As Hurricane Sandy showed us once again, our cities and infrastructure are vulnerable to powerful natural forces. On their own, these forces can be devastating. Throw climate change into the mix, whether it’s stronger, amped up storms or sea level rise, coastal cities are in for some tough times. Well, unless you live in North Carolina...

At least for a little while after Sandy, our awareness is on resilience, the rather academic way of saying we're trying to figure out how our cities and infrastructure systems (like sewers, electric grid, roads, and subways) can withstand natural disasters. How can cities protect valuable infrastructure and ensure that cities stay up and running in times of large-scale natural disasters?

In the case of Sandy, New York City's subway system was flooded parts of the five boroughs lost electricity for a long time along with a whole host of other issues that go along with being under a deluge of water (and other stuff).

One technology that I find particularly intriguing is a giant inflatable balloon that can be used to plug up subway tubes. The New York Times wrote about the project led by researchers at the West Virginia University and Pacific Northwest National Laboratory:

The idea is a simple one: rather than retrofitting tunnels with metal floodgates or other expensive structures, the project aims to use a relatively cheap inflatable plug to hold back floodwaters.

In theory, it would be like blowing up a balloon inside a tube. But in practice, developing a plug that is strong, durable, quick to install and foolproof to deploy is a difficult engineering task, one made even more challenging because of the pliable, relatively lightweight materials required.

Now, this seems more like an emergency patch that would render the subway network unusable in times of emergencies, but if it’s a choice between a giant inflated balloon plugging the subway tube and the East River, I’m sure most people would opt for the balloon.

As the Times notes, this technology poses some interesting materials challenges. The challenge is to design a lightweight, yet strong and flexible, material that can effectively fill a given volume without getting punctured by whatever lurks in subway tubes.

More robust solutions like sea walls will probably be needed, but at least somebody is thinking outside the box! To see how awesome this technology is, I suggest watching this video of a test from early in 2012. Enjoy: