Bioretention Systems for Stormwater Management: Assessment, Performance and Changes Over Time
Bibliographic record
Abstract
Bioretention systems function to mimic natural hydrology, by retaining stormwater runoff from routine rain events and returning it to infiltration and evapotranspiration, instead of runoff. This thesis consists of four studies which answer these research questions: How do we assess performance, and how does bioretention performance change over time? A systematic scoping review of 320 studies found that bioretention performance is defined in terms of hydrologic controls, while investigations into mechanisms of contaminant transport and fate are overlooked. Bioretention field research has been primarily conducted by a small number of institutions (26 institutions were responsible for 50% of the research) located mainly in high income countries, and primarily on new systems for a short period of time. Following the definition of performance, a field survey of mature systems (>3 years operation) was conducted on bioretention cells across Ontario, Canada. Saturated hydraulic conductivity (KSat) (a measure of hydrologic performance) was above minimum guidelines for all sites, and KSat improved for 6 of 9 sites. Soil-water interaction properties, such as plant available water and wilting point, more closely resembled loam soils than sandy soils, which may be due to the development of a soil structure over time. A more in-depth analysis of bioretention performance was conducted using a bioretention cell located in Vaughan, Ontario. The hydrologic and water quality performance was compared over two monitoring periods: new (immediately post-construction) and mature (4-5 years post-construction). The hydrologic performance was maintained in the mature system (median volume reductions of 100%) and mature effluent water quality was improved compared to the new condition for some parameters (e.g., dissolved solids, nitrogen species). A complete water balance of the system was performed using inflow, outflow and evapotranspiration data (via a weighing lysimeter). The water balance was further broken down by event size, where the event size was determined by rainfall frequency analysis. Recharge was the largest component of the water balance overall (86 % of inflow), and evapotranspiration was the next largest water balance component (7 % of inflow overall). Evapotranspiration was a significant component of inflow (21 %) when considering small events with a 50% chance of occurrence.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.009 | 0.011 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.004 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".