River Dredge Creates Islands for Salmon

Engineers on the Lower Columbia River have repurposed dredged sediment into artificial islands, initiating a long-term experiment for wildlife habitat restoration. This project, initiated in October 2020, involved pumping 225,000 cubic yards of sediment to construct four small islands and a side channel near Woodland.

The initiative addresses the significant loss of natural tidal habitat along the river, with approximately 75% disappearing due to dams and shoreline alterations. This loss critically impacts young salmon, which rely on shallow, slow-moving areas for resting, hiding, and feeding during their journey to the ocean.

The newly created Woodland Islands, covering about seven acres, aim to slow erosion and provide a crucial refuge. Native plants have been introduced and are thriving, with natural river currents further shaping the islands and bringing organic material.

Researchers are actively monitoring the islands, collecting fish samples and studying land changes, plant growth, and species presence. This ongoing research will determine the habitat's productivity and effectiveness compared to natural areas.

Furthermore, scientists are evaluating five potential sites for future sediment placement projects scheduled to begin in 2027. Baseline data collection at these locations will inform site selection for optimal habitat creation while maintaining commercial shipping channels.

Success in restoring habitat through this dredged material approach could establish a new model for environmental management in the Pacific Northwest, demonstrating how essential maintenance activities can simultaneously support ecosystem recovery and aid threatened salmon populations.