What is Stormwater Runoff?
You may have heard the term “stormwater” being used on the news. It might have been related to conversations about floods, pollution, and our water bodies. But all of these terms may lead you to wonder: What is stormwater? Why is it harmful? What can we do about it? Lucky for you, we will answer all of those questions in this post.
Stormwater runoff is described as rain or melted snow that flows over impervious surfaces (surfaces that don’t allow fluid to pass through like roads, sidewalks, and house roofs) and collects pollutants from these surfaces. Without proper infrastructure, impervious surfaces can lead to problems with flooding because the water has nowhere to go. To solve this problem in roads, cities add stormwater drains where the water can flow into. Based on city design, water flows from these drains through underground pipes and ends up at various stormwater outfalls around water bodies which deposit the runoff into our lakes, rivers, and ponds. This stormwater is not treated, so pollutants that enter this system go directly into our water bodies.
But how is stormwater harmful?
Stormwater is harmful because along its path across communities and into drains, the runoff picks up pollutants like harmful chemicals, litter, and debris, which it carries into water bodies. These pollutants come from a few different sources:
The first is during construction. When an area is being prepared for construction, the soil on the site is loosened, meaning that the sediment from this construction site can easily be carried into our waterways. Additionally, construction products that are not correctly sealed can spill and be swept away, posing a danger for aquatic life.
From an industrial perspective, the EPA has 11 different categories for industrial waste runoff from paper mills to food processing to hazardous waste facilities. The pollutants from these facilities can be deposited in the surrounding area and dragged into our waterways through stormwater runoff.
Finally, pollutants from your yard can get into waterways. When fertilizers are overapplied, the excess is swept away by runoff and transported into water bodies. One nutrient in particular, phosphorus, is a key component for cyanobacteria (blue-green algae) growth so excess amounts of this lead to algal blooms. These algal blooms reduce the oxygen content in the water and can even produce toxins, harming aquatic life and preventing recreational activities.
So, what can we do about it?
As a member of the community there are a few ways you can help keep pollutants out of stormwater drains.
The first is just keeping streets clean. When food packaging, pet waste, and bottles and cans get swept up by runoff, they block stormwater drains, increasing flooding. Even if the pollutants are small enough to fit through the drains and not physically block them, the litter goes directly into our waterways and can harm aquatic life. If you see any litter near a stormwater drain, be sure to pick it up.
Next, make sure not to over apply fertilizer on your lawn as the excess gets carried into waterways. In particular, unless your lawn is newly established or has low phosphorus levels when tested, you do not need phosphorus-containing fertilizer.
Finally, if you expect a rain event, make sure all possible pollutants like cans of paint or containers of chemicals are tightly sealed and tucked away as spillage can occur from the force of rainfall.
In addition to changing your own behaviors, you can advocate for better stormwater infrastructure in your community. Municipal solutions such as installing catch basins, permeable pavement, infiltration basins, and stormwater filtration systems can go a long way in protecting our water bodies.
If you’d like to read more about this topic, here are the sources I used:
https://www.epa.gov/npdes/national-menu-best-management-practices-bmps-stormwater
https://www.mass.gov/info-details/stormwater
https://www.epa.gov/npdes/npdes-stormwater-program
https://www.epa.gov/nutrientpollution
https://www.mass.gov/guides/massachusetts-stormwater-handbook-and-stormwater-standards
https://www.michigan.gov/documents/deq/ess-nps-savvy-bmp_209386_7.pdf