• 2016-2023

Highlights of Phase 2:

  • Hydraulic Modelling and Mapping in BC’s Lower Mainland

  • Lower Mainland Flood Risk Assessment

  • Flood and Environment Atlas

  • FloodWise website

  • Lower Mainland Dikes: An Analysis of Freeboard and Vulnerability

Final Reports for Phase 2:

  • Pathways to Action report

  • Synthesis of Technical Analysis report

Phase 2 Highlights

The Lower Mainland Flood Management Strategy (LMFMS) initiative wrapped up in 2023. This multi-year initiative was aimed at supporting the development of a regional strategy to reduce the risks associated with Fraser River and coastal flooding and to increase the flood resilience of BC Lower Mainland communities.  A multi-governmental leadership committee oversaw Phase 2 and the final reports.

Technical Highlights

Phase 2 expanded on the technical work begun in Phase 1. The following projects were completed:

  • Hydraulic Flood Modelling and Mapping in the Lower Mainland (2019)
  • Flood and Environment Atlas (2019)
  • Lower Mainland Flood Risk Assessment (2020)
  • FloodWise website (2020)
  • Lower Mainland Dikes: An Analysis of Freeboard and Vulnerability (2022)

Strategic Work

During Phase 2 of the LMFMS, a preliminary working draft of a strategy was developed and input was invited from governments having various flood responsibilities. The process identified areas of consensus but also differences. The Pathways to Action report sets the background and 10 recommendations to frame the next steps for government-to-government collaboration on flood risk reduction.

To move forward on the issues, the multi-governmental leadership committee overseeing the initiative recognized that more work lay ahead, including the need to align regional or subregional flood planning in the Lower Mainland with the upcoming BC Flood Strategy. It also recognized the need to co-create flood risk reduction approaches with First Nations in the context of the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP).

The Province of BC will follow up to discuss the Pathways to Action report with First Nations and other orders of government. One of the early priorities for flood risk reduction recommended in the Pathways report is protecting critical infrastructure and essential services in the region.

Phase 2 Final Reports

These are the final reports and related materials from Phase 2 of the LMFMS initiative.

Pathways to Action for Flood Risk Reduction and Resilience
Summer 2023

The Pathways to Action report summarizes progress to date on key issues relevant to flood management and opportunities for all orders of governments to move forward collaboratively to reduce flood risk, increase resilience and adapt to climate change.

The Pathways to Action Report and recommendations were developed at the direction of the LMFMS Leadership Committee, with input from a multi-jurisdictional Pathways to Action Working Group and the Emergency Planning Secretariat.

Synthesis of Technical Analysis
Summer 2023

The Synthesis of Technical Analysis report summarizes the information and tools developed and shared with flood authorities and other organizations through the LMFMS initiative respecting Fraser River and coastal flood hazards and risks. The report was prepared by the Fraser Basin Council.

Related Materials on Final Reports

Phase 2 Technical Reports and Materials

Here are the Phase 2 technical project reports, maps and other deliverables. Phase 2 regional maps are available in Flood Strategy Maps.

In 2019 the Lower Mainland Flood Management Strategy (LMFMS) initiative completed new modelling and mapping for the Lower Fraser region. The work was carried out for participants in the flood strategy work by Northwest Hydraulic Consultants.

The floodplain model is based on an updated digital elevation model that encompasses both the river channel and the floodplain.

The modelling shows how water would be expected to move down the river and across the floodplain under specific flow scenarios.  The model can also be used to analyze the effects of dike breaches; to create flood hazard maps that show the extent, depth and velocity of floodwaters; and to evaluate the effectiveness of proposed flood mitigation options.

Since completion of this work, local governments and First Nations, as well as some non-governmental organizations, have used the hydraulic model and associated maps in 60+ flood-related projects to date.

Explore the Maps

Check out the Project Primer and Video \

On this page see:

  • Flood Modelling and Mapping in BC’s Lower Mainland: A Project Primer
  • A narrated video that illustrates three flood scenarios from the project: Lower Mainland Flood Scenario Examples


In 2017, Northwest Hydraulic Consultants was retained to:

  • conduct a bathymetric survey to collect data along the lower Fraser River from Hope to the river’s mouth at the Strait of Georgia, and
  • combine the newly-collected data with existing bathymetric and topographic data to develop a digital elevation model.

