Tidal Wetland

Bayview Oxbow

The Bayview Oxbow is located on the northern end of Alsea Bay where historical tidal wetlands once thrived. Efforts to restore these wetlands have been in the works for years and aim to reconnect the oxbow with Alsea Bay so that water can flow over the natural floodplain once again. The Wetlands Conservancy, which owns most of the western portion of the Bayview Oxbow, completed preliminary designs for restoration at Bayview Oxbow in 2019 in coordination with adjacent landowners and other stakeholders.

Currently, these designs have been picked up by the Oregon Central Coast Estuary Collaborative (OCCEC) which will be conducting a thorough technical review of culvert removal and bridge replacement in coordination with Lincoln County and partners. The Bayview Oxbow has been identified by OCCEC as a Focused Investment Partnership (FIP) project site and will receive a holistic approach to reconnect the oxbow and address infrastructural concerns with the larger goal of increasing resilience to sea level rise and other climate change impacts.

The Bayview Oxbow used to consist of extensive tidal wetlands, with tidal flows traveling into the oxbow during high tide and flowing out during low tide. This regime has been dramatically altered by dikes, tidegates, and other infrastructure. There were also spots within the oxbow complex that have been identified as historical forested swamp habitat, a once abundant wetland type along the Oregon Coast. In the past 150 years of land use, these wetlands have been converted for agriculture and industry.

1939 aerial image of the Bayview Oxbow referenced in text below.

The earliest photos of the Bayview Oxbow from 1939 show the site already diked, ditched, and utilized by early settlers. Land use priorities have contributed significantly to the decline of wetland habitat along the Oregon Coast; tidal wetlands declining by an average of about 60% and forested and scrub-shrub swamp by an average of about 95% since European settlement. Addressing these massive changes in wetland composition along the Oregon Coast is necessary to restore natural ecosystem processes that have been deeply disturbed by human land use.

In the next few years, project partners expect to begin restoration actions in response to a comprehensive project design. Utilizing a variety of grant sources and collaboration with a host of partners, the Bayview Oxbow restoration project aims to reconnect the oxbow with the Alsea Bay, promoting wetland wildlife and generating community resilience to projected sea level rise in line with landowner interests and concerns.

 

Lint Slough

Lint Slough has been the site of Midcoast-involved restoration work since 1998 with goals of restoring tidal interaction with Alsea Bay. Since, Midcoast and partners have removed water controlling infrastructure, such as dikes and dams, restoring tidal access and promoting the establishment of historical wetland habitat. 

The first restoration projects along the Lint Slough were motivated by the lasting impacts of a salmon rearing facility which proved a lasting barrier to tidal interaction even after it was discontinued in 1972. To restore the natural flow of Alsea Bay tides into the slough, Midcoast and partners removed various instream infrastructure that was left from the facility. 

While early projects at this site succeeded in reconnecting historical wetland habitat and tidal influences, there still remain barriers to fish passage and even more habitat upstream to be reconnected. 

While lower portions of the Lint Slough area have been restored, further opportunities exist upstream and are being explored by MidCoast and our partners in the Oregon Central Coast Estuary Collaborative (OCCEC) within the Focused Investment Partnership (FIP) “Restoring Resilience to Two Estuaries.” A majority of these upstream areas are ranked high or medium-high in MCWC's Landward Migration Zone study, making them targets for work now to build resilience to sea level rise and climate change, preparing them to be future tidal wetlands. 

Early project partners include USFWS, ODFW, City of Waldport, and USFS.

 

Lower Drift Estuary

Regrowing lost habitats

Drift Creek flows into the Siletz Bay just south of Lincoln City, where it forms a beautiful estuary habitat. The area is now part of the Siletz Bay National Wildlife Refuge, but the habitat has been severely degraded in the last 150 years. Several partners are restoring the wetland’s natural functions by removing tidal flow restrictions, digging new channels for the tides to flow through, and promoting native plants.

 

The Lower Drift project aims to restore roughly 40 acres of tidal wetlands in 2023 through the removal of dikes, restructuring and connecting of tidal channels, creating small mounds and planting native species, placement of large woody debris (LWD), and controlling invasive species. An additional 40 acres will be restored in 2024. These restoration efforts added to 86 acres of previously restored wetlands within Siletz Bay National Wildlife Refuge.

The value of estuaries’ ecosystem functions have not been prioritized in recent history. Instead, Oregon’s tidal wetlands have been diked, ditched, developed, or grazed to the point that the area of Oregon’s tidal wetlands has declined by an average of about 60%.

Once a common habitat along the Oregon Coast, forested swamps have declined by an average of roughly 95%. New research shows that forested swamps provide important ecosystem services such as shelter and foraging grounds for salmonids, multi-layered wildlife habitat and stream shading, and high levels of carbon storage in the soil. 

  • Wetlands are areas where water covers the soil, or remains close to the surface all or most of the year. Both marshes and swamps are types of wetlands. Marshes are wetlands that are dominated by soft-stemmed plants such as grasses. Swamps are wetlands that are dominated by woody plants such as trees or shrubs.

