November 17, 2024 Tsunami: Columbia River Valley, WA, United States

Reference #13858:

Earthen cliffs directly west of Colville Flats Beach gave way this weekend, causing a sizable wave in Lake Roosevelt that damaged several area docks downstream from Kettle Falls.

“It looks like a wall of water went up into the trees,” Weatherman said. “As the water returned back, it took out tons of and tons of trees and vegetation. Actually, it looked almost like an avalanche. All the debris was on the back side of the trees, which is a thing that big waves do.” Even the water depth changed along the shoreline, he said. “When we pulled up in our boat, areas in front of the slide that had been 3 to 5 -feet deep are now 10 to 15 -feet deep,” he said. “It displaced the river bottom, as well as the standing bank.”

“I’m going to say (the shore) lost 150 feet” back from the shoreline, he said. “There were trees on all of that area. All of that timber is in different states. Some of it’s buried, some is jammed into the bottom. Some of those were 70-foot trees and now only 15 feet are sticking out of the water.” Weatherman said it appears the slide caused a massive wave from north to south as the land gave way. It then surged east toward Colville Flats Beach. “Colville Flats was completely covered in water, and I think it took 10 years of accumulated debris there and refloated it,” he said. “The debris is everything from softball-sized to 70-foot trees and root balls.”

“I’ve seen two or three others, but not this big in terms of cubic yardage,” he said. “I’ve never seen a slide this tall. I’m going to say it was nearly 200-feet tall.”

Staci Lehman, spokeswoman for the Washington state Department of Fish and Wildlife, said the wave hit strong enough to dislodge a dock at Sherman Creek Hatchery, which is north of the slide. The wave sent a dock and several fish pens full of triploid rainbow trout for a ride. Sherman Creek Hatchery is located on the west side of Lake Roosevelt, the same side as the slide. It’s also located up a creek from a bay, meaning that the wave had to have come inland some way before it caused the damage. “We are not positive when it happened,” Lehman said. “One of our employees went to check on the net pens on Sunday morning. They saw that the dock had floated away.” Crews jumped in a barge and went looking for the dock, which was quickly located down river from the hatchery.

Reference #14153:

A pair of landslides, forming a single larger landslide complex, occurred on the west bank of Lake Roosevelt reservoir near Kettle Falls in a location locally known as Reed terrace on November 17, 2024. The landslides generated tsunamis within Lake Roosevelt that impacted shoreline areas within 2–3 mi of the slides.

Observed evidence includes scour; flattened (inundated) grasses; sand, gravel, and debris deposits; debris trapped in tree branches; and scarred tree bark. Based on these observations, we estimate the tsunami wave height was 11–14 ft above the lake level and tsunami runup (maximum height above lake level of tsunami inundation) was as much as ~47 ft in the most impacted area diminishing to no runup several miles up- and down-river of the landslides. The tsunami inundated as far as 800–900 ft from the shoreline in areas of flat topography

Note: Timing of landslides based on seismic signals 07:45am on 17 November LT and 04:13pm 17 November LT.

Note: only a subset of survey points (incl. highest elevation points) have been included in NCEI/WDS database