Top 10 cities with increased flooding

According to a NOAA report these are the top 10 areas in U.S. with an increase in nuisance flooding since 1960, and the percentage increase seen:

1) Annapolis, Md. 925%

2) Baltimore, Md. 922%

3) Atlantic City, N.J. 682%

4) Philadelphia, Pa. 650%

5) Sandy Hook, N.J. 626%

6) Port Isabel, Texas 547%

7) Charleston, S.C. 409%

8) Washington D.C. 373%

9) San Francisco, Calif. 364%

10) Norfolk, Va. 325%

Flooding has always been a problem in Charleston, where the mayor in 1837 offered gold to anyone who could come up with a solution, but rising sea levels have made things worse according to a new study.

According to the National Oceanic and Atmospheric Administration, "nuisance flooding" has increased more than fourfold in Charleston since 1960, and it's expected to get worse.

"Flooding now occurs with high tides in many locations due to climate-related sea level rise, land subsidence and the loss of natural barriers," said William Sweet, oceanographer at NOAA's Center for Operational Oceanographic Products and Services. "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, probably more so than any other climate-change related factor."

Charleston was number seven on the study's list of the top 10 places in the U.S. with increases in nuisance flooding. The top five were all in Maryland, Pennsylvania and New Jersey.

While sea levels have been rising, the Charleston area has also been subsiding - falling - which amplifies the higher seas. Plus, rapid development in the Charleston area has given stormwater fewer places to go, which can also make flooding worse, or more frequent.

According to the NOAA report, Charleston averaged fewer than five flooding days from 1957 through 1963, but averaged more than 23 flooding days yearly from 2007 through 2013.

The report is aimed at providing information to help coastal communities to understand the impact of rising sea levels and develop ways to respond.

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

In Charleston, no one ever claimed the $100 gold piece offered by the mayor in 1837, but the city has been building deep tunnels and massive pumping stations to deal with flooding on the peninsula. Flood-control projects costing millions have also taken place in some suburban areas.

Reach David Slade at 937-5552