Study finds estuary restoration would expand habitat and aid flood resilience; excavation of Unical site not required to reduce flooding

Summary

A year-long study presented to the Edmonds City Council found estuary restoration at the Edmonds Marsh would double habitat, support juvenile Chinook, and provide flood risk benefits to Harbor Square; modeling showed fully excavating the Unical property would not materially reduce future marsh flooding but would increase habitat area.

City engineers and consultants presented findings July 1 from a year-long Edmonds Marsh Estuary Planning Study, concluding that restoring a tidal connection between the marsh and Puget Sound could expand habitat, support juvenile Chinook usage and provide flood protection for Harbor Square — and that full excavation of the Unical site, while beneficial for habitat, is not necessary to achieve the modeled flood-reduction benefits.

What the study looked at: Blue Coast Engineering constructed a two-dimensional hydraulic model that combined freshwater inflow from Willow and Shalimar creeks with tidal and storm surge conditions in Puget Sound. The model validated existing flooding observations from the December 2022 king-tide/storm event and simulated future scenarios including a 3.2‑foot sea-level rise scenario (a higher-end projection drawn from University of Washington Climate Impacts Group guidance used in regional planning).

Key technical findings: Kathy Keteridge, principal coastal engineer…

Study finds estuary restoration would expand habitat and aid flood resilience; excavation of Unical site not required to reduce flooding

Summary

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