Houston’s perfect storm is coming — and it’s not a matter of if but when.

The city has dodged it for decades, but the likelihood it will happen in any given year is nothing to scoff at; it’s much higher than your chance of dying in a car crash or in a firearm assault, and 2,400 times as high as your chance of being struck by lightning.

As ProPublica and the Texas Tribune reported in our interactive story Hell and High Water, such a storm would devastate the Houston Ship Channel, shuttering one of the world’s busiest shipping lanes.

Flanked by 10 major refineries — including the nation’s largest — and dozens of chemical manufacturing plants, the Ship Channel is a crucial transportation route for crude oil and other key products, such as plastics and pesticides. A shutdown could lead to a spike in gasoline prices and many consumer goods — everything from car tires to cellphone parts to prescription pills.

If a storm hits the region in the right spot, “it’s going to kill America’s economy,” said Pete Olson, a Republican congressman from Sugar Land, a Houston suburb.

“It would affect supply chains across the U.S., it would probably affect factories and plants in every major metropolitan area in the U.S.,” said Patrick Jankowski, vice president for research at the Greater Houston Partnership, Houston’s chamber of commerce.

Houston’s perfect storm would virtually wipe out some of the fastest-growing communities in the United States. Hundreds of thousands of homes and businesses would be severely flooded.

Galveston Island and low-lying communities like San Leon, which lies right on Galveston Bay in the Houston metro area, would be completely underwater hours before the hurricane even hit.

Many hoped Hurricane Ike’s near miss in 2008 would spur action to protect the region. Scientists created elaborate computer models depicting what Ike could have been, as well as the damage that could be wrought by a variety of other potent hurricanes, showing — down to the specific neighborhood and industrial plant — how bad things could get.

Several proposals have been discussed. But none have gotten much past the talking stage.

“We’re sitting ducks. We’ve done nothing.” said Phil Bedient, an engineering professor at Rice University and co-director of the Storm Surge Prediction, Education, and Evacuation from Disasters (SSPEED) Center. “We’ve done nothing to shore up the coastline, to add resiliency … to do anything.”

The pressure to act has only grown since Ike, as the risks in and around Houston have increased. The petrochemical complex has expanded by tens of billions of dollars. About a million more people have moved into the region, meaning there are more residents to protect and evacuate.

For more about how the perfect storm could devastate Houston and impact the rest of the U.S., explore our interactive. You can also read about how we made it and why.

Art direction and production by David Sleight.