During the week of October 20, 2003, the largest flood measured in the last century in the Skagit River, Washington, resulted in potentially dramatic changes in river habitats. Teams working with Earthwatch Institute's Pacific Northwest Conservation Research Initiative (CRI) in summer 2004 will be ideally placed to assess the flood's impact on habitats critical to endangered Pacific salmon.

"This was the largest measured flood in the Skagit since the dikes to control flooding were nearing completion in the 1920's, and since good measurements were possible," said Dr. Ralph Riley, field director for Earthwatch's Pacific Northwest CRI. The Skagit River is the largest river draining into the Puget Sound from headwaters in the northern Cascade Range.

The flood, which crested at the town of Concrete, Washington, on Tuesday morning, October 21, reached 42.2 feet, more than 14 feet above flood stage and nearly a foot higher than the highest flood of record in 1995. The river flowed at about 166,000 cubic feet per second (cfs), almost 17 times its average of 10,000 cfs for this time of year, as a result of rains and glacial melt in the upper watershed.

"This will make our salmon habitat projects for 2004 very interesting," continued Riley. "There was a huge amount of large woody debris in the river suggesting the flood has moved a lot of material around. There is bound to be a substantial impact on the estuary as well as on upriver sites."

The Skagit River watershed has some of the healthiest salmon runs in the lower 48 states of the United States, including all five species of Pacific salmon-all of them listed as Endangered or Threatened under the U.S. Endangered Species Act. In partnership with the Skagit Watershed Council and the U.S. National Park Service, the goal of Earthwatch's Pacific Northwest CRI is to manage the watershed so that its complex ecology, salmon fishery, and human livelihoods can be sustained.

One of the Earthwatch-supported research projects in the Skagit basin, directed by Drs. Peter Kiffney and Correigh Greene (Northwest Fisheries Science Center), has been collecting detailed data on river food webs in tributary streams. Comparative data from next season will reflect the impact of the flood on ecological patterns of critical salmon habitat.

A second research project, directed by Steve Hinton and Dr. Greg Hood (Skagit System Cooperative), has been monitoring what is happening to former estuary habitat after dikes are removed. The restoration of estuary habitat is considered critical to the recovery of some salmon populations, who use estuaries for feeding grounds before heading out to sea, and the flood has likely substantially altered the habitat, perhaps accelerating the restoration process.

A third research project starting next year, headed up by Riley, will assess upriver salmon habitat restoration efforts and the impact of the flood on these efforts.

"This will be a great opportunity to see how the flood has affected things," said Riley. "A lot of salmon habitat restoration work involves placing logs in streams, removing dikes, and planting vegetation to shade streams and control erosion. The flood may have dramatically affected all these things in some places: moving logs, shifting streambeds, and removing vegetation."

In the wake of this large flood, Earthwatch's Pacific Northwest CRI and the research projects it supports stand to make a significant contribution to the understanding of river processes and their impact on salmon habitat. Through Earthwatch's partnership with the Skagit Watershed Council and the U.S. National Park Service, this information will help inform future salmon habitat management efforts.

For information on volunteering on the Pacific Northwest CRI projects, click here

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