Sea Level Rise Update - 2020 CRD Coastal Flood Inundation Mapping Project (Staff Report)
A staff report from the Senior Planner providing an update on local initiatives and mapping projects related to Sea Level Rise and coastal inundation.
TOWN OF VIEW ROYAL
Planning and Development Report
TO: Committee of the Whole DATE: April 7, 2021 FROM: Jeff Chow, Senior Planner MEETING DATE: April 13, 2021
SUBJECT: Sea Level Rise Update - 2020 CRD Coastal Flood Inundation Mapping Project
RECOMMENDATION:
THAT the April 7, 2021 report from the Senior Planner title “Sea Level Rise Update - 2020 CRD Coastal Flood Inundation Mapping Project” be received for information.
CHIEF ADMINISTRATIVE OFFICER’S COMMENTS:
I concur with the recommendation.
DIRECTOR OF DEVELOPMENT SERVICES’S COMMENTS:
I concur with the recommendation.
PURPOSE OF REPORT:
To provide an update on local initiatives addressing the potential impacts of coastal inundation from Sea Level Rise prior to commencing a Sea Level Rise and storm surge mitigation and adaptation policy.
BACKGROUND:
Increased awareness of global Sea Level Rise over the past two decades led to a 2018 amendment to the 2004 Provincial Flood Hazard Area Land Use Management Guidelines. Many coastal communities are working to understand what the potential impacts of coastal inundation from Sea Level Rise might be and how to address them. Accordingly, development of a Sea Level Rise and storm surge mitigation and adaptation policy is identified in the Strategic Plan.
a. Provincial Guidelines
Staff presented a report at the November 14, 2017 Committee of the Whole meeting on amendments to the 2004 Provincial Flood Hazard Area Land Use Management Guidelines that came into effect January 1, 2018 (excerpt in Attachment 1). The guidelines were amended to include sea level rise as a consideration for establishing Flood Construction Levels (underside of flooring systems in buildings) and Flood Setbacks for new development in coastal areas. The guidelines recommend planning for a global Sea Level Rise of 0.5m by 2050, 1.0 m by 2100 and 2.0m by 2200, all relative to the year 2000. The guidelines have provisions for accessory buildings, carports, garages, entryways, and renovations to existing buildings (maximum 25% additional floorspace).
The guidelines are an important consideration in land use applications for rezoning, subdivision, development permits, and building permits. The Town has been following them by requiring development applicants to provide recommendations from qualified engineers for Flood Construction Levels and Flood Setbacks with consideration to coastal hazards. Qualified engineers base their recommendations on the Provincial guidelines and additional professional practice guidelines from their professional body, Engineers and Geoscientists BC.
b. Mapping
To understand the potential impacts on coastal communities, the Province conducted high level mapping in 2012, but it was at a 1:250,000 scale that was not useful for local governments. The Capital Regional District (CRD) Sea Level Rise Planning Project is a multi-year research and analysis project to understand potential implications of future sea level rise inundation and to identify potential adaptation approaches that are appropriate for the region. The Coastal Sea Level Rise Risk Assessment report was produced in 2015 looking at potential economic impacts on key public infrastructure and private assets in 24 focus areas (see executive summary in Attachment 2) including Portage Inlet. It found different levels of inundation may occur across the CRD because of varying topography, with principal impacts on network infrastructure for water and wastewater, and some road bridges.
DISCUSSION:
This report discusses the following:
- 2020 CRD Coastal Flood Inundation Mapping Project
- Implications for the Town
- Regional response
- Next steps
1. 2020 CRD Coastal Flood Inundation Mapping Project
The CRD Coastal Flood Inundation Mapping Project (executive summary in Attachment 3) is a report conducted in partnership with Victoria, Saanich, and Oak Bay municipalities. The methodology involved dividing the shorelines into reaches, examining a sample transect within in each reach to project the extent of inundation, mapping the potential extent under different scenarios (including tsunami risk) and estimating general Flood Construction Levels. There are differing professional interpretations of the methodology from the 2017 Flood Mapping in BC - APEGBC Professional Practice Guidelines V1.0 and there may be some follow-up work to refine the assumptions. Staff is continuing to monitor this discussion of the underlying assumptions.
