Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8637
Title: Channel-planform evolution in four rivers of Olympic National Park, Washington, USA: The roles of hydrology, sediment supply, and trophic cascades
Author: Amy East, Kurt Jenkins, Patricia J. Happe, Jennifer Bountry, T. J. Beechie, Timothy Randle
Publication Year: 2016
Journal: Earth Surface Processes and Landforms
Volume: Early view
Keywords: Channel dynamics,channel evolution,hydrology,sediment,trophic cascades
Abstract:

Identifying the relative contributions of physical and ecological processes to channel evolution remains a substantial challenge in fluvial geomorphology. We use a 74-year aerial photographic record of the Hoh, Queets, Quinault, and Elwha Rivers, Olympic National Park, Washington, U.S.A., to investigate whether physical or trophic cascade-driven ecological factors—excessive elk impacts after wolves were extirpated a century ago—are the dominant drivers of channel planform in these gravel-bed rivers. We find that channel width and braiding show strong relationships with recent flood history. All four rivers widened significantly after having been relatively narrow in the 1970s, consistent with increased flood activity since then. Channel planform also reflects sediment-supply changes, evident from landslide response on the Elwha River. We surmise that the Hoh River, which shows a multi-decadal trend toward greater braiding, is adjusting to increased sediment supply associated with rapid glacial retreat. These rivers demonstrate transmission of climatic signals through relatively short sediment-routing systems that lack substantial buffering by sediment storage. Legacy effects of anthropogenic modification likely also affect the Quinault River planform.

We infer no correspondence between channel evolution and elk abundance, suggesting that trophic-cascade effects in this setting are subsidiary to physical controls on channel morphology. Our findings differ from previous interpretations of Olympic National Park fluvial dynamics and contrast with the classic example of Yellowstone National Park, where legacy effects of elk overuse are apparent in channel morphology; we attribute these differences to hydrologic regime and large-wood availability.

Description:

Journal article describing drivers of channel planform dynamics in Olympic National Park Rivers.

URL1: The next link will exit from NWFSC web site http://dx.doi.org/10.1002/esp.4048
Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Characterize relationships between habitat and ecosystem processes, climate variation, and the viability of organisms.