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Geomorphic and archaeological study of the Ohanapecosh River: Estimating anadromous fish distribution up to 7,000 years ago

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Author(s): April L. Kelly, Paul M. Kennard

Document Type: Unpublished Internal Report
Publisher: Mount Rainier National Park
Published Year: 2019
Pages: 32
DOI Identifier:
ISBN Identifier:

The objective of this geomorphic study is to determine presence or absence of anadromous fish in the Ohanapecosh River during the early historic and pre-European contact periods up to 7,000 years ago. It does so by identifying fish barriers and habitat in the upper reaches of the Cowlitz-Ohanapecosh River watershed. Because anadromous fish were a critical resource staple for indigenous people in the Pacific Northwest for at least the last 4,000 years, information on salmonid presence and abundance in a watershed is important to developing accurate archaeological interpretations regarding site function and regional occupation patterns.

The present study area encompasses the confluence of the Ohanapecosh and Cowlitz Rivers (figure 1) near the southeast corner of Mount Rainier National Park (described in section 2, below). Anadromous fish species of particular interest include chinook, coho, and steelhead trout that existed in the project area prior to dam installation on the lower Cowlitz. Despite absence of clear visual evidence of major obstructions downstream of Silver Falls on the Ohanapecosh River, Blue Hole at the confluence with the Clear Fork Cowlitz River well downstream of Silver Falls appears to be the upper limit for fisheries as documented by historical research, the archaeological record, and Cowlitz Indian tribal members.

In this study, we develop a general approach that can be applied to a wide variety of river systems. This generic approach identifies operative landscape disturbance regimes (such as landslides or changing glaciers) that affect the geomorphic controls to fish presence or absence (such as physical fish blockages or unsuitable fish habitats), during the time-period of interest (centuries to millennia). This specific study identifies alpine glacial recession as the dominant disturbance type in the Ohanapecosh River canyon, and subsequent river incision over the last 7,000 years that exposed present-day fish barriers. The timing of barrier exposure is a key factor in determining whether or not anadromous fish were present or absent in the Ohanapecosh River. The research reveals that one true vertical barrier to fish passage, known as Slippery Falls, exists today. Based on our archeological, ethnographic, and geomorphic analyses, there were likely negligible anadromous fish runs beyond the current fish distribution (below Slippery Falls, near Blue Hole, Figure 2) starting at least 7000 years ago.

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Suggested Citations:
In Text Citation:
Kelly and Kennard (2019) or (Kelly and Kennard, 2019)

References Citation:
Kelly, A.L. and P.M. Kennard, 2019, Geomorphic and archaeological study of the Ohanapecosh River: Estimating anadromous fish distribution up to 7,000 years ago: Unpublished Internal Report, Mount Rainier National Park, 32 p..