Friday, February 21, 2014

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

No pictures of the slide as I was away and am away from my old pictures of the slide. Hope to get out there soon. 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.

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

The clay of the Clay Banks is glacial marine drift silts and clays deposited during the late stages of the last glacial period.

1 comment:

Judy Hopkinson said...

So is this because of receding glaciers? (uncovered underlying rocks washing downstream?) Or something else?