For nearly a century, two enormous concrete barriers interrupted Washington State’s Elwha River.

The Elwha Dam, completed in 1913, and the Glines Canyon Dam, completed in 1927, generated hydroelectric power that supported the economic development of the Olympic Peninsula. Neither, however, provided effective passage for the salmon and steelhead that historically migrated from the Pacific Ocean deep into the Elwha watershed.

The consequences stretched far beyond fish.

The dams blocked migrating salmon from most of the watershed. They trapped the sand, gravel, wood and nutrients that a free river would naturally transport downstream. Reservoirs accumulated enormous quantities of sediment. The river below the dams became sediment-starved, while the Elwha delta and nearby coastline eroded.

Then, after decades of campaigning by the Lower Elwha Klallam Tribe and its allies, the United States made an extraordinary decision.

Instead of building another structure to compensate for the damage, it would remove the structures causing it.

Congress passed the Elwha River Ecosystem and Fisheries Restoration Act in 1992. After nearly two decades of planning, dam demolition began in September 2011. The lower Elwha Dam disappeared in 2012. The larger Glines Canyon Dam followed, with removal completed in the summer of 2014.

For the first time in roughly a century, the river flowed uninterrupted from the Olympic Mountains to the Strait of Juan de Fuca.

What happened next turned the Elwha into one of the most important ecological restoration experiments ever attempted.

Salmon crossed former dam sites.

Millions of tons of sediment moved downstream.

Beaches began growing where they had been eroding.

Plants colonized hundreds of acres that had spent generations beneath reservoirs.

Wildlife moved into newly exposed landscapes.

And satellites orbiting hundreds of kilometers above Earth recorded the transformation.

The Elwha did not instantly return to some perfect pre-industrial condition.

Its recovery is still unfolding.

But the project demonstrated something profound:

Sometimes restoring an ecosystem does not mean engineering more of it. Sometimes the most powerful intervention is removing the barrier and allowing natural processes to begin working again.

Where Is the Elwha River?

The Elwha River flows for roughly 45 miles through Washington State’s Olympic Peninsula before reaching the Strait of Juan de Fuca.

Much of its watershed lies inside Olympic National Park, meaning the upper river is surrounded by a comparatively protected landscape rather than dense development. This made the Elwha unusually promising for restoration: once fish passage was restored, salmon would gain access to extensive high-quality habitat upstream.

The National Park Service describes the Elwha watershed as one of the largest ecosystem-restoration projects in the agency’s history.

But long before it became an international restoration case study, the river was central to the lives and culture of the Lower Elwha Klallam people.

Salmon were not merely an ecological resource.

They were food, livelihood, tradition and part of the cultural relationship between the Tribe and the river.

Before the Dams, Salmon Could Travel Deep Into the Watershed

Pacific salmon are migratory fish.

They hatch in freshwater, migrate to the ocean, spend part of their lives at sea and later return to freshwater to reproduce.

That life cycle depends on connectivity.

A river can contain beautiful spawning habitat hundreds of kilometers upstream, but if a concrete barrier prevents the fish from reaching it, that habitat effectively disappears from the salmon’s world.

Before dam construction, the Elwha supported numerous runs of anadromous fish.

The dams fundamentally changed that system. Together they ultimately blocked fish from approximately 90% of the watershed accessible to migrating species.

The first barrier was particularly consequential because it stood only about five river miles from the sea.

A fish travelling from the ocean could barely begin its upstream journey before encountering concrete.

The Elwha Dam Was Built Without Fish Passage

Construction of the Elwha Dam began around 1910 and finished in 1913.

The project generated electricity for the growing Port Angeles area and helped support industrial development.

But it lacked a fish ladder.

National Park Service historical materials note that obstructing salmon and steelhead streams was illegal under Washington law when the dam was constructed. A hatchery was later created as mitigation, but it proved ineffective and was abandoned in 1922.

Tribal oral histories remembered adult salmon gathering below the new barrier, unable to reach upstream spawning grounds.

A second structure made the problem even larger.

Glines Canyon Dam Extended the Barrier

The Glines Canyon Dam was constructed between 1925 and 1927 farther upstream.

It stood roughly 210 feet high and created Lake Mills inside what later became Olympic National Park.

Like the Elwha Dam, it lacked fish passage.

The two dams created Lake Aldwell and Lake Mills.

They generated electricity.