A forested tidal swamp (Photo by Laura Brophy)

In addition to directly supporting the preservation of estuary wildlife, the Lower Drift project plays a part in strengthening Oregon’s coastal climate change resiliency. Estuaries have a built-in system to adapt to rising sea levels. As sediment flows into the estuaries from the tides and river, it collects in vegetation and increases the elevation of the wetlands. Estuaries are also “blue carbon” ecosystems (such as mangrove forests and seagrass beds) which are even more efficient at storing carbon from the atmosphere than tropical forests!

How?

  • Improving topographic diversity higher elevation spots for spruce and native shrubs are present.

    Placing LWD to create potential nurse logs.

    Planting of spruce and native shrubs and managing invasive species. 

  • Removing tidal flow barriers such as old dikes, culverts, and riprap to allow for natural deposition of sediment.

    Placing of LWD to aid in catching of sediment.

    Creating elevation gradient to promote sediment deposition.

  • Increasing tidal channel connectivity through channel shaping and removal of tidal flow barriers.

    Placing of LWD to create shelter for aquatic species and coastal birds alike.

    Planting of native plants.

 

The first phase of the Lower Drift restoration began the summer of 2023 when stream diversion and fish salvage took place in July prior to the restructuring of tidal channels using large machinery. During fish salvage, species such as shiner perch, greenling, rockfish, gunnel, stickleback, and Coho salmon were successfully salvaged from the active work area and safely moved to habitat downstream. 


Project partners include US Fish and Wildlife Service, Oregon Coast National Wildlife Refuge Complex, US Forest Service, Bureau of Land Management, private landowners, the Lincoln Soil and Water Conservation District, the Wild Salmon Center, National Oceanic and Atmospheric Administration, and the Confederated Tribes of the Siletz Indians.

To learn more check out these resources:

 

Poole Slough

Poole Slough is a tidally influenced channel in the lower reaches of Wright Creek, just before it flows into the Yaquina River Estuary.

Map of planting sites and road removal.

Poole Slough was dramatically simplified historically by removing large wood, building roads that are no longer in use, and the removal of wetland trees and shrubs. These actions reduced the quality and quantity of habitat for fish and wildlife.

1939 aerial photo showing simplified channel and now obsolete logging road

MCWC worked with partners to remove the obsolete road to allow full tidal exchange through the Slough, now owned by VanEck Forest Foundation and The Wetland Conservancy. This was paired with several large wood placements to increase channel complexity and encourage formation of side channels.

Excavator lowering road

Dumptruck removing fill

Water flowing freely over road at high tide

Our crews also planted spruce and crabapple along the slough to create scrub-shrub swamp habitat, over 90% of which has been lost along the Oregon Coast. These trees will provide large wood input to the slough long term.

Areas around Poole Slough were identified as future tidal wetlands when sea levels rise in our 2017 Landward Migration Zone study. To increase resiliency long term to climate change, large wood was placed in the areas identified. As they decompose, they will act as nurse logs for young spruce trees. In the meantime, they are habitat for birds, insects, mushrooms, and all the other beings that depend on fallen trees.

Partners include ODWF, VanEck Forest Foundation, ODFW, The Wetlands Conservancy, USFWS, The Forest Service, Pacific Forest Trust, and others.

Yaquina Estuary (Y27)

Reconnecting Tidal Marshes

The tide has large influence on rivers, even miles upstream of the ocean. High tides create temporary aquatic habitats that are extremely important to juvenile salmon and other fish.

Across the Yaquina River from Elk City Road near Cannon Quarry Boat Launch, MCWC and partners improved habitat for coho, chum and Chinook salmon by restoring the tidal marsh known as “Y27”.

Map of the Y27 working area

Y27 at high tide

Y27 at low tide

Contractors removed sections of the failing dike and filled artificial drainage ditches to encourage water to use reconnected natural channels and newly dug channels. We protected spruce trees from a 2001 restoration planting project.

Our crew planted the entire site with spruce and other wetland species and will tend to them over several years to establish forested tidal wetland habitat and control invasive species. Trees and root wads were placed into the channels to immediately provide cover for fish.

As tides carve the channels we started and form new ones, the river will deposit its sediment and actually raise the elevation of the area over time. The new sediment and vegetation will increase the areas resiliency to flooding and sea level rise. This project is informed by the history of restoration on this parcel and estuary science from around the coast.

Funding for this work was received from the Oregon Watershed Enhancement Board, the US Fish and Wildlife Service Fish Passage Program, with additional support from the Pacific Marine and Estuarine Fish Habitat Partnership and the Oregon Wildlife Foundation. Project partners include the City of Toledo, the Confederated Tribes of Siletz Indians, the Wetlands Conservancy, Pacific States Marine Fisheries Commission, Oregon Department of Fish and Wildlife and US Fish and Wildlife Service Partners for Fish and Wildlife.

News articles about this project