Minor Coastal Flooding

The number of days of nuisance flooding, or minor coastal flooding, is likely to increase in the next 12 months. A study predicts between eight and 14 days in Atlantic City.

Atlantic City and Cape May are poised for an upcoming 12-month stretch with more coastal flooding events than the previous year, all a continuing part of a trend with more days of closed roadways, cars that have to be moved and water inundation.

Between May 2020 to April 2021, Atlantic City is expected to have anywhere between eight and 14 high-tide flooding days, while Cape May is expected to have between six and 11. During the last coastal flooding year, Atlantic City had nine flood days, while Cape May saw 7, according to a report from the National Oceanic and Atmospheric Administration.

Across the United States, the median average of coastal flooding was four days in the 2019 flooding year, just shy of the record set during the 2018 flooding year.

The administration released its annual State of U.S. High Tide Flooding, which include a recap of the 2019 flooding year (May 2019-2020), as well as an outlook for the May 2020 to April 2021 period.

The report, which was released earlier this month, specifically documents the change in nuisance flooding, which is also known as minor flood stage, typically when tides are 1.75 to 2 feet above the daily average high tide.

“America’s coastal communities and their economies are suffering from the effects of high tide flooding, and it’s only going to increase in the future,” said Nicole LeBoeuf, acting director of NOAA’s National Ocean Service.

NOAA forecasts that the peak season for coastal flooding will be during the fall. While nor’easters typically bring the most significant flooding during the winter, the minor, nuisance flooding days the report focuses on happen while the water temperatures are warmest.

“During the fall, you do have a change of seasons occurring, you tend to get more northerly winds. ... There’s an important seasonal cycle occurring as well,” said William Sweet, oceanographer, NOAA’s National Ocean Service and lead author of the report. “Sea levels are higher during the fall time, than the winter times. That’s on the order of a half foot. ... When the winds begin to really blow in September and October, the sea level heights are higher.”

The northeast Atlantic Ocean, which includes New Jersey, is already a hot spot for flooding. Compared with the rest of the country, the region has the highest likelihood of seeing the most number of coastal flooding events, between six and 11 days throughout the May to April reporting period.

“There’s a very wide, shallow continental shelf in the Atlantic Ocean. The West Coast has a steep continental shelf. ... The East Coast has a high rate of sea level rise,” Sweet said.

NOAA scientists says a neutral El Nino Southern Oscillation (ENSO) cycle, which is based off of the waters around the equator in the Pacific Ocean, played a role in this forecast. However, this role doesn’t sway the forecast one way or another.

Rather, NOAA scientists say, climate change is a factor. About a third of sea level rise is due to the thermal expansion of the ocean. The warmer the waters, the more space the ocean occupies, creeping up the shoreline.

“Long term, we know that the sea level rise has been happening. We’ve seen that from NOAA over the years,” said Lou Belasco, floodplain manager for the city of Cape May. “From a flooding standpoint, we look to bolster our natural systems. We’ve looked to bolster the shoreline along the harbor front. If we can increase those wetlands and soak up some of the sea level rise, we can offset some of the losses,” he said, adding, “It’s a two-pronged approach. ... We also recognize that there are hardscape solutions that need to be done. There are areas that we look to raise the roadway, like on Yacht Avenue. We’ve had talks with the Army Corps of Engineers for Wilmington and Beach to raise the road there.”

The 2019 flooding year, from May 2019 to April 2020, saw water temperatures nearly 1.5 degrees above the 20th Century average between 60 degrees north and 60 degrees south latitude, continuing a positive streak seen each year since the late 1970s.

SST Anomaly Graphic

Sea surface temperatures (SST) were 1.5 degrees above the 20th Century median during 2019 between 60 degrees north and south latitude, where New Jersey resides. SSTs have been above average consistently since the late 1970s. 

“The national takeaway is ... the underlying trend is accelerating,” Sweet said.

After a seasonable June, Atlantic City’s water temperatures have been running above average for much of July, with a 75 degree reading July 16, five degrees above the 70-degree average.

Atlantic City Water Temperatures

Water temperatures in Atlantic City from June 1 through July 16. Sea surface temperatures rose to well above average levels by July 16, whose 75 degree temperatures is warmer than the average temperature at any point during the year. 

The forecast flooding events are both below the projections expected for 2030, where 20 to 35 days of high tide flooding is expected in Atlantic City and 15 to 30 days of flooding are expected in Cape May.

“It’s (minor flooding not from a storm) not something I remember as a kid. It happened hardly ever. Usually, flooding was associated with some kind of weather system,” Belasco said.

According to a Rutgers University report released in 2019, sea levels rose an average of 1.5 feet along the New Jersey coast from 1911 to 2019, compared with the global average of 0.6 feet.

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