Rising waters from a flash flood threaten to engulf a house before its residents can evacuate, but then a wall pops out of the ground, protecting the structure from harm. It's not magic, it's an automatic dam created by Johann van den Noort, a civil engineering consultant in the Netherlands. He builds walls from lightweight foam-core polyester, encloses them in a casing, and buries them in the ground around a building. If flooding occurs, water flows into a pipe that fills the casing. The walls float up out of the ground, forming a self-closing barrier. When the waters recede, a pump empties the casing and the walls sink back into the ground. "I use the water itself to protect the land against the water," Van den Noort says. He has successfully tested the dam around a factory in the Netherlands. It could also shield homes, businesses, or even whole towns.
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