Urban flooding events are a significant driver of disaster loss, resulting in insured and uninsured losses, property damage, and negative impacts on residents and communities in Canada and internationally. The risk of flooding in urban environments is affected by watershed characteristics, environmental conditions, and the presence and condition of flood management and mitigation technologies. Several building- and lot-scale (or private-side) flood mitigation options are available to better protect properties from the risk of flooding, including backwater valves and foundation drainage systems to reduce the risks of sewer surcharge and infiltration flooding into basements, respectively. The overall success of private-side approaches to reduce the risk of flooding into buildings is reliant upon consistent installation procedures, building code interpretation and enforcement, public engagement, and maintenance. Current research into private-side approaches is presenting many opportunities and solutions for improved flood protection against water-related disasters at home. A greater understanding of the performance of private-side technologies under complex site-specific conditions can help to appoint flood prevention strategies better suited to individual home characteristics. This review paper explores the inter-related factors that affect the risk of basement flooding and explores the challenges and opportunities associated with the adoption and success of private-side flood mitigation approaches. Developing a greater understanding of basement flood vulnerability at the lot-scale will assist in identifying and prioritizing private-side strategies for homeowners to adopt and reduce the risk of flooding based on site-specific conditions affecting flood vulnerability. Continued efforts to evaluate and identify flood risk factors and the performance of private-side strategies are needed to better manage urban flooding events.

Rainfall Intensity–Duration–Frequency (IDF) curves are among the most essential datasets used in water resources management across the globe. Traditionally, they are derived from observations of historical rainfall, under the assumption of stationarity. Change of climatic conditions makes use of historical data for development of IDFs for the future unreliable, and in some cases, may lead to underestimated infrastructure designs. The IDF_CC tool is designed to assist water professionals and engineers in producing IDF estimates under changing climatic conditions. The latest version of the tool (Version 4) provides updated IDF curve estimates for gauged locations (rainfall monitoring stations) and ungauged sites using a new gridded dataset of IDF curves for the land mass of Canada. The tool has been developed using web-based technologies and takes the form of a decision support system (DSS). The main modifications and improvements between version 1 and the latest version of the IDF_CC tool include: (i) introduction of the Generalized Extreme value (GEV) distribution; (ii) updated equidistant matching algorithm (QM); (iii) gridded IDF curves dataset for ungauged location and (iv) updated Climate Models.

Flood-affected households in Canada rely on a complex arrangement of public disaster assistance and partial private insurance coverage for flood recovery. Recently, calls have been made for a review of the role of private insurance in residential flood losses; however, there are many challenges associated with the introduction of private flood insurance. Some ways to increase the viability of flood insurance include providing flood coverage for a variety of flood types, limiting coverage for very high-risk households and implementing risk-based coverage. To be effective, flood insurance will further require households, insurers and governments to participate in the reduction of flood risk. Governments and insurers should work toward a national, consistent approach to flood hazard assessment that includes assessment of a variety of flood types that affect households and supports both non-structural flood risk reduction and insurance pricing. Governments and insurers should further work to reduce the number of very high-risk households and improve the quality and accessibility of flood loss data. Furthermore, households will have to become better informed of the specifics of insurance coverage and bear a portion of flood losses through risk-based insurance pricing and conditions.

Extreme rainfall–related urban flooding and consequently, basement flooding due to sewer surcharge, has become one of the most significant drivers of disaster losses in Canada. It has been recommended that homeowners living in flood-prone regions protect their properties against basement flooding by installing backwater valves on sewer laterals and branch lines connected to plumbing fixtures. The most common causes of valve failure are identified and categorized into the following groups: (1) flow rates; (2) valve condition; (3) lateral slope; (4) lateral condition; and (5) wastewater material. A testing protocol developed through experimental design with respect to the failure-mode classifications is proposed to determine the lifecycles and maintenance intervals for different backwater valve models. The results may be used to create policies and recommend maintenance procedures to ensure an acceptable level of backwater valve function and to mitigate the occurrence of basement flooding events due to sewer surcharge.

Pluvial flooding in urban areas is one of the most significant drivers of disaster loss in Canada. Damages during pluvial flood events are associated with overwhelmed urban drainage (stormwater and wastewater) systems. During the period from 2013 to 2021, Canadian property and casualty insurers reported approximately CAD 2 billion in personal property (residential) pluvial sewer backup claims during flood catastrophes. There has been growing interest in managing pluvial urban flood risk, notably through newly funded national programs focused on climate change adaptation. These programs have included the development of new guidelines and standards focused on managing the underlying factors contributing to urban and basement flooding. Inflow and infiltration (I/I) has received limited attention in the pluvial flood literature, however. Informed by significant engagement with practitioners in Canada, this paper provides a review of the issue of I/I into wastewater systems and its relation to pluvial flooding. The paper will address concerns related to private property engagement in I/I and urban pluvial flood reduction programs. Both improved technical standards and administrative support are needed to ensure that wastewater infrastructure is less susceptible to I/I over its lifecycle.