Hurricanes are expensive. RMS, an organization that makes catastrophe risk models for insurance companies, knows that better than most. It estimates Hurricane Katrina caused $45 billion in flood losses and $63 billion in wind losses. Superstorm Sandy bred over $60 billion in total damages.
But cities that have so far escaped the wrath of devastating hurricanes shouldn’t assume that places like New Orleans, the New York metro area, and Florida will be hit hardest in the future. Sometimes, it’s the places you least expect that are the most at risk for large losses.
RMS ran the numbers for 12 coastal cities, looking at what percentage of what’s called “the 100-year return period loss” (the monetary loss that has a 1% chance of being exceeded in any given year) of hurricane-driven damage caused by coastal flooding. The chart below shows the likely proportions of loss for the 12 cities.
Notice anything strange? In cities such as Baltimore and Biloxi, hurricanes have a higher likelihood to cause damage from coastal flooding compared to cities such as Miami, where wind drives most of the hurricane related damage, and the coastal flood risk is relatively low.
There are a handful of factors that go into predictions on how damaging future hurricanes will be, according to Robert Muir-Wood, a leader of science and technology research at RMS. Whether cities are located at or below sea level and are near shallow-sloping sea beds makes a big difference. “The shallower the water for a longer distance, the bigger a storm surge rises up,” he says. “It can make a threefold difference in the height of a storm surge.”
Hurricanes are often viewed as threatening because of their high wind speeds, but storm surges are often more dangerous. During Sandy, the storm surge ultimately caused more economic and insurance damage than the storm itself, which weakened before landfall.
RMS provides a helpful overview of the factors that go into a threatening storm here:
“People tend to focus a lot on the events that have happened. Our work is in modeling,” says Muir-Wood. “People have a tendency to hope that things that haven’t happened won’t happen.”