This article originally in the October print issue in the Brain Storm column titled "Healthy Canadian Waterways"
Storm water management regulation is being modernized in Canada to deal with some of the issues created by increased urbanization. Storm water management should be considered as occurring at two levels: the property location level and the community level (municipal, provincial and national). By regulating storm water management at the property level, the effects of unmanaged storm water at the community level can be mitigated.
The effects of unmanaged storm water can be damaging. Large cities have many impervious surfaces, and as cities grow, so does the volume of storm water. This has become an increasingly serious infrastructure problem as storm systems become unable to handle the volume.
Typical natural grasslands allow approximately 70% of rainfall to infiltrate the ground, and the remaining 30% becomes storm water. In a typical city, only about 10% of the rainfall infiltrates the ground, and 90% becomes storm water. That is a 300% increase in storm water volume over the same area. The area of Toronto, ON, Canada, is approximately 630 sq kilometers, and rainfall of 5 mm over this area can translate into more than 3 million cu meters of rainwater or 2.7 million cu meters of storm water.
In this regard, traditional storm systems are effective at moving billions of liters of storm water in a relatively small timeframe. However, in much larger rainfalls, the infrastructure can fail to meet the challenge. The resulting flooding can cause untold damage to other infrastructure, personal property and human life.
The less obvious effect of unmanaged storm water is more often seen at the provincial and national level, as storm water picks up contamination. Eventually, this nutrient-rich sediment and toxic storm water enters natural waterways, causing two major negative impacts. First, it may poison the water with the collected toxins, and the nutrient-rich sediment can disrupt the natural balance of the flora and fauna. Secondly, an increase in nutrients could cause an algae bloom, which would increase the biological oxygen demand of the water.
Bylaws & regulations
In Canada, there are agencies at every level of government that may have regulations affecting a property owner and the development of their property. Regulations at the federal and provincial levels dictate how municipalities can interact with natural waterways, and municipalities regulate how property owners can interact with the local storm water systems. In this way, storm water entering waterways can be controlled to prevent negative effects. Almost every jurisdiction has differing bylaws, so it is important that property owners are comfortable with the regulations.
The Canadian Standards Assn.
Generally, there are two methods for managing storm water: onsite and offsite. In an effort to unify the rainwater harvesting regulations across Canada, and offer guidance on methods and technologies, the Canadian Standards Assn. (CSA) published the CSA B805 Standard for rainwater harvesting systems in April 2018. In the preface, the standard states, “It provides a framework for both designers and code officials to confidently implement systems that meet the intent of the building, plumbing, health, and even fire codes.“ The 2020 update to the National Building Code will reference the standard.
Given the proper guidance at the federal level, provincial and municipal governments will join communities like Guelph, ON, Canada, and Nanaimo, BC, Canada, to start encouraging the use of rainwater harvesting systems as a means of onsite storm water management. To this end, the Canadian Association of Rainwater Management (CANARM) has been advancing the industry in the form of training, providing resources, documentation and support for the rainwater harvesting community.
Property owners are responsible for understanding the context of storm water in their community and for planning how to manage it for their own and the community's benefit. CSA will provide the guidance required for building the framework, and various levels of government provide the policy and legislation to provide the regulations.