Edgecomb Creek: Stream Restoration in the Pacific Northwest
Josh Allen
SWCA Environmental Consultants
Charlotte, North Carolina
Authors: Josh Allen (SWCA), Joseph Zhang (SWCA), Ben Wright (Soundview Consultants)
Completed in early 2023, the restoration of Edgecomb Creek in Snohomish County, Washington, has significantly improved ecological function over the previously degraded stream corridor. The project was funded by NorthPoint Development with the goal of providing compensatory mitigation credit for the adjacent industrial development. Prior to restoration, the stream channel flowed onsite through an inactive alluvial fan and then excavated linear ditches through agricultural fields. These ditched lacked substantial native riparian vegetation, meanders, cobbles or sorting, riffle or pool structures, large woody debris, or floodplain connectivity. Three undersized and partially clogged culverts along the ditch were acting as fish barriers, preventing accessibility to the site and upstream reaches. Today, the restored 2-mile stream channel consists of a meandering channel connected to side channels and wetland habitats within a riparian corridor containing native trees, shrub, and emergent plant communities. The mainstem and side channels were enhanced with large and small woody debris, streambed gravels, and pool and riffle bed features. The complex channel system with natural channel sinuosity, pool and riffle structures, and side channels that will provide spawning, rearing and foraging opportunities; and connectivity to wetland and floodplain habitats that provides additional water quality improvements, hydrologic regulation, and flood refugia benefits. Once established, the riparian habitat corridor will provide immediate and long-term benefits for salmonids and other fish through native plantings that will provide streambank stability, stream shading, stormwater filtration, and wood recruitment. Fish accessibility to the site and upstream reaches of Edgecomb Creek will be further improved in 2024 by the replacement of two of the culverts that currently act as partial fish passage barriers.
About Josh Allen
Josh Allen works for SWCA Environmental Consultants as a Principal Restoration Engineer. Based in SWCA's Charlotte, North Carolina office, he focuses on engineering and design support for ecosystem restoration projects across the country. HIs experience as a consulting civil/environmental engineer spans more than 15 years. Of note, he has served as project manager/lead design engineer for numerous fluvial geomorphological assessment and stream restoration, wetland restoration, stormwater quality, and flood control design projects spanning across North Carolina, South Carolina, Texas, Kansas, Vermont, Massachusetts, Washington, Idaho, and Oregon. These projects have been implemented in numerous physiographic settings across the country, including the mountain, piedmont, prairie, coastal and central plains, and estuarine provinces.
