Here's a look at work underway in the Lower Mainland Flood Management Strategy.
Also see summaries of related flood projects:
The Lower Mainland Flood Management Strategy has developed a Lower Fraser Floodplain Model. Following an RFP process, Northwest Hydraulic Consultants was retained for the work, initial runs underway in the fall of 2018, and the work completed in late 2019.
The floodplain model is based on a new digital elevation model that encompasses both the river channel and the floodplain.
The new modelling work provides a better understanding of how water moves down the river and across the floodplain under various 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) have been produced in the modelling project: see Lower Mainland Flood Maps.
Completed: March, 2018
Photo: 2017 bathymetric survey of the Lower Fraser
In 2017, Northwest Hydraulic Consultants was retained to:
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.
In Progress | Completion: March 2020
With funding from the National Disaster Mitigation Program, FBC and the LMFMS partners began work on the Lower Mainland Flood Risk Assessment in late summer 2019. The project is expected to be completed in March 2020.
This assessment improves on the Regional Assessment of Flood Vulnerability by:
Key Elements of the Flood Risk Assessment Risk Areas
In Progress | Flood Strategy Interim Report (Draft):2020
1) Regional Flood Mitigation Priorities
Lower Mainland local governments and other flood authorities were surveyed in the fall of 2017 about their short- and long-term priorities for flood mitigation, and what factors should be weighed when setting regional priorities.
Survey respondents identified factors of importance when setting flood mitigation priorities for the region. These include public safety and a number of other factors (in no specific order):
Additional technical analysis, consultation and dialogue will be facilitated to further refine priorities for the Lower Mainland Flood Management Strategy.
2) Flood Mitigation Options
In consultation with the Joint Program Committee for Integrated Flood Hazard Management, FBC has identified a range of approaches to flood mitigation to consider in the context of a regional strategy.
An initial assessment of mitigation options for the Lower Mainland will be presented in a Flood Strategy Interim Report (Draft), expected for late spring 2019. These include:
In assessing mitigation options, FBC and project advisory committees will look at a range of considerations. In no specific order, these include:
3) Funding and Decision-Making Models
An initial inventory and analysis is in progress to document past, present and emerging approaches on funding and decision-making related to flood risk. Examples from BC and other jurisdictions are being reviewed. Near-term funding opportunities are being explored, as well as the potential to establish a new funding program for longer-term strategy implementation. The business case for proactive investment and regional cost-sharing is also being developed.
The results of this work will be presented in a discussion paper and in the Flood Strategy Interim Report (Draft) for initial consideration by participants in the LMFMS and made available for public comment in late 2020.
In Progress | Completed in 2019
An online map atlas and document library has been developed to identify environmental values and features along the lower Fraser River and coastal foreshore areas – in the context of flood hazards and flood management.
The atlas can help identify potential environmental benefits and adverse impacts of flood mitigation works or policies. Decision-makers can use the atlas to flag issues likely to require review in regulatory processes and identify potential candidate sites for habitat protection, conservation, restoration or compensation.
The atlas is hosted on the Community Mapping Network. Thanks to several governmental and non- governmental agencies that have made data available, information will include:
In Progress | Completion: March 2020
A first-stop flood education website is in development to support better awareness of flood hazards and the opportunities for flood risk reduction in the Lower Mainland.
The site will support the Lower Mainland Flood Management Strategy through information, story maps and a series of short videos. The site will also profile best-in-class flood information resources and case examples relevant to BC.
While the initial focus of the site will be on the Lower Mainland, the site may also be expanded in future to profile other flood initiatives in British Columbia. The site is scheduled to launch in March 2020.
RELATED FLOOD PROJECTS
In Progress | Scoping Study: Late Fall 2018 | Completion: 2020-21
The Province introduced seismic guidelines for new and existing high-consequence dikes in 2011 (updated in 2014). The aim was to better protect the diking system 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.
The Province of BC has provided funding to:
This initiative is expected to improve understanding of seismic vulnerabilities and to develop and implement a well-defined and regionally accepted program to improve the seismic resilience of Lower Mainland dikes.
In Progress | Completion: Summer 2020
The Fraser Basin Council has retained a consultant to review risk assessment methodologies and recommend a methodology that would be suitable to assess orphan dikes in BC – that is, dikes with no local authority for operations and maintenance.
Province-wide, there are 101 orphan dikes and erosion protection works, totalling more than 85 km in length. These works were either constructed or funded by the Province 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.
A second phase of work will involve assessment of the orphan dikes using the recommended methodology, including field assessments. The project will evaluate the condition of the orphan dikes, the associated risks of failure and what is 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 orphan dikes are in the Lower Mainland, the project will help identify any significant risks associated with them.
The project is funded by the Province of BC with the aim of helping local governments, the public, and the Province to quantify and understand the risks that these structures pose to BC communities. The project will also assist interested local governments that wish to mitigate these risks by assuming the role of diking authority, if warranted.
The BC Storm Surge Forecast model provides important 5-day forecasts of coastal flood conditions in the Georgia Strait.
Coastal partners in the LMFMS and the Province of BC have cost-shared the operation of the BC Storm Surge Forecast Model over the 2016-17 and 2017-18 storm seasons (October through March). Funds for continued operation and enhancement of the forecast model have been secured for the 2018-19 and 2019-20 storm seasons.
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Note to Strategy partners: The Fraser Basin Council sends the Flood Strategy Briefing to your organizations via your chief administrative officer or executive officer (or other contact on request) for internal distribution, as well as to those in your organization who are participants on LMFMS committees.