Chilliwack and B.C. no stranger to mudslide risk

Landslides and land instability profile the Chilliwack region with the potential for dire consequences.

The fatal mudslide in Snohomish County, Washington, came without warning and took no more than one minute to rip out homes and kill at least 24 people. At the time of writing, some 90 people remain unaccounted for.

The devastating slide has all but obliterated the tiny town of Oso, 88 kilometres north of Seattle. One geologist reported that the slide was over 1,300 metres wide and that in places debris was over 10 metres thick. Nearly 50 structures have been destroyed.

Horror has given way to despair as desperate survivors wait for word of missing loved ones while the grim tally mounts. They cling to hope, praying for miracles, as rescuers struggle through the quagmire of dangerously unstable mud pushed up into berms of clay and quicksand. Navigating over that terrain is both agonizingly slow and treacherous. Rescuers were helping rescuers to stay safe.

The cause for this tragedy has been excessive rains which saturated the land making it extremely unstable. A smaller slide happened in 2006 and a past report allegedly warned of the potential for catastrophic failure. When the slope let go, it released mud, rock, trees, and debris that blew down the hillside at a staggering 20 metres a second. Anyone in its path didn’t stand a chance.

Landslides are no stranger to people in B.C. In January 2005 a mudslide in North Vancouver destroyed two homes and killed a woman sleeping in her bed. In 2008 the Sea to Sky highway near Whistler was closed for five days after a massive rockslide almost took out a passenger bus. It happened again in 2011 when a rockslide near Lions Bay destroyed a vehicle and released rocks the size of cars down the slope.

In July 2010 an aging dam gave way near Oliver, releasing mud, water, trees and debris down the hillside and destroying five homes and several farms. A month later, a two-kilometre wide landslide in the Pemberton River Valley put one thousand residents on flood alert. In July 2012 four people died when a massive landslide destroyed several homes in the Kootenay community of Johnson’s Landing. And just two months ago, a rockslide on Highway 3 near Keremeos closed the route completely.

Landslides and land instability profile the Chilliwack region with the potential for dire consequences. In June 2011 a landslide east of Chilliwack roared across four lanes of the highway and onto the railway track. It slightly injured one woman whose car was rolled by the debris.

“There is a history of small landslides and debris flows in the Chilliwack River valley between Slesse Creek and the mouth of the valley,” said Dr. John Clague, Canada Research Chair in Natural Hazards Research, Simon Fraser University. “Although none has been fatal, a few have caused property damage. Property owners are exposed to a not well-documented risk from landslides and debris flows from the valley walls; these steep slopes are developed in glacial sediments. There is also the possibility that a landslide in these sediments could block or impede the flow of Chilliwack River, with downstream consequences.”

Many slides are triggered by excessive rains that saturate and destabilize the ground but earthquakes, volcanoes, and extremes of alternate freezing and thawing are also triggers. In the Fraser Valley, as in western Washington, we’ve had an excessive amount of rain this month. As at March 25, Chilliwack had received 247 mm, well in excess of the March average of 176.l mm.

“Because the degree of risk (in the Chilliwack valley) is ill-defined, and in light of the landslide at Oso, Washington, it is my opinion that the Fraser Valley Regional District should commission a geotechnical study to evaluate the hazard,” said Clague.

Just Posted

Opioids, meth, firearms seized at known Chilliwack drug house

Home on Broadway Street raided on Feb. 15 where homicide occurred Jan. 31

GW Graham basketball girls savour Fraser Valley championship

It’s been a long wait for the Grizzlies, who lost the FV title game the last two seasons.

Chilliwack Curling Club holding open house

If you’ve ever wanted to try the sport, the club invites you to take the plunge this weekend.

Chilliwack MLA John Martin says NDP budget will hurt business, punish taxpayers

‘Family-owned businesses will struggle to respond to this’

Chilliwack-Kent MLA decries ‘classic, big tax-and-spend’ NDP budget

Laurie Throness says budget relies on strong economy but contains no ideas to help it grow

VIDEO: Top 10 B.C. budget highlights

The NDP is focusing on childcare, affordable housing and speeding up the elimination of MSP premiums

Team USA beats Canada 3-2 on the shootout to take home Olympic gold

Americans win their first gold medal since 1998

Two Haida men detained for crossing U.S.-Canada border

Edenshaw and Frisby travelled from Alaska to Prince Rupert for the All Native Basketball Tournament

Alberta takes out full-page ads in B.C. over strained relationship

It’s the latest move between the two provinces over progress on Trans Mountain pipeline expansion

B.C. teacher suspended over allegedly using N-word in worksheets

Trafalgar Elementary teacher under investigation by Vancouver School Board

Toddler swept away in Ontario floods

Toddler missing as flooding forces thousands from their homes in Ontario

BC BUDGET: New money helps seniors’ care shortage

Job stability for care aides key to recruitment, union leader says

Mixed messages on B.C.’s efforts to cool hot housing market

Economist says undersupply of homes in Metro Vancouver, Victoria and Kelowna will keep prices high

Foot found near Victoria belonged to missing Washington man

Coroner says no foul play suspected in death of 79-year-old Stanley Okumoto

Most Read