Nooksack River Flood History

The Nooksack River is located in the northwestern portion of Washington, near the Canadian border. The river begins in the Mount Baker-Snoqualmie National Forest via three forks, the north, middle, and south, then flows west through agricultural lands before feeding into Bellingham Bay on the Pacific Coast. Drastic changes due to periodic flooding events have altered the path of the Nooksack River multiple times in the past.

Flooding History

The Nooksack River's course has changed multiple times in the past because of periodic flooding. The Nooksack, like many rivers in the Pacific Northwest, has a strong current fed by glacial melt waters and easily erodible soils and sediment composed of fine glacial silt. When periods of high rain fall, coupled with ambient glacial melt, the valleys are particularly prone to flooding. Only in recent years have scientists begun to understand the degree to which the Nooksack River has been influenced by human settlements that have modified the river to minimize the risk of flooding.

Factors That Influence Flooding

Human activities have long influenced the natural flow of the Nooksack River. One of the earliest influences was the fur trade. Beavers are ecosystem engineers. They modify the flow rate of small tributaries, which, during periods of high rain help prevent flooding downstream. The removal of beavers and the subsequent loss of their damns damaged many species of fish as well as increased the vulnerability to flooding. Fallen trees are also a major factor in flooding events in the Nooksack River. Large trees that fall across the river channel can trap other trees and create a logjam that can act as a natural dam and alter the course of the river.

Avulsions in the Nooksack River

Rivers are constantly eroding the channels in which they flow. Normally, erosion takes place at a slow rate, and changes in the river's course, called avulsions, occur over very long time periods. However, flooding events can cause avulsions to occur rapidly. The Nooksack River is particularly vulnerable to avulsions as the soils of the river channel are fine and easily erode along its meandering path. In addition, the surrounding forests provide sources of debris for the occurrence of log jams. Avulsions due to logjams and flooding have altered the path of the Nooksack River many times in the past.

Monitoring and Flood Prevention

The U.S. Geological Survey has 17 monitoring sites in the Nooksack River watershed to monitor flow rates and water quality data. Many sections of the Nooksack River have been channeled near urban environments to minimize the risk of flooding and property damage.

Interesting Facts about the Nooksack River

The Nooksack River is the most northern river in Washington that feeds into the Puget Sound. The north fork of the Nooksack is listed as a National Wild and Scenic River and is famous for its whitewater. Because the north fork is fed by glacier melt, the river runs high and strong with class III rapids late in the season, when other rivers have calmed from their summer snow melt. The north fork is also home to all five native salmonid species in the Northwest, the most significant being the Chinook salmon, protected under the Endangered Species Act.

References

• University of Washington College of the Environment: Before and After the Treaties: the Environmental History of the Puget Sound
• Western Washington University: Nooksack Avulsion
• Prescott College: Tidewater to Timberline, Forest to Steppe: Natural History of the Greater North Cascades Ecosystem
• Americanwhitewater.org: Nooksack, N. Fork