Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8660
Title: Changes in streambed composition in salmonid spawning habitat of the Elwha River during dam removal
Author: R. J. Peters, Martin Liermann, M. L. McHenry, Paul Bakke, G. R. Pess
Publication Year: 2017
Journal: Journal of American Water Resources Association
Volume: Early view
Keywords: dam removal,stream restoration,Elwha river dam removal,habitat features,Stream habitat,

One primary uncertainty associated with large dam removal is the amount of downstream streambed aggradation and associated short-term biological effects of sedimentation. Recent studies have found that downstream sediment deposition following dam removal tends to be influenced by proximity to the source and river transport capacity. The potential biological effects of such sediment deposition, however has not been extensively studied. Changes to sediment deposition and associated streambed composition in the Elwha River watershed, Washington have been monitored since 2010, spanning the time before and during the simultaneous removal of two large dams over 30 and 60 meters in height. This data was collected by sampling 20 of 46 riffle crests in the mainstem, and 18 floodplain channel locations during late summer 2010-2014. Substrate composition during dam removal varied substantially by year and channel location but weakly correlated with distance from source and channel gradient. Floodplain riffles fined and remained sand-dominated throughout the time period sampled. Fine sediment accumulation in floodplain riffles exceeded levels known to be detrimental to incubating salmonids. Mainstem riffles tended to fine to gravel but have returned to cobble after the majority of the sediment was released and transported through the Elwha River. Future monitoring will occur to gain a better understanding of the change in streambed composition post dam removal.


The objective of this paper is to quantufy the changes in streambed particle size before and during dam removal on the Elwha River.

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Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Characterize relationships between habitat and ecosystem processes, climate variation, and the viability of organisms.
Characterize the interaction of human use and habitat distribution, quantity and quality.