The bathymetric survey measured the underwater depths of the river. It was conducted by boat using single (sonar) beam hydrographic equipment and software. The final elevation data from the survey was combined with data collected by Public Works & Government Services Canada in 2015, LiDAR topographic data commissioned by the Province of BC and other data.

A digital elevation model (DEM) has been derived using these datasets. The DEM provided a critical input for the development of the Lower Fraser Floodplain Model.

Flood and Environment Atlas

The Lower Mainland Flood and Environment Atlas was developed as part of the Lower Mainland Flood Management Strategy initiative. The atlas contains flood extents for the Lower Mainland for select flood scenarios along with a range of environmental values and features along the lower Fraser River and coastal foreshore areas.

The atlas is a resource for decision makers when considering potential environmental benefits (and adverse impacts) of floods as well as flood risk reduction projects or policies.

The flood levels shown on this portal are based on the 2015 Analysis of Flood Scenarios and mapping from the 2016 Lower Mainland Flood Vulnerability Assessment.

In 2020 a Lower Mainland Flood Risk Assessment was completed to inform the Lower Mainland Flood Management strategy initiative and to support governments and others with flood management responsibilities in their work. The risk assessment identifies potential impacts of flood hazards in the region on people and vulnerable assets (buildings, infrastructure and other things of value) to develop a regional baseline profile of flood risk.

Components of the Risk Assessment

Flood Scenario Analysis

The risk assessment evaluated 16 different flood scenarios of different magnitude and likelihood. There were eight scenarios for each of two types of flood:

  • Spring freshet flooding on the Fraser River and
  • Winter storm surge flooding along the coast and Fraser delta

Vulnerability Analysis

Based on these flood scenarios, a vulnerability analysis was undertaken to estimate potential flood impacts across the Lower Mainland, based on best available and accessible data within the project timeline and budget. Five consequence categories were assessed:

  1. Tangible direct damages to buildings, contents and infrastructure
  2. Intangible community consequences
  3. Social vulnerability
  4. Environmental consequences and
  5. Lifeline disruptions.

Challenges and Limitations

Assessing flood risk is extremely complex. The consequences of flooding depend on:

  • geography
  • size of the flood, how far it will spread, how deep it will be and how long it will last
  • location, elevation and resilience of buildings and infrastructure, and
  • how prepared a community is for floods of different magnitudes, including the potential for failures in flood protection infrastructure

A flood risk assessment cannot therefore predict all impacts of a specific flood. Moreover, many consequences cannot be easily measured – such as impacts to human health and well-being; loss of cultural, archaeological and traditional use sites; and contamination of the environment.

Finally, limitations on time, budget and available data limit the level of analysis – so more work will be needed over time. Examples include flood risks associated with First Nations values, interests and assets; the natural environment; and additional types of critical infrastructure.

Risk Assessment Report

The Risk Assessment report was prepared in 2020 for participants in the Lower Mainland Flood Management Strategy work. The report sets out methods and data and summarizes the technical results. Governments and other organizations with flood management responsibilities in the region can also access a data portal for select scenarios. Contact the FBC flood team for more information.

FloodWise is a first-stop flood education website, launched in 2020 by the Fraser Basin Council. The site helps Lower Mainland residents learn about past and future floods in the region and the work of governments and other organizations to reduce flood risk.  

Explore the site!

Regional Flood Maps

 Regional flood maps and animations developed during the LMFMS initiative are accessible in Lower Mainland Flood Strategy Maps.

Flood History & Story Map

For a look at early floods that seriously impacted the Lower Fraser Region, explore flood history and story map

When the Waters Rise Video Series

When the Waters Rise is a two-part video series from 2020 that offers an overview of Fraser River and coastal flood hazards in British Columbia’s Lower Mainland, the expected impacts of a large-scale flood in the region, and opportunities for flood risk reduction:  

  • Part 1:  Preparing for the big flood in BC’s Lower Mainland  
  • Part 2; Priorities and choices in BC’s Lower Mainland  

The focus of the videos is large-scale Fraser River and coastal floods, which are the floods most likely to have widespread impacts across the Lower Mainland. Other types of flood, however, can also be serious. These include periods of heavy, sustained rainfall, such as the atmospheric rivers that resulted in the Nooksack River flooding of Sumas Prairie in November 2021.


