PROJECT UPDATE: Alder Island Marsh Restoration Project

A new culvert was installed within the levee on the Alder Island Project.

A recent project on the central Oregon coast has restored valuable tidal marsh habitat at the Siletz Bay National Wildlife Refuge near Lincoln City. In partnership with the U.S. Fish and Wildlife Service (USFWS) and the Salmon Drift Creek Watershed Council, DU developed engineering plans and permit documents for the Alder Island Marsh Restoration Project.

Located along the Siletz River adjacent to the iconic Pacific Coast Highway (Highway 101), the project restored tidal hydrology into the island. Historically a tidal marsh, Alder Island was altered by construction of a perimeter levee as part of a residential development planned in the 1960’s. Development never occurred, and the artificial levee prevented tidal exchange and impaired the functionality of the traditional tidal basin that once provided valuable habitat for waterfowl, waterbirds and salmon.

The objective of the restoration project was to re-establish tidal hydrology within Alder Island by breaching the levee and installing two culverts at strategic locations to allow for sufficient water flows during low and high tides. Additionally, interior swales and tidal channels were constructed within Alder Island to improve the movement of water throughout the site. Large woody debris piles were also placed within the channels to provide habitat features that are beneficial to salmon. By breaching the surrounding levee and establishing tidal flows, the project improves the connectivity of Alder Island with adjacent marsh areas, mudflats and the Siletz River.

The Alder Island Marsh Restoration Project area is only eight acres in size, yet provides increased public use and recreation opportunities. A hiking trail around the island remains on the previously constructed levee. In addition, the USFWS installed a new parking lot for Refuge visitors. DU and USFWS are currently planning a subsequent phase of the project that will include a kayak portage for paddlers, fisherman and hunters to easily access the marsh and river. Support for the restoration activities was provided by USFWS, Stanard Foundation, Salmon Drift Creek Watershed Council, Oregon Watershed Enhancement Board, Oregon Hunter Association – Lincoln City Chapter, Freshwater Trust, Tillamook Anglers, and DU major donors.