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Annapolis, Baltimore lead nation for rise in 'nuisance flooding' events

The average number of days Annapolis and Baltimore see flooding that causes road closures or overwhelmed storm drains has grown ten-fold over the past 50 years, the largest increase in the nation, according to the National Oceanic and Atmospheric Administration.

What NOAA calls "nuisance flooding" events occurred an average 39 days each year in Annapolis from 2007 to 2013, up from an average of just fewer than four days per year from 1957 to 1963. That increase of 925 percent is the highest in the United States, according to NOAA.

And Baltimore's increase of 922 percent ranks second. Nuisance flooding occurs an average of 13 days per year, up from 1.3 days per year from 1957 to 1963.

Other cities that have seen dramatic rises in flooding include Atlantic City and Sandy Hook in New Jersey; Philadelphia; Port Isabel, Texas; Charleston, S.C.; Washington, D.C.; San Francisco; and Norfolk, Va.

NOAA officials said they hope the data encourages adaptation to rising sea levels.

"The nuisance flood study provides the kind of actionable environmental intelligence that can guide coastal resilience efforts," Holly Bamford, NOAA assistant administrator of the National Ocean Service, said in a statement.

In Annapolis, a 0.29-meter rise above the mean higher high water mark is enough to cause nuisance flooding, according to the data, the lowest among the 10 areas that have seen the most dramatic increases in nuisance flooding events. In Baltimore, a 0.41-meter rise can cause nuisance flooding.

Flood warnings have been somewhat common this year across the region given that rainfall is 6 inches above normal.

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