Indigenous Services Canada, in partnership with coastal First Nations in British Columbia, is seeking to understand the risks posed to infrastructure and assets in coastal communities from flooding due to climate change, storm events, and earthquakes.
CWA was commissioned to work with communities located on the north coast and mid-coast of British Columbia to identify key infrastructure and determine the extent of potential flooding caused by sea level rise, tsunamis, storm surges, and wind events. To accomplish this, CWA created two-dimensional hydrodynamic models, which were developed using topographic, hydrographic, and historical storm data. Simulations were run based on specific design criteria to predict wave run-up and inundation for each community. Using the results of the simulations, flood hazard maps were produced to identify at-risk infrastructure and assets to aid communities in long-term planning initiatives.
CWA met with community stakeholders to discuss the intentions of the study and to identify critical infrastructure and assets including:
- Water and sewer systems.
- Electrical and power stations.
- Emergency response facilities such as fire halls and medical centres.
- Public buildings such as schools, churches, and administration offices.
To establish the locations of identified critical infrastructure, georeferenced digital aerial images and topographic maps were obtained via LiDAR and camera systems mounted to the underside of an aircraft that was flown over each community. The survey data obtained was used to establish the baseline topography for the hydrodynamic models.
Two scenarios were modelled for each community, both of which incorporated the predicted climate change-induced sea level rise for the year 2100, as follows:
- Site-specific tsunamis corresponding to 1 in 2,475-year earthquake events.
- Storm surge and wind waves corresponding to 1 in 200-year events.
Three different earthquake locations were considered for scenario 1, including two hypothetical cases along the Queen Charlotte fault off the coast and to the south of Haida Gwaii and one historical case simulating the 1964 Great Alaska Earthquake. The selection of the specific earthquake locations was based on a review of the probabilistic seismic data as well as the identification of which locations would likely cause the largest waves at the communities.
For scenario 2, storm and local extreme wind events characterized by wind and pressure changes were modelled simultaneously to simulate storm surges and wind waves. The wind direction and magnitude were determined based on historical data from the nearest applicable weather stations.
From the simulations, levels of water inundation and wave run-up were established and overlain onto the georeferenced aerial images to produce flood hazard maps, which were used to identify the critical infrastructure and assets that are at risk of damage from potential flooding.
These maps can be used by community planners to generate long-term planning initiatives to prepare for and mitigate the consequences of climate change in support of safe and resilient communities.