2050 will mark the ‘tipping point’ in coastal flooding in the US, according to the National Oceanographic and Atmospheric Administration (NOAA), whose research says that nuisance floods – defined as being one to two feet above local high tide – will occur 30 or more times a year in most coastal areas by the mid-century.
East coast cities will need to improve flood defences sooner than expected, according to the research, with New York City and Washington DC among cities that can expect more nuisance floods. The research excluded the Miami area due to insufficient data.
‘Coastal communities are beginning to experience sunny-day nuisance or urban flooding much more so than in decades past,’ said William Sweet, an oceanographer who co-authored the study. ‘This is due to sea level rise. Unfortunately, once impacts are noticed, they will become commonplace rather quickly.’
NOAA tide gauges show that daily flooding at new levels is already five to ten times more likely today than 50 years ago.
‘We find that in 30 to 40 years, even modest projections of global sea level rise – 1½ feet by the year 2100 – will increase instances of daily high tide flooding to a point requiring an active, and potentially costly response, and by the end of this century, our projections show that there will be near-daily nuisance flooding in most of the locations that we reviewed,’ Sweet added.
The research used the Intergovernmental Panel for Climate Change projections, which put sea level rises at 1½ to 4 feet by 2100. These were combined with local geographic information, such as subsidence.