For an uncomfortable couple of hours on Monday, 19 October—following a magnitude 7.5 earthquake off the coast of Alaska—British Columbia coastal communities held their breath awaiting confirmation of a possible tsunami. Fortunately, the strike-slip earthquake caused little damage and the resulting wave was minimal, but the episode served as a poignant reminder of the need to prepare for tsunamis.
Figure 1. One of thousands of sensors connected to Ocean Networks Canada’s internet-connected ocean observatory, this bottom pressure recorder gathers continuous real-time data about wave height and volume (depth 2195 metres).
Ocean Networks Canada (ONC) supports tsunami resilience in at-risk coastal communities by integrating high tech monitoring, real-time data and detailed geographic mapping into models for public safety.
ONC and Natural Resources Canada’s deep-sea and land-based sensors and oceanographic radars provide real-time observations of earthquake shaking and tsunami events. While seismometers measure an earthquake’s magnitude and inform British Columbia’s earthquake early warning system, wave heights are measured using bottom pressure recorders (Figure 1), which inform official tsunami alerts issued by Alaska’s National Tsunami Warning Center. Additional real-time wave height, ocean surface current and wind direction data are provided by high resolution coastal radars, including a state-of the art WERA system in Tofino.
The data from these monitoring systems combined with digital elevation models (DEM) of the coastline—both below and above water—provide important details on the behaviour of the tsunami waves as they move toward and impact densely populated coastlines.
Since 2016, ONC has been working with at-risk coastal communities—including Port Alberni, Tofino, Prince Rupert and Semiahmoo First Nation—to improve their understanding of the impact that a large tsunami wave could have on their unique coastline, community and infrastructure. High resolution DEMs are essential tools in tsunami forecasting and water level inundation modelling, contributing to tsunami preparedness, response, resilience and recovery.
In 2019 ONC collaborated with national and international partners to develop the first high-resolution DEM of a region surrounding the Semiahmoo First Nation on British Columbia’s lower mainland (Figure 2). This cross-border model integrates 40 distinct sources of land, river, and sea elevation and bathymetric data and covers an area 92 kilometres by 83 kilometres, revealing the complex geographic features that influence the behaviour of tsunami waves and currents as they move towards and impact the densely populated Salish Sea coastline.
Figure 2. The first high-resolution and seamless land-river-sea DEM of the cross-border Salish Sea region includes Vancouver, White Rock, Surrey and Whatcom County, Washington. Made up of ~40 distinct sources of data obtained from a wide variety of sources, project charter members include Natural Resources Canada, Defence Research and Development Canada, Geological Survey of Canada, Fisheries and Oceans Canada, University of Victoria, Province of British Columbia, Indigenous Services of Canada and ONC.
“Using science to improve our understanding of tsunami risks in our community will support improved emergency planning, risk awareness and development decisions,” says Paul Gadbois, Emergency Program Coordinator for Semiahmoo First Nation in British Columbia.
This Salish Sea DEM—which includes the most detailed understanding to date of the marine environment—supports public safety for at least 2.5 million residents in Greater Vancouver, a region that could experience strong currents and wave impacts in the event of a Cascadia subduction zone earthquake and resulting tsunami. Led by Natural Resources Canada, this DEM was collaboratively developed (Figure 3) as the first case study of the Canadian Safety and Security Program’s Coastal Flood Mitigation project, a nation-wide initiative to better understand Canada’s coastal flood risks launched in 2018.
Figure 3. The Salish Sea DEM was developed during a workshop in December 2019, thanks to expertise from NOAA’s National Centers for Environmental Information (NCEI). Twenty-five U.S. and Canadian participants included representatives from Natural Resources Canada, Royal Canadian Navy, Canadian Army, BC Ministry of Forests, Lands, Natural Resource Operations and Rural Development, Capital Regional District, District of Oak Bay, City of Victoria, District of Sooke, Township of Esquimalt, City of Surrey, City of White Rock, Northwest Hydraulic Consultants and NOAA Center for Tsunami Research.
A Canadian first: DEMs for Port Alberni
In 2016, ONC was instrumental in bringing DEM expertise to Canada by hosting the country’s first DEM training workshop with experts from NOAA's National Centers for Environmental Information (NCEI).
Figure 4. This tsunami inundation model shows the simulation of a buried rupture earthquake triggering a tsunami at Barkley Sound, including time of arrival, wave height and inundation maps. It was developed in 2016 by ONC, Emergency Management British Columbia, University of Rhode Island and the City of Port Alberni using earthquake source scenarios from Natural Resources Canada.
This ground-breaking workshop resulted in a Port Alberni region DEM—covering an area 32 kilometres by 7 kilometres—along with animated tsunami inundation model results (Figure 4). In 1964 this at-risk community was devasted by a tsunami following a magnitude 9.2 earthquake off the coast of Alaska (read more). These tsunami models were integrated into Emergency Management British Columbia’s first ever full-scale earthquake and tsunami response exercise in 2016.
Tofino
In 2015, ONC installed a high-frequency oceanographic WERA radar at Tofino’s Long Beach Airport to deliver real-time, continuous ocean wave height data (Figure 5). The system is capable of detecting large events, storm surges and tsunamis up to 80 kilometres from shore. These data could provide detailed local observations of incoming waves to support situational awareness, as well as beach closure and evacuation decisions. This WERA radar provided real-time data in 2016 when Typhoon Songda triggered a meteo-tsunami (read more).
“Real-time data from an instrument like the WERA radar supports critical and lifesaving decision making for coastal communities,” commented Keith Orchiston, Tofino’s Emergency Program Coordinator.
Figure 5. ONC’s high frequency WERA radar system was installed at Tofino Airport in 2015. This shore-based remote sensing system includes four transmitting and 12 receiving antennas that monitor ocean current speed in real-time.
Prince Rupert
In 2018, Prince Rupert worked with Northwest Hydraulic Consultants and ONC to better understand the port city’s tsunami risk and support their emergency response, public education and preparedness and long-term development planning (Figure 6).
Figure 6: Two planning scenarios were modelled for Prince Rupert using the Alaska 1964 and Cascadia 1700 earthquakes, as well as two sea-level rise scenarios, to model future conditions. Model outputs showed that the Alaska earthquake scenario would have more impact in the area than a Cascadia earthquake, with a maximum wave height of approximately 1.5 metres.
“The tsunami study that was completed in 2018 tested the different risk factors for our local area and helped us update our emergency plans,” said Chad Cooper, Prince Rupert Deputy Fire Chief. “We’ve been able to use the modelling in our outreach to waterfront industries and the community at large, and has really helped support better understanding of how different types of tsunamis might impact Prince Rupert.”
How can ONC help your community?
With several successful collaborations now under our belt, ONC is excited to continue working with coastal communities, including a new project with the Strathcona Regional District to develop a DEM for an area approximately 184km by 46km in 2022 to support a tsunami risk assessment for northwest Vancouver Island.
“We collaborate with local, national and international partners to help communities assess and understand the potential risks in their unique location, and to be better prepared in the event of a tsunami,” says Teron Moore, ONC’s Public Safety Program Manager. “We are excited to continue to support critical public safety programs by leveraging ONC’s deep scientific resources and sophisticated tsunami models to help protect lives and property from coast to coast to coast.”
ONC is available to support your community in assessing tsunami risk and developing emergency plans. For more information, contact Gordon Rees, ONC's Associate Director, Applied Science Solutions: gordrees@uvic.ca.
Watch Teron Moore's recent webinar "Shake Out, Don't Freak Out: Earthquake Preparedness, Risk and Response".
