Protected and Restored Habitat
Area of estuarine wetlands restored to tidal flooding
Vital Sign Indicator
Acre (acres)

By 2020, restore 7,380 quality acres of estuarine wetlands basin-wide, which is 20% of total estimated restoration need.

Tish Conway-Cranos
Contributing Partners
Last Updated
10/22/2020 9:02:14 AM
Map shows the location (blue point) and footprint of estuarine wetlands restored to full (blue) and muted (yellow) tidal inundation in Puget Sound's 16 large river deltas between 2006-2020. The delta extent (orange) represents both functional and potential (disconnected) estuary area. Pan and zoom in on the map to explore estuarine restoration projects throughout Puget Sound.
This indicator tracks the annual area of estuarine wetlands restored to tidal flooding in Puget Sound's 16 large river deltas. The recovery of estuarine wetlands through the full reconnection of tidal flows is directly tied to the provision of ecosystem services, and produces immediate benefits to estuary dependent organisms like juvenile salmon.
Vital Sign Indicator Chart
Area of estuarine wetlands restored to tidal flooding
By: Area Restored
Surface area (acres) of estuarine wetland restored to full tidal flooding in Puget Sound large river deltas by year. Purple line shows cumulative acres restored beginning in 2006.

This indicator tracks the amount of land returned to tidal flooding in the deltas (the landform that is formed at the mouth of a river where it meets Puget Sound) of Puget Sound's 16 major rivers (Deschutes, Dosewallips, Duckabush, Dungeness, Duwamish, Elwha, Hamma Hamma, Nisqually, Nooksack, Puyallup, Quilcene, Samish, Skagit, Skokomish, Snohomish, Stillaguamish). Tidal wetlands offer a suite of ecosystem services, including providing rearing habitat for salmonids.

Restoration of tidal flooding is the critical act that begins the process of recovery—the restoration of fish access and sediment supply, and development of salt adapted vegetation and soils. Evidence collected to date indicates that full reconnection of tidal flows produces immediate benefits to estuary dependent organisms like juvenile salmon. More sophisticated project monitoring is underway to evaluate various sources of risk to sustained recovery of delta ecosystems.

Key Vital Sign Indicator Results
  • There has been incremental progress in restoring river estuaries in Puget Sound since 2006. However, this indicator is behind expectations for restoration in certain areas.
  • Using the new, standardized method to delineate the extent of estuary restoration, approximately 3,430 acres, or about 46 percent of the 2020 target, of estuarine river delta wetlands were restored to tidal flooding between 2006 and 2020.
  • In 2019, the Leque Island Estuary Restoration Project restored 250 acres of tidal marsh habitat in the Stillaguamish River delta. No projects to restore tidal inundation were completed in 2020 in Puget Sound's large river deltas. 
Monitoring Program

Washington State Department of Fish and Wildlife Estuary and Salmon Restoration Program

Data Source

Washington State Department of Fish and Wildlife Estuary and Salmon Restoration Program

Washington State Recreation and Conservation Office’s Project Information System (PRISM)

Estuary restoration projects have been planned, funded, and implemented over two decades by local, state, tribal and federal governments, non-profit organizations, conservation districts, and private parties. The data shown in this report are an estimate of the surface area affected by restored tidal inundation. Puget Sound Partnership staff compiled data for each year since 2006. Projects are primarily identified from the Washington State Recreation and Conservation Office’s Project Information System (PRISM) database under the criteria that they 1) restore tidal inundation, 2) occur within the large river delta boundaries, and 3) were completed in 2006 or later.

As part of a joint effort between the Puget Sound Partnership, Washington Department of Fish and Wildlife, National Oceanic and Atmospheric Administration, and the University of Washington, a standardized method has been developed to characterize and report on the extent (surface area) of restored tidal inundation to the 16 largest river deltas in Puget Sound. The methodology and its application to restoration projects is described in Ramirez 2019. This GIS-based method is intended to eliminate inconsistencies in reporting across projects and to provide a repeatable method for mapping tidal wetland extent, which can facilitate more sophisticated analyses of ecosystem function following restoration.

For each project selected, project level information was gathered to identify tidal hydrology changes associated with barrier removal or relocation. Where tidal inundation was restored, project information, aerial imagery, and LiDAR digital elevation models were referenced to digitize a polygon within the estuary extent (PMEP 2017) to determine the footprint of estuarine wetlands restored to tidal inundation.

Pacific Marine and Estuarine Fish Habitat Partnership (PMEP). 2017. West Coast USA Current and Historical Estuary Extent. PMEP Spatial Data System. Portland, Oregon.

Ramirez, M. 2019. Tracking Estuarine Wetland Restoration in Puget Sound: Reporting on the Puget Sound Estuaries Vital Sign Indicator. Report prepared for the Puget Sound Partnership at the University of Washington, Seattle, WA.

