Justin Ehrenwerth thinks a lot about where to put dirt. He leads the Water Institute of the Gulf, a nonprofit research group based in Baton Rouge, Louisiana. And one of the reasons he cares so much about dirt is that Louisiana is losing a lot of it. That means when Ehrenwerth and his team happen upon a mountain of dirt, they use computer models to figure out where the water is coming next so they can use the dirt, and the trees and wetlands planted on top of it, to prevent future erosion. And some of those models are developed by scientists in the Netherlands, which has been combating water for hundreds of years.