North Shore Sea Level Rise Risk Assessment and Adaptive Management Strategy

The North Shore partnership conducted a coastal flood consequence assessment to estimate the potential impacts of sea level rise with coastal flooding scenarios in order to understand the consequences of not undertaking sea level rise adaptation measures, i.e. a “do nothing” approach. The assessment was completed to identify and quantify the consequences of coastal flooding under two future coastal stillwater scenarios if no adaptation measures are undertaken:

• 1 m sea level rise during a major storm, 10% annual probability stillwater level (10-year return period), and
• 2 m sea level rise during an extreme storm, 0.5% annual probability stillwater level (200-year return period).

A total of 24 variables representing major elements across the following six sectors were used to estimate and assess the potential flood impacts: 1) Number of residents that could experience flooding; 2) Cost of building damage; 3) Amount of building damage debris; 4) Number of businesses that could experience flooding or power outage; 5) Area of parkland that could flood; 6) Number of cultural and heritage places that could flood. Methods used to estimate and assess the potential flood consequences for the variables included: census-based modeling using the Canadian version of the HAZUS model for population displacement, building and contents damage, and building and contents debris generation; business disruption modelling and power outage assessments; and spatial identification of variables within the scenario flood extent using GIS.

The strategy sets the direction for continuing to build resilient North Shore communities, and includes six priority actions:

1. Formalize a working group with North Shore sea level rise partners to continue adaptation planning
2. Continue building our knowledge about the impacts of sea level rise
3. Establish comprehensive adaptation plans
4. Integrate findings from strategy into community flood management initiatives
5. Continue generating public awareness about coastal flooding and sea level rise
6. Coordinate coastal flood management with different levels of government

The strategy proposes creating comprehensive adaptation plans for low-lying areas where coastal flooding is anticipated to reach further inland than waterfront properties. These areas will require further technical analysis and assessment, as well as further consultation with affected communities. These areas include: Horseshoe Bay, Stearman Beach, Dundarave, Ambleside, Capilano, Norgate and Mosquito Creek, Mission-Lonsdale, Lynn Creek, and Maplewood.

The strategy proposes some preliminary concepts for each area that includes a combination of options, including nature-based designs, raising land through development, building dikes, and flood-proofing buildings. The strategy also proposes managing risk posed by sea level rise by using findings to inform regulation and policies, such as bylaws, Development Permit areas, land use planning, and infrastructure planning. Consideration will be given to areas both within and beyond the comprehensive adaptation plan areas.
The Strategy went through an extensive engagement process with the public, Squamish Nation membership, port terminal operators, and other key groups. Engagement findings were used to refine the adaptation planning resources in the Strategy.

With a vision “to work together to reduce risk and strengthen community resilience to sea level rise across the North Shore”, the partners acknowledge that sea level rise does not respect jurisdictional borders between their communities and that their collaboration strengthens their planning efforts. The Strategy includes an Implementation Plan outlining the next steps to implement the Strategy and recommendations for measuring adaptation progress over time. The Strategy provides a toolkit of adaptation measures and policy basis and concepts for coastal adaptation to support North Shore partners in developing adaptation strategies tailored to their local contexts. The Strategy provides a platform of shared understanding about sea level rise risks and consequences and the various options available. These measures are outlined at a high level and many require additional study, feasibility, and design before they can be implemented. Furthermore, while this shared understanding provides an important starting point, ongoing coordination between North Shore partners and other actors will make it possible to develop adaptation measures that are compatible along the shoreline and jurisdictional boundaries. Coordination can also create opportunities for cost-sharing and efficiencies and support consistent messaging around risks and action across the region.

The Strategy recommends a set of potential indicators for tracking implementation progress and outcomes of sea level rise adaptation. Suggested progress indicators are be categorized into two groups:

• Process Indicators that monitor the progress of implementing the Strategy in alignment with the strategic vision and principles; and
• Outcome Indicators that evaluate whether progress towards adaptation is being achieved. Since sea level rise adaptation is a long-term process, it is not anticipated that the whole North Shore will achieve full adaptation within the next 10 years (the timeframe of this Strategy).

The Strategy recommends that the North Shore Sea Level Rise Adaptative Management Strategy be reviewed by the Working Group in 10 years (2030), or within 10 years if major changes occur, such as changes to sea level rise projections, that would trigger a review.

The Strategy was finalized by all partners in February 2021 and the North Shore partners recognize that adapting communities to sea level rise is a long-term process. Further technical work will be required to consider the options for each area, along with estimated costs. The implementation of the Strategy intends to further engage Tsleil-Waututh Nation (TWN is undertaking a separate Climate Change Resiliency Planning program that also considers sea level rise adaptation) and other key North Shore groups (e.g. CN Rail). This Strategy is intended to provide guidance for the next 10 years and is considered an initial step in what will likely be a multi-decade collaborative initiative. The strategy aims to address sea level rise adaptation from a variety of perspectives, but a major focus is on flood risk assessment and reduction through the application of a variety of policies, land use planning, building floodproofing, and structural flood protection measures.

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