2. Implications for the Town
The full report estimates Flood Construction Levels along Esquimalt Harbour and Portage Inlet under different Sea Level Rise scenarios: no change, 0.5m (Year 2050), 1.0m (Year 2100) and 2.0m (Year 2200). Detailed mapping for Portage Inlet (Attachment 4) shows potential inundation impacts for the Provincial guidelines’ target year of 2100. There is not detailed mapping for the Town’s coastline on Esquimalt Harbour. Long term impacts to a specific property will depend on physical shoreline characteristics, proximity to the sea edge, and elevation above sea level.
- Low-lying properties close to the sea may be subject to temporary (tidal) or permanent inundation.
- Properties on coastal bluff may be subject to impacts from erosion.
- Properties set back from the sea may be subject to effects from wind and waves.
This report and the 2015 Coastal Sea Level Rise Risk Assessment report highlight several issues to explore for the Sea Level Rise and storm surge mitigation and adaptation policy, including:
| Issue | Considerations |
|---|---|
| Flood Construction Level | How to address height variance requests when Flood Construction Levels result in challenges for compliance with Zoning Bylaw requirements. |
| Setbacks | How to address setback variance requests when Flood Setbacks result in challenges to site a building in accordance with Zoning Bylaw requirements. |
| Soil Deposit | How to address potential demand to alter or raise the grades in yards that could be affected by Sea Level Rise. |
| Development Permit Area guidelines | • Including Sea Level Rise and storm surge considerations for land along the shoreline. • Consider a guideline to replace existing sea walls and other hard armoring with natural restoration. |
| Existing Town infrastructure | Mitigation strategy for existing roads, parks, servicing, and other infrastructure vulnerable to Sea Level Rise and storm surge impacts. |
In the interim, the CRD report is a valuable reference for staff’s continuing practice of requiring covenants for Flood Construction Levels and building setbacks relating to subdivisions (by the Approving Officer) and building permits (by the Building Official) near the shore. The report will also be useful for planning new infrastructure.
3. Regional Responses
Municipalities in the region are taking a variety of approaches, including the following:
- Victoria is considering a policy for a Flood Construction Level.
- Colwood has commissioned the consultants for the CRD project to conduct a more in-depth and more site-specific study to consider a Flood Construction Level policy that considers both Sea Level Rise and tsunami risk. The report is expected to be published in a few months.
- North Saanich has pioneered work in the region beginning 2013 and considered development permit areas before recently pivoting towards marine area Official Community Plan amendments and a Coastal Flooding Mitigation Bylaw – currently on hold while the CRD report is examined.
- Esquimalt is currently following the Town practice in using the CRD report as a reference when considering development and building applications.
4. Next Steps
The CRD Coastal Flood Inundation Mapping Project will be a key reference for the Sea Level Rise and storm surge mitigation and adaptation policy. Staff proposes to follow up with options for policy development. At that time, staff can provide another update if any further information is received from the CRD Coastal Flood Inundation Mapping Project and if the Colwood report is available as an example of a comprehensive approach.
RECOMMENDATION:
THAT the April 7, 2021 report from the Senior Planner title “Sea Level Rise Update - 2020 CRD Coastal Flood Inundation Mapping Project” be received for information.
SUBMITTED BY: Jeff Chow, MCIP, RPP Senior Planner
REVIEWED BY: Lindsay Chase, MCIP, RPP Director of Development Services
Attachments
- 2004 Provincial Flood Hazard Area Land Use Management excerpt (11 pages)
- 2015 Coastal Sea Level Rise Risk Assessment report executive summary (2 pages)
- 2020 CRD Coastal Flood Inundation Mapping Project executive summary (20 pages)
- 2020 CRD Coastal Flood Inundation Mapping Project excerpt – mapping (2 pages)
Document Images
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