Flood Control and Floating Wetlands: Adapting Stormwater Strategy in a Changing Climate
This cache is for the SCAR 2025 event, and should not be sought out until after 5:30 pm on May 23rd, 2025.
Logging Tasks:
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In your own words, explain how climate change affects urban flood management and how FTWs contribute to a sustainable solution.
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From the view of the pond, would you say it looks naturally shaped, or artificially shaped?
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What is another name for a retention pond?
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If a Retention pond is usually full, where do you think the overflow would be located? Near the top or near the bottom of the basin?
Photo:
Take a photo of yourself or your GPS near the FTWs (without showing answers to the logging questions). Optional but encouraged!
You may post this log with the photo when you arrive on-site, however, If I don't receive the required information from you within 24 hours, I'll have to delete your log.
DO NOT POST ANSWERS IN YOUR LOG BUT PLEASE ADD YOUR PHOTO TO THE LOG. Please don’t provide the answers in when logging the cache online, but use “Send answers” feature. Please remember to answer to the best of your ability. As long as you give it your best effort, we'll be happy to accept your responses. You will probably find some of the answers you are looking for in this description page, or on the interpretive sign!
Earth Science Topic:
Hydrology, Climate Change Adaptation, and Biogeochemical Cycling
Earth Science Lesson:
Urban stormwater ponds are engineered basins designed to temporarily store runoff during rainfall events, reducing flood risk downstream and improving water quality. But climate change—through more intense rainfall, unpredictable weather patterns, and longer dry periods—demands new strategies to keep our communities resilient.
One innovative approach implemented in Saskatoon is the use of Floating Treatment Wetlands (FTWs): man-made floating islands planted with native vegetation that "float" on the water’s surface. At the Kensington #1 Storm Pond, 12 FTW islands were installed as part of Saskatoon's broader stormwater and flood control strategy.
In the heart of Saskatoon, where concrete paths cross native prairie, twelve green rafts float calmly on the surface of a stormwater pond. At first glance, they seem almost decorative—a natural flourish in a suburban landscape. But these floating treatment wetlands (FTWs) are doing the gritty, necessary work of cleaning stormwater, regulating runoff, and supporting urban biodiversity.
They are part of a collaboration between the City of Saskatoon, Meewasin, Environment and Climate Change Canada, and the Saskatchewan Association of Watersheds—an initiative that brings together natural science, engineering, and ecological restoration.
These floating islands aren’t just pretty faces. Beneath the surface, their roots dangle like aquatic beards, forming a matrix that traps sediments, absorbs nutrients, and plays host to microorganisms. Together, they mimic the function of natural wetlands—a function urgently needed in our modern, urbanized world.
Lots of birds and invertebrate (insects or bird food on wings) out today (Yay!) This shows a great functioning food web and ecosystem before Elk Ridge neighbourhood is built.
What Do Floating Treatment Wetlands FTWs Do?
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Flood Mitigation: FTWs don’t directly store extra water, but they support the stormwater pond’s function by improving long-term performance. Healthy vegetation slows surface flow and reduces erosion.
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Water Quality Treatment: Plant roots hang beneath the floating mats and act like living filters, absorbing excess nutrients (like nitrogen and phosphorus) and trapping sediment and heavy metals.
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Carbon Sequestration & Biodiversity: The biomass of the FTWs traps carbon and supports wetland-style habitats for birds and insects in an otherwise urban landscape.
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Climate Resilience: Increases in intense rainfall due to climate change can overload traditional infrastructure. FTWs help offset this by improving the long-term storage and cleansing capacity of pond.
Climate change is making storms more intense and unpredictable, which means cities are facing heavier rainfall in shorter periods of time. This puts extra pressure on stormwater systems that weren’t built to handle such sudden surges, leading to more frequent and severe urban flooding. With more pavement and fewer natural spaces in cities, rain can’t soak into the ground like it used to — instead, it runs off quickly, overwhelming drains and stormwater ponds.
Floating Treatment Wetlands (FTWs) offer a sustainable solution by improving the way stormwater ponds function. These floating islands of native plants help clean the water by absorbing nutrients and trapping pollutants before the water flows into rivers or lakes. They also help regulate water temperature and provide habitat for wildlife. By boosting the natural treatment capacity of retention ponds, FTWs make urban stormwater systems more resilient to climate change while supporting healthier ecosystems.