Critical Definitions
Interpretation of Results

Large acreage has been gained on the Dungeness, Quilcene, Skokomish, Skagit, Nooksack, Stillaguamish, Snohomish and Nisqually river deltas (figure below). In particular, work in the Quilcene, Skokomish, and Nisqually has restored almost the full extent of historical tidal flows.

While substantial gains have been made in the Nooksack, Skagit, Stillaguamish, and Snohomish estuaries, acreages remain modest when compared to the mammoth historical extent of these river deltas. Many smaller projects have been completed in the industrialized Duwamish and Puyallup river deltas as a result of salmon recovery actions as well as Natural Resource Damage Assessments linked to Superfund cleanups.

Additional projects have restored estuary wetlands outside of the deltas, at natal estuaries for salmon other than Chinook. These efforts are much smaller in scale, but are significant in that migrating fish also benefit from a distributed network of high quality shoreline rearing opportunities. We will ultimately benefit from developing strategies that track the protection and restoration of more distributed networks of tidal wetland habitats.

Although the acreage area restored to tidal flooding is our primary indicator, many efforts are concerned with how river flows are distributed over deltas. For example, in conjunction with the well-publicized restoration of tidal flow in the west bank Nisqually Refuge, the Nisqually Tribe was completing efforts to restore river flooding over the east bank into Red Salmon Slough. By contrast, the removal of Elwha dams has allowed the expansion of the sediment starved Elwha Delta through natural processes. Salmon recovery targets on the Skagit hinge on reconnecting Skagit river flow through a middle distributary to Fir Island marshes.

At the current rate of progress, the indicator will be far short of the 2020 target. Project work is constrained by limited human resources, unpredictable capital funding flows, and social conflicts over returning low lying farmland to the tides.

Surface area (acres) of estuarine wetland restored to full tidal inundation in Puget Sound large river deltas by year.



Link to interim targets

Progress toward 2018 interim target.
2018 Interim Target Was it met? Explanation
6,204 acres of river deltas regain tidal flow. No A total of 3,178 acres regained tidal flow between 2006 and 2018.


Of the 16 major rivers in the Puget Sound watersheds, the largest rivers drain the Cascade Mountains, and the smallest drain the Olympic Mountains. These estuaries and wetlands were a cornerstone of the Puget Sound ecosystem and served as a critical nursery for historically large populations of now-threatened Pacific salmon.

Over the last 150 years, the region has suffered dramatic losses of intertidal wetlands. Of the approximately 62,000 vegetated acres of mapped historical swamp and marsh, only an estimated 14,640 acres remain. The swamps of the Skagit and Snohomish alone once contained over 37,000 acres of vegetated wetlands (compared to around 1,620 acres for all the Olympic deltas combined). In the most highly developed river mouth estuaries, such as the Duwamish and Puyallup rivers, estuarine habitat has been reduced to only a tiny fragment of its original extent, and is unlikely to be recovered.

These losses can be attributed to agricultural and industrial development. Estuaries and tidal wetlands provided an opportunity to develop flat land near water, and were diked, drained, and in some cases filled. Diking and drainage allowed for development of farms on rich fertile marsh soils, and dredging and filling enabled the construction of modern ports and industrial sites. Loss of intertidal wetlands has contributed to the decline of many species, especially Chinook and chum salmon that depend on river delta estuaries for rearing habitat.

In addition to direct conversion, the management and modification of our large rivers has affected delta health and resilience. Dams and reservoirs capture sediment that would otherwise build deltas. Flood defenses pipe the remaining sediments into deeper water, burying historical eelgrass meadows. The load of nutrients and toxins now in our waters have known effects on some biota, but poorly understood effects on delta ecosystems overall.

Diverse salmon recovery and watershed restoration groups are working with the support of local, state, and federal funding to set local watershed-specific restoration targets, identify willing landowners, and work through sometimes intense local politics to restore estuarine wetland habitat. These efforts are technically complex, and often require strong partnerships in a challenging social, economic, and natural environment.

Habitat losses still occur, but by more subtle mechanisms than the large-scale historical losses. While dredging, log rafting, nutrient loading, and toxic storm water continue, perhaps the most significant risk to existing estuarine wetlands may now come from sea level rise. Where river sediments are insufficient and dikes prevent migration landward, wetlands may ultimately be squeezed out of existence by rising tides. The predicted subsidence of diked land, rising seas, more violent storms, and increased river flooding portend a developing crisis that will define the future of river delta landscapes.

Advances in remote sensing technologies, current investments in long term fish monitoring, and strategic investment in delta restoration science promise to improve our understanding of the effects of habitat gains and losses and the natural dynamics of delta ecosystems, allowing us to improve our efficiency by informing where and how to restore these unique and irreplaceable landscapes.


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Reporting Guidance
Reporting Instructions
Area Restored
Cumulative Acres Restored, Acres Restored, 2020 Recovery Target