Assessing local mandatory measures to reduce flood risk and Inflow & Infiltration in existing homes
By Joanna Kyriaziz, Laura Zizzo and Dan Sandink
Severe rainfall and associated basement flooding are leading causes of damage to Canadian homes. Over the past decade, residents in municipalities across Canada, including Montreal, Thunder Bay, Winnipeg, Mississauga, Burlington, Toronto, Saskatoon, Edmonton and Calgary, have been affected by severe rainfall events resulting in hundreds of millions of dollars in insured and uninsured losses. Numerous factors, including increasing urbanization, issues associated with age, design and construction of infrastructure and climate change are expected to increase urban flood risk in many parts of Canada over the coming decades. Inflow and infiltration (I&I) is also an ongoing concern in many municipalities, as it both increases sewer backup risk and contributes quantities of excess stormwater to wastewater treatment systems, reducing capacity, increasing operating costs and increasing risk of bypasses.
Many local governments have been taking action to ensure that wastewater and stormwater do not enter and damage private property. Both public-side and lot-level (private-side) measures are important for effective mitigation of urban flood risk. While considerable knowledge exists about the design and management of buildings and infrastructure to reduce the risk of damage from basement flooding and sewer backup, many municipalities have experienced difficulty in encouraging homeowners to engage in measures to reduce basement flood risk. In many cases, fewer than 10% of eligible households take advantage of subsidy programs designed to increase uptake of lot-level urban flood protection measures (notably backwater valves, foundation drain disconnection, sump systems and/or downspout disconnection). A significant body of research has revealed that households frequently fail to engage in risk reduction measures for natural hazards. This finding has been consistent for many decades across a range of hazards.
Programs addressing private-side storm and wastewater infrastructure deficiencies are increasingly being implemented throughout North America. Programs range in approach and design, incorporating one or more of the following:
• Mandatory or enforcement-based approach, • Funding or incentive-based approach, and • Education or outreach-based approach.
This report focuses on mandatory or enforcement-based approaches adopted by North American municipalities. It explores legal tools that could be used to require private property owners in existing developments to better manage stormwater and protect against flood risk, and it examines the legal implications of applying these tools in the Canadian municipal context. Findings and discussion in this report may also be of interest to officials concerned with managing I&I, Combined Sewer Overflow and other related issues, even if they have not engaged in basement flood risk reduction programs.