A tsunami alert was mistakenly broadcast on weather radio channels in the region earlier this week, but a seismologist says the error still serves as a good reminder of the threat that exists around large, inland bodies of water like Okanagan Lake.
Before it was yanked off the air, the warning followed automated forecasts on Weatheradio Canada stations in Penticton (162.475 MHz) and Kelowna (162.55 MHz) on Tuesday and Wednesday.
“A tsunami alert has been issued for locations in your broadcast area by the Provincial Emergency Program. Stay tuned for further information,” the pre-recorded announcement stated.
The stations, which can only be heard on VHF radios like those used by first responders, are run by Environment and Climate Change Canada and tied into warning systems operated by other agencies, such as the U.S. National Oceanic and Atmospheric Administration.
“The announcements that a warning has been issued would only be triggered to play once when the transmitter first received a warning from the storm prediction centre. The warning itself would then be included in the program cycle,” ECCC spokesperson Chelsea Steacy explained in an email.
“It appears that the configuration file that controls the lineup of forecast messages became corrupted and inserted one of these pre-recorded announcement messages into the regular program cycle – in this case the message stating that a tsunami alert had been issued.”
Tsunamis are typically associated with earthquakes at sea that move the ocean floor and displace large volumes of water, in some cases creating tidal waves that cause great damage when they reach shore.
While tsunamis also happen on lakes, they’re more likely to result from weather-driven landslides that rush into the water and make waves, according earthquake seismologist John Cassidy, who works for Natural Resources Canada.
“They’re really rare events,” he said, “but these events can and do happen.”
One notable example occurred in December 2007 on Chehalis Lake near Chilliwack, when a steep hillside let go and sent approximately three million cubic metres of debris – enough to fill 1,200 Olympic-sized swimming pools – into the water.
Three campgrounds were destroyed, along with approximately 25 hectares of forest.
“It was fortunate that it was in the wintertime, because the wave that was generated was 10 metres in height and ran up to the 38 metres on the other side of the lake,” said Cassidy.
This past November, an estimated 7.7 million cubic metres of debris poured into Bute Inlet, approximately 200 kilometres north of Vancouver, as a result of a landslide that went undetected until a helicopter pilot spotted the flotsam from the air.
Farther back in time, a 7.3 magnitude earthquake set off hundreds of landslides on Vancouver Island, including one that blocked off a river and created the aptly named Landside Lake, which is now a popular recreational spot in Strathcona Provincial Park.
Such earthquake-driven landslides are also possible on Okanagan Lake, said Cassidy, but the risk is low because this is “a relatively quiet earthquake hazard region.”
Still, he cautioned anyone who sees a landslide or feels the earth shaking while their near water to head for higher ground immediately.
“It would be a really rare event,” said Cassidy, “but it’s a good reminder.”
Meanwhile, the two Weatheradio Canada transmitters that broadcast the mistaken tsunami warning this week are among 48 of 230 across the country that are under consideration for decommissioning by Environment and Climate Change Canada.
The agency collected feedback on the proposal last year, but hasn’t yet decided what it’s going to do, according Steacy, its spokesperson.
“Further consultation will be conducted within the next few months to obtain a more complete picture of the extent of Weatheradio usage in regions where concerns about decommissioning were raised,” she said in her email.
“ECCC will not proceed with decommissioning prior to a full investigation of user dependencies.”