Rising sea levels due to climate change are expected to increase the flood threat for the District of Squamish and Howe Sound. The community is responding by developing an updated flood response plan that works with nature to protect communities and economic activity. Risks due to sea level rise are significant and the fundamental problem of human settlement on the flood plain remains despite much planning and mitigation.
Author: David Roulston, Municipal Engineer, District of Squamish
Reviewer: David Roche, Senior Water Resources Engineer, Kerr Wood Leidal Associates Ltd.
Banner Photo Credit: David Roulston
Squamish is located at the north end of Howe Sound in a floodplain with five major river systems and is therefore exposed to both coastal and river flood hazards. Climate change is expected to increase the risk of flooding due to impacts on weather systems (e.g., rainfall) and sea level rise. The Provincial Government issued guidance for communities to begin planning for one metre of sea level rise by year 2100 and two metres by year 2200 (Figure 1). Sea level rise of this magnitude would have significant impacts on Squamish, since the existing downtown core and surrounding area sits at an elevation just above present-day sea level and significant coastal development is anticipated over the next 10 to 20 years.
To appropriately manage community flood risk, the District of Squamish is completing an Integrated Flood Hazard Management Plan (IFHMP) that will improve community flood protection while accommodating anticipated community growth. The project includes a comprehensive analysis of flood hazards, provides river and coastal flood mitigation strategies and produces a final plan that summarizes recommendations on land use, flood policy and structural (dike) improvements.
The final IFHMP will develop flood management policy related to appropriate land use, establishing flood levels for new development, identifying and preserving floodways and determining a prioritized plan for ongoing dike improvements. The final IFHMP will be utilized for capital planning, development review, and community planning until the next planned update in five to 10 years.
Why is it important?
One of the most important climate change impacts is sea level rise due to warmer ocean temperatures and melting of polar ice. The Squamish District is protected by a system of dikes and floodgates constructed over the past century with the majority built in the 1970s and 1980s. Downtown Squamish is partially protected by a sea dike, however, some sections remain incomplete and must be upgraded as soon possible to protect both existing and planned new development. Without mitigation, the area of Squamish that could be impacted by coastal flood hazards based on one metre of sea level rise is significant (Figure 2), and includes several large coastal properties near downtown Squamish that are expecting significant redevelopment. Over the next 20 years, development proposals like the Squamish Oceanfront Development lands at the south end of downtown are expected to accommodate up to 6500 new residents and direct employment of more than 2300 jobs within the coastal floodplain.
New coastal development provides both opportunities and challenges for Squamish. The development will enhance the community’s connection to the coast, creating both economic and social opportunities. However, new development must overcome many technical challenges to mitigate both environmental impacts and long-term community risk. The analysis and recommendations of the IFHMP provide the necessary foundation that will allow new development to proceed in a safe and sustainable manner.
First Nations Connections
Skwetsás – Squamish Great Flood Story
“In the long ago, in the time of our Ancestors, the waters rose up. The Squamish River got higher and higher. It rained and rained, big drops, bigger than two hands together. And the drops kept falling and falling. And the water rose up and up until it covered Mumtem (Grouse Mountain) and all the little mountains. It covered all the mountains except three peaks: Xwsa7k (Mount Baker), Nch’kay (Mount Garibaldi) and Sxe’ltskwu (mount Sakus) way up the Squamish River. The people in their canoes rose up and up and as they steered through the cedar trees, one of them broke off the branches and another twisted them and made a big cedar rope about four inches thick. They tied the rope around the top of Mount Garibaldi to make the canoe fast. The remnants of this rope are still present at the very top of that peak today.” – As told by Xatslanexw-t (August Jack), Squamish Nation, 1867-1967.
– reproduced with permission from “Where Rivers, Mountains and People Meet”, Squamish Líl’wat Cultural Centre
What is the current status?
The District of Squamish completed its first Flood Hazard Management Plan (FHMP) in 1994. The 1994 FHMP included updates to Provincial floodplain mapping as well as recommendations on land use management, flood related policy and dike improvements. Since the original FHMP, the community has experienced significant growth and new information and technology have become available. These are being incorporated into an updated plan to ensure that the District is using the best information to inform its decisions. The updated IFHMP utilizes new technical data (river flows, wind speeds, tide levels, and bathymetric/topographic information) as well as state of the art technology and software to produce the river and coastal flood mapping that informs the resulting mitigation strategies.
Ongoing coastal processes can result in a natural loss of habitat. In addition, construction of sea dikes to protect new and existing development can impact environmentally sensitive coastal areas by disturbing, altering or encroaching into natural habitat. The IFHMP seeks to recognize and preserve the environmental value of the estuary and other sensitive areas while providing important community flood protection. A significant example of this is included in the community’s long-term sea diking options that envision a Green Shores approach along environmentally sensitive areas such as the Squamish estuary (Figure 3). A sea dike that incorporates this treatment would utilize shallower slopes and “bio-engineering” (reinforced vegetation) to provide the required erosion protection. In addition, the District seeks to preserve the sensitive and valuable habitat and manage flood risk by concentrating growth in the existing downtown and to avoid development within the estuary’s Wildlife Management Area.
What can you do?
Some Actions Contributed by CORI
Individual and Organization Actions:
- Become familiar with the current IFHMP. Be aware of flood hazards in your area and be prepared for an emergency at your home and workplace.
- Help prevent climate change by producing fewer greenhouse gasses. Adopt green policies and practices within your organization.
Government Actions and Policy:
- Conduct further studies on impacts of flood control on environmental processes and continued alternatives that work with nature.
- Improve strategic dike protection for the community using techniques that reflect a Green Shores approach.
- Continue to raise awareness of flood risks and responsible watershed stewardship.
- Incorporate latest climate change hazard assessments into emergency response planning.
- Complete complementary flood studies for unique hazards beyond the scope of the IFHMP as funding permits.
- Maintain a toolkit (e.g., models, guidelines, and best practices) to support staff analysis and recommendations to Council.
- Promote closer relationships with stakeholders from the river headwaters to Howe Sound to facilitate working together.
- Continue to renew the IFHMP every five to 10 years.
- Manage development in flood hazard areas through updated OCP, DP guidelines, bylaws, etc.
- Limit continued densification in the highest hazard areas.
- Begin planning for opportunistic retreat of key facilities and infrastructure from high flood hazard areas at the end of their service life.
- Action and policy to reduce greenhouse gas emissions and meet or exceed current targets.