Phase 2 Flood Strategy Projects
Here is a summary of projects from Phases 1 and 2 of the Lower Mainland Flood Management Strategy initiative.
See also: Flood Strategy Resources and LMFMS Maps for reports, maps and other related resources.
Phase 2 Projects
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 a new 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.
- Maps of a number of Lower Fraser flood scenarios (present day, 2050 and 2100) from the modelling and mapping project: see Lower Mainland Flood Management Strategy Maps.
- A project primer and narrated video that illustrate three of the flood scenarios from the project: see Flood Strategy Resources
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.
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
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:
- Tangible direct damages to buildings, contents and infrastructure
- Intangible community consequences
- Social vulnerability
- Environmental consequences and
- Lifeline disruptions.
Challenges and Limitations
Assessing flood risk is extremely complex. The consequences of flooding depend on:
- 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.
Regional Flood Risk Reduction Priorities
Lower Mainland local governments and other flood management organizations need to consider short-, medium- and long-term priorities for flood risk reduction, and what factors should be weighed when setting regional priorities. These include such factors as:
- Public safety
- Critical infrastructure and essential services
- Economic values
- Social and cultural values
- Environmental values
- Agriculture / food security
The Phase 1 Regional Assessment of Flood Vulnerability, and the Phase 2 Lower Mainland Flood Risk Assessment provide a starting point in understanding the relative flood risks across the Lower Mainland region. Additional technical analysis, consultation and dialogue will be facilitated to inform priorities for the Lower Mainland Flood Management Strategy. It is proposed that a range of flood management options would be considered and assessed for their suitability to address flood risk priorities.
Completed | Updates ongoing
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.
Featured on the site is a look at early floods through a flood history story map and the two-part video series “When the Waters Rise.” The videos explain the likelihood and expected impacts of a large-scale Fraser River or coastal flood. The site makes available flood maps, animations and a video that illustrate a range of flood scenarios developed during the Lower Mainland Flood Management Strategy initiative, together with information about different risk reduction measures. New resources for the public and flood managers will be added regularly to the Flood Toolkit.
Other Flood Projects
Here are some current flood projects relevant to the Lower Mainland, though not part of the Lower Mainland Flood Management Strategy initiative.
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 Resources for Flood Managers.
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 have been 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.
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 provides important five-day forecasts of coastal flood conditions in the Georgia Strait. The Fraser Basin Council has 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.
Visit the StormSurge BC website.