Knotweed elimination is an important factor in preserving habitat for fish species. It is also important for elk and deer and other species that forage on the floodplain, where knotweed is out-competing native vegetation.

Both the North Fork and South Fork of the Calawah River originate in the Olympic National Park. They converge close to the town of Forks and the Calawah flows into the Bogachiel on the west side of Forks. The Calawah is 31 miles in length, with a drainage basin of 133 square miles.

In 2006 the Quileutes surveyed the Calawah, recording 344 sites, all downstream from the North Fork-South Fork confluence.

In 2007 the Quileutes treated approximately 202 acres of land on the Calawah River. Most of this was giant knotweed and responded well to treatment.

In 2008 the Quileutes found very few surviving plants. Bohemian knotweed in terrestrial areas of the Calawah was treated.
In 2009 the Quileutes again monitored and re-treated the Calawah, finding a few large patches that had possibly been overlooked in previous years. Only 1.59 gallons of herbicide were used.

In 2010 the Quileutes did an early-season assessment of the Calawah River and found no large patches of knotweed remaining but there was a small amount of re-growth from previously-treated areas. A very small amount of re-treatment was done.