10 years later: Ted Buehner recalls Oso landslide sweeping everything in its path

It was a Saturday morning. The sun was peeking through the clouds, offering a pleasant early spring day. The North Fork of the Stillaguamish River was receding in the wake of three days of dry weather following a wet winter.

Then, just past 10:30 a.m. that morning, a large segment of a hillside gave way, surging across the valley just east of Oso in less than 60 seconds, sweeping away everything in its path including the Steelhead neighborhood.

Finding Summer: A brother’s mission to find his sister after the Oso slide

It remains unclear what triggered the massive slide. Was it the river nibbling at the foot of the hillside? Was it the weight of all the winter rainfall soaked into the hillside? Were other factors involved? Geologically going back centuries, similar landslides had occurred in the valley.

The landslide temporarily blocked the river. Water in the river backed up, flooding homes just upstream of the slide area.

What happened on the day of the Oso landslide?

As the day wore on, concerns about the landslide-blocked river steadily rose, raising theories about the blockage suddenly giving way and producing a flash flood-like surge of water downstream. There were some authorities and downstream communities who felt it was imperative to evacuate from the threat of flash flooding in Arlington and downstream into Stanwood, adversely impacting the Interstate 5 (I-5) bridge over the Stillaguamish River.

At the time, I was the Warning Coordination Meteorologist with the National Weather Service (NWS) in Seattle, a key liaison position with the emergency management community. From home on that Saturday, I was collaborating throughout the day with the NWS Seattle team on duty. That group also worked with the NWS River Forecast Center (RFC) in Portland on what are called dam break scenarios.

The RFC conducted several scenarios throughout the day as the situation evolved and found that when water managed to create a gap in the landslide blockage, the threat of downstream flash flooding was quite low.

The emergency manager for Snohomish County, John Pennington, called me at home late that afternoon to ask whether he should authorize activating the Emergency Alert System (EAS) to evacuate downstream communities and close the I-5 bridge as a result of flash flooding. Given the NWS information collected throughout the day, I advised him of the dam break scenario results and he chose not to activate EAS. That decision turned out to be wise. Late in the day, water in the river did manage to create and flow smoothly through a gap in the landslide debris, easing fears of flash flooding downstream.

During the initial response and six-week recovery efforts at the scene, spring showers and even a few thunderstorms hampered crews at work. Yet, response crews and their support teams did a monumental job with the recovery of those lost.

In September of that year, rebuilding State Route 530 was completed and fully reopened, and a roadside memorial was put in place near the landslide site, marked by 43 trees that honored those lost in the landslide. A mailbox sculpture was added in 2019.

More on the Oso disaster: Firefighter recalls days spent responding to tragic Oso landslide

Oso, 10 years later

On Friday, March 22, a dedication ceremony will be held for a new expanded SR 530 Slide Memorial. The $5 million project funded in large part by donations was started in 2019, and designed and installed by local artist Tsovinar Muradyan and the Classic Foundry. Many dignitaries including Gov. Jay Inslee, will help dedicate this new memorial.,

The memorial has exhibits that honor the victims, survivors and those who responded to the catastrophic event, serving to educate visitors about the disaster. Donations continue to be accepted at the Oso Landslide Memorial website.

On Friday, March 22, let’s remember and honor those who lost their lives on this date 10 years ago.

Ted Buehner is the KIRO Newsradio meteorologist. You can read more of Ted’s stories here and follow him on X, formerly known as Twitter.