Herrera is pleased to see the Downey Farmstead project near completion. Work to reshape the 22-acre historic homestead site began in 2008 with the goal of enhancing salmon habitat in the Green River.
During this multi-phase, grant-funded project, Herrera assisted the City of Kent with alternatives analysis, coordination with key stakeholders, design for incremental construction, and construction inspections. This work consisted of evaluating restoration alternatives that maximize salmonid rearing habitat in a new side channel or backwater slough, while considering the effects on existing wetlands, flooding/flood storage, sediment transport, recreational uses, pedestrian and vehicle traffic, historical and cultural resources, seismic stability of the State Route 16 embankment, and environmental permitting.
To inform the preferred design configuration, Herrera completed hydraulic modeling to assess expected and sustainable side channel flow characteristics and effects on peak flood elevations in the river. Modeling results also supported sediment transport analysis that remains an essential part of the design – seeking to avoid the potential for sediment carried in the river’s flow to deposit and partially plug the proposed side channel.
Following modeling efforts, Herrera’s team collaborated with the City to prepare final project design plans, which include a network of side channels excavated into the high ground of the former tree nursery site, engineered logjams, smaller log structures, and native riparian plantings. Construction of the side channels and log structures was completed in early fall 2022, with riparian vegetation planting to follow through this winter.
Our team is proud to see this important project come to fruition, providing ecological benefits for salmon and trout in the Green River while reducing peak flood water levels for years to come.
Please contact Mark Ewbank for more information on this project.