They also transformed the movement of an entire river system.

Water continued downstream.

Much of the river’s solid material did not.

Rivers Carry More Than Water

A river is not simply a pipe transporting water downhill.

Healthy rivers move:

• Sand
• Gravel
• Silt
• Logs and woody debris
• Organic material
• Nutrients
• Seeds

Those materials create channels, gravel bars, floodplains, spawning beds, estuaries and beaches.

When a dam blocks sediment, the reservoir acts like an enormous settling basin.

The water continues downstream.

The heavier material accumulates behind the barrier.

USGS researchers estimated that roughly 19 million cubic meters of sediment had accumulated behind the two Elwha dams before their removal. Later studies described approximately 21 million cubic meters, or roughly 30 million tonnes, exposed by reservoir drawdown.

That sediment had once been part of the river’s natural delivery system.

For almost a century, much of it never reached the lower river and coast.

The Coast Was Starving for Sediment

This is one of the least appreciated effects of dams.

A dam located kilometers inland can alter a beach.

Before dam removal, the lower Elwha River and its coastline were deprived of the sand and gravel normally transported from the mountains toward the sea.

USGS researchers found that this reduced sediment supply contributed to long-term erosion around the river’s coastal delta.

The coastline was essentially losing material faster than the river could replace it.

So when scientists discussed removing the dams, they were not only asking whether salmon would return.

They were asking what would happen when a century’s worth of stored sediment suddenly became available to a river again.

Congress Eventually Chose Restoration

The fight to restore the Elwha took decades.

The Lower Elwha Klallam Tribe played a central role in advocating for recovery of salmon and the river ecosystem.

In 1992, Congress passed the Elwha River Ecosystem and Fisheries Restoration Act, authorizing federal acquisition of the hydroelectric projects and measures required to restore the native anadromous fisheries and river ecosystem.

Studies eventually concluded that full dam removal offered the best path toward meaningful restoration.

But deciding to remove two major dams was easier than actually doing it.

Removing the Dams Could Not Happen All at Once

Imagine releasing enormous reservoirs and millions of cubic meters of sediment simultaneously.

The consequences downstream could have been severe.

Engineers therefore removed the structures gradually.

Dam removal began in September 2011, with water levels lowered in stages so the river could progressively cut through accumulated reservoir sediment.

The Elwha Dam was gone within roughly six months.

Glines Canyon required a longer removal process and was completed in 2014.

By then, a transformation visible from space was underway.

NASA Watched the Reservoirs Disappear

NASA used satellite imagery to document the Elwha restoration.

Images from the Landsat program show the former reservoirs shrinking as the dams were dismantled and the river re-established channels through sediment that had previously been submerged.

A later NASA comparison between 2011 and 2018 shows an especially dramatic contrast.

Before removal, Lake Aldwell and Lake Mills appear as large artificial bodies of water interrupting the river.

Afterward, the reservoirs are gone.

In their place are exposed valley floors, vegetation and a river channel reconnecting the upper watershed to the sea.

Satellite imagery makes the transformation appear almost instantaneous.

On the ground, however, rebuilding an ecosystem takes much longer.

The River Began Moving Sediment Again

Once reservoir drawdown exposed the sediment, the Elwha started doing what rivers do.

It eroded it.

Transported it.

Rearranged it.

Deposited it somewhere else.

A major scientific analysis found that approximately 20.5 million tonnes of trapped reservoir sediment were eroded during the early years following dam removal.

Another USGS study found that more than 10 million cubic meters moved out of the former reservoirs during the first two years, with approximately 90% of that material transported down the Elwha toward the coast.

Scientists had worried about what such an enormous sediment pulse might do.

Some ecological disruption did occur.

But downstream, something extraordinary also happened.

The Elwha Began Rebuilding Its Own Delta

For decades, the coast had been sediment-starved.

Now sand was arriving again.

National Park Service monitoring found that sediment released after dam removal produced more than one meter of sediment accumulation in parts of the estuary and expanded the river-mouth delta landform by more than 400 meters.

USGS researchers reported that sand began accumulating again along coastal habitats and helped reverse the long-term erosion associated with sediment deprivation.

This is one of the most visually remarkable parts of the story.

Removing dams far upstream did not merely alter the river channel.

It created new coastal land.

More Than 26 Hectares of New Delta Surface Formed

A 2024 review of vegetation and landscape response found that sediment deposition created approximately 26.8 hectares of new land surfaces around the delta.

