Floods: Prevention, preparedness, response and recovery

Climate change is driving an increase in daily extreme precipitation in Canada, which when combined with other landscape factors, such as urbanization, deforestation, and loss of wetlands, can result in flood events. From an environmental health perspective, flooding increases the risks of harm and disease due to physical hazards, water and food contamination, mould, and numerous other physical, biological, and chemical hazards. Extreme flood events may also result in evacuation and long-term displacement from homes and social support networks, adversely affecting health and well-being.

This subject guide provides a collection of key resources on preventing extreme flooding and mitigating its risks, as well as resources to assist during the response and recovery phases. Key points of interest range from developing resilient infrastructure and public flood risk education campaigns to addressing home remediation and mental health in the recovery stages after a flood.

Designing for flood prevention and mitigation

This section provides research on how flood risk can be minimized by adaptation at the local, regional, and watershed scales.

• Flood resilience in the face of climate change (Federation of Canadian Municipalities, 2023)
  This website, developed with the support of Infrastructure Canada, offers tools for municipalities to use when planning and implementing flood mitigation.
   
• Fires, floods & hurricanes: Protecting Canadians by identifying and managing threats to safe drinking water (Emelko, 2022)
  This NCCEH webinar uses a discussion of how cyanobacteria blooms are precipitated by landscape disturbance to show how Canada’s natural resource-based infrastructure can be leveraged to mitigate water quality impacts due to climate change.

• Reducing urban flood risk through building- and lot-scale flood mitigation approaches: Challenges and opportunities (Sandlink and Binns, 2021)
  This article looks at the various drivers of and means to prevent basement flooding in urban areas, with a focus on “private-side” strategies that can be employed by homeowners.

• Developing a research-specific emergency management programme for municipal resilience following the 2013 flood in southern Alberta (Bowerman, 2017)
  This article discusses the Calgary Emergency Management Agency’s emergency management programme for community leaders that came about in the wake of the 2013 Alberta floods.

• Health co-benefits of green building design strategies and community resilience to urban flooding: a systematic review of the evidence (Houghton & Castillo-Salgado, 2017)
  This systematic review examined evidence linking green building strategies in the Leadership in Energy and Environmental Design (LEED) rating system with the potential to reduce negative health outcomes following flooding events. Green building design is found to reduce the risk of waterborne disease, flood-related morbidity and mortality, and psychological harm.

• Preventing disaster before it strikes: developing a Canadian standard for new flood-resilient residential communities (Moudrak and Feltmate, 2017)
  This report highlights the need for flood risk education in Canada, identifies priority areas of focus, and develops best practices for building new residential communities that are more resilient to flooding. Best practices were developed using criteria based on national applicability, effectiveness in reducing flood damage from severe rain events, technical feasibility for implementation, and cost-effectiveness.

• Reducing flood damage (Government of Canada, 2013)
  This webpage offers historical background of flooding in Canada, relevant protective legislation and detailed information on non-structural measures (such as floodplain management, forecasting and warning, and emergency measures) as well as structural measures (such as dams, channel improvements, ice booms, and flood proofing).

Engaging the public in prevention and preparedness

Prevention and preparedness depend heavily on voluntarily action by community members. This section offers toolkits and resource to assist with community engagement. It also includes resources that look at other means through which the risk of disasters can be more evenly shared between the public and private sectors.

• Get Flood Ready (Government of Canada, 2023)
  This toolkit provides resources on flood prevention and mitigation, as well as videos and infographics for quick dissemination via social media.

• Flood protection resources (INTACT Centre on Climate Adaptation, n.d.)
  This toolkit from the University of Waterloo provides detailed resources and checklists to help homeowners install and maintain key flood protections. Information on understanding insurance coverage and accessing flood protection grants is also provided.  Some resources are also available in French and Chinese.

• Engaging Canadians in flood risk management: Lessons from the international community (Centre for International Governance Innovation, 2017)
  This policy brief provides a scan of international initiatives intended to foster flood risk awareness, engage the public, and encourage changes that support flood risk management. Two key lessons for flood risk management policy are discussed and the brief provides three policy recommendations on how to better engage Canadians in flood risk management.
   
• Municipal flood risk sharing in Canada: A policy instrument analysis (Thistlethwaite and Henstra, 2017)
  This article examines some of the way in which Calgary, Toronto, and other Canadian cities are sharing the responsibilities and costs of flood risk mitigation through a range of policy tools. The paper also discusses some of the key flaws in the way municipal flood risk planning is undertaken and was followed up with a survey of Canadians’ willingness to share risk in a 2018 study.

