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Slippery Slopes: Principles of Water-Slide Design

Each passing summer seems to see water slides climb to terrifying new heights. Check out Groupon’s overview of what flows through these thrill rides’ massive veins.

As of 2013, the tallest water slide in the world rises 197 feet from the ground. The fastest sends riders traveling at speeds of more than 65 miles per hour. And one slide—the Serpent Slide at the Atlantis Resort in the Bahamas—shoots riders through a translucent tube immersed in a pool of live sharks. But even with such imaginative flourishes, water-slide designs must always adhere to the laws of physics, taking into account the effects that forces such as gravity, friction, and air resistance have on the human body.

Erratic Eddies

Unlike a roller coaster, which delivers an almost identical trip each time, a water slide is at the mercy of the mercurial substance that propels it. As water zooms down the tube, it’s susceptible to the slide’s shape, slope, and surface, all of which can be controlled by the slide designer. However, an almost endless array of variables—such as a rider’s bathing-suit material, body weight, and any blades of grass glued to their skin—can cause eddies in the water, making the rider’s exact path hard to predict. As a result, engineers run countless digital models, as well as real-world tests on eager human guinea pigs, before the ride can open. They also implement standard safeguards, such as tall, inward-curving sides that keep passengers from flying off open-air slides.

Bonus Points

• It’s much easier to predict the behavior of an inflatable tube or giant glazed donut than a human body, so speeds are much more consistent on tube slides, regardless of who’s riding them.
• Naturally, despite all the variables, experience plays a big role in slide design. As one engineer told Discover magazine, “After 20-odd years, you know that if a typical person with a typical bathing suit rides a fiberglass slide at a 9 to 10 percent slope, there aren’t going to be any problems.”
• As of early 2014, a new slide known as Verrückt—the German word for “insane”—is under construction in Kansas City, and builders promise it’ll soon take the crown for fastest and tallest water slide in the world.