Terminology Tuesday

Published on December 23rd, 2014 | by GrowWNY Intern


Terminology Tuesday: Bioswales


Despite the long list of specific forms of green infrastructure, one term that has caught my attention is “bioswales.” If you’re thinking “What the heck is a bioswale?” then you are in the same boat as I was when I first heard the term. Unable to deter my curiosity, I began to research bioswales in order to find the answer to that question. After some extensive research, I learned that bioswales are a type of green infrastructure used to combat water pollution as a result of storm water runoff. However, before going into detail on the specific structure of bioswales, it is important to analyze the main issue first.

Although you may not realize it, anytime it rains there has to be a system in place that allows the stormwater to seep into the ground or flow back into local waterways. It’s part of the water cycle that we all learned about in science class. However, modern infrastructure, such as buildings and roads, can disrupt the infiltration stage of the water cycle as they are non-porous and cause rain to run off rather than seep in. When water runs over these non-porous surfaces, it is more likely to pick up pollutants. Additionally, an increase in stormwater runoff can lead to combine sewer overflows (CSOs) – a problem that plagues Buffalo due to our preexisting infrastructure.

In the natural environment, stormwater runoff is rarely an issue because of the plants and layers of sediment that filter out any pollutants. Essentially, bioswales are a replication of this natural filtration process and are strategically placed along roadways and other areas where water might run off from. Similar to how roads are sloped to remove water, bioswales are sloped inward to help collect storm water.

In order to spot a potential bioswale, keep an eye out for a long linear depression that contains a large amount of vegetation. Below the ground, a cross section of a bioswale would appear as several layers of various sediments, like sand, dirt, gravel, stone, etc., that are specifically chosen to help the vegetation grow and improve the filtration process. Above ground, local plants with deep roots are the preferred vegetation used to cover the bioswale. In WNY, this vegetation would most likely be a combination of grasses and marsh based plants such as cattails. Functionally, the deep roots further help filter the stormwater runoff and aesthetically they are able to blend into the surrounding environment. Engineered to efficiently clean stormwater runoff at a pace the sewage system can handle, bioswales will eventually pass off their naturally treated water to the sewage systems.

Want to learn more about the problem with stormwater runoff? Read our other blog on the difference between combined sewer overflows and sanitary sewer overflows here.

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