Baltimore, Annapolis set records for sunny-day flooding in 2018 — and it could eventually occur every other day

On days with otherwise pleasant weather, Baltimore and Annapolis flooded a dozen times each in 2018, setting records in both cities for what meteorologists call “nuisance” flooding. And that is expected to become even more frequent in the coming decades.

In reporting the data Wednesday, the National Oceanic and Atmospheric Administration warned that such flooding could occur as often as every other day in Central Maryland, more than almost anywhere else in the country, by 2050.

Greg Dusek, one of the authors of the NOAA flooding report, said Baltimore starkly illustrates the impacts of sea level rise.

Its flood gauge is one of the oldest in the country, dating to 1902. In the gauge’s first 34 years documenting the city’s tides, waters rose enough to inundate streets a total of 12 times on days with no storms or heavy rainfall. The gauge reported the same number within less than a year in 2018, Dusek said.

“This is a good example of just how dramatically high-tide flooding is changing due to sea level rise,” he said.

Around the United States coastline, such flooding occurred about five times at each of 98 tide gauges in 2018. That tied a record set in 2015.

But the flooding was especially prevalent in the Mid-Atlantic, NOAA said. The median number of high-tide flood days was 10, with as many as 22 reported in Washington.

In a conference call with reporters, NOAA researchers noted that the flooding routinely inundated parking spaces and disrupted shopping in Annapolis and sent salt water spilling onto farm fields elsewhere in Maryland.

The report also issued forecasts for nuisance flooding in 2019 and beyond. This year, a median of eight high-tide flooding days are expected in the Mid-Atlantic, fewer than last year but a 140% increase relative to observations from 2000.

About 6-10 nuisance flood days are forecast specifically in Baltimore and Annapolis this year.

The researchers expect the number to grow exponentially in the coming years, though. The Chesapeake Bay region is expected to see as many as 25 sunny-day floods each year by 2030 and 170 of them by 2050.

“Without adaptation, impacts are likely to become chronic sooner than later,” said William Sweet, another of the study’s authors.