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Open-File Report 2011–1228

Prepared in cooperation with the University of Washington and the Lower Columbia River Estuary Partnership

Columbia River Estuary Ecosystem Classification: Concept and Application

By Charles A. Simenstad, Jennifer L. Burke, Jim E. O’Connor, Charles Cannon, Danelle W. Heatwole, Mary F. Ramirez, Ian R. Waite, Timothy D. Counihan, and Krista L. Jones

Thumbnail of and link to report PDF (6.7 MB)Executive Summary

This document describes the concept, organization, and application of a hierarchical ecosystem classification that integrates saline and tidal freshwater reaches of estuaries in order to characterize the ecosystems of large flood plain rivers that are strongly influenced by riverine and estuarine hydrology. We illustrate the classification by applying it to the Columbia River estuary (Oregon-Washington, USA), a system that extends about 233 river kilometers (rkm) inland from the Pacific Ocean. More than three-quarters of this length is tidal freshwater. The Columbia River Estuary Ecosystem Classification (“Classification”) is based on six hierarchical levels, progressing from the coarsest, regional scale to the finest, localized scale: (1) Ecosystem Province; (2) Ecoregion; (3) Hydrogeomorphic Reach; (4) Ecosystem Complex; (5) Geomorphic Catena; and (6) Primary Cover Class. We define and map Levels 1-3 for the entire Columbia River estuary with existing geospatial datasets, and provide examples of Levels 4-6 for one hydrogeomorphic reach. In particular, three levels of the Classification capture the scales and categories of ecosystem structure and processes that are most tractable to estuarine research, monitoring, and management. These three levels are the (1) eight hydrogeomorphic reaches that embody the formative geologic and tectonic processes that created the existing estuarine landscape and encompass the influence of the resulting physiography on interactions between fluvial and tidal hydrology and geomorphology across 230 kilometers (km) of estuary, (2) more than 15 ecosystem complexes composed of broad landforms created predominantly by geologic processes during the Holocene, and (3) more than 25 geomorphic catenae embedded within ecosystem complexes that represent distinct geomorphic landforms, structures, ecosystems, and habitats, and components of the estuarine landscape most likely to change over short time periods.

First posted September 30, 2011

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Suggested citation:

Simenstad, C.A., Burke, J.L., O’Connor, J.E., Cannon, C., Heatwole, D.W., Ramirez, M.F., Waite, I.R., Counihan, T.D., and Jones, K.L., 2011, Columbia River Estuary Ecosystem Classification—Concept and Application: U.S. Geological Survey Open-File Report 2011-1228, 54 p.



Contents

Executive Summary

Introduction

Approach

Methods

Results

Discussion

Acknowledgments

References Cited

Appendix A. Summary of location, geographic and geomorphic setting, major landforms, geologic content and history, characteristic geomorphic and hydrologic processes, and anthropogenic factors affecting key processes in eight Hydrogeomorphic Reach forming the Columbia River Estuary Ecosystem Classification


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