the city has plans to install many more tide check valves.
“We have about 100 stormwater culverts city wide and we're evaluating the remaining 70-plus to see where we need to install the next set of tide check valves,” he said. “We're putting $200,000 a year into installing tide check valves for the next 10 years or so in our capital improvement plan.”
But this technology can only do so much.
“Every one of these storms, it's a game of inches,” Regan said Monday. “I think we can do quite a bit to reduce the type of flooding from this type of storm [Dorian], but there is a point when the surge is higher and comes over all sea walls.”
That’s why the city is also moving forward with other plans to address nuisance flooding and major storm events, like flood proofing pump stations and flood mitigation projects at Avenida Menendez and Lake Maria Sanchez.
But Cullum warned that these projects will take time and money, and the city only has a budget of $60 million. The Lake Maria Sanchez project alone is projected to cost as much as $20 million.
Still, Vice Mayor Leanna Freeman thinks these efforts to adapt, and other efforts across the state, should give residents hope.
“We now have a state resiliency officer for the very first time and locally we are going to have a staff member who is also going to be dedicated to that issue,” she said during Monday’s City Commission meeting. “I feel like we're on the cusp, statewide and locally, of moving forward on these issues. I think that it’s encouraging.”