North Cascades Highway (SR-20) Debris Flow

July 30, 2009

A landslide has come down across Highway 20 at about 4pm, July 29 (2009). The landslide follows days of high heat and thunderstorms. Here is the rain total for the last few days.

July precipitation totals with landslide location

July precipitation totals with landslide location

I am switching the format around a bit to include Google Maps into the posts for a more interactive view.

According to the WSDOT website: “They have about 300 yards of mud and debris in a 10-foot-deep swath across the highway to remove, and need to ensure the slope is stable before they will reopen the road.” That is a good sized debris flow.

The debris flow appears to have come down somewhere near (or maybe in?) Swamp Creek, a tributary to Granite Creek.

Update

Here is some more information from the fine folks at WSDOT. The amount of material removed for the landslide was approximately 650 (or more) cubic yards of material. A dump truck carries, on average, 10 cubic yards, so we are looking at 65 dump truck loads of dirt. The work was completed by WSDOT road crews (sometimes this get contracted out for landslides) and the cost was probably a bit more than $3,000. That is dependent on a few factors, wages and equipment, but also dirt transportation and deposit (which becomes more costly the further out you have to go).

Here are some images from the WSDOT Flickr Site

SR 20 Debris Flow, looking up slope, of July 29, 2009 (WSDOT Photo)

SR 20 Debris Flow, looking up slope, of July 29, 2009 (WSDOT Photo)

SR20 Debris Flow over roadway, of July 29, 2009 (photo from WSDOT)

SR20 Debris Flow over roadway, of July 29, 2009 (photo from WSDOT)

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