Restoring habitats to altered floodplain systems requires understanding how rivers interact with their floodplains. (An aerial view of river-floodplain connections, showing lateral migration

Project Title

Dynamics of river-floodplain ecosystems

Description

Habitat formation on river floodplains is a continuous process, and river movement across a floodplain creates a wide array of habitat types suitable for many different aquatic species and life stages. However, most floodplain rivers have been dramatically altered by construction of levees, installation of dams, grazing and channel incision, or other processes. Restoring diverse habitats to these altered river-floodplain systems requires an understanding of how rivers interact with their floodplains and create the ecosystems to which salmon have adapted.

The first part of this study will describe how the dynamics of channel-floodplain ecosystems vary with channel pattern (e.g., braided, meandering, straight). Different channel patterns exhibit differing floodplain "turnover" rates, so diversity and persistence of habitat types should vary with channel pattern. The second part examines how channel patterns are distributed on the landscape, indicating where different types of ecosystem dynamics should be expected. The third part of the study examines in greater detail the dynamics and ecosystem attributes of a pilot study reach of the Sauk River in northwest Washington. The study documents the history of channel movement and evolution of off-channel habitats, as well as the temporal and spatial dynamics of floodplain vegetation, and invertebrate and fish communities.

We are also quantifying changes to channel and habitat dynamics in regulated and unregulated rivers (downstream of the Elwha dams and in three reference reaches) using the historical aerial photograph record. After dam removal, we will use subsequent aerial photographs to document impacts of sediment release on channel-floodplain dynamics, as well as recovery of the channel-floodplain system following passage of the initial sediment pulse.

Investigators

Tim Beechie, Michael Pollock, Martin Liermann, Sarah Morley, and George Pess

Collaborators

Kris Kloehn (Frank Orth)

Support

NOAA Fisheries

Project Status

One manuscript in press, one manuscript in review.

Relevant Publications

Beechie, T.J., M. Liermann, M.M. Pollock, S. Baker, and J. Davies. In Press. Channel pattern and river-floodplain dynamics in forested mountain river systems. Geomorphology.

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