Municipal liability for flooding?

As climate change increases the intensity of storms, and as insurers become more reluctant to insure basements that are known to flood, we notice more and more lawsuits against municipalities for basement floods. Municipalities generally benefit from statutory immunities against lawsuits in nuisance for water escaping from lawfully operated sewage works. However, they enjoy no such protection against claims in negligence.

One key feature of negligence claims is foreseeability. In Southern Ontario, the August 2005 storm created intense flooding, which put many municipalities on notice of flaws in their drainage systems. Municipalities have responded to this threat with varying degrees of urgency. and the courts have responded with varying degrees of sympathy.

For example, In Lissack v. Toronto (City), 2008 CarswellOnt 8281 (Ont Superior Court of Justice),  the plaintiff succeeded in a negligence claim against the City following a storm sewer backup that flooded his basement. The storm sewers on the plaintiff’s property had been built around 1961 and designed, in accordance with industry standards at the time, to accommodate 2-year storms. Following the 100-year storm in August 2005, as a result of which many basements – including the plaintiff’s – were flooded, the City set up a Work Plan to alleviate the backup problem. The City divided its area into 31 chronic areas that required attention. In 2006, before the Plan was implemented, the plaintiff’s basement flooded again. The court awarded compensation for this second flood, concluding that the City had failed to implement the plan quickly enough.

However, a similar claim was rejected on appeal in

In Salamon v. Toronto 2011 ONSC 4192, the City successfully defended a negligence claim for  basement flooding caused by a sanitary sewer backup. The claim was brought in negligence, because, like most municipalities,  the City is immune from actions in nuisance for sewer backup (see s. 393 of City of Toronto Act, 2006).

The plaintiffs had won, at trial, on the ground of duty to warn. Unfortunately, the plantiff had not pleaded this cause of action, so the appeal court overturned this part of the judgment.

In any event, positive duties to warn are exceptional, and while defendant conceded duty “to warn of harm that is foreseeable”, no basis existed to find a positive duty on the City “to warn [plaintiffs] about ways to manage storm water or avoid sewer backups”

Although the City has a duty to maintain the sewer, it had met that duty by adopting and implementing a work plan with a seven-year cycle for investigations of sewers, starting with a four-year period for assessing areas of chronic sewer flooding. The work plan was a “policy decision” and “there has been activity undertaken in compliance with the time frames for sewer inspection adopted by [City] in the body of the work plan”. As the  sewer on plaintiffs’ street was last flushed in 2005, defendant “was compliant with the policy decision in the Work Plan to investigate on a seven-year cycle”. Accordingly, the City used reasonable care in the circumstances.


  1. Martin Shaw

    The number of 100-year storms in Ontario are actually below those expected as I explained in a previous email. Basement flooding is at the leisure of municipalities and e.g. sewer constrictions (eg like those on Weston Road, Toronto). It's not just a question of adhering to a policy. It's a question of site specific engineering and what damage does the policy equate to. Are the policies designed to cause flooding of e.g. 50 basements/yr? If so then the municipality should be liable for those costs. Sewer design, in general, is like Ford's calculation as to whether it's cheaper to make the gas tank on the Pinto safer or pay the additional lawsuits. If basements in Orillia get flooded repeatedly, the city may have abided by their policies but not been diligent. It certainly wasn't the homeownwer's fault.


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