The Nooksack River is a river in western Whatcom County of the northwestern U.S. state of Washington, draining extensive valley systems within the North Cascades around Mount Shuksan, Mount Baker and the Twin Sisters, and a portion of Fraser Lowland south of the Canada–United States border.
The river proper begins with the merging of three main tributaries, namely the North Fork, Middle Fork and South Fork, near Deming. All three forks originate in the Mount Baker Wilderness, and the North Fork, the longest of the three, is sometimes considered the main river.
Middle Fork
The Middle Fork Nooksack River, about long, originates on the southern slopes of Mount Baker near Baker Pass. It flows generally northwest between Mount Baker and Twin Sisters, and drains into the North Fork opposite Welcome, about northeast of the confluence between the North and South Forks.
The traditional name of the Middle Fork in the Nooksack language is Nuxwt’íqw’em ("always-murky water"). It flows briefly south, entering Skagit County, then northwest to re-enter Whatcom County. It flows past the town of Acme, and due north until merging with the North Fork near the State Route 9 bridge, southeast of Deming and the Nooksack Indian Reservation.
The traditional name of the South Fork in the Nooksack language is Nuxw7íyem ("always-clear water").
River modifications
The river supplies the nearby town of Glacier, Washington with hydroelectric power from a dam on the North Fork near Nooksack Falls. The Middle Fork was partially blocked with a diversion dam built by the City of Bellingham in the late 1950s for diverting water into Lake Whatcom, which supplies the city's drinking water. As of July 2020, this old water diversion system has been modified to remove the dam and restore the river channel for the benefit of critical salmon spawning habitat.
In the late 19th century, most of the stream flow of the Nooksack River near its mouth flowed through the present channel of the short Lummi River to Lummi Bay, northwest of Bellingham Bay. Near the start of the 20th century, a log jam plugged the channel to Lummi Bay, forcing the river to change its channel to the present one. The accumulation of the new river delta has been an ongoing field of research regarding the new wetlands it has created. The river only resupplies the previous delta on Lummi Bay during high-flow conditions.
Floods
The river is subject to flooding due to high rainfall amounts in the region and some of the deepest snow packs in the country. The Pineapple Express, a weather pattern that brings central Pacific wind and rain to the northwest, can sometimes catalyze flooding. For example, flooding in Everson occurred 14 times from to 1936 to 2003.
Specific examples of floods are:
- In November 1990, flooding caused over $20 million in damage and the closure of the Trans-Canada Highway for 26 hours.
- In November 1995, flooding caused $4 million in damage in Whatcom County.
- In November and December 2021, water from the Nooksack River filled the Sumas Prairie in Canada's Fraser Valley. This resulted in evacuations because of a landslide, $1 billion in damage in Abbotsford, British Columbia, and further damage elsewhere.
- The river is expected to top levees in Lynden, Washington December 12, 2025 during the 2025 Pacific Northwest floods
Both the U.S. and Canada have faced long-term political hurdles to adequate flood prevention. "On the Washington side, there has been a reluctance to spend money to benefit Canada", and on the Canadian side, "B.C. has been reluctant to use the International Joint Commission following a 1988 report that resulted in the cancellation of the Sage Creek coal mine on the Flathead River".