Now Playing:


Environment | Land

What Climate Change Could Mean for Northwest Landslides

One of the busiest stretches of railway in Washington State runs along the shores of Puget Sound between Seattle and Everett. It’s also one of the most high-risk corridors for landslides.

Every day about 40 trains full of freight or passengers travel these tracks, en route from Seattle and points south toward Canada.

But for the moment, anyway, you won’t hear any approaching trains. Instead, you’ll hear some sea lions bantering offshore and some men in orange vests operating heavy machinery a little ways down the track.

A front end-loader is removing debris. A massive truck overflowing with exposed tree roots and mounds of earth rolls past, clearing the tracks after a recent landslide.

Gus Melonas is spokesman for BNSF Railway. He says this has been a bad year for slides.

Gus Melonas. Credit: Ashley Ahearn

“This would rate right at the top – definitely top five as far as slide after slide – some feel top three,” he says.

That’s top three worst years for landslides in BNSF’s recorded history. The company has been keeping a tally since 1914.

A massive landslide that pushed 200,000 cubic yards of earth down the west side of Whidbey Island grabbed national headlines in March.

Landslides have also caused numerous delays in passenger and freight rail along Puget Sound.

The winter of 2012-2013 has been one of the worst on record for landslide destruction. And that has some wondering if the problem will get worse in the Northwest as a result of climate change.

Landslides are caused by a lot of different things: Increases in housing development on bluffs, changes in vegetation.

But ultimately, what causes a landslide is gravity, according to Jonathan Godt, a scientist with the US Geological Survey who has studied landslides in Western Washington.

“You’ve got a steep slope and gravity wants to pull everything down and when water enters the soil it changes the stress of the soil,” Godt explains.

That’s right, water stresses out soil. It pushes the particles apart, weakening the composition of say, a bluff overlooking Puget Sound, and making the soil heavier with moisture.

Climate change experts predict that in the Northwest we could see more precipitation overall, with heavier downpours and storm events.

In Washington the average annual precipitation has increased by about one-third of an inch each decade since the beginning of the 20th century. And this winter saw above average rainfall in the north Puget Sound region. That’s where BNSF says 95 percent of its landslide problems have occurred.

Story continues below…

Rain Keeps Falling

The blue line represents normal precipitation levels, the red line represents actual precipitation for Paine Field in Everett.

Source: University of Washington Department of Atmospheric Sciences

“That has certainly arisen as a very prominent issue and one for which there is a very clear climate connection,” says Lara Whitely-Binder with the Climate Impacts Group at the University of Washington.

Whitely-Binder says that while you can loosely tie individual rain events to mudslides - the USGS has done research to correlate precipitation levels and likelihood of a slide in the Seattle area - there’s no way to prove that climate change is to blame for this year’s bout of landslides.

Story continues below…

The Rain-and-Landslide Connection

This graph shows how the amount of precipitation correlates with the likelihood of landslides.

landslide threshold
Source: USGS

Landslides are nothing new for the Northwest. BNSF Railway has documented 900 slides on its tracks in the past 100 years.

But Whitely-Binder says there could be more wet winters like this past one.

“We would anticipate seeing a greater risk of landslides moving forward in time,” she says.

The Washington State Department of Transportation had 55 rail cancelations and 63 disruptions due to mudslides in 2012.

Carol Lee Roalkvam is the lead on environmental policy at WSDOT. She co-authored an assessment of its vulnerability to climate change.

“We’re aware now of more upriver flooding than we’ve seen in the past,” she says. “More extreme rain events – the sudden and intense rain that we’ve been experiencing more frequently so a lot of the state routes are vulnerable to landslides today and the projections are that those will be worse.”

But Roalkvam says she’s confident that WSDOT has strategies in place to respond to the infrastructure risks posed by climate change.

“I don’t think anyone can design themselves away from risk but I think we have a lot going for us here,” she says.

Melonas with BNSF agrees that there are a lot of near-term engineering solutions for the railway.

“We’ve made appropriate drainage, ditching, we’ve put up catchment walls, retaining walls, slide detection fences, the marine wall along Puget Sound,” he says.

Melonas adds that the railroad has spent “millions and millions of dollars” on rail upkeep – but he could not give a specific figure.

The federal government has provided $16.1 million to fund landslide reinforcement at 6 sites along this problematic stretch of railroad.

Meanwhile, passenger rail traffic is on the rise and if a proposed coal export terminal is built near Bellingham, rail use could jump as much as 50 percent above existing traffic levels here.

More Winter Rains

As this chart illustrate, the amount of precipitation recorded in winter months is trending upward — even though in any given winter, rainfall can be well above or below the historic average.

Source: NOAA

More News

More OPB