During Phase 2 work Strategy partners were briefed via email updates, meetings of the multi-organizational Joint Program Committee for Integrated Flood Management, working group meetings, and presentations to municipal committees.

Several Flood Strategy Briefings were also issued in the course of the work:

A briefing note and distribution of the final reports was made in 2023.

This project used the 2D hydraulic model that was developed in this inititive to compare potential flood levels near the dikes (water surface elevation) for the 50-year, 100-year, 200-year, 500-year and 1894 flood scenarios, with dike crest elevations surveyed most recently by the Province of BC between 2019 and 2020. Excel tables were prepared for each lower Fraser River dike that is regulated under the BC Dike Maintenance Act, to compare the modelled flood levels with dike crests and associated freeboard.

The dike analysis helped to inform flood authorities by:

  • identifying potential locations for dike overtopping or loss of freeboard during Fraser River freshets
  • support the operations, maintenance and flood mitigation planning for diking authorities in advance of the 2022 Fraser freshet

Notes on limitations: The analysis was limited to Fraser River freshet flood scenarios and did not include potential flooding from other rivers or from coastal storm surge. It also did not guarantee identification of all possible locations. The analysis was limited to comparing dike height with flood levels. It did not include other potential causes for dike failure that could occur prior to and separate from dike overtopping (e.g., erosion, seepage, piping).

Flood Modelling and Mapping in BC’s Lower Mainland:  A Project Primer

Here’s an overview of the hydraulic modelling and mapping project in Phase 2: Flood Modelling and Mapping in BC’s Lower Mainland: A Project Primer.

In this project, Northwest Hydraulic Consultants was contracted to develop a comprehensive flood model to run a range of future flood scenarios for the Lower Mainland, based on different climate conditions, river flows and potential dike breaches.

Looking for the Maps?

For maps and short animations from the project, see LMFMS Flood Maps.

Learn About the Flood Modelling & Mapping!

Flood Primer Video

This video from 2019 illustrates three sample flood scenarios simulated using the Lower Fraser 2D Flood Model during Phase 2. The flood model was used to simulate over 20 different sample scenarios to reflect floods of different sizes, projected climate change impacts and hypothetical dike breaches.

When the Waters Rise Videos

Who’s Been Involved in Phase 2?

Over 60 governments, agencies and other bodies with responsibilities and interests in flood management have been involved in the Lower Mainland Flood Management Strategy initiative. In some cases, these participants have provided funding support, inkind support or input on components of the work. 

Other Flood Projects of Interest

Here are some current flood projects relevant to the Lower Mainland, though not part of the Lower Mainland Flood Management Strategy initiative.

The Province of BC is committed to developing high-quality floodplain maps for BC communities that are exposed to riverine, lakeshore and/or coastal flood hazards.

A new floodplain mapping initiative is underway by the Province of BC, with support from the Fraser Basin Council and guidance from a Technical Committee and direction from a Steering Committees. The technical work is being undertaken by consulting professionals, in collaboration with communities.

Communities to Be Mapped

Communities in six regions of BC where there is a high risk of flood (but a lack of updated flood maps) have been invited to take part in the new floodplain mapping initiative, with work beginning in 2022.

With the agreement and collaboration of participating communities, several regions will be mapped in the first two years (2022-2024) of this multi-year, co-funded (federal-provincial) program. These are:

  • Lower Fraser and Coquihalla Rivers
  • Nicola and Coldwater Rivers
  • Upper Fraser and Nechako Rivers
  • Bulkley and Skeena Rivers
  • Shuswap Lake Region
  • Upper Columbia River

The initiative will generate floodplain maps that are of high quality and of a standard appropriate to support Indigenous governments and local governments in their regulatory and decision-making responsibilities.

The new maps will identify and describe flood hazard areas and help assess potential impacts to people, critical infrastructure and other assets and values. Communities can use them to:

  • support land use planning policies (e.g., floodplain bylaws and flood construction levels) and development decisions
  • prepare and update emergency response plans, and
  • plan disaster mitigation and climate adaptation measures

The maps will also be accessible to the public through a web portal. The hydraulic models will be available for future map updates or for additional flood assessments.

