New York City warned of more Sandy-like storm surges

Damaging surge floods in Manhattan, similar the one that accompanied Hurricane Sandy, could hit the city regularly by the end of the century, a new study suggests.

Sandy, which hit the Caribbean and the East Coast of the US in late October of 2012, caused $71 billion in damages, and left 157 dead in the US alone. 

At the time it was seen as a once-in-a-lifetime event, but these types of storms could become commonplace, the study by researchers from Princeton and Rutgers universities and Woods Hole Oceanographic Institute says.

“To effectively prepare for future hurricanes, we need to know what coastal cities will be facing in the coming decades, but past models have not accounted for all of the significant dynamic factors involved in predicting surge floods,” lead author Ning Lin from Princeton said in a media release.

“You need numbers to plan, and this analysis puts sea-level rise and storm surge climatology together on a quantitative basis.”

Lin’s work on storm intensity was complemented by modelling of future sea levels by Rutgers climate scientist Robert Kopp and a review of past storm surges by Jeff Donnelly of Woods Hole.

The work was published in the Proceedings of the National Academy of Sciences.

Their computer simulations found that, based on sea-level rises alone with all other variables remaining constant, Sandy-like storm surges  – the rising of the sea resulting from a storm’s wind and pressure – may become 4.4 times more frequent from now until 2100. This compares with a 300% estimated increase in this type of surge in the 200 years from 1800 to 2000, according to the paper. 

When researches incorporated changes to storm climatology, their model suggested surge flooding would become between three and 17 times more common. 

The team noted, however, that, because it is still unclear whether hurricanes are increasing in rate and intensity, there is a large amount of uncertainty in the models.

Sandy-like storm surges would not necessarily result in the flooding seen in 2012, because of the high tide that coincided with the storm.

But the study says that, even if hurricanes occur in the future at the same rate and intensity, flooding will still increase due to sea-level rise caused by increasing global temperatures. 

“Our model for the first time pulls together probabilistic estimates for sea-level rise and storm surge to produce long-term predictions of flood stages,” Lin said.

“These two variables, although largely uncertain, are critical in determining the extent of coastal flooding from future hurricanes.”