North Fork Bend Tidal Restoration Design Technical Assistance

The North Fork Bend Tidal Restoration Design Technical Assistance will advance the goal of restoring tidal wetland habitat and natural estuarine ecosystem function at a 247-acre property located in the Siuslaw River estuary, northeast of Florence, Oregon, in Lane County. The property is composed of diked and drained former tidal wetland and is separated into two hydrologically-disconnected grazing pastures, each drained by ditches and protected from tidal inundation by tidegates. This property is a segment of the lost tidal wetland habitats in the Siuslaw River estuary. An estimated 67% of tidal wetlands in the Siuslaw River estuary have been lost as a result of agriculture, development, and transportation infrastructure land use actions. Estuarine habitat quantity and quality are identified as key limiting factors in the health of the Siuslaw watershed and its ability to support healthy populations of species such as Oregon Coast coho, making restoration of estuarine habitat a high priority for local and regional organizations.

This project proposes to advance tidal wetland restoration design to the 30% design threshold. This includes collecting supplemental survey data, hydraulic modeling, assessing and identifying a restoration alternative, producing 30% designs, and a geotechnical review of native soil materials. A feasibility study for restoration at this project site was completed in 2018, supported by OWEB. Partners on this TA project include McKenzie River Trust (MRT), The Nature Conservancy (TNC), and the Siuslaw Watershed Council (SWC).

The objectives of this TA project support restoration of property in the Siuslaw River estuary. Healthy estuaries provide critical habitat for overwintering coho juveniles by providing shelter, abundant food sources, and access to a diversity of salinities. Recent studies suggest that estuaries also support increased variation in coho life histories, an important strategy for species resilience (Jones et al., 2014). In the Siuslaw basin, 67% of the pre-1850s tidal wetlands have been critically altered as a result of human land use practices, and restoration of these wetlands restores the habitats that support resilient populations of anadromous fish.
Protecting and restoring estuary systems helps these fish in multiple phases of their life history. For juvenile fish, estuarine wetlands provide a food-rich environment that promotes rapid growth and increased chances for survival, refuge from predators in narrow, winding channels with overhanging vegetation, and brackish salinities, allowing salmon smolts to make the physiological transition between fresh and salt-water environments. Estuarine wetlands are also important for adult salmon, providing the necessary transition and holding areas for the fish before they begin their upstream migration.