Evacuations and shelters

Although evacuation may be necessary to ensure life safety, evacuation itself can become a secondary disaster, especially if evacuees cannot return for long periods of time. In the early stages of a disaster, evacuation centers and shelters must be assessed to ensure they are operating safely. In case of long-term evacuations, our recent work has identified numerous considerations for minimizing harm when communities and families are dispersed.

• Health and social impacts of long-term evacuation due to natural disasters in First Nations communities: A summary of lessons for public health (NCCPH, 2021)
  This summary document details the public health lessons gained from two case studies of Indigenous communities that experienced catastrophic events necessitating long-term displacement. The cases studies examined the experiences of the Ashcroft Indian Band during the Elephant Hill Wildfire (2017) and the Siksika Nation during the Bow River flood (2013).

• Disaster shelter assessment (US Centers for Disease Control and Prevention, 2020)
  This modifiable toolkit helps EPH professionals to rapidly assess shelter conditions on 10 general areas of environmental health ranging from basic food safety to pet wellness. The resources are also available in French and Spanish.

Re-entry: Short-term health risks and hazard mitigation

These resources address some of the immediate health hazards encountered when re-entering flood affected areas, which may be encountered in homes, but also businesses and public spaces like parks and playgrounds. Priority activities during re-entry include cleanup and disinfection, mould remediation and addressing food safety and water system safety concerns.

Re-entry hazards and assessing structural integrity

The flood zone poses many hazards to members of the public and environmental health practitioners who may be called upon to conduct site assessments, including debris, gas leaks, structural failures, live electrical wires, living and dead animals, and many others.

• Flood zones are danger zones: Be aware of the risks (NCCEH, 2021)
  This poster quickly identifies some of the hazards existing in flood zones, both during the flood event and after the water has receded, with a QR code that links the user to further resources.
   
• Flood zones are danger zones (BC Centre for Disease Control, 2021)
  This website summarizes the primary physical, chemical, and microbiological risks for members of the public who are trying to re-enter a home in a flood zone. The resources provided within this document are specific to British Columbia.

• Post-disaster building assessment training (BC Housing, 2021)
  This toolkit offers online resources and training to rapidly capacitate practitioners, enabling them to perform first-pass structural assessments on buildings impacted by flooding or other disasters.

• Reopening outdoor public spaces after flooding (US Centers for Disease Control and Prevention, 2021)
  This website provides suggestions for public health officials who must assess public parks and playgrounds and determine what action should be taken before reopening to the public.

• Re-entering your flooded home (US Centers for Disease Control and Prevention, 2020)
  This website helps homeowners identify the major hazard encountered during clean up. Additional checklists for structural safety and for inspecting household utilities are provided by the American Red Cross.
   
• Emergency wound care after a natural disaster (US Centers for Disease Control and Prevention, 2017)
  This guidance document and accompanying printable factsheet emphasize the importance of not only maintaining personal hygiene, but also quickly cleaning and covering wounds. Wounds exposed to floodwaters have a high likelihood of infection and rapid first aid can be critical.

Cleanup, disinfection, and dealing with indoor air quality hazards

Cleaning up a flooded building requires an action plan that encompasses the necessary information and personal protective equipment to prevent exposures to hazards such as mould, asbestos, carbon monoxide, pathogens, and contaminated dust.

• Mould: assessment, remediation and building for resilience (NCCEH, 2023)
  This NCCEH subject guide offers resources specific to mould assessment and remediation, including both resources for general public communication and education, as well as training resources for environmental public health professionals.
   
• Flooded homes cleanup guidance (US Environmental Protection Agency, 2023)
  This website provides useful information on steps to clean up, personal protective equipment, specific hazards like pests and carbon monoxide exposure due to improper generator usage, and first aid.
   
• Clean up safely after a disaster (US Centers for Disease Control and Prevention, 2021)
  This website provides a comprehensive checklist related to personal protective equipment, using hazardous tools, heat exposure and exhaustion, and preventing mould.
   
• The impact of flood and post-flood cleaning on airborne microbiological and particle contamination in residential houses (He et al., 2014)
  This article conducted a comprehensive, multi-parameter, indoor and outdoor measurement campaign to assess the effects of flooding on air quality and the role of prompt cleaning activities in reducing airborne exposure risks.
   
