Study: Miami's Causeways Highly Vulnerable to Sea-Level Rise

Miami's cross-bay bridges are a treasure. Some of the city's purest joy comes when you're careening over the Julia Tuttle or Rickenbacker Causeway with the windows down, watching Biscayne Bay sprawling out under you as you laugh maniacally at how cool your life is compared to your college friends' lives up north. It's a small joy Miamians get to experience year-round.

That is, of course, until the rising seas swallow those roads whole.

According to a November Miami-Dade County Commission report on global warming, Miami's causeways — the Tuttle and Rickenbacker specifically — are some of the most vulnerable roads in the county. The report was compiled from information in a 2015 Federal Highway Administration study as well as subsequent investigations.

Causeways "to the barrier islands such as Key Biscayne and Miami Beach were found to be highly exposed, in part due to the low elevations, and also due to the long detour lengths that would result if a roadway was impacted," the new study concludes.

A map from the Highway Administration paints a gigantic red warning sign on the Tuttle and Rickenbacker. Key Biscayne could eventually be cut off from the rest of Florida:

A second study, which shows how sea-level rise will affect storm surges in the event of major storms or hurricanes, is also coming. As one would expect, things have not improved over the past decade or so. The study warns that the vast majority of the county's roads will likely be disrupted in the event of a large storm. Roads linking the barrier islands to the mainland will be particularly affected.

The study was ordered this past May. It concludes that some roadways on the mainland could be raised to protect them from flooding. But depending upon their elevation, this just might lead to more flooding in lower-lying areas of the city. The study recommends the county look into increasing the mainland's capacity for "drainage" — that is, its ability to suck water away from the streets — as well as fortifying things such as power lines and road signs to ensure they can withstand a little H2O.

Importantly, the study also recommends Miami-Dade take a hard look at its evacuation plans, to make sure routes don't vanish under the ocean in a decade or two. And this includes the causeways.

The report also mentions that both the Florida Department of Transportation and the Federal Highway Administration are working diligently to prepare Miami's roads for climate change. But given the fact that state and federal governments are headed by people who consider climate change and the flat-Earth theory roughly equivalent, we might be in for a very wet century of driving.