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‘Nuisance flooding’ exceeds trends, breaks records in the United States: NOAA


June 8, 2016   by Canadian Underwriter


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‘Nuisance flooding’ exceeded trends and broke records, especially in the southern United States and Gulf Coast, possibly due to a strong El Niño compounding already rising sea levels, the National Oceanic and Atmospheric Administration (NOAA) said on Wednesday.

PHOTO - Alexandria King St - NOAA - 3920x1869 - landscape

Nuisance tidal flooding during 2015 generally exceeded historical averages in the United States. Photo: NOAA.

The frequency of nuisance tidal flooding in many U.S. cities increased as predicted for the 2015 meteorological year, from May 2015 to April 2016, according to a report issued by NOAA titled 2015 State of U.S. “Nuisance” Tidal Flooding.

Wilmington, N.C. saw an all-time high of 90 days of nuisance flooding, nearly one quarter of the year. Other cities with record numbers of flooding days included Charleston, S.C.; Port Isabel, TX; and Mayport, Virginia Key, Key West, and Fernandina Beach, FL. Some cities in the Mid-Atlantic and West Coast also experienced greater tidal flooding frequencies above normal trends, including Norfolk, VA; Baltimore, MD; and San Francisco and La Jolla, CA.

“On average for the nation, nuisance tidal flooding during 2015 generally exceeded historical averages,” the report said. “In many locations, the 2015 increase even exceeded the increasing rate suggested by trends in recent decades.”

Nuisance flooding, which causes such public inconveniences as frequent road closures, overwhelmed storm drains and compromised infrastructure, now occurs with high tides in many locations due to climate-related sea level rise, land subsidence and the loss of natural barriers, NOAA said in a statement.

The 2015 outlook indicated that mid-Atlantic and West Coast communities could experience an increase over the trend in the number of nuisance flooding days due to likely higher sea levels during El Niño, which increases the reach of storm surges and high tides.

“Sea level rise is continuing and flooding impacts are happening now,” said William Sweet, an oceanographer with NOAA’s Center for Operational Oceanographic Products and Services. “The upward trend in nuisance flooding is an ongoing issue. Last year we broke several records, and trends show that we’ll likely continue to do so in the future. Coastal communities should expect a new normal in nuisance tidal flooding and prepare for potential impacts.”

The 2015 State of U.S. Nuisance Tidal Flooding report highlights nuisance flood during the 2015 meteorological year and compares it to the outlook at 28 NOAA tide stations around the U.S., which have collected data for more than 50 years. It also provides a new outlook for the 2016 meteorological year, taking into account the La Niña conditions anticipated to develop in the coming months. La Niña typically has less effect on tidal flood frequencies compared to El Niño, however the nuisance flooding trend is still increasing, the statement said.

The outlook for 2016 shows that the cities with the highest frequency of nuisance flooding will likely be:

  • Annapolis, MD, with 47 days;
  • Wilmington, N.C., with 42 days;
  • Washington, D.C., with 30 days;
  • Charleston, S.C., with 27 days; and
  • Atlantic City and Sandy Hook, N.J., with 26 days

Along the California coast, less than 10 days are expected at La Jolla and San Francisco, a decrease from 13 and 20 days observed in 2015, respectively.

Nuisance flooding is increasing along U.S. coasts due to sea level rise, the statement said, with the extent of such flooding depending on multiple factors, including topography and land cover. The study defines nuisance flooding as a daily rise in water level above minor flooding thresholds set locally by NOAA weather forecasters and emergency managers for coastal areas prone to flooding.


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