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El Niño Caused Tidal Flooding in Many U.S. Cities

Matt Ball on June 22, 2016 - in Corporate, Maintenance, Stormwater

The frequency of nuisance tidal flooding in many U.S. cities increased as predicted for the 2015 meteorological year, according to a NOAA report released on June 8, 2016.

In some cities, the days of nuisance flooding exceeded trends and broke records, especially in the southeastern U.S and Gulf Coast, which may be due to a strong El Niño compounding already rising sea levels.

Wilmington, North Carolina, 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 are Charleston, South Carolina; Port Isabel, Texas; and Mayport, Virginia Key, Key West, and Fernandina Beach, Florida, the report said. Some cities in the Mid-Atlantic and West Coast also experienced greater tidal flooding frequencies above normal trends, including Norfolk, Virginia; Baltimore, Maryland; and San Francisco and La Jolla, California.

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.

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

  • Annapolis, Maryland with 47 days
  • Wilmington, North Carolina with 42 days
  • Washington, D.C. with 30 days
  • Charleston, South Carolina with 27 days
  • Atlantic City and Sandy Hook, New Jersey 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.

These findings are a continuation of annual nuisance flooding monitoring and experimental predictions led by NOAA scientists William Sweet, Ph.D., and John Marra, Ph.D. The 2015 outlook, beginning in May 2015 through April 2016, showed that mid-Atlantic and West Coast communities may experience an increase over the trend in the number of nuisance flooding days is likely due to higher sea levels during El Niño, which increases the reach of storm surges and high tides.

Nuisance flooding is increasing along U.S. coasts due to sea level rise. The extent of nuisance flooding depends 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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