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Crisis Management
Tidal valves reduce impact
By BETH ANNE BRINK-COX | The Municipal
At first glance, the phrase “king tides” might make you think of Mardi Gras. It almost sounds festive, doesn’t it? But it’s not. The king tide is the highest predicted high tide of the year, higher than the highest water levels on any average day. These tides cause localized flooding, and they damage shoreline developments, housing and infrastructure. That damage is gravely compounded, should these tides occur at the same time as hurricanes or cyclones. What about their other name, perigean spring tides? Perigee is the point in the orbit of the moon or a satellite at which it is nearest the earth, and as we all know, that’s the kind of thing that affects all sorts of weather and accompanying issues: hurricane season is June 1-Nov. 30 this year. Add to that the knowledge that South Florida is very flat, and you can see why flooding is a major issue, especially with climate change and sea level rise factored in. Basically, because of global warming, when it rains, it pours more. The National Oceanic and Atmospheric Administration examined the 2016 record-breaking rainfall in Louisiana and determined that these rains were at least 40% more likely and 10% more intense, due to climate change. “High tide flooding, sometimes referred to as 60 THE MUNICIPAL | JULY 2022
nuisance flooding, sunny-day flooding, or king tide flooding, is occurring more frequently every year as sea levels continue to rise, and is increasingly disrupting coastal community life,” according to the NOAA website. West Palm Beach, Fla., is working in every way possible to deal with these tides and their subsequent flooding, with an $800,000 project to install tidal valves. Construction began in 2020 and was originally expected to be completed in 2023. Armando Fana, assistant city manager for the city of West Palm Beach, agreed. “The sunny-day tidal flooding has been an issue for the last five to seven years, and it is progressing annually. We realized over five years ago that we had to do more, due to the rising sea level predictions as well as
what we were experiencing in real time. The causes of flooding issues in the city include a high water table, low-lying residential streets, sea level rise, aging infrastructure, absence of stormwater infrastructure and a lack of green space (i.e., excessive impervious area). As the sea level rise issues continued to increase, the impact of these factors all became progressively more evident. These were not significantly noticeable prior to five to seven years ago.” As you would expect, there were earlier solutions that worked well for a time. Fana explained, “Sandbagging a perimeter around the catch basins and inlets in the street held back or contained tidal waters, and for a time, this worked. When we did that, we were able to prevent or control tidewaters from breaching onto the roadways. Over time, and currently as the sea level rise continues to worsen, no matter how much we stack the sandbags, the water overflowed onto the roadway, causing flooding. When it comes to today or sunny-day flooding, the city will post flood warning signs in areas known to be susceptible to tidal flooding.” Enter tidal valves. Fana said, “Tidal valves will help reduce flooding of both high tide and king tide events. In previous years, tidal
