The amplification of flood frequencies by sea level rise is expected to become one of the most economically damaging impacts of climate change for many coastal locations, scientists warned. In a recent study, undertaken by researchers from Princeton and Rutgers universities, it was found that along the US coastline, the average risk of a 100-year flood will increase 40-fold by 2050. Places such as New York City, Seattle, and San Diego are set to be deluged by far more frequent and severe flooding events if greenhouse gas emissions aren’t slashed. Some of the worst affected areas would be in Hawaii, with Mokuoloe island, situated off Oahu, forecast to be deluged by 130 floods a year that is currently considered to be 100-year events.
Understanding the magnitude and pattern of which the frequency of current flood levels increase is important for developing more resilient coastal settlements, particularly since flood risk management, including infrastructure, insurance, and communications, is often tied to estimates of flood return periods. “Most coastal areas will experience relatively large increases in flooding events” Michael Oppenheimer, a co-author of the paper, told The Guardian, adding that New York City is set to get a 100-year flood every 20 years by 2050 but this frequency would leap to a large flood every other month by 2100. Previous research estimated the damages from coastal flooding could soar to $1tn a year by 2050. Lead author Maya Buchanan, from Princeton University, said coastal flooding is “responsible for the loss of life and property, as well as long-term damage to local and regional economies and municipal services.”
Buchanan added that working out the future frequency of flooding is “particularly important because coastal infrastructure management, federal flood insurance, and flood risk communications are typically tied to estimates of flood return periods.”
Climate change is causing sea levels to rise at about 4mm per year, as ice caps melt and the oceans warm and expand. This will continue for many years due to the carbon dioxide emitted into the atmosphere. Sea level rise of just a few centimeters is enough to significantly raise the risk of flooding, with the problem exacerbated by an increase in the severity of storms due to a warming, moisture-laden atmosphere.
Projections of sea level rise vary, with the UN’s Intergovernmental Panel on Climate Change estimating in 2013 an increase between 30cm and 100cm by 2100. But more recent research has suggested the great ice caps are more vulnerable than expected in a warming world and that ocean levels could rise more rapidly to reach 200-300cm by the end of the century. The scale of the global challenge posed by sea level rise was outlined in a study from the University of Illinois at Chicago last month, with researchers predicting there will be doubling in the frequency of severe coastal flooding. The most vulnerable places, including large cities in Brazil and Ivory Coast, and small Pacific islands, are expected to experience the doubling within a decade.