• Cleaning the house after a flood (Alberta Health Services, 2013)
  This detailed guidance document provides advice on how to safely clean and prepare homes for re-entry. The guide focuses on personal protective equipment, food safety, floors, walls, ceilings, electrical equipment, lights, fixtures, wiring, appliances, furnaces, water heaters, plumbing, and what to discard and what to save. AHS has also provided these helpful checklists to help prioritize and address specific areas of the house to allow safe re-habitation.
   
• Asbestos (BC Centre for Disease Control, n.d.)
  This webpage explains the risks associated with asbestos exposure, which may occur when a home’s drywall is damaged or must be removed. Asbestos removal should only be carried out by a qualified professional

Food safety and security

Flood events may threaten food safety through contamination of food products in homes and food businesses, but may also threaten food security due to destruction of soils, farm animals, and facilities.

• The questions on salvaging flooded crops (North Carolina State University Extension, 2022)
  This FAQ document overviews some of the most common questions regarding reconditioning, washing, or further processing crops that have been in contact with flood water.

• Keep food safe after a disaster or emergency (US Centers for Disease Control and Prevention, 2021)
  This website discusses what to do with perishable and non-perishable foods that may have been compromised during a power outage or have come into contact with flood water.

• Post-disaster food assessment and salvaging best practices (Alberta Health Services, 2020)
  This literature review examines the evidence and rationale underlying post-disaster food safety practices from Canada, the US and Australia. The review identifies those practices which are scientifically sound, and which are precautionary in nature, and flags several potential issues that require additional research.

• Managing the impact of floodwater contaminants on soil and produce in residential, community and school vegetable gardens (North Carolina State University Extension, 2020)
  This guidance document helps small producers understand the risk associated with various parts of the plant and provides advice on how to mitigate risks due to mosquitos, clean up and contaminated soil.

• Farm flood readiness toolkit (Upland Agricultural Consulting, 2020)
  This toolkit created on behalf of BC Ministry of Agriculture helps farmers assess their flood risk and put in place measures to limit damages, farm-related contamination, the loss of livestock, and disruption to the food system.

• Food safety for Southern US food crop producers after flooding (Alabama A&M and Auburn Universities Extension, 2019)
  This guidance document helps producers determine whether crops are safe for consumption and how to mitigate various health risks due to flooding around the farm. Information on soil testing and remediation are provided.
   
• Reopening your food establishment after flooding (Alberta Health Services, 2013)
  This guidance document helps operators to complete a self-inspection and address the major challenges of a flooded food premises. They also have a document for personal services establishments.

Water safety during flood events

Flood waters are highly contaminated and can compromise drinking water and wastewater utilities of all sizes. However, smaller systems, including private water wells and small community water systems, will be at greatest risk due to lack of knowledge on how to respond to floods.

• Use safe water after a natural disaster or emergency (US Centers for Disease Control and Prevention, 2021)
  This website explains the ways in which drinking water may become contaminated and provides advice on how to find safe water sources and what they can be used for.

• Septic and onsite wastewater systems (US Centers for Disease Control and Prevention, 2021)
  This toolkit aggregates resources from several US agencies with advice on how to manage sewage systems that may have been impacted by a flood event, and what to do before and during an emergency to limit risk to human health.

• Finding safe water in an emergency (NCCEH, 2019)
  This video helps residents understand their likely water needs in an emergency and how to source or collect water around their homes in a safe manner. For instructions on embedding it in your website, please reach out to [email protected].
   
• Be Well Aware - Ensure your well water is safe during and after emergencies (Government of Canada, 2019)
  This guidance document explains the risks that floods pose to wells. Homeowners should also receive information on how to shock chlorinate and test their wells post-flooding. Detailed information on well testing in eight languages can be found here.

• Flood resilience: A basic guide for water and wastewater utilities (US Environmental Protection Agency, 2015) 
  This guidance document helps small and medium utilities, which are more numerous and less resourced than large utilities, to address their flood-related vulnerabilities.

• Sewage systems and flooding: Safety, sanitation, and clean-up (Government of British Columbia, n.d.)
  This guidance document describes how to assess whether a septic system has been compromised by flood and steps to restore it to service.

Recovery: Long-term health and community impacts

In addition to the acute health impacts related to flooding and the hazards encountered upon re-entry, individuals and communities may also experience long-term psychosocial impacts due to material loss, grief, displacement, and family separation. This section draws on the peer-reviewed literature to better understand these impacts and how to address them.

• Psychosocial impacts: Resources for mitigation, response, and recovery (NCCEH, 2023)
  This NCCEH subject guide provides general literature on the psychosocial impacts of disasters.