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Credit Clemson University
Rethinking the Urban Water Cycle
When most of us think about the water cycle, we picture rain falling from clouds, soaking into the ground, evaporating in the sun, and condensing to fall again. But in cities, the cycle takes a detour.
Infiltration—rain soaking into the soil—and runoff—rain flowing over the surface—are the two parts most altered by urban life. In natural environments, precipitation seeps into the ground, recharging aquifers and filtering through soil layers. But in towns and cities, rain hits rooftops, streets, and sidewalks. It’s rushed away by gutters and pipes before it can nourish the earth below.
Here in Saskatoon, water is brought in by municipal systems and exits through storm drains or wastewater treatment—often without ever touching the soil. As such, the urban water cycle is more like a water highway, bypassing the processes that would normally purify and slow the flow.
That’s where stormwater retention ponds—like this one—come in.
What Is a Retention Pond (or Stormwater Pond)?
Also called a wet pond, a retention pond is a permanent, engineered wetland or a stormwater pond. It’s also sometimes called a wet pond because it holds water all the time, unlike dry basins that only fill up during rain events. Stormwater ponds are designed to manage runoff from rain and melting snow in urban areas by capturing it, slowing it down, and letting sediments and pollutants settle before the cleaner water flows into nearby rivers, lakes, or wetlands. It’s an end-of-pipe measure—meaning it’s the last stop before urban stormwater re-enters natural waterways. These ponds hold stormwater long enough for gravity and biology to do their work:
- Sediments settle to the bottom.
- Debris and pollutants get trapped or broken down.
- Water slowly exits through an outlet pipe at a controlled rate.
Because these ponds are designed to always hold water, they become small but stable aquatic ecosystems, supporting wetland plants, frogs, insects, and birds. They’re like miniature lakes, with a job to do.
The location of this stormwater pond, is the southern most retention pond in the proposed Elk Point Neighbourhood north of Kensington neighbourhood. Image Credit Saskatoon City Council. (n.d.)
How Water Moves—and Why It Matters
As stormwater moves over driveways and through sewers, it picks up sediment, salt, oil, fertilizers, and litter. The faster the water moves, the more material it can carry. Picture a steep, narrow pipe versus a wide, shallow pond—the former rushes water along; the latter slows it down.
Slowing down stormwater is critical:
- It reduces erosion.
- It allows sediments and pollutants to settle out.
- It protects downstream rivers and lakes.
Floating Treatment Wetlands FTWs add an extra layer of filtration, using roots and microbial communities to absorb nutrients like nitrogen and phosphorus—key contributors to algal blooms in downstream waterways.
Google Satellite View of the Stormwater Pond
Biodiversity, Climate, and the Bigger Picture
Stormwater ponds with FTWs also help wildlife by mimicking the edges of natural wetlands. Birds nest in them. Insects hatch around them. Amphibians hide among their roots.
In terms of climate, they help mitigate flooding and store carbon. Saskatoon, like many prairie cities, is grappling with increased storm intensity and shorter snowmelt cycles. By holding water longer and reducing downstream surges, retention ponds offer resilience.
Some communities—like Sherwood Park, Alberta—connect these ponds in networks through underground piping. Water flows from neighborhood to neighborhood, balancing the load and reducing flood risk.
Dry vs. Wet Ponds:
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Dry Ponds are engineered depressions that temporarily fill with water during heavy rains, then drain. They are dry between storms and serve mainly for flood control.
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Wet Ponds (like Kensington #1) are designed to hold water permanently, offering both flood control and water treatment benefits. FTWs are ideally suited for wet ponds.
BIBLIOGRAPHY:
Atlan Stormwater. (n.d.). Floating Wetlands. Retrieved from https://atlanstormwater.com/floating-wetlands/
Borne, K. E., Fassman-Beck, E. A., & Tanner, C. C. (2013). Floating treatment wetland retrofit to improve stormwater pond performance for suspended solids and copper. Retrieved from https://canadianpond.ca/wp-content/uploads/2021/02/Borne-et-al-2013-Floating-treatment-wetland-retro%EF%AC%81t-to-improve-stormwater-pond-performance-for-suspended-solids-copper.pdf
Clemson University. (2024). An Introduction to Floating Wetlands for Stormwater Ponds. Land-Grant Press. Retrieved from https://lgpress.clemson.edu/publication/an-introduction-to-floating-wetlands-for-stormwater-ponds/
City of Saskatoon. (n.d.). Storm Ponds. Retrieved from https://www.saskatoon.ca/services-residents/power-water-sewer/storm-water/storm-water-system/storm-ponds
City of Saskatoon. (n.d.). Wetlands Design Guidelines. Retrieved from https://www.saskatoon.ca/sites/default/files/documents/transportation-utilities/construction-design/new-neighbourhood-design/wetlands_design_guidelines.pdf
Clark, J. (2018). Floating Treatment Wetlands: A Simple & Effective Tool for Enhanced Stormwater Management. Presented at Latornell Conservation Symposium. Retrieved from https://www.latornell.ca/wp-content/uploads/2025/04/Latornell_2018_W2D_Josh_Clark.pdf
Crandon Lakes Association. (2024). Floating Treatment Wetlands. Retrieved from https://crandonlakes.org/news/2024/10/25/floating-treatment
Escamilla, C., Scaroni, A. E., & White, S. A. (2024). An Introduction to Floating Wetlands for Stormwater Ponds. Land-Grant Press. Retrieved from https://lgpress.clemson.edu/publication/an-introduction-to-floating-wetlands-for-stormwater-ponds/
International Institute for Sustainable Development (IISD). (n.d.). Floating Treatment Wetlands. Retrieved from https://www.iisd.org/story/floating-treatment-wetlands/
Lakeview Community Association. (n.d.). Storm Water Pond Safety Review. Retrieved from https://www.lakeviewca.com/uploads/1/1/4/8/114865543/attach_2_-_storm_water_pond_safety_review-2.pdf
Midwest Floating Island. (2015). Floating Treatment Wetlands: An Innovative Option for Stormwater Quality Applications. Retrieved from https://midwestfloatingisland.com/wp-content/uploads/2015/05/Floating-Treatment-Wetlands-an-Innovative-Option-for-Stormwater-Quality-ApplicationsFloating-Treatment-Wetlands-an-Innovative-Option-for-Stormwater-Quality-Applications.pdf
SaskToday.ca. (2024). Floating Treatment Wetlands to Grow in Kensington Stormpond. Retrieved from https://www.sasktoday.ca/north/local-news/floating-treatment-wetlands-to-grow-in-kensington-stormpond-9473742
Saskatoon.ca. (2024). Floating Treatment Wetland Installation – Kensington #1 Storm Pond. Retrieved from https://www.saskatoon.ca/news-releases/floating-treatment-wetland-installation-kensington-1-storm-pond-august-28
Saskatchewan Association of Watersheds (SAW). (2024). Newsletter - September 18, 2024. Retrieved from https://saskwatersheds.ca/wp-content/uploads/2024/10/SAW-Newsletter-September-2024-1.pdf
Saskatoon City Council. (n.d.). Elk Point Neighbourhood Concept Plan – Wetland Demonstration Project. Retrieved from https://pub-saskatoon.escribemeetings.com/filestream.ashx?DocumentId=38159
Wired. (2011). Artificial Floating Islands Revive Aquatic Dead Zones. Retrieved from https://www.wired.com/2011/04/st-floatingislands
Wired. (2024). Polluted Lakes Are Being Cleansed Using Floating Wetlands Made of Trash. Retrieved from https://www.wired.com/story/planet-pioneers-nagdaha-small-earth-nepal-soni-pradhanang-ftws-floating-treatment-wetland-systems-water-cleaning-pollution
In 2025, geocaching is celebrating 25 glorious years—and to mark this milestone, we’ve embraced Back to Nature theme in the second quarter of the year. Don't forget to check what is coming up in the third quarter! If you’re participating, don’t forget to share your Back to Nature finds on social media! Tag @geocaching and use #GeoHT25 for a chance to be featured on Instagram. Optional step (this is not an ALR: "Additional Logging Requirement".)
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