Crash Test Cities: Protecting Against Nuclear Blasts and Other Disastersby Lifeboat Foundation Scientific Advisory Board member Wil McCarthy.
It’s a fact of life: Vehicles crash. Over an average 12-year lifespan, about 20 percent of passenger cars and trucks will be involved in at least one major accident. Being well aware of this, auto makers design their vehicles with crashes in mind. There are other factors to consider, such as comfort, price, appearance and fuel economy, but today’s cars are fundamentally built around crash safety. As a result, while total traffic volume has increased 225 percent in the past 30 years, the annual number of road fatalities has actually declined by about 50 percent worldwide, to around a million a year. That’s still a huge number, but it shows that safety measures really do work and are worth the added cost. In a traffic-safety sense, not many of us would go back to 1975 if we had the chance.
Unfortunately, there hasn’t been any comparable progress in the safety of our cities. This might seem an odd comparison, but cities actually have a much higher accident rate than cars do. Think about it: Once founded, cities rarely pack up and move. They’re persistent artifacts that last for thousands of years. And while large-scale natural disasters are rarer than car accidents, they do come in a bewildering variety: There are earthquakes, volcanoes, hurricanes, fires, droughts, hailstorms, floods, landslides, blizzards, plagues, famines… and, yes, tsunamis.
More Vulnerable Than We ThoughtUntil recently, weather scientists believed that the heat islands and airflow patterns of a major downtown area would repel a tornado. But on May 12, 1997, a F1orida twister with 100-mph winds skittered through Biscayne Bay and across downtown Miami. Miraculously, no one was killed or seriously injured, but the myth was shattered: Cities are just as vulnerable to these monsters as prairie farm towns. The only reason more downtowns aren’t hit is that they’re so small against the vastness of the world.
Even less likely is an asteroid strike, like the one that carved out Meteor Crater in Arizona, or the 1908 devastation of hundreds of square miles of forest in Tunguska, Siberia. To the best of my knowledge, in all of history there’s never been a recorded case of a city suffering major damage from space debris; these strikes are rare, and our cities just aren’t that big a bullseye. But luck is a poor substitute for safety; stand in one place for long enough and, sooner or later, lightning will strike. Indeed, a meteor landing in the ocean could easily produce coastal devastation on a scale that dwarfs last month’s tsunami (as in Arthur C. Clarke’s classic novel, Rendezvous With Rama).
When you consider man-made surprises like economic crashes, war and terrorism, the picture gets even less rosy. Let’s face it: Every city on Earth is due for multiple disasters in its long, long future. Through the lens of history, the urban crash rate is 100 percent. Should we despair? No. But we should accept the inevitable and plan accordingly. We should crash-proof our cities.
A good place to start is with an evacuation and shelter plan, coupled to an effective emergency warning system. The lack of these in South Asia is, I’m sure, a major contributor to the death toll there. For sudden disasters like earthquakes, where advance warning is problematic, we can beef up our science to improve forecasting and toughen our building standards to reduce the dangers of collapse and falling debris. But what about that quickest and most devastating of disasters, where a microsecond is enough to hurl a city into flaming ruin? What about a nuke? Are we helpless before such Promethean might? Thankfully, no the answer may be as simple as building a wall.
Deflecting the InevitableWell, OK, more like a berm or a dike. Imagine it with me, all right? With a slope of 45 degrees, it’d be climbable by pedestrians and even cars. Like a dam, it would be made of earth and rock, possibly sealed in reinforced concrete. A heavy structure like that could take a lot of pounding and still hold together. More importantly, it would deflect shockwaves and shrapnel. Imagine the difference between a firecracker closed inside your hand and one sitting in a bowl that directs the main force of the blast upward. Which one will hurt you less?
Unfortunately, the bowl won’t do much for a firecracker going off over your head. In fact, depending on the position of the blast and the exact geometry of the bowl, it might even reflect additional force into your face. That’s not good, obviously.
Still, a fairly simple workaround is to drill a bunch of holes through our dike, connecting vertically and horizontally in a Swiss-cheesy sort of way. This will break up any shockwave into dozens of smaller waves, going different directions and arriving at different times. Acoustic ceiling tiles use the same principle to break up sound and dampen echoes. For better or worse, this would also impose rigid borders on the districts and neighborhoods of a city. In our nuke-resistant future, Chinatown will have a much harder time spilling over into Little Italy.
I know what you’re thinking, but there’s no reason these blast walls should have to be ugly. Like the levees of New Orleans or the canals of San Antonio, the Great Wall of China or the skyscrapers of Manhattan, they could be works of great beauty, snaking through our cities like terraced, ivy-covered gardens. Far from blocking the view, these walls will BE the view! They won’t necessarily impede traffic, either, since road and pedestrian tunnels could be an important part of the Swiss cheese. In fact, let’s get rid of subways and elevated tracks/roadways altogether, and use the blast walls as an integral and aesthetically elegant part of our transportation network. People could live inside them, too, and in a flood or storm we can simply close off the holes and use the barriers as actual dams and windbreaks. How cool is that?
Ideally you’d want the dikes to be higher than the buildings they were protecting, but this would use up a lot of costly real estate. We’ll have to make do with a larger number of smaller barriers instead, and let the taller buildings take their chances. That, unfortunately, is life in the real world: If you can’t save everything, you should at least do your best to save something. I’m imagining three of these walls cutting east-west across the island of Manhattan, and four of them slicing the L.A. Basin into the world’s largest tic-tac-toe board. But our disaster-hardened city has other aesthetic features as well: large, raised central parks where debris can’t fall, and where disaster survivors can gather to wait for help. We’ll have lakes and ponds full of fresh, clean water, and cathedral-like underground galleries stocked with food and medicine. A science-fiction movie set here would get high marks for visual splendor!
But one of the most chilling images from last month’s disaster is the laughter. Yes, laughter: You can see it here and there in the faces of fleeing people, who simply haven’t grasped the enormity of what’s about to happen. They see the wave, yes, and they don’t want it breaking over their heads and getting them all wet. Beyond that, there doesn’t seem to be much of a plan. Not that I’m criticizing; we’ve all seen big waves before, and experience does not tell us which ones are going to wash entire coastlines out to sea. So, most importantly of all, our future city is full of tough, clever people who, like good drivers, have been trained to cope with the unexpected. In any age and any danger, there’s no better survival strategy than that.
ReferencesThe Encyclopedia Britannica, 2004 Edition (“Tunguska Event”)
Tornado Skips Across Miami
The U.S. House Subcommittee on Highways and Transit Hearing on Relieving Highway Congestion through Capacity Enhancements and Increased Efficiency
We Are All Safer: NTSB-Inspired Improvements in Transportation Safety
Wikipedia: (“Car Accident”)