Mandatory Downspout Disconnection Program

Responding to a series of costly flooding events, in 2007 the City of Toronto, Ontario decided to make its previously-voluntary downspout disconnections program mandatory in the hopes of reducing the volume of fresh water flowing into the sewer system during storm events. When a house’s downspout, the pipe that drains water from the rooftop, is connected directly a municipal sewer system the chance for sewer backup flooding increases. If a downspout is disconnected from the sewer system and instead drains onto a lawn or into a rain barrel, not only is less water in total entering the system, but it is also being deposited over a longer timeframe, giving the sewer system more time to discharge the water currently being handled and reducing the chances of that water backing up into homes.

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Understanding and Assessing Impacts

Toronto has been affected by many widespread, and very costly, flooding events in the past several decades. The city was struck by flooding in 2000, 2005, and 2013. As climate change affects local weather patterns, it is expected that extreme rainfall events will only grow more common as time goes on. This makes the need for programs such as Toronto’s downspout disconnection program all the more important. When a downspout is connected directly to the local sewer system, either sanitary or storm, the water collected on the rooftop is deposited directly into the sewers. This can result in large volume of water entering the system and doing so very quickly. As a result, the sewer system, which is often combined in Toronto, can quickly be have its capacity overtopped and result in water and raw sewage backing up the private sewer lateral and into people’s homes. Furthermore, this problem is not limited to just those houses with a downspout connected to the system, it happens on a wide scale in which houses that are complying with the bylaw will be just as affected as those that are not. Another issue that arises with connected downspout is the fact that rainwater washing off of roofing can be quite polluted as particles of roofing material and other pollutant become entrained in the water as it flows over the roof. If a downspout instead feeds onto a lawn or garden, the plants and soil will act a filter for these pollutants and prevent them from being deposited into the nearby water bodies.

Identifying Actions

Toronto has long placed issues of flooding and water quality at the forefront of its planning and policy decisions. It has a history of progressive, forward-thinking measures to help reduce the damages that extreme rainfalls events can cause. The recent decision to change the downspout disconnection program from voluntary one to a mandatory one in but one more iteration of an effort that has been ongoing since at least 1998 (if not longer). It was in 1998 that the first voluntary downspout program was initiated in an effort to decrease stormwater loads in the sewer system. The program targeted homes where downspouts were legally connected to either the combined or separate sanitary sewer system at the time of construction. Toronto offered to disconnect the downspouts at no cost to property owners. Around 2006, just prior to switching the program to mandatory, the city had budgeted roughly $1.5 million for disconnection efforts. The 2003 Wet Weather Flow Master Plan identified downspout disconnection as an effective and critical step toward increasing resilience in Toronto. Following this, the program was made officially mandatory in 2007, with plans to have the bylaw in enforceable effect by 2011 and to have all regions of the city covered by 2016.

Implementation

The shift from a voluntary program to a mandatory one presented several challenges to the City of Toronto and necessitated several major changes to the way the program was being handled. The city needed to communicate to citizens, elected officials, and various other stakeholders about how the underground plumbing system worked and why such a program was necessary. The City also needed to expand its operational capacity as well, requiring the acquisition of more resources in the form of computer systems and tools for communications, applications, processes, and reporting to process applications for exemptions. Unlike the voluntary system, the City of Toronto does not readily provide funding for downspout disconnection in the mandatory system. It does, however, provide financial assistance to low-income seniors or low-income people living with disabilities up to a maximum of $500. The city’s website offers advice for homeowners on how to properly disconnect their downspout.

Outcomes and Monitoring Progress

The City of Toronto did encounter resistance from citizens who felt that the disconnection program should not apply to them. This was especially so in areas with a separated sewer system.

Resources

Link to Full Case Study

Additional Resources:

Using climate change projections enables better adaptation decisions, as it allows you to better understand how the climate may change. To learn how to choose, access, and understand climate data, visit ClimateData.ca’s Learning Zone.
For more information on variables that may be useful in work related to flooding, visit ClimateData.ca and click “Explore by Variable”. Here you will find pertinent future climate projections related to:

  1. Historic and climate change scaled IDF data
  2. Maximum 1-day total precipitation
  3. Wet days (>1mm, >10mm, >20mm)