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Article
Tidal-Fluvial and Estuarine Processes in the Lower Columbia River: II. Water Level Models, Floodplain Wetland Inundation, and System Zones
Estuaries and Coasts
  • David A Jay, Portland State University
  • Amy B. Borde, Pacific Northwest National Laboratory
  • Heida Diefenderfer, Pacific Northwest National Laboratory
Document Type
Article
Publication Date
9-1-2016
Subjects
  • Columbia River Estuary (Or. and Wash.) -- Environmental conditions,
  • Watershed ecology -- Pacific Northwest,
  • Estuaries -- Hydrodynamics,
  • Columbia River Estuary (Or. and Wash.) -- Ecology
Abstract
Spatially varying water-level regimes are a factor controlling estuarine and tidal-fluvial wetland vegetation patterns. As described in Part I, water levels in the Lower Columbia River and estuary (LCRE) are influenced by tides, river flow, hydropower operations, and coastal processes. In Part II, regression models based on tidal theory are used to quantify the role of these processes in determining water levels in the mainstem river and floodplain wetlands, and to provide 21-year inundation hindcasts. Analyses are conducted at 19 LCRE mainstem channel stations and 23 tidally exposed floodplain wetland stations. Sum exceedance values (SEVs) are used to compare wetland hydrologic regimes at different locations on the river floodplain. A new predictive tool is introduced and validated, the potential SEV (pSEV), which can reduce the need for extensive new data collection in wetland restoration planning. Models of water levels and inundation frequency distinguish four zones encompassing eight reaches. The system zones are the wave- and current-dominated Entrance to river kilometer (rkm) 5; the Estuary (rkm-5 to 87), comprised of a lower reach with salinity, the energy minimum (where the turbidity maximum normally occurs), and an upper estuary reach without salinity; the Tidal River (rkm-87 to 229), with lower, middle, and upper reaches in which river flow becomes increasingly dominant over tides in determining water levels; and the steep and weakly tidal Cascade (rkm-229 to 234) immediately downstream from Bonneville Dam. The same zonation is seen in the water levels of floodplain stations, with considerable modification of tidal properties. The system zones and reaches defined here reflect geological features and their boundaries are congruent with five wetland vegetation zones.
Description

To the best of our knowledge, this work was authored as part of the Contributor's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.

DOI
10.1007/s12237-016-0082-4
Persistent Identifier
http://archives.pdx.edu/ds/psu/18098
Citation Information
Jay, D. A., Borde, A. B., & Diefenderfer, H. L. (2016). Tidal-Fluvial and Estuarine Processes in the Lower Columbia River: II. Water Level Models, Floodplain Wetland Inundation, and System Zones. Estuaries and Coasts, 39(5), 1299–1324. http://doi.org/10.1007/s12237-016-0082-4