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Climate and the Rising Threat of Hurricane Floods

By John McQuaid (Forbes) - February 15, 2012

One of the more obvious fallacies of modern life is that the future will be like the past. As if various cultural, economic and technological changes weren’t disproving that every day. But it’s even harder to accept that the planet earth itself is changing quite rapidly due to warming temperatures, and with that our surroundings. More heat in the atmosphere is likely to cause (and arguably is already causing) more extreme weather events, including intense heat, cold, droughts, floods, and storms.

Problem is, governments and other institutions are built on the same set of “future = past” expectations, and when “future ≠ past”, very bad things can happen.

For one example, look to a study in Nature Climate Change, examining the effect of climate on hurricanes and coastal flooding. Researchers used a series of computer models to simulate different climate scenarios and their possible effects on hurricanes and storm surges on New York City. They found that big storm surges were likely to increase in frequency:

Today, a “100-year storm” means a surge flood of about two meters, on average, in New York. Roughly every 500 years, the region experiences towering, three-meter-high surge floods. Both scenarios, Lin notes, would easily top Manhattan’s seawalls, which stand 1.5 meters high.

But with added greenhouse gas emissions, the models found that a two-meter surge flood would instead occur once every three to 20 years; a three-meter flood would occur every 25 to 240 years.

Such studies, based on models of models, are inevitably going to be speculative. But it’s not like such results are shocking. This exact problem befell New Orleans and contributed to the Katrina disaster. The city’s hurricane levees were designed based on outdated information, and offered far less protection than advertised (of course, most of flooding in the city was due to an even worse oversight: design errors in floodwalls that collapsed). Even today, New Orleans’ improved “100-year” protection from storm surge flooding is considerably less safe than it sounds, and the Corps of Engineers must cope with an eroding landscape, sea level rise, and quite possibly more frequent big storms that will drive up the risk to residents in coming decades.

New Orleans used to be unique in this regard. But the evidence suggests that other coastal cities will be facing similar dangers. As the article points out, in general infrastructure is designed on the assumption the past will be like the future, and the environment is stable and predictable. If it isn’t, all bets are off. If major floods are more frequent, that means more risk to lives and property. It has all kinds of implications: for public safety and insurance of course, but also for politics: do you divert more resources to building flood control structures? Where do you get the money? If you don’t, and disaster strikes, what then? Given that our political system cannot agree that climate change is even happening, I’d say we won’t begin to grapple with this until after a few more big disasters.