Annapolis Faces 30 Days or More of Flooding a Year. And It’s Not the Only Community.

Annapolis is past the point where nuisance flooding is a climate change theory. The National Oceanic and Atmospheric Administration (NOAA) reports that from here on out, Annapolis — along with Washington, DC and Wilmington, NC — will experience at least 30 days of flooding every year due to the rising sea level.

The National Weather Service says the flooding will be one to two feet above local high tide and it’ll happen 30 or more times a year, meaning a large full moon combined with high tide can cause a flood, not just powerful rain storms and large snowfalls. That’s a nuisance.

Annapolis flooding
Annapolis, Maryland, pictured here in 2012, is one of three major East Coast urban areas already being faced with nuisance flooding in excess of 30 days per year. (Credit: With permission from Amy McGovern.)

“Coastal communities are beginning to experience sunny-day nuisance or urban flooding, much more so than in decades past,” says oceonographer William Sweet. “This is due to sea level rise. Unfortunately, once impacts are noticed, they will become commonplace rather quickly.”

City Dock in Annapolis floods more easily now, closing off access to the lower downtown area. And it’s creeping closer to the historic, colonial buildings housing popular restaurants and high-end shops.

Sweet is co-author of a NOAA report that says by 2050, a majority of U.S. coastal areas are likely to be threatened by 30 or more days of flooding each year due to dramatically accelerating impacts from sea level rise. (Read the new NOAA study published in the American Geophysical Union’s online peer-reviewed journal Earth’s Future.)

“We find that in 30 to 40 years, even modest projections of global sea level rise — 1½ feet by the year 2100 — will increase instances of daily high tide flooding,” Sweet adds, “to a point requiring an active, and potentially costly response, and by the end of this century, our projections show that there will be near-daily nuisance flooding in most of the locations that we reviewed.“

NOAA: Most of U.S. coast may see 30 or more days a year of floods up to 2 feet above high tides

But not all flooding is due to climate change. Some areas of the country, such as New Orleans, are on sinking land. It’s a natural occurrence also.

The report lists areas across the country that are facing Annapolis’ nuisance flooding fate. A number are in the Chesapeake Bay region. NOAA predicts that by 2020, Baltimore and Lewes, DE will join Annapolis. And by 2050, a majority of coastal areas will face 30-days or more of flooding a year.

coastal inundation from sea level rise
NOAA water level (tide gauge) locations numbered as listed in Table 1 and showing NWS defined nuisance flood levels above the 1983–2001 MHHW datum (colored dots) and coastal areas below the nuisance elevations and potentially at risk during nuisance flood events (red contours)

Based on that criteria, the NOAA team is projecting that Boston; New York City; Philadelphia; Baltimore; Washington, D.C.; Norfolk, Virginia; and Wilmington, North Carolina; all along the Mid-Atlantic coast, will soon make, or are already being forced to make, decisions on how to mitigate these nuisance floods earlier than planned. In the Gulf, NOAA forecasts earlier than anticipated floods for Galveston Bay and Port Isabel, Texas. Along the Pacific coast the earlier impacts will be most visible in the San Diego/La Jolla and San Francisco Bay areas.

NOAA nuisance flooding chart

NOAA suggests local communities and property owners look at retreating further inland or create a combination of “green” infrastructure using both natural resources such as dunes and wetland, along with man-made sea walls and redesigned storm water systems.


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