• Sea level rise and public health implications (CLIMAtlantic, 2023)
  This NCCEH project in partnership with CLIMAtlantic describes the risks due coastal communities due to climate-related flooding through a series of jurisdictional and evidence reviews.
   
• A guide to post-flooding community-level psychosocial response and recovery in Canada (Myre and Glenn, 2023)
  This NCCEH report summarizes the findings from our pan-Canadian engagement with leaders in emergency response and recovery, which identified seven key public health practices for psychosocial recovery in the wake of a disaster. The accompanying webinar, held on March 30^th, 2023, discusses the report’s findings and offers live discussion with an expert panel.
   
• Post-flooding community-level psychosocial impacts and priorities in Canada: A preliminary report (Glenn and Myre, 2022)
  This NCCEH report draws on the literature, practice-based sources and engagement with a pan-Canadian practice advisory committee to reveal some of the experiences, challenges, and priorities for action regarding the psychosocial impacts of floods and community recovery.
   
• Climate change, floods, and your health (Public Health Agency of Canada, 2021)
  This  factsheetidentifies the short-term dangers (such as drowning and injuries) and long-term dangers (such as disease spread through water contamination and sewage backup, food contamination, and insects, as well as carbon monoxide poisoning, and mental health effects) of flooding. The factsheet also outlines actions to take to mitigate these health risks.

• Impact of climate change and wild weather on mental and physical health, lost time from work and the need to prepare (INTACT Centre for Climate Adaptation, 2021)
  This NCCEH webinar discusses the less quantifiable impacts of extreme flooding events and provides Canadian examples of flood mitigation activities.
   
• Environmental health effects attributed to toxic and non-infectious agents following hurricanes, cyclones, flash floods and major meteorological events (Erickson et al., 2019)
  This narrative review considers the complex issue of contamination in flood waters, outlining the wide range of infectious and non-infectious hazards and some of the work done around monitoring and assessing vulnerability to these hazards.
   
• Naturally occurring asbestos in an outdoor setting (Miller and Wiens, 2018)
  This evidence brief looks at assessing risk and sampling for naturally occurring asbestos, which can be deposited through flooding.

• Health risks of flood disasters (Paterson et al., 2018)
  This short commentary provides a quick overview of the most common acute health impacts of flood events, including drowning, trauma, exacerbation of chronic health conditions, mental health disorders, damage to health infrastructure and increases in cutaneous, gastrointestinal, respiratory, and vector-borne diseases.

• Surface water flooding, groundwater contamination, and enteric disease in developed countries: a scoping review of connections and consequences (Andrade et al., 2018)
  This systematic review identifies and synthesizes the literature on surface flooding, groundwater contamination, and human gastroenteric outcomes. The authors discuss strategies to increase awareness about potential sources of contamination and to motivate precautionary behaviour.

• Linking water infrastructure, public health, and sea level rise: Integrated assessment of flood resilience in coastal cities (Allen et al., 2018)
  This study describes a project that integrated public health, planning, and water utility managers into tabletop exercises carried out by emergency managers, leading to a much more thorough understanding of the hazards involved in specific emergency situations.

• Wellbeing in the aftermath of floods (Walker-Springett et al., 2017)
  This study analyzed several processes that explain wellbeing for those experiencing flooding. Key pathways to wellbeing outcomes included perceptions of lack of agency, dislocation from the home, and disrupted futures. There were offsetting positive impacts to these negative effects via community networks and interactions.
   
• Flooding and mental health: A systematic review (Fernandez et al., 2015)
  This systematic review mapped and assessed scientific evidence on mental health impacts of floods caused by extensive periods of heavy rain in river catchments. Four broad areas of findings were identified: 1) main mental health disorders, post-traumatic stress disorder, depression, and anxiety; 2) factors associated with mental health among those affected by floods; 3) the narratives associated with flooding and long-term stressors; and 4) management actions.
   
• No calm after the storm: A systematic review of human health following flood and storm disasters (Saulnier et al., 2017)
  This systematic review analyzed morbidity and mortality linked to floods or storm disasters with attention to how the burden of disease varies during different phases after floods and storms. The review included 113 studies and found that poisonings, wounds, gastrointestinal infections, and skin or soft tissue infections all increased after storms and that gastrointestinal infections were more frequent after floods. The majority of health changes occurred within four weeks of floods or storms.
   
• Health effects of flooding in Canada: a 2015 review and description of gaps in research (Burton et al., 2016)
  This review summarized the epidemiological evidence of flood-related health effects and the Canadian susceptibility to these effects. Recommendations are also offered for addressing the health-related effects of flooding.