Real 65+ Foot Tsunami Dangers Hide in the Center of Washington

Most people worry about the Cascadia earthquake but this popular area in central Washington holds the actual largest danger for huge tsunamis.

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The Real Tsunami Danger in Washington State

Did you know that in 2009 a huge wall of water buried a popular campground in Washington State, washing multiple people offshore and causing over $250,000 in damage? It surprisingly didn't happen anywhere near the ocean but inland in the center of Washington State. These large tsunamis have been happening simi-regularly around this huge body of water in Washington State since around the 1950s. Multiple 65+ foot tsunamis have been witnessed in this area however common knowledge of this danger remains mostly hidden and forgotten. So what is causing these dangerous and sudden tsunamis if not earthquakes?

Lake Roosevelt Landslides Caused Large 65+ Foot Tsunamis

These sudden and very dangerous tsunamis are caused by huge landslides into Lake Roosevelt. If you are not familiar, Lake Roosevelt is located in the north-central part of Washington State and is over 150 miles long with over 126 square miles of water. One of the largest tsunamis recorded so far was a 65-foot tsunami that hit the small town of Lincoln, Washington on July 27, 1949. Disturbingly, another 65+ foot tsunami was created in 1952 near the Kettle Falls Bridge that was observed by people as far as 6 miles away. There have been at least 20 large landslides on Lake Roosevelt since 1950 with the most recent in 2009.

Porcupine Bay Tsunami: August 2009

In the early afternoon of August 25, 2009, a large number of people were enjoying the weather at Porcupine Bay also located on Lake Roosevelt when they heard a large crash. A 20-foot wave had formed after a large landslide fell into the lake directly across the shore from the campground. It took about 35 seconds for the large wall of water to hit the shore while people scrambled to get out of the lake from swimming and boating. When the tsunami hit the shore at over 12 feet high, it crashed through the campsite damaged the docks, several boats, and pulled many people out to water. The wave caused over $250,000 in damage but luckily no major injuries or deaths.

Not the First Time & Won't Be the Last Time

The reasons why Lake Roosevelt is so susceptible to large landslides/tsunamis have been known for years. Lake Roosevelt was created when the reservoir was filled with water behind the Grand Coulee Dam back in 1941. The water level is controlled by the dam and if changes too fast in a short period of time, it causes instability in the soft soil deposits that surround the lake. Basically, the water seeps into the soil and when removed it creates a gap and instability that can trigger these dangerous large slides. The problem has been mostly controlled by minimizing the amount of water level changes per day, however, it has not completely taken away the danger.

Evidence of Large Landslides Everywhere on Lake Roosevelt

Just look at the shoreline with Google Maps and you can see multiple places all over the lake with evidence of both past and recent large landslides. In the summer months, Lake Roosevelt is filled with campers and boaters all over the shoreline and campgrounds because of its amazing space and beauty. I spent most of my life camping, swimming, and boating on this lake and have never had a problem but now will be much more aware of the dangers around me.