Scoping Studies

As part of the broader initiative, scoping studies have also been initiated for the Lower Mainland and coastal BC to:

  • better understand community flood mapping interests and needs
  • identify available data, models and data gaps
  • identify priorities and develop a work plan for future flood mapping projects.

Scoping studies in other regions of BC are also expected under the program.

The provincially funded initiative Investigations in Support of Flood Strategy Development in British Columbia is intended to gain and share a better understanding of challenges and opportunities in flood management in BC. 

Consultant teams prepared 11 technical reports on a range of flood management topics. The summary report (2021), prepared by the Fraser Basin Council, points to the value of enhanced funding, capacity and governance for flood management, including to support foundational information tools, flood management planning, emergency response planning, and implementation of flood mitigation measures. 

Find the underlying project reports, authored by different firms, in Flood Management Resources. 

Read the summary report

The Province of BC introduced Seismic Design Guidelines for Dikes in 2011 (updated in 2014). The aim was to reduce the vulnerability of high-consequence dikes from earthquake damage. Local authorities and design professionals in the Lower Mainland have found the standards are technically challenging to implement in many locations and/or cost-prohibitive.  

Two projects were undertaken to address these issues:  

Geotechnical Investigations and Seismic Assessment  

This project was undertaken to fill information gaps about the seismic vulnerability of high-consequence dikes through geotechnical investigations and engineering analysis. 

Professional Practice Guidelines – Seismic Assessment and Seismic Design of Dikes in BC
2021, Engineers and Geoscientists BC (EGBC). Hosted on the EGBC site.  

EGBC Seismic Assessment and Seismic Design of Dikes in BC

This project was managed by Engineers and Geoscientists BC (EGBC) to provide guidance to professionals on the seismic assessment and design of high-consequence dikes. The project had provincial funding and support from the Fraser Basin Council. The guidelines supplement the provincial Seismic Design Guidelines for Dikes. 

In BC there are 101 orphan dikes and erosion protection works, which total more than 85 km in length. These works were either constructed or funded by the Province of British Columbia over the past 50 years to respond to emergency flooding situations or were built by others and abandoned. These works generally lack adequate planning and engineering design due to the emergency conditions under which most were constructed. They are not typically maintained or inspected by a diking authority.

The Fraser Basin Council, which oversaw the project, retained a consultant to review risk assessment methodologies and recommend a methodology that would be suitable to assess orphan dikes in BC. A second phase of work involved an assessment of the orphan dikes using the recommended methodology, including field assessments. The project evaluated the condition of the orphan dikes, the associated risks of failure, and what would be needed to bring each up to provincial standards and into a state of readiness to establish a local authority. While only a small number of these orphan dikes are in the Lower Mainland, the project helped identify any significant risks associated with the structures.

The project was funded by the Province of BC with the aim of helping local governments, the public and provincial officials to quantify and understand the risks that orphan dikes pose to BC communities. The project results are also helpful to interested local governments that wish to mitigate risks by assuming the role of diking authority, if warranted.

The BC Storm Surge Forecast Model has provided important five-day forecasts of coastal flood conditions in the Georgia Strait. The Fraser Basin Council coordinated funding, contract management and cost-sharing arrangements with coastal communities for the the Province of BC for storm seasons (October through March) from 2016-17 through 2021-22.

The  2022-23 season is scheduled to be the final season for the BC Storm Surge Forecasting Program.  Environment and Climate Change Canada will be assuming surge notifications for the public in the coming years for all coastal communities in Canada.  If you or your organization has any questions about the future of surge forecasting, please post them through the contact form on the StormSurge BC website.

Lower Mainland Flood News

  • BC Flood Strategy Intentions Report

BC Flood Strategy

June 7th, 2023|Categories: Resource|Tags: |

— BC Flood Strategy — The Province of British Columbia is working on a new BC Flood Strategy to help to reduce flood risks and enhance the resilience of communities to future flood events. An Intentions Paper called From Flood Risk to Resilience was the

  • Flood Modelling and Mapping in BC's Lower Mainland: Project Primer

Resource Profile: Flood Scenarios

May 18th, 2022|Categories: Resource|Tags: |

— Resource Profile: Flood Modelling Scenarios — May 2022 The Lower Fraser 2D Flood Model was used to simulate over 20 different scenarios to reflect floods of different sizes, projected climate change impacts and hypothetical sample dike breaches. Find an overview of this work in


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