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Flood mapping types and process

The importance of flood mapping

Flood maps are tools used to help prepare for floods and reduce their impacts. They outline potential flood hazards that help decision-makers with:

  • flood preparedness and mitigation
  • land use planning
  • emergency management
  • public awareness of flood risk

Types of flood maps

Flood maps identify the areas covered by water during actual or potential flood events. They can identify the probability of floods and its impact on structures, people, and assets. The following are the different types of flood maps used in Canada:

Flood extent map example showing permanent water bodies, open and vegetation covered flooded areas at a study site along the St. Lawrence River

Inundation Maps:

Maps that show the floodwater extent of real flood events, or that show potential floodwater coverage for flood events of different magnitudes. They are intended to aid in emergency preparedness plans for communities in floodplains and flood hazard zones.

Flood inundation map example showing water levels at a Lake Ontario study sit

Flood Extent/Emergency Maps:

A type of inundation map that shows the distribution or extent of water during real-time events. They aid in emergency response and preparedness for communities situated within floodplains.

Flood Hazard Map example portrays cross sections of flood levels at a study sight along the Rideau River

Flood Hazard Maps:

Shows the results of hydrologic and hydraulic investigations, including areas of potential flooding in different scenarios. Flood hazard maps are engineering maps, often used as regulatory maps for land use planning related to flood mitigation.

Flood Risk Map example by the Toronto and Region Conservation Authority using red to indicate areas of high risk, yellow areas are medium risk, and green areas are low risk to the community in Toronto, should a flood occur.

Flood Risk Maps:

Demonstrates potential negative consequences that communities may face during a flood scenario. Consequences include social, economic, environmental and cultural aspects.

Flood awareness Map example by Grand River Conservation Authority that includes a map of areas at risk, information about areas, and images of past floods in the New Hamburg area.

Flood Awareness Maps:

Communication maps that provide a narrative along with flood risk/hazard maps and show the history of flooding in their communities. They also show the potential for future flooding and the associated risks.

What is the difference between Flood Hazard and Flood Risk maps?

Flood hazard maps indicate geographic areas that could be covered by a flood. Flood risk maps use this information to identify vulnerability and estimate the consequences in terms of people impacted, damage to buildings, and/or other impacts of the hazard.

Federal Flood Mapping Guidelines

The documents contained in the Federal Floodplain Mapping Guidelines Series are a resource for floodplain mapping projects and activities undertaken across Canada. These guidelines are meant to advance and standardize flood mapping activities.

These guidelines aim to provide advice to:

  • provinces and territories, whose responsibility it is to provide technical guidance to those implementing flood measures
  • individuals and organizations in Canada that need to understand and manage flood risks and their consequences to communities

For more information on the guidelines, visit Federal Flood Mapping Guidelines Series.

Flood mapping process

The creation of a flood hazard/risk map requires several steps and the expertise of many people. Steps in flood map creation range from community engagement and data acquisition to producing the map. The diagram below demonstrates the different steps of the process to create a flood map.

circular diagram demonstrating the steps taken with community and stakeholder engagement when producing a flood map. 1)	 Understand priorities-      Hazard identification and priority Setting2)	 Data Acquisition-      such as LiDAR, meteorological, terrain, and historical data3)	 Hazard Assessment-      Climate Change Considerations4)	 Flood Delineation-      Hydrologic and Hydraulic Studies5)	 Map Production & Dissemination-      Geomatics Requirement6)	 Risk Assessment-      Risk Assessment-      Damage Estimation7)	Flood Mitigation-      Land Use Planning
Text version

Community and Stakeholder Engagement

Understand priorities
- Hazard identification and priority Setting

Data Acquisition
- LiDAR Data

Hazard Assessment
- Climate Change Considerations

Flood Delineation
- Hydrologic and Hydraulic Studies

Map Production & Dissemination
- Geomatics Requirement

Risk Assessment
- Risk Assessment
- Damage Estimation

Flood Mitigation
- Land Use Planning

Examples of science and research that contributes to flood maps

Making accurate flood maps requires detailed information and a lot of science and engineering. The Government of Canada is dedicated to science and research that can support flood mapping and risk assessment. Below are a few examples of activities from Natural Resources Canada:

Flood extent map example showing permanent water bodies, open and vegetation covered flooded areas at a study site along the St. Lawrence River

Watershed uncertainty and delineation

NRCan undergoes analysis of the uncertainty of watershed size or extent. This analysis is based on errors in digital terrain models representing elevation data, and location of the watershed outlet or pour point.

Flood inundation map example showing water levels at a Lake Ontario study sit

Artificial intelligence and feature extraction

Earth observation data like satellite and aerial imagery furthers understanding of a territory. Machine learning techniques (a branch of artificial intelligence) allows for the processing of a large volume of images with automatic and rapid identification of elements such as buildings, lakes and rivers, forests and roads. This data can then integrated into flood models to measure flood impacts.

Flood Hazard Map example portrays cross sections of flood levels at a study sight along the Rideau River

CanFlood

CanFlood is an open source flood risk calculation toolkit designed for Canada. It is freely available online via Github or as a plugin in QGIS software.

Find out more about flood mapping
Educational resources

Reach out to us

For more information, please email geoinfo@nrcan-rncan.gc.ca

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