Vegetation subsequently colonized roughly 16.4 hectares of those newly created surfaces.

In other words, sediment that had spent decades trapped behind concrete was transported downstream and transformed into:

• Beaches
• River bars
• Intertidal areas
• Marsh habitat
• New surfaces for plants

The river was not being manually reconstructed meter by meter.

Natural processes were rebuilding geography.

The Former Reservoirs Became Hundreds of Acres of New Land

The disappearance of Lake Aldwell and Lake Mills exposed approximately 290 hectares—more than 700 acres—of previously submerged sediment.

At first, much of that landscape looked barren.

Reservoir sediment stretched across large sections of the valley.

But the National Park Service and restoration partners had prepared for this stage.

They wanted native vegetation to establish quickly enough to stabilize soils and reduce opportunities for invasive plants.

Hundreds of Thousands of Native Plants Were Raised

Olympic National Park developed an ambitious revegetation program.

Its goals included:

• Re-establishing native forests
• Restoring ecosystem processes
• Limiting invasive species

More than 80 native plant species were incorporated into restoration planning. The park’s native plant program produced approximately 320,000 plants and 7,000 pounds of seed for the former reservoirs and associated restoration areas.

Species included:

• Douglas fir
• Western red cedar
• Red alder
• Black cottonwood
• Willow
• Salmonberry
• Snowberry
• Riverbank lupine

But restoration workers did not plant everything.

Natural recolonization was also allowed to occur.

That became another experiment.

Nature Did Not Follow the Restoration Plan Perfectly

One of the most valuable scientific lessons from the Elwha is that ecosystems often surprise the people attempting to restore them.

Researchers found that early predictions did not perfectly forecast which plants would thrive on different reservoir sediments.

Fine sediments, coarse sediments, reservoir drawdown timing and local landforms all influenced vegetation in different ways.

Planting trees and shrubs increased species richness but did not necessarily accelerate woody cover as much as expected.

Seeding reduced some non-native vegetation and performed differently depending on sediment type.

Meanwhile, native plants often established naturally from nearby forests.

The lesson was not that active restoration failed.

It was that successful restoration often combines human assistance with the ecosystem’s own capacity to organize itself.

Then the Salmon Started Going Upstream

The biological transformation that attracted the most attention involved salmon.

Removing both dams reopened more than 70 miles of mainstem river and tributary habitat to migratory fish.

After being excluded from the upper watershed for generations, salmon began appearing upstream of the former dam sites within months.

That is perhaps the clearest demonstration of what connectivity means.

For decades, high-quality habitat existed upstream.

The salmon did not need humans to explain where to go.

They needed the wall removed.

Fish Have Reached Above Both Former Dam Sites

Monitoring using snorkeling surveys, radio telemetry, sonar and environmental DNA has documented migratory fish recolonizing habitat beyond the former dams.

Chinook and coho salmon have achieved some of the widest distributions in the restored watershed, while steelhead have also shown strong recovery signals.

Researchers even found an encouraging genetic result in Elwha steelhead.

Fish populations isolated above the dams had retained enough genetic resilience that, once reconnection occurred, migratory steelhead could re-emerge without evidence that decades of isolation had erased their natural genetic diversity.

That suggests ecological potential can sometimes survive behind barriers for far longer than expected.

But the Salmon Story Is Not “Mission Accomplished”

It would be tempting to tell the Elwha story like this:

Dams removed.

Salmon returned.

Problem solved.

That would be wrong.

NOAA’s 2024 assessment found that Chinook salmon were showing increases in abundance and distribution, but adult productivity remained below recovery targets. Chinook therefore remained in what managers call the “Preservation” stage of recovery.

Steelhead had progressed further into a “Reintroduction” phase.

The National Park Service also reports that pink and chum salmon remain at critically low levels.

The Elwha therefore demonstrates both the power and the limits of dam removal.

Removing the barrier restores possibility.

It does not instantly repair a century of ecological disruption.

Salmon Recovery Can Take Generations

Salmon populations are shaped by much more than one river barrier.

Their survival is influenced by:

• Ocean conditions
• Water temperature
• Habitat quality
• Predation
• Fisheries
• Disease
• Genetics
• Climate change
• Hatchery interactions

A river can be restored while conditions elsewhere remain difficult.

The National Park Service cautions that full ecosystem recovery could take at least a generation or longer.

