Willamette River Bank Stability Study
City of Eugene

Vigil-Agrimis, Inc. (VAI) is performing a six-mile-long bank stability study of the Willamette River within Eugene, Oregon. VAI has completed the first phase of the project, during which we assessed the current geomorphic, hydrologic, habitat, and natural resource conditions of the river environment and identified areas of problematic riverbank erosion, bank failures, and potential harm to land, infrastructure, and private property.

In support of this effort, VAI performed extensive field work in order to fully understand the geomorphology, hydraulics, river dynamics, habitat conditions, and bank instability issues. River mapping included locations of riffles, meander bends, thalweg, areas of high velocity, existing bank protection, vulnerable infrastructure, and sites of existing bank erosion. The project reach was divided into 42 riverbank sections and twenty-four attributes were collected and incorporated into GIS for each section, including observations of riverbank and riparian vegetation, habitat, bank material, and soils, amongst others. Historical channel sinuosity and channel migration were also analyzed.

Deliverables included a report on river bank conditions, GIS mapping of the project reach linked to a database of identified areas of concern, and photo documentation. During the second phase of the project, VAI is working with the City of Eugene to develop a protocol for prioritizing areas of concern. Each area of concern will receive detailed site analysis, including geomorphic, engineering, and geotechnical investigations; cross-section surveys; and habitat assessments to support subsequent analysis and conceptual design tasks. Finally, VAI will develop multiple conceptual alternatives for bank repair/restoration designs at each site and will look for opportunities to improve water quality and habitat. We will then work with City staff to select a single design alternative for each site which will be developed to a level of detail sufficient to prepare construction and design cost estimates, as well as identify key design and permitting challenges, and a final bank stability study report with GIS maps will be produced.