In the wake of Toronto’s recent flood (July 8, 2013), it seems appropriate to discuss the role of design in water management. As Mark Mattson (@waterkeepermark) of Lake Ontario Waterkeeper explained on today’s Metro Morning, Toronto’s sewer and stormwater infrastructure is combined. When it is overrun during heavy rain events, our rainwater and sewage end up mixing, bypassing our treatment system to be discharged directly into the lake (or in the case of yesterday’s storm, our streets, subways and basements!).
The resulting spread of bacteria can have detrimental effects on human and ecological health. And while we continue to build in the city (including countless condos in the downtown core), the capacity of our infrastructure remains the same, thus increasing the likelihood of system overload. Given this reality, it is all the more important that we design for water management.
Low Impact Development (LID) refers to site-specific landscape design that manages stormwater and prevents pollution. LID makes use of Integrated Management Practices (IMPs) and/or Source Control Technologies to prevent and mitigate runoff (through absorption, evaporation and transpiration), and to treat and reuse water onsite. Examples of these measures include implementing green roofs, rain gardens, permeable pavement, rain barrels, retention ponds and greywater systems. Demand reduction is also essential, and can be achieved in part by planting drought-tolerant vegetation, using strategically timed drip irrigation, and installing dual- and low-flush fixtures, aerators, and air cooled refrigerators and freezers. Together these strategies can reduce the burden that new and existing buildings place on our water infrastructure.