Report: Mid-Atlantic has largest rise in nuisance flooding since the 1960s


Downtown Annapolis nuisance flooding on April 30, 2014. (Brian Mead via Facebook)

Sea level rise is increasing the number of nuisance flooding events on all three U.S. coasts, and the largest increase in these events is happening right here in the Mid-Atlantic, according to a report released by the National Oceanic and Atmospheric Administration.

Annapolis, Md. and Baltimore, Md. have by far seen the highest percent increase in nuisance flooding events since the 1960s. The study, which analyzed data from 45 water level gauges around the country, found that the number of these events in Annapolis has increased 925%. Baltimore has seen an increase of 922%. The third-ranking city on the list is Atlantic City, N.J., with a 682% increase.

Washington D.C. (8th, 373%) and Norfolk, Va. (10th, 325%) were in the top ten, as well. In fact, eight of the top ten cities that have seen an increase in nuisance flooding are on the East Coast.


The Fish Market in Southwest, D.C. on April 30, 2014, during a flood event in which southerly winds pushed Potomac water onshore. (Jason Kopp)

In Annapolis, the average number of nuisance flood days from 1957 to 1963 was 3.8. From 2007 to 2013, that number had increased to 39.3. In D.C., the number increased from 6.3 days to 29.7.

Nuisance flooding is exactly what it sounds like — a nuisance. It clogs storm drains, closes roads, and makes your day a little bit more difficult. It’s the kind of event where the water level seeps onto higher ground, but causes no major property damage. It is technically covered by the National Weather Service as “minor flooding.”

Worldwide, sea level has risen about eight inches since the late 1800s, the result of warming ocean water, melting glaciers and ice caps, and the ever-decreasing Greenland and West Antarctic ice sheets. However, sea level hasn’t risen the same amount in every location. Some locations are less lucky than others, including the eastern and Gulf coasts of the United States (where sinking land exacerbates sea level rise), and earlier this year the National Climate Assessment projected that sea level will continue to increase one to four feet by 2100.


Via the report: “Figure shows estimated, observed, and possible amounts of global sea level rise from 1800 to 2100, relative to the year 2000. Estimates from proxy data (for example, based on sediment records) are shown in red (1800-1890, pink band shows uncertainty), tide gauge data in blue for 1880-2009, and satellite observations are shown in green from 1993 to 2012. The future scenarios range from 0.66 feet to 6.6 feet in 2100. These scenarios are not based on climate model simulations, but rather reflect the range of possible scenarios based on other kinds of scientific studies. The orange line at right shows the currently projected range of sea level rise of 1 to 4 feet by 2100, which falls within the larger risk-based scenario range. The large projected range reflects uncertainty about how glaciers and ice sheets will react to the warming ocean, the warming atmosphere, and changing winds and currents. As seen in the observations, there are year-to-year variations in the trend.” (U.S. Global Change Research Program)

According to NOAA oceanographer William Sweet, lead author on the report, the uptick in minor flooding gives us a glimpse into the future of more serious events. “The effects of rising sea levels along most of the continental U.S. coastline are only going to become more noticeable and much more severe in the coming decades,” says Sweet. “Probably more so than any other climate-change related factor.”

The full list of cities and percent increases from the report:

Annapolis, Md.: 925%

Baltimore, Md.: 922%

Atlantic City, N.J.: 682%

Philadelphia, Pa.: 650%

Sandy Hook, N.J.: 626%

Port Isabel, Texas: 547%

Charleston, S.C.: 409%

Washington, D.C.: 373%

San Francisco, Calif.: 364%

Norfolk, Va.: 325%

Angela Fritz is an atmospheric scientist and The Post's deputy weather editor.
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