Hydrologic response of engineered media in living roofs and bioretention to large rainfalls: experiments and modeling |
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| Authors: | Ruifen Liu Elizabeth Fassman‐Beck |
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| Affiliation: | 1. Department of Civil and Environmental Engineering, Faculty of Engineering, The University of Auckland, Auckland, New Zealand;2. Department of Civil, Architectural and Environmental Engineering, Hubei University of Technology, Wuhan, China;3. Department of Civil, Environmental and Ocean Engineering, Stevens Institute of Technology, Hoboken, NJ, USA |
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| Abstract: | The hydrologic response of engineered media plays an important role in determining a stormwater control measure's ability to reduce runoff volume, flow rate, timing, and pollutant loads. Five engineered media, typical of living roof and bioretention stormwater control measures, were investigated in laboratory column experiments for their hydrologic responses to steady, large inflow rates. The inflow, medium water content response, and outflow were all measured. The water flow mechanism (uniform flow vs. preferential flow) was investigated by analyzing medium water content response in terms of timing, magnitude, and sequence with depth. Modeling the hydrologic process was conducted in the HYDRUS‐1D software, applying the Richards equation for uniform flow modeling, and a mobile–immobile model for preferential flow modeling. Uniform flow existed in most cases, including all initially dry living roof media with bimodal pore size distributions and one bioretention medium with unimodal pore size distribution. The Richards equation can predict the outflow hydrograph reasonably well for uniform flow conditions when medium hydraulic properties are adequately represented by appropriate functions. Preferential flow was found in two media with bimodal pore size distributions. The occurrence of preferential flow is more likely due to the interaction between the bimodal pore structure and the initial water content rather than the large inflow rate. |
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| Keywords: | engineered media hydraulic properties preferential flow Richards equation stormwater control measure stormwater management |
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