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Lower Dosewallips Floodplain & Estuary Restoration Update

Lower Dosewallips Floodplain & Estuary Restoration Update

Dosewallips River Restoration Continues

Lower Dose 10

Work continued in the summer of 2009 on the Wild Fish Conservancy and Washington State Park’s ongoing restoration of the lower Dosewallips River in Jefferson County, Washington. We removed a 400-feet levee on the south bank of the river upstream from the US-101 bridge, opening up 2.5 acres of floodplain to natural river process. The levee was built in the early 20th century, and at one time was likely part of an approach for an old bridge across the river. The footprint of the levee was in direct contact with the river, with about half of the length running along an active side channel, and the other half running along the mainstem of the river.

Wild Fish Conservancy contracted Sea Level Bulkhead Builders to do the levee removal work, which was carried out with two excavators and a convoy of dump trucks. The levee was constructed of a mix of very large rip rap and gravel, and in two weeks we removed over 4000 cubic yards of material. Numerous trees had grown on the levee since it was constructed so before we could take the levee out the trees had to be removed. As much as we encourage the retention of riparian vegetation, in this case removing the trees was for the greater good of the river.  But these trees were not removed from the system entirely. Instead of using chainsaws to fell the trees we pushed the trees over with excavators, so that the root wads of the trees would still be attached to the trunks. We then used the trees to create woody debris structures on the footprint of the levee once it was removed. Root wads are like Velcro in the floodplain; tree trunks that still have their root wads attached are much more likely to be retained in the river rather than flushing downstream during the first flood.

We were encouraged watching the site evolve during the fall floods of 2009 and 2010. The mainstem of the river is now actively occupying a portion of the footprint of the levee, and during the highest flows, a side channel of the river that had previously been cutoff by the levee flowed for the first time in at least 80 years. Following these first floods, we were able to determine the best place to plant trees on-site given the new water depths that were observed during the floods, and WFC worked in collaboration with a Washington Conservation Corps crew to replant the site.  We look forward to the additional changes that the Dosewallips River will continue to bring to the site.

Update by Micah Wait, Director of Conservation, Wild Fish Conservancy

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