Geomorphic Framework Development for Willamette Valley Reservoirs to Support Cultural Resources Management

Summary

This is an abstract from the "Future Directions for Archaeology and Heritage Research in the Willamette Valley, Oregon" session, at the 88th annual meeting of the Society for American Archaeology.

High-head, multipurpose dams and reservoirs constructed in the 1940–1960s in the Willamette Valley encompass a diverse array of landscapes utilized by humans for thousands of years. These reservoirs overlap numerous cultural sites that are subject to dynamic erosion and deposition processes. Although the reservoirs share broad-scale hydrogeomorphic processes, controls, and resultant landforms, each reservoir’s geomorphology is a distinct expression of local valley topography, streamflows, sediment inputs, shoreline erosion, and dam operations. For example, Fall Creek Lake is located in a steep, narrow valley draining the volcanic rocks of the Western Cascade Range; this setting combined with annual 50 m lake-level fluctuations that drain the reservoir have maintained primary tributary channels and created erosional channels and terrace landforms carved through unconsolidated reservoir floor sediments in the lower reservoir. In contrast, Fern Ridge Lake is located in a broad, low-gradient valley draining marine sedimentary rocks of the Oregon Coast Range; preliminary evaluation of this site reveals annual 15 m lake-level fluctuations have influenced different styles of erosion and deposition in multiple tributaries throughout the reservoir. Therefore, a geomorphic framework synthesizing the reservoirs’ geological, historical, and operational factors will aid cultural resource managers in their assessment and addressal of threatened sites.

This Resource is Part of the Following Collections

• Future Directions for Archaeology and Heritage Research in the Willamette Valley, Oregon   •
• Society for American Archaeology 88th Annual Meeting, Portland, OR (2023)

Keywords

Record Identifiers

Abstract Id(s): 35604.0