According to the research, carried out by Princeton and Rutgers universities, without cutting carbon emissions, the US coastline’s risk of a "100-year flood" is likely to see an average 40-fold increase by 2050.

Lead author Maya Buchanan, from Princeton University, said: "Coastal flooding is an extremely damaging environmental hazard. It is often responsible for loss of life and property, as well as long-term damage to local and regional economies and municipal services.

"Even a small amount of sea-level rise magnifies the height of a flood caused by a storm surge or tidal event. So it’s critical to understand the magnitude and pattern by which the frequency of current flood levels increase, to help develop more resilient coastal areas.

"This is particularly important because coastal infrastructure management, federal flood insurance and flood risk communications are typically tied to estimates of flood return periods."

To reach their conclusions, the researchers combined the probability distributions of historical flood frequency and projected sea-level rise (SLR) to calculate what is known as the amplification factors – the measure by which the frequency of flooding of a given height increases – and their uncertainties over time.

Co-author Michael Oppenheimer, from Princeton University, said: "Under probabilistic relative sea level (RSL) projections, we estimated a median 40-fold increase (ranging from 1 to 1314-fold) in the expected annual number of local 100-year floods for tide-gauge locations along the US coastline by 2050.

"Some places, mostly along the US Atlantic and Gulf coasts, should expect a larger amplification of moderate floods – say the current annual or 10-year flood – than of severe floods, like the current 500-year flood.

"Other locations, mostly along the Pacific coast, face greater amplification of rarer events, meaning a particularly fast-growing risk of historically unprecedented flooding."

The authors recommend policy makers increase resilience to historical flooding in areas where disproportionate increases in moderate flooding are expected and prepare for largely unprecedented flooding in areas facing large increases in severe flooding.

Buchanan said: "Policies should be flexible, allowing for adjustment over time, to address flooding eventually dominated by high tides and permanent inundation."

Related links

Amplification of flood frequencies with local sea level rise and emerging flood regimes. M K Buchanan et al 2017 Environ. Res. Lett. 12 064009