Tuesday, June 19, 2012

Nooksack Levee at Deming

The Nooksack River does a lot of moving around in its upper reaches. Fortunately there is not a lot of development along these reaches of the river. Perhaps some of the development that did take place in the past has been washed away. One exception is at Deming, an unincorporated town. The town has one advantage in that the Burlington Northern Santa Fe Rail Road track passes through the town between the town and the river. The rail line with its elevated tracks and prism of rocks has provided a level of protection to the community as well as other development further down stream. However, development has crept over the rail line, and this reach of the Nooksack has become one of the more expensive stretches of the river in terms of flood hazard investment. At Deming the Nooksack River made a major coarse shift to the north in the 1980s and began to threaten the bus and shop facilities of the Mount Baker High School as well as the high school sewer treatment facility. The river also threatened to take out the Nooksack Casino drain field.  

The new river bank was lined with a heavy angular rock rip rap levee to reduce flood risk and prevent further migration of the river. Initially the river approached the upper east end of this heavy armored levee at nearly a 90 degree angle. But over the past decade the river has progressively migrated to the west taking aim at different portions of the levee as it progressed. Overall the levee has held up well with some relatively minor rock replacement.

The progression of the river along the levee has been fascinating to watch:






Whatcom County Flood Zone District is working toward doing improvements on the east end of the dike. If the river shifts back to the east again which it will eventually, the east end would fail and the river would get back behind the dike. To prevent this scenario a new levee section will be constructed from the current east end of the heavy armored levee to the edge of the Burlington Northern Railroad. 

As can be seen in the last image, the river will likely migrate to the west end of the levee. That will likely lead to a fairly broad area of rapid channel migration if the river holds its current pattern. Fortunately, the river has a lot more room to meander down stream of Deming without threatening structures or public facilities as the forest bottom lands have been occupied by the river within the past 100 years and will likely be occupied again. 

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