That makes sense.

A forest cannot mature in five years.

A salmon population cannot regain all of its historical abundance in one spawning cycle.

Restoration operates on ecological time rather than political time.

The Return of Salmon Affects Far More Than Salmon

Pacific salmon transport marine nutrients into freshwater and terrestrial ecosystems.

They spend part of their lives feeding in the ocean and then return upstream carrying those nutrients in their bodies.

After spawning, their carcasses become food for other organisms.

Olympic National Park notes that salmon support more than 130 species of insects, birds, fish and mammals during their life cycle.

Bears catch them.

Birds feed on them.

Aquatic insects consume biological material.

Nutrients eventually reach soils and plants.

So reopening migration routes does more than recover fish.

It restores a pathway connecting the Pacific Ocean with a mountain forest.

Wildlife Has Begun Using the Former Reservoirs Too

The reservoir beds did not remain empty spaces.

Camera-trap studies documented at least 15 mammal species using the newly exposed landscapes, including:

• Black bears
• Elk
• Deer
• Cougars
• Coyotes
• Bobcats
• Snowshoe hares

Researchers found that wildlife communities were already establishing on the recovering reservoir beds, although full restoration will take decades.

The former lake bottoms are gradually becoming terrestrial habitat again.

A place that spent nearly a century underwater is being incorporated back into the surrounding forest ecosystem.

Dam Removal Also Made the River More Dynamic

Ecological recovery is not always neat.

Without the dams controlling sediment and portions of river behavior, the Elwha became more dynamic.

Channels migrated.

Floodplains changed.

Logs moved downstream.

Flooding affected infrastructure, including roads and former campground areas.

National Park Service planning documents note that the river continues adjusting to its restored sediment regime and can shift channels as logjams form and high flows reshape the valley.

This highlights a difficult aspect of “restoring nature.”

People often want a restored river to behave predictably.

Natural rivers are not always predictable.

They move.

Flood.

Erode.

Deposit sediment.

Create channels and abandon others.

Restoring natural processes can therefore require humans to give rivers physical space.

The Elwha Was Not Simply an Environmental Project

For the Lower Elwha Klallam Tribe, restoration was also cultural.

The dams had severed people from salmon runs central to tribal life for generations.

The Tribe spent decades pushing for the river’s restoration and later participated directly in fisheries management, habitat restoration, revegetation and scientific monitoring.

That dimension is essential to understanding the project.

The Elwha story is sometimes presented as:

Scientists discovered dams were bad and removed them.

The real history is much longer.

Indigenous people living beside the river had objected to the loss of salmon generations before dam removal became mainstream environmental policy.

Is the Elwha Still the Largest Dam Removal Ever?

It was the largest dam-removal project in U.S. history when demolition began, and for years it remained the world’s defining example of large-scale dam removal.

It has since been surpassed in scale by the Klamath River dam-removal project in Oregon and California.

The final of four major Klamath dams targeted for removal came down in October 2024. The project reopened access toward hundreds of miles of habitat and has become the next enormous real-world laboratory for studying how rivers respond when century-old barriers disappear.

In a sense, the Elwha helped make the Klamath imaginable.

Scientists learned from the Elwha how sediment, vegetation, fish and river channels respond to large dam removals.

Now those lessons are informing restoration on an even larger river system.

What Did NASA’s Satellites Actually Show?

NASA’s Elwha imagery is powerful because it compresses years of ecological change into a pair of pictures.

The 2011 view shows:

• Lake Aldwell
• Lake Mills
• Two reservoir systems
• A river divided by infrastructure

Later imagery shows:

• Reservoirs largely gone
• Former lake beds exposed
• River channels crossing those sediments
• Vegetation beginning to establish
• A fundamentally different landscape

NASA specifically highlighted how dam removal restored sediment flow and allowed salmon access to upstream habitat.

Satellites cannot count every salmon.

They cannot record tribal cultural restoration.

But they can reveal something astonishing:

human infrastructure altered an entire landscape—and removing that infrastructure allowed the landscape itself to change again.

Did Removing the Dams Really Reverse Coastal Erosion?

Near the Elwha River mouth, yes, evidence strongly supports that conclusion.

The dams had reduced the sediment supply reaching the delta.

After removal, sand and gravel once again moved downstream and accumulated along the coast. USGS explicitly reports that this renewed sand supply helