Normally, Muench says, the solution isn't too complicated: just build higher infrastructure. But engineers can't build roads and bridges to survive every disaster, which would lead to expensive, overbuilt projects that “would take generations to complete,” Muench says.
'Rice Krispie' roads
When engineers build roads from scratch, they have also started using different materials to account for the possibility of a lot of water arriving very quickly. Over the past decade, road builders have increasingly built permeable, 'spongy' roads.
Permeable concrete, unlike regular concrete, usually excludes sand from the typical “gravel, sand, cement, water” recipe. It also has a lower water-to-cement ratio, which creates a thick paste before it dries. “It looks like caramel popcorn or a Rice Krispie bar,” says Nara Almeida, who studies the substance as an assistant professor in the civil engineering program at the University of Washington Tacoma.
On normal concrete roads, water pools and accumulates, with the standing water eventually damaging the various layers, especially the critical underlying layers, which support the heavy loads of vehicles. But the greater porosity of permeable concrete allows water to flow more easily through the material, allowing it to reach and be absorbed into the ground – a nice feature for roads that are subject to a lot of wetness.
Water-permeable concrete has its disadvantages. It is weaker than regular concrete, meaning it is better suited for sidewalks, parking lots and streets with little traffic than highways that expect a lot of heavy trucks. (Research into reinforcing the material with steel, natural, glass and synthetic fibers is ongoing.) Its porosity makes it unsuitable for cold climates, where water can seep in, freeze and break down the material inside . The concrete should also be pressure washed or vacuumed regularly to 'unclog' it of the type of material commonly found on the roadway: dust and leaves. Because states sometimes have to switch suppliers and processes to use the newer material, the projects could cost them more. But in some places the material has ended up on the shoulders of highways, Almeida says, where tires are much less likely to be bashed on a regular basis.
But ultimately, there's not much you can do when a huge amount of water quickly flows over a roadway or the base of a bridge, creating what engineers call “scour.” “We've all been playing in the backyard with water and hoses; it's very harmful,” said Muench, the engineering professor. Part of climate resilience is planning ahead – and putting the materials that can be quickly repaired nearby – so that communities can rebuild quickly.
