November 2, 2012
Ranger Beason checks a "trim line" caused by the flood along the Nisqually River near Cougar Rock. (Laura Walkup)
Mount Rainier National Park geologist Scott Beason reports that a small glacial outburst flood occurred at Mount Rainier National Park on Saturday, October 27, 2012 at approximately 9:00 PM. This event, while significant, was localized in scale, caused no damage to park facilities, and was not volcanic in origin. It likely originated from the Nisqually Glacier as result of moderate to intense rainfall. A stream gauge located at Longmire registered a 2.8 foot (0.85 meter) rise in river water level between 8:30 and 9:45 pm and the spike was seen on other gages downstream of the park. Field data concur with the stream gage and show evidence of a several-foot surge of water in the Nisqually River.
While this event was small, it highlights one of the many hazards at Mount Rainier. It also shows that potentially destructive and hazardous events can occur even during “small” storms that are common in the fall and winter at Mount Rainier. Workers and visitors near rivers should always be aware of geologic hazards. Remember, if you feel the ground shaking or hear a freight train coming down the valley, get uphill as quickly as you can!
Outburst floods have happened in the park before. A series of such floods in the 1980s and 90s washed out parts of the West Side Road, and in 2005, a debris flow on Van Trump Creek was captured on video as it roared over Christine Falls. You can see that video on YouTube at http://youtu.be/SrYqJlCuppA.
Source: Mount Rainier National Park (facebook)