Flood mapping in Canada: Q&A

6 years ago

Submitted by Natural Resources Canada, Canada Centre for Mapping and Earth Observation, Ottawa, ON

Floods are the most costly and frequent natural disasters in Canada, causing over $1B in damage to homes, property, and infrastructure annually (IBC, 2018).

Accurate and updated flood maps are critical tools for flood risk identification and mitigation. Currently, many existing flood maps in Canada are out-of-date and lack consideration of rapid urban development or the impacts of climate change.

A key requirement in flood mapping is good quality foundational elevation data to properly map flood risk. Natural Resources Canada (NRCan) provides leadership and advice to the flood mapping community and focuses on acquiring and sharing high-resolution spatial data to support flood mapping in a sample set of high-risk areas of Canada as well as strengthening the Federal Flood Mapping Guidelines Series.

Question 1: What are flood maps?

Flood maps identify the areas covered by water on normally dry land during actual or potential flood events. They can identify the specific risk of flooding on structures, people and assets. The following are the types of flood maps used in Canada.

Inundation Maps: Maps that show the floodwater extent of real or potential flood events. They aid in the management of emergency preparedness plans for communities situated within floodplains. For example, For example, NRCan’s Emergency Geomatics Service, a division of the Canada Centre for Mapping and Earth Observation, relies on satellite imagery acquired during natural disasters to extract flood extent information and disseminate inundation maps in near real-time (<4 hours).

Figure 1. Inundation Map by the Toronto and Region Conservation Authority

Flood Hazard Maps: Engineering maps that display the results of hydrologic and hydraulic investigations and show areas that could be flooded under different scenarios. These maps are used for regulatory planning purposes related to land use planning and flood mitigation.

Figure 2. Flood Hazard Map by the Toronto and Region Conservation Authority

Flood Risk Maps: Maps that indicate the potential adverse consequences associated with floods, including social, economic, environmental and cultural consequences to communities during a specific potential flood scenario.

Figure 3. Flood Risk Map by the Toronto and Region Conservation Authority

Flood Awareness Maps: Communication maps that serve to inform members of the public regarding the history of flooding in their communities, as well as the potential for future flooding and the risks that such flooding would pose to residential properties, businesses, cultural assets, infrastructure, and human life. These interactive web maps or printed poster-style maps include a range of additional content types, such as photographs, descriptive text, and graphics.

Figure 4. Flood Awareness Map by the Grand River Conservation Authority

 

Question 2: Why are flood maps important?

Flood maps serve as critical decision-making tools in flood mitigation, land use planning, emergency management, and public awareness. They offer the following advantages to communities in all aspects of the emergency management cycle.

Preparedness – They empower citizens and property owners with information that allows them to make informed decisions related to flood risks.

Mitigation – They provide a cornerstone for land use planning such as restricting development within flood zones and other structural flood mitigation strategies.

Response – They are useful to first responders, citizens and emergency management officials during a flood event by showing evacuations routes, evacuation centres, and the population at risk.

Recovery – They inform recovery practices by promoting knowledge of potential risk to infrastructure and properties; thus enabling communities to “build back better.”

Question 3: Are flood maps available?

Currently provinces and territories set their own standards for flood mapping, and different data sources are used across Canada. NRCan considers the use of consistent and authoritative geospatial data supporting the production of flood maps to be essential for evidence-based decision-making.

Access to accurate flood maps by Canadians varies by municipality nation-wide; however, in many parts of Canada, flood maps are out-of-date. NRCan has been working to improve knowledge of the current state of flood mapping in the country through the following recent and ongoing activities:

  • Workshops:
    • Inclusion of Indigenous Knowledge and considerations for the Federal Flood Mapping Guidelines Series with Innovation 7, March 2019;
    • Flood Mapping Workshop with the Canadian Water Resources Association, Montreal, Quebec, December 2018;
    • Flood Risk Assessment Workshop, Vaughan, Ontario, March 2018; and
    • Integration of Climate Change Considerations for Flood Mapping, Edmonton, Alberta, March 2018.
  • Webinars:
  • Projects:
    • Contracted a consultant to evaluate existing national flood hazard models for Canada, March 2019
  • Opportunities:
    • Digitization of existing flood hazard maps in Canada, including Flood Damage Reduction Program maps, is ongoing. Please contact Etienne.bonnhomme@canada.ca if you wish to contribute any flood maps.

Question 4: Is there guidance on flood mapping in Canada?

NRCan has developed a Flood Mapping Framework that captures all components of the flood mitigation process, from flood hazard identification to the implementation of flood mitigation efforts. The following flow chart illustrates the relationship between these components and links them to the relevant Federal Flood Mapping Guidelines Series document (see Figure 5).

Figure 5. Federal Flood Mapping Framework, NRCan

NRCan also developed the Federal Flood Mapping Guidelines Series to champion common flood modelling techniques in Canada and to encourage geospatial data dissemination and sharing. This series of documents provide details on technical aspects of the following flood mapping-related activities:

  • Hydrologic and hydraulic investigation;
  • Flood mapping;
  • Flood risk assessment;
  • Estimating the effects of climate change forecasting on flood modelling;
  • LiDAR data acquisition; and
  • Land use planning.

All documents in the Series are evergreen and will adapt as new technological and scientific developments emerge. Published guidelines are available on the Public Safety website. For more information on current initiatives to promote flood mapping contact: geoinfo@canada.ca.

IBC (2018) Facts of the Property and Casualty Insurance Industry.  Insurance Bureau of Canada Publication.

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