USGS officials warn that the area is dangerous as additional debris flows can occur and stream water continues to move rocks and sediments. “If you feel ground shaking and hear rumbling like an approaching freight train, get off the valley floor as quickly as possible, a debris flow can travel a lot faster than you can run,” said Carolyn Driedger, hydrologist and public information officer at the USGS Cascades Volcano Observatory in Vancouver, Wash.
The Ridley Creek and Elbow Lake trails cross the Middle Fork Nooksack River in the debris flow area on the Mt. Baker-Snoqualmie National Forest. Floods washed out the bridges on those trails in 2003, forcing hikers to ford the river. Elbow Lake is a popular fishing spot and both trails are used to access the Mt. Baker National Recreation Area.
Driedger said debris flows are not uncommon in glacial valleys where rock debris clings tenuously to valley walls, but they are unpredictable. “Over the past few decades we have seen dozens of similar events at Mount Rainier, Mount Hood, and elsewhere. A previous event near Deming Glacier occurred in June, 1927, and traveled about two miles down the Middle Fork Nooksack Valley,” she said.
Last week's flow was initiated at 2:54 a.m. and was followed by a series of much smaller flow events later in the week. Staff at USGS-Cascades Volcano Observatory and the USGS Washington Water Science Center timed the events using seismograph and hydrograph readings.
Photos, statistics: http://nwgeology.wordpress.com/category/mount-baker-volcano-research-center/
Blog, photos, YouTube video, story: http://mbvrc.wordpress.com/2013/06/05/large-debris-flow-in-middle-fork-nooksack-river-may-31-2013/
Seismograph signal: http://www.pnsn.org/seismogram/2013/05/31/mbw/ehz/uw