Spatial and Temporal Analysis of Hydraulic Conductivity, Snow Depth, and Soil Properties of a Bioretention System

At present, the size of cities has exceeded a threshold limit where centralized drainage and sewer treatment systems are no longer physically viable. Bioretention cells (BC) are a low impact development (LID) technology developed to provide distributed storm water quantity and quality control closer to the source through infiltration, retention, and evapotranspiration of storm water. Although water quantity and quality research has been done on BCs, most research envisages BC as a black box with specific temporal processes between the input and the output. Our research aims to consider BCs as heterogeneous systems with different physical processes occurring in different magnitudes spatially and temporally. For this study, a 4-year-old BC at the Kortright Centre for Conservation in Vaughan, Ontario, is used as an investigation area. Snow depth and soil properties are measured physically in seventeen points throughout the BC. More than a hundred hydraulic conductivity (K) measurements are measured using Guelph permeameters. K has been measured during freezing/non-freezing temperatures in winter, spring, summer, and fall. Snow depth contour maps show that low-lying water flow paths and sloppy locations in the BC thaw more rapidly. Ksat is spatially negatively correlated with moisture content. Temporally, Ksat was found to be larger during late winter/early spring thaw (~0.10 mm/s) than the summer or fall (~0.0228 mm/s). Design recommendations for BCs have been proposed based on the research findings.