Editor's Note: As students and staff are busily finding their way around campus this fall, have a care for where you step! This guest blog by U of L student Alix King tells us what bioswales are, and how we can save them from becoming soggy ditches!
Walking around the University of Lethbridge campus, you probably didn’t notice the unsung watershed heroes lying underfoot. You may have walked right over them, not realizing you were damaging a vital storm water filtration system, called a bioswale.
Bio-what, you say?
From above, a bioswale looks like a long-channeled depression in the landscape, usually containing vegetation such as shrubs, grasses, and organic matter such as mulch, to slow water infiltration and remove pollutants. At first glance bioswales may not seem significant, but underground, they are highly intricate and engineered purification systems.
Bioswales are engineered to filter out pollution and slow storm water runoff before it flows into storm drains. This is critical because in Lethbridge, like in most cities, storm water goes directly into the Oldman River, untreated.
How do they exercise their mighty powers?
Bioswales act as a filtration system because of a thick and porous layer of engineered soil hidden beneath the grass. Phytoremediation, the use of plants to rid contaminants from water, is used in conjunction with these filtration systems especially in areas of high salt and pollutant concentrations. Together, the plants and soil act like a sponge, soaking up water and slowly releasing it, while holding onto all the pollution.
A fully functional bioswale that is not being damaged by foot traffic, at the University of Lethbridge.
The University of Lethbridge has invested in bioswales as a way to manage storm water on campus. There are six bioswales in total on campus, and although they may go completely unnoticed by many, these systems are key in sustainably directing, filtering, and removing storm water from the campus.
At the University, these areas would be found by large parking lots including lots G, E, and F. Grasses, flowering herbs, and shrubs are planted for remediation of the soil and water as well as to improve the aesthetic of the landscape. Bioswales are particularly key for areas close to parking lots because of the quickened rate of water runoff from concrete that greatly increases the risk of flooding during severe events. The elevated storm drains that are found in bioswales are designed as such to give storm water time to be naturally filtered and rid of contaminants before entering the drain and into the Oldman River.
Watch where you walk!
A bioswale damaged by foot traffic, becoming a non-functional ‘soggy ditch’.
Unfortunately, in areas of high foot traffic, specifically lot E at the University, the integrity of bioswales is compromised, and its functionality as a storm water filtration system is greatly reduced. Two major problems arise from people walking across bioswales:
- Salt/contaminant-tolerant plants are stunted and or killed
- The porous layer of engineered soil under the grass that filters water is compressed and no longer capable of accepting water to infiltrated.
Both problems result in a dysfunctional bioswale - or as Phil Dyck, the head of the grounds crew at the University, refers to it, a “soggy ditch.” A soggy ditch is no longer beautiful or functional. When storm water is unable to infiltrate the pores of the soil due to compaction from people walking across it, polluted storm water will sit stagnant in the bioswale, undergoing little to no remediation before being deposited into the Oldman River.
The infamous soggy ditch between Lot E and the rest of the campus at U of L is caused by excessive degradation of the engineered soil by foot traffic (as seen in left picture below). Pathways between vehicles are subject to most disruption, therefore causing the most compaction and destruction.
Left: Compaction and soil degradation due to foot traffic. Right: Stunted growth of irises that were planted for phytoremediation. Both are ramifications of consistent foot traffic from people cutting across the bioswale.
Phil Dyck, Grounds Manager at University of Lethbridge.
Walk this way
We all have the power to protect these unsung heroes. Between the time you park your vehicle and walk to your first class, you have the opportunity to make a difference. All that you have to do is stay on the designated pathways while walking to the university and let the bioswales function as they were meant to.
If you have any questions or are curious about bioswales please feel free to contact Phil Dyck at the University of Lethbridge.
Because no one likes a soggy ditch!
Alix King
Student, University of Lethbridge
