What we’re learning about hurricanes. And how societies handle them.
I’ve lived through impressive tropical storms, twice on sailboats safe in harbor, but I can’t really imagine a hurricane with 150 mph winds like Ida. That’s the business of coastal scientists, engineers and other experts. Here’s what they’re telling me:
- It might not always seem this way, but in the past few years the National Hurricane Center has notably upped its game for predicting storm tracks.
- Structural engineers can now simulate hurricane risks for each individual building in a region, by combining advanced storm simulations with machine learning tricks to predict each building’s shape and strength. Coastal Louisiana, appropriately enough, is one testbed for this NSF-funded open collaboration.
- The lamentable history of New Orleans before and after Hurricane Katrina is beautifully described in Andy Horowitz’s Katrina. Once again Hurricane Ida is highlighting society’s lack of interest in guarding the vulnerable, while maintaining systemic foulups like police focused on protecting property rather than people.
- The rebuilt New Orleans levee system “is less ambitious than the one Louisianans lobbied for after Katrina, and the protection it offers grows weaker every day, as the wetlands that buffer the city from the Gulf of Mexico get wetter,” as Horowitz wrote in the New York Times. “But it kept the Gulf of Mexico out of the city, which was its job.”
- That was a straightforward goal for the Army Corps of Engineer’s $15-billion New Orleans levee project. Achievable goals may be far less clear for megaprojects under consideration for other U.S. cities. Case in point, Miami just turned thumbs down on a Corps plan built on a massive seawall.
- Miami is among the urban areas hoping to adopt “nature-based systems” (oyster reefs, salt marshes, sea grass meadows, mangroves… ) as part of their resiliency efforts. NBS is a big theme in the Texas coastal spine proposal, centered not just on enormous sea gates but on miles of sand dunes. As with traditional gray engineering, NBS measures have strengths and weaknesses; salt marshes retain no magic if they’re buried under a surge of seawater.
- There remains the little problem of paying for coastal adaptation measures–ideally, before disasters hit. Boston, which is doing a commendable job of planning for climate change, is among the cities puzzling to find the vastly greater sums needed for actual construction.
- Traditional benefit/cost analyses for such projects that consider only financial factors “might lead a government to protect only the parts of a city that contain high-value properties while dismissing parts of a community where less advantaged people live,” notes a National Academies report on localized climate action.
- There’s much talk about “managed retreat” from endangered coastal sites but so far this radical step is taken only when there is no choice at all. “There are reasons people live where they live,” as one prominent engineer pointed out to me.
- Hurricanes can rip away the accoutrements of civilization over surprisingly huge areas–for instance, Ida killed more people in the Big Apple than the Big Easy. But with the huge exception of rainfall, the worst structural damage is usually highly localized. Properly designed and constructed buildings often survive hurricanes surprisingly well, and the big problem for their occupants becomes waiting for restored power, water, roads and other lifelines.
See also What survives the storm