A Mesocosm Study of Bioretention Functionality Under Frozen Conditions

Elliot, Sean

A Mesocosm Study of Bioretention Functionality Under Frozen Conditions

dc.contributor.advisor	Cey, Edwin
dc.contributor.author	Elliot, Sean
dc.contributor.committeemember	He, Jianxun
dc.contributor.committeemember	Hayashi, Masaki
dc.date	2023-11
dc.date.accessioned	2023-06-23T17:55:28Z
dc.date.available	2023-06-23T17:55:28Z
dc.date.issued	2023-06
dc.description.abstract	Urbanization interrupts the natural hydrologic cycle through the development of large impervious areas that prevent infiltration and introduce contaminants to stormwater. Bioretention is a green stormwater management strategy designed to restore natural hydrologic conditions in urban areas by promoting infiltration and removing contaminants at the source. Bioretention technology has proven to be effective in warm climates, but questions remain regarding how the systems perform in cold climates. This study investigated how bioretention systems function under frozen conditions using 24 mesocosm cells in Okotoks, Alberta. The mesocosm cells were lined and had three types of media, three types of vegetation, and two different impervious to pervious ratios. Media types included two typical bioretention media as well as an experimental mixture of clay loam and woodchips. Simulated spring melt events were conducted at the end of March 2021 and March 2022, with an additional event included at the beginning of March 2022 to observe the influence of midwinter melts on bioretention performance. Datasets were analyzed to compare frozen performance among the different design parameters and simulated events, and were also compared to unfrozen conditions using existing datasets from a separate study conducted at the site. The results of this study showed an average 80% decrease in infiltration rate under frozen conditions relative to unfrozen, with significant difference in infiltration rate depending on media type. The findings show that hydrologic performance is largely based on media type, and more specifically, the ability of the media to support preferential flow under frozen conditions. Preferential flow also limited the effects of refreezing midwinter meltwater, as no significant difference in infiltration rate was seen following the midwinter melt event. Nutrient performance was comparable between frozen and unfrozen conditions, with most cells leaching relatively low concentrations of nutrients. Nutrient removal was largely dependent on media type, but plant nutrient uptake also appeared to play an important role. Overall, the results of this study showed that bioretention systems function well under frozen conditions, but the reduced infiltration rates and effects of preferential flow must be taken into consideration when designing the systems.
dc.identifier.citation	Elliot, S. (2023). A mesocosm study of bioretention functionality under frozen conditions (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.
dc.identifier.uri	https://hdl.handle.net/1880/116650
dc.identifier.uri	https://dx.doi.org/10.11575/PRISM/41493
dc.language.iso	en
dc.publisher.faculty	Graduate Studies
dc.publisher.institution	University of Calgary
dc.rights	University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subject	Hydrogeology
dc.subject	Bioretention
dc.subject	Low Impact Development
dc.subject	Stormwater
dc.subject	Frozen Soil
dc.subject.classification	Geology
dc.subject.classification	Hydrology
dc.title	A Mesocosm Study of Bioretention Functionality Under Frozen Conditions
dc.type	master thesis
thesis.degree.discipline	Geoscience
thesis.degree.grantor	University of Calgary
thesis.degree.name	Master of Science (MSc)
ucalgary.thesis.accesssetbystudent	I do not require a thesis withhold – my thesis will have open access and can be viewed and downloaded publicly as soon as possible.