In general, Muench says, the solution isn’t too complicated: Just build the infrastructure higher. But engineers can’t build roads and bridges to survive all disasters, which can lead to expensive, overbuilt projects that “will take generations to complete,” Muench said.
‘Rice Krispie’ Streets
When engineers are rebuilding roads from scratch, they have also started using different factors to account for the possibility of more water coming in more quickly. Over the past decade, road builders have installed “sponge-free” roads that are more accessible.
Continuous concrete, unlike conventional concrete, usually does not include sand in the standard “stone, sand, cement, water” recipe. It also has a low water-to-cement ratio, making it possible to apply a thick paste before it dries. “It’s like caramel popcorn, or a Rice Krispie bar,” said Nara Almeida, who studies the literature as a teaching assistant professor in the civil engineering program at the University of Washington Tacoma.
In normal concrete roads, water accumulates and collects, stagnant water ends up damaging its various layers, and especially the bottom, which carries heavy vehicle loads. But the increased porosity of flowable concrete allows water to flow more easily through the material, so it can reach and be absorbed by the soil—a good feature for roads subject to a lot of moisture.
Leaky concrete has its disadvantages. It’s weaker than regular concrete, which means it’s better suited for sidewalks, parking lots, and low-traffic roads than medians that expect a lot of heavy trucks. (Research into reinforcing the material with steel, nature, glass, and synthetic fibers is ongoing.) Its depth means it’s not well-suited for cold weather, where water can seep in, freeze and break the material inside. Concrete also needs regular washing or cleaning, to “open” it to the type of material that is often found on the road—dust, leaves. Because districts sometimes have to change vendors and processes to use new materials, projects can be expensive. But some areas have put things on the shoulders of intersections, Almeida said, which may be too small to be hit by tires.
Ultimately, though, there’s not much that can be done when a large volume of water flows quickly across a road or under a bridge, which engineers call a “scour.” “We’ve all played behind a house with water and pipes—it’s devastating,” said Muench, the engineering professor. Part of climate resilience is planning ahead—and having quick fixes nearby—so communities can rebuild quickly.