Editorials, Opinion

To prevent floods, need less concrete and more ‘sponges’

When MPO Executive Director Bill Austin met with The Dominion Post Editorial Board, he talked about building resiliency into the Metropolitan Transportation Plan.

Resiliency is creating infrastructure that lasts, but also creating infrastructure that can survive a changing environment that swings between weather extremes. It means constructing bridges that can withstanding the pummeling of more frequent and severe floods. It means building roads that can withstand harsh and icy winters. It means developing a transportation plan that accounts for our changing climate.

We’ve recently discussed the terrible flooding in and around Morgantown (June 13 and July 29, in particular). We’ve talked about the way climate change has shifted floodzones and how our stormwater infrastructure must be updated to accommodate “100-year floods” that happen multiple times a year. But there’s one thing we haven’t discussed: The impact of impervious surfaces — like roads — on stormwater runoff that contributes to flooding in urban areas.

“Impervious surfaces” is the fancy term for basically everything rainwater touches except dirt. Roofs, buildings, roads, parking lots, sidewalks — anything manmade that can’t absorb the water. Why are impervious surfaces a problem?

The U.S. Geological Survey gives a useful analogy to explain the impact: Imagine the ground and the banks leading to a body of water — in this example, a stream — are layered sponges. When it rains, the ground/sponges absorb most of the water, but some of the rainwater still flows directly into the stream. That runoff causes the stream to rise slightly. After the rain stops, the sponges begin slowly releasing their water into the stream, as gravity drags the water through the layers of sponge and out into the stream. This means the water level will remain elevated for several days before going down.

When the sponges are replaced with impervious surfaces, such as buildings and parking lots, less water is absorbed and more water runs directly into the stream. (Runoff from impervious surfaces also leads to more water pollution, as the runoff picks up contaminants on its way to the stream, but we’re going to focus on the flooding aspect.) This means the water level rises much higher, much more quickly, causing flooding.

What does this have to do with the MTP? When we create or expand a transportation network, we create and/or expand impervious surfaces. As the MPO and Morgantown, Star City, Westover, Granville and Mon County look to form a long range transportation plan, they need to consider balancing the construction of more impervious surfaces with remaining or new sponge-like surfaces.

For example, one of the projects coming up is a roundabout on Green Bag Road. Making the center of the roundabout a greenspace instead of filling it with concrete will help with some runoff. Leaving grassy spaces on the sides of roads or filling wide medians with plants and dirt should also help absorb some of the rain from those 100-year storms we’re seeing more often and will hopefully reduce flooding.

 Striking that balance between creating a better transportation network and maintaining natural spaces will be key to making infrastructure more resilient in the long term — and key to keeping standing water out of our homes.