John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
It's maybe not such a dumb idea.
Ask a 6-year-old kid chewing on a Lego how we can get rid of tornadoes and the answer you might receive is, "Build a big wall." But maybe that's not such a dumb idea, according to a partly U.S. Navy-funded study that looked into fortifying the Midwest with titanic, twister-blocking barriers.
Rongjia Tao of Philadelphia's Temple University proposed this unusual solution after studying how world geography affects tornado propagation. His focus is Tornado Alley in the south-central United States, an area of extremely high and violent twister activity. The region's vast expanse of flat ground provides the perfect mixing bowl for cool polar and warm subtropical air masses, leading to supercell thunderstorms and roaring monstrosities like the dual funnels that hit Pilger, Nebraska, last week:
Taming the fury of Tornado Alley might come down to studying other places that have a relative lack of twisters, Tao writes in the International Journal of Modern Physics B. Specifically, he thinks there are lessons to be learned in China:
United States and China have similar geographic locations. In particular, the Northern China Plain and the Eastern China Plain is also in the zone of mixing, similar to Tornado Alley. However, very few violent tornadoes occur in this region of China because there are three east-west mountain ranges to protect these plains from tornado threat. The first one is 300km long Yan Mountain which lies at the northern boundary of these plains. The second one is 600km long Nanling (Nan Mountains) at the south boundary of these plains. The third one is 800km long Jiang-Huai Hills through the middle of the plains. Especially, Jiang-Huai Hills are only about 300 meters above sea level, but effectively eliminate the major tornado threat for the areas....
Tao believes the mountains' dampening powers are evident because in one place where there's a gap in the Jiang-Huai Hills—creating an open plain—the area is known as "Tornado Hometown" for its regular tumultuous outbreaks. "It is thus clear that Jiang-Huai Hills are extremely effectively in eliminating tornado formation," he claims.
So, three mountain ranges and few twisters: is it possible to artificially create that situation in the U.S.? In the theoretical universe, Tao indicates it's feasible. He would put gigantic walls running mostly west to east in three parts of the country: North Dakota, the middle of Oklahoma, and Texas to Louisiana, the last to counter tornadoes in "Dixie Alley." And he'd start by first building them around frequent tornado targets, like perhaps Moore, Oklahoma, and then gradually extending them throughout the land as if the Great Wall of China had little babies.
Well, make that giant, mutant offspring so towering they'd blot out the sun. Extrapolating from the size of mountain ranges, Tao estimates that to be effective the barriers would need to be 984 feet high and 164 feet wide. To put that height into perspective, I've sketched this highly technical diagram of an anti-tornado barricade next to other national landmarks:
The price and labor of erecting these super-walls would be so monstrous that Tao had better be conducting a second study about it right now. (Still, if the U.S. can afford to maintain a colossal border fence that doesn't even work well, perhaps it's worth at least considering?) Here's some of the math he's done to justify the walls' basic cost-per-mile, though:
In Philadelphia, there is one skyscraper building, Comcast Center, about 300 meter high. From the cost of Comcast Center, we estimate that to build one mile [of] such wall, we need about $160 million. On the other hand, the damages caused by single tornado attack in Moore, Oklahoma on May 20, 2013 alone were multibillion dollars. Therefore, it seems that the cost for building such a wall is affordable.