Covering the roof of a building with soil and vegetation can look beautiful, but that’s not why cities across America are having green roofs installed on their buildings. As climate change continues to create more intense storms, green roofs are a good way to prevent flooding by stopping storm water from reaching the ground in the first place. The soil acts as a sponge to rainfall, with one study estimating that a green roof can absorb as much as 61 percent of annual rainfall on a building. And by reducing runoff, you stop less water from picking up oil, trash and other pollutants from roadways, which then get pushed into sewers.