High tides set, tie records for Naples, Fort Myers in 2017

Adam Friedman
Naples Daily News
A staircase at Lake San Marino in North Naples was submerged from heavy rains brought on by Hurricane Irma on Tuesday, Sept. 12, 2017. Hurricane Irma caused severe flooding and damage to mobile homes and trailers in North Naples.

A combination of rising sea levels and Hurricane Irma created the perfect conditions for Naples and Fort Myers to set or tie records for the number of high tide flooding days in 2017, the National Oceanic and Atmospheric Administration reported.

A high tide flooding day does not necessarily mean urban flooding occurred, only that tides were high enough above the expected tides on those days to cause flooding in most places where NOAA has studied its 99 tide gauges around the country.

Still, the study shows higher than expected high tides have become more common in Southwest Florida. 

According to NOAA, Naples experienced three days of high tide flooding in 2017, which broke the record of two set in 2016. Fort Myers experienced six high tide flooding days, which tied its record of six, also set in 2016.

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NOAA’s two gauges in Southwest Florida are at Naples Pier and on the Caloosahatchee River in Fort Myers. The gauges measure only the water height and not the conditions or specifics of where flooding might occur.

The two cities were also among 28 NOAA sites where the gauges broke or tied their record for high tide flooding days in 2017.

Since NOAA began collecting its data in 1965, the sea level has risen an average of 3 millimeters a year at the Fort Myers and Naples gauges, or roughly just less than an inch every eight years.

According to Gregory Dusek, a chief scientist at NOAA, weather and timing of the high tide can be an important factor in whether flooding occurs.

For the eastern Gulf Coast, and particularly Southwest Florida, the high tide flooding days for 2017 were caused by weather but made worse by sea level rise, Dusek said.

“You don’t see the large tide changes in the eastern Gulf like you do elsewhere, but because of higher sea levels, storms have a more significant impact on tides,” he said.

Two of the recorded high tide flooding days for both Naples and Fort Myers happened on Sept. 11 and 12 in the aftermath of Hurricane Irma. NOAA’s gauge expected the tide in Naples to be 2.9 feet, but the actual tide was recorded at 7 feet.

High tide flooding isn’t always caused by a tropical storm or hurricane. A strong thunderstorm combined with a higher-than-expected tide can also cause problems.

“The combination may not cause direct damage, but it brings more water into an already full stormwater system, which is never a good thing,” said Gregg Strakaluse, director of the Streets and Storm Water Department at the city of Naples. “The water can also take longer to drain, leaving temporary standing water on the streets.”

But sometimes a storm doesn’t even have to occur for minor high tide flooding to cause problems.

“In Collier we don’t see sunny day street flooding yet,” said Jerry Kurtz, a civil engineer for the Collier County Stormwater Management Department. “But we are seeing roadside ditches connected to tidal waters overflowing during sunny days, killing all the grass and sometimes destroying people’s lawns.”

According to both Kurtz and Strakaluse, the damage is limited and happens only a handful of days a year. But people are already starting to adjust to the problem by covering up any exposed muddy areas and using decorative rock in some places instead of grass.

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NOAA’s 2017 high tide flooding day tracking dates are from May 1, 2017, to April 30, 2018, and they track high tide flooding in three stages: minor, moderate and major.

According to NOAA oceanographer William Sweet, minor flooding is defined as water between 1½ and 2 feet higher than the expected high tide.Stormwater systems often become overwhelmed, leading to property and infrastructure damage.

Major flooding is associated with tides 3.9 feet above the expected high tide; moderate flooding is defined as 2.6 feet above the expected high tide.

The third recorded day of high tide flooding in Naples was Oct. 7, which was classified as minor flooding.

The other four dates in Fort Myers were June 7 and Oct. 7-9, which were also considered minor. 

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Climate Central using NOAA’s data has created an interactive map that shows how many feet above the normal tide level would put your home at risk for any type of flooding.

Map:View a larger version of the map

Other takeaways from NOAA's Report

NOAA also released its overall trends and the outlook for 2018.

The 2018 outlook expects more high tide flooding days in both Naples and Fort Myers, following the same pattern as previous years, with one more day of high tide flooding expected.

However, Sweet, the NOAA oceanographer, warned that as high tide flooding becomes more noticeable, it often becomes problematic and chronic relatively quickly.

“The underlying trend (nationally) is quite clear: Because of sea level rises, the high tide flooding frequencies are 50 percent higher than 20 years ago and 100 percent higher than 30 years ago,” Sweet said.