How stormwater runoff affects parking structures and places

Paul Wessel
Published on: 

Stormwater runoff is a principal cause of urban waterway pollution nationwide, fouling rivers, lakes, beaches, and drinking water supplies. To reduce the environmental and public health threats posed by polluted stormwater and to comply with the Clean Water Act, cities nationwide are making significant investments to reduce stormwater runoff.

Impermeable pavement, which doesn't allow water to percolate into the soil, is associated with parking and roadway surfaces, and comprises up to 70 percent of the total paved area in an ultra-urban setting.

Therefore, parking and roadway surfaces play a significant role in how stormwater runoff affects our environment. These surfaces often collect polycyclic aromatic hydrocarbons (PAHs) associated with petroleum products, bacterial contamination and metals, among other pollutants, which in turn are associated with brake pad wear. These pollutants wash off the surface during rainfall and flow into downstream waters without the chance to filter into the ground.

However, traditional solutions that rely solely on fixing or expanding existing sewer and stormwater infrastructure can be extremely expensive and fail to address the root cause of the problem: impervious spaces in the built environment that generate 10 trillion gallons of untreated runoff per year.

Fortunately, in response to stormwater problems, many cities are developing ambitious plans to effectively unpave city land as a way to stop directing polluted runoff into municipal waterways and to begin managing rainwater on-site through “green infrastructure” practices. These practices include trees, rain gardens, permeable pavement and other green development that mimic natural processes to infiltrate, clean, evapotranspire or reuse stormwater on or near the site where it falls.

Learn more about managing stormwater runoff from this Washington State University project and about green parking lots from this EPA guide.