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The ocean in our backyard is rising millimeters per year and what has been imperceptible is clearly apparent in the past couple of months.
If it weren’t for Hurricane Irma’s heavy rain, Hurricane Nichole would claim the area’s worst storm surge since the early 1900s.
Storm tides in the November 10 storm surpassed levels reached recently by Hurricane Ian when it crossed Florida in October and brought a surge almost as high as Irma.
Nicole nearly tied the 3.61-foot high watermark Irma sent into Mayport. At that gauge, Nicole’s surge reached 3.57, the second highest since 2017. The morning high tide coincided with the waves peaking at 19 feet offshore sending a surge into the St. Johns River mouth.
Winds gusted just over 70 mph at the coast which would send a bulge of water at the river mouth toward downtown hours later in the day.
Streets and parks flooded reminiscent of images from Hurricane Irma but it stopped feet short of the city’s worst flooding 5 years ago.
For perspective at the Southbank, the water topped out at 3.26 feet coming in higher than Hurricane Ian’s 2.75′ surge and well below Irma’s 4.89 ft.
The tide gauge at the Buckman Bridge reached its second-highest water level just behind Irma.
November tropical systems don’t carry as much tropical moisture as summer storms. Irma was a tremendously wetter system that dumped 2.2 trillion gallons of rainwater in early September contributing to street flooding when the surge swelled the stormwater outfalls.
From a hydrological perspective, it was interesting to see how the river rose for two hours after the high tide crest along the Southbank. I expected to see this abnormal lag response and warned the river would continue to rise for hours after high tide when the surge at the coast worked its way upstream through the afternoon.
Coastal dunes took a battering with the beach surge reaching over 3 feet.
Fernandina Beach reached 3.81 feet, the third highest in recorded history behind Hurricane Matthew’s 4.17′ peak water level and the record 6.91 foot 1898 Hurricane surge.
When will it end?
That was the question many viewers asked the Weather Authority about the persistent flooding along the St. Johns River for weeks after Ian passed.
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Along Pottsburg Creek the water typically reached up 1 to 2 feet above the daily average high tide long after Hurricane Ian passed to our south.
Nearly every day in October witnessed high tide flooding along the riverbanks where overflow or excess accumulation of ocean water at high tide covered low-lying areas. November brought more water spilling over bulkheads and backed up sewers even before Hurricane Nicole took the spotlight.
Extreme is the new normal
Decades of steady sea level rise have reached unprecedented heights making coastal infrastructure more vulnerable to storm damage.
High-tide flooding often referred to as “king tides,” “nuisance,” or “sunny day” flooding, is becoming increasingly common due to years of sea level rise.
This didn’t happen nearly as regularly decades ago. As sea level rise continues, damaging floods now happen more regularly, like during a full moon or with a change in prevailing winds or currents.
Flooding occurs almost three days more per year since 2011 compared to the 1950s in Jacksonville.
Mundane nor’easters and average astronomical spring tides are being accentuated by the long term sea level rise that has increased more than six inches at Mayport between 1960 and 2021.
The effects of sea level rise and the deepening of the St. Johns River are not confined to Pottsberg Creek but to many areas along the watershed.
Based on hourly water level data publicly available from NOAA, flooding in Fernandina Beach is the second worst in the state just behind Cedar Key.
The frequency of flooding in Fernandina Beach averages 4.6 flood days each year nearly four times more common than in the 1950s.
Every site measured along the East Coast has experienced an increase in coastal flooding since the 1950s and the rate of growth is accelerating at most locations including those in the Gulf.
Evidence suggests sea level along the U.S. coastline will rise 10 to 12 inches by 2050—as much as the rise measured from 1920 to 2020.
