Date: Mon, 31 Mar 2014 01:30:17 EDT
Summary: There have been no significant changes since yesterday: the North Fork Stillaguamish River continues to flow across the debris dam that formed due to a large landslide and the water continues to gradually erode a larger channel.
There have been no significant changes since yesterday: the North Fork Stillaguamish River continues to flow across the debris dam that formed due to a large landslide and the water continues to gradually erode a larger channel.
Streamflows due to heavy rains peaked early Sunday morning. The outlet of the lake appears to be enlarging. Based on turbidity readings, it appears that erosion of the channel across the debris dam continues to be mostly gradual. Catastrophic failure of the debris dam is considered unlikely but conditions will be monitored closely.
Three USGS scientists were on site to monitor the landslide with local and state agencies and scout locations for deployment of the sensors of an automated landslide monitoring system. A three-person USGS instrumentation team traveled to the site to start the installation of the monitoring system.
Two USGS scientists measured streamflow discharge at the North Fork Stillaguamish River at Arlington gage (station 12167000) near the peak, and two additional USGS scientists measured discharge and took suspended-sediment samples at the newly installed gage about two miles downstream from the landslide (station 12166300).
One USGS scientist was stationed at FEMA's coordination center in Bothell, WA, to provide assistance and coordinate with other federal agencies. Numerous USGS scientists and support personnel provided technical and administrative support remotely.
New information was added to the Oso landslide webpage (http://wa.water.usgs.gov/data/oso.html).