Clackamas Confluence Restoration Project

McLoughlin Bridge

Located at Dahl Beach Park at the confluence of the Clackamas and Willamette Rivers, the Clackamas Confluence Restoration Project focused on riparian and in-stream habitat enhancement for the improvement of fish populations in the Lower Clackamas River.  Dam and levee construction, bank erosion, and basin wide development has reduced mainstem interaction with floodplain habitats.  Additionally, large scale sediment dredging of the Willamette River has greatly impacted the hydrology of the Clackamas River.  Under pre-project site conditions, the Western Basin was only connected 40% of the time, and the Eastern Basin 20% of the time from April through July.  This time frame is critical for migrating juvenile salmon and smolts looking for off-channel refugia.  The Dahl Beach Park and Natural Area’s historical importance as a dynamic natural area, its location at the confluence of the Clackamas and Willamette Rivers, and its remaining intact seasonally inundated forested wetlands made it a prime location for floodplain restoration.

HENDERSON was selected to address key limiting factors of the Lower Columbia River, including floodplain connectivity, large wood, and overall habitat complexity.  The Clackamas River Basin Council began work to remove non-native vegetation, and replace it with endemic trees and shrubs.  Our scope of work included cutting sill elevations at the Western and Eastern Basin sites down to 13 feet, thereby increasing forest floodplain connectivity, and installing four engineered log jam structures within the forested floodplain to provide fish cover, habitat complexity, and streambank stabilization.  This work was identified as a high priority in the 2005 Clackamas River Basin Action Plan.

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