National Climate Report - May 2017
2016 State of U.S. High Tide Flooding and a 2017 Outlook

« National Climate Report - May 2017

2016 State of U.S. High Tide Flooding and a 2017 Outlook

This month's State of the Climate report includes an annual update of the state of coastal high tide flooding. Sometimes called nuisance or sunny day flooding, this type of flooding occurs when water levels measured at a NOAA tide gauges exceed locally established heights associated with minor impacts, such as water on low-lying streets or infiltration into storm-water systems. Such coastal flooding is increasing in frequency, depth and extent in many areas of the U.S. due to on-going increases in local relative sea level.

Decades ago, coastal flooding mostly occurred during strong storms. Today, it occurs more frequently during high-tide cycles and calmer weather. Though high tide flooding today is rarely life threatening, it is a serious concern in several communities, such as Norfolk, Virginia, Charleston, South Carolina and Miami, that are not protected by flood control structures that cities like New Orleans have in place.

  1. Several cities experienced more than a month (30 days) of daily flooding in 2016: Wilmington, NC (84 days); Charleston, SC (50 days); Honolulu, HI (45 days); Annapolis, MD (42 days); Savannah, GA (38 days); Washington D.C. (33 days); and Port Isabel, TX (31 days) due to a combination of low-lying coastal topography and high sea levels during 2016.
  2. Compared to the number of flood days during 2015 (4 days), Honolulu experience a more than a 1,000 percent increase during 2016 (45 days).
  3. Charleston (50 days) and Savannah, GA, (38 days) broke their historical record for days with high tide flooding during 2016; Key West, FL, (14 days) tied its record.
  4. In most locations, the number of days with high tide flooding during 2016 exceeded national historical trends established over recent decades; annual trends are accelerating in 19 out of 28 locations examined.
  5. Compared to 1995, trends in flooding during 2016 have increased by 130 percent on average, ranging from 30 to 270 percent.
  6. Due to the possible development of El Nino conditions, the 2017 projections for high tide flooding are 25 percent higher on average than trend values at several East and West coast locations.

Find the complete coastal flooding report here: https://www.ncdc.noaa.gov/monitoring-content/sotc/national/2017/may/2016_StateofHighTideFlooding.pdf .

Citing the complete report: Sweet, W.V., J. J. Marra and G. Dusek, 2017: 2016 State of U.S. High Tide Flooding and a 2017 Outlook. Supplement to State of the Climate: National Overview for May 2017, published online June 2017, retrieved on [date] from https://www.ncdc.noaa.gov/monitoring-content/sotc/national/2017/may/2016_StateofHighTideFlooding.pdf