Landslide diverts Nooksack River near Deming, Washington

View up river from top of Clay Banks in a snowstorm. Landslide toe in river is at right center. Photo by D. Tucker. Click to enlarge photos.

View up river from top of Clay Banks in a snowstorm. Landslide toe in river is at right center. Photo by D. Tucker. Click to enlarge photos.

A landslide about 1 AM February 21 diverted the Nooksack River. The slide occurred at the infamous ‘Clay Banks’ about 1.8 miles upstream of the Baker Highway bridge at Nugents Corner, near Deming. I’m passing along the essentials from Dan McShane’s Washington Landscapes blog. I visited the site this morning with geologists Scott Linneman (WWU) and Eric Grossman (USGS), and have posted a few photos and a new Google Earth map. The river has cut through the low-relief landslide toe, and there is now no impoundment of the river. According to residents we spoke with there was another large landslide a couple (?) of weeks ago. They said they could hear a deep rumbling when the February 21 slide released.

T'photo of slide toe in river. The river has cut around the toe, and also through its body. Photo by D. Tucker

T’photo of slide toe in river. The river has cut around the toe, and also through its body. Photo by D. Tucker

Annotated Google Earth screen capture. D. Tucker

Annotated Google Earth screen capture. Blue lines indicate river channel as of AM, Feb. 22, 2014. D. Tucker

Access to all viewpoints is on various private properties, which are amply posted ‘No Trespassing’, etc, etc. You can’t see anything from anywhere without trespassing. Watch for possible updates. We’ll make and effort to get more information and better photos soon.

The Clay Banks consist of Pleistocene glacial till sitting on top of a very permeable sand layer, which in turn sits on top of older glacial till. It is very prone to sliding and has destroyed two houses that were built in the forest several hundred yards back of the top of the bluff in the late 1980s or early 1990s.

John Thompson's photo from the gravel bar, Feb. 21, 2014.

John Thompson’s photo from the gravel bar, Feb. 21, 2014.

This house was gradually undercut and has slid off the brink of the Clay Banks. Photo by Dave Tucker, Feb. 2013.

This house was gradually undercut and has slid off the brink of the Clay Banks. Photo by Dave Tucker, Feb. 2013.

Dan’s post:

Nooksack River Temporarily Blocked by Landslide

Via a network of folks that pay attention to the Nooksack River:. The flow on the river at the Cedarville gage took a brief plunge last night from 2,300 cfs to 400 cfs.
 

At Lynden 11 miles downstream a less substantive, but still sharp drop and recovery took place. Lynden Public works reported a sharp increase in river turbidity.

USGS staff noted the dip in the discharge and Whatcom Flood Division confirmed a large landslide at the Clay Banks had blocked the current main channel and deflected the river back to an older channel.

Clay Banks landslide can be seen at bottom center
Topo of Nooksack River and Clay Bank

…As can be seen the river has been up against the steep bluff in the past. However, the frequency and duration of the river being against the steep bluff has been enhanced by the construction of a high rip rap levee on the opposite bank preventing the natural meander of the river.

1998
Note the slide on lower left and rock levee on the opposite upstream bank

Posted by at 9:35 PM

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