Wetland Characteristics of the Upper Elwha River

Wetlands are dynamic ecosystems that provide essential habitat for a multitude of plant and amphibian species. Wetlands associated with dynamic river systems are destroyed by dams and the reservoirs they impound. Restoration following removal of two large dams on the Elwha River provides an opportunity to study successional stages of wetlands from severe disturbance. Although restoration in the Elwha ecosystem involved the largest and most comprehensively studied dam removals ever conducted, wetland responses are poorly understood. We focused on characteristics of wetlands in the former Mills reservoir and relatively undisturbed wetlands in Geyser Valley, the nearest upriver reach containing wetlands. In each study area, we mapped wetlands, classified them according to Washington Department of Ecology criteria, and measured plant species composition and stature. We compared wetland characteristics in the two study areas using two-sample t-tests. Our results suggest that wetlands in the former Mills reservoir are in an early stage of development and Geyser Valley wetlands provide a good baseline to for wetland restoration in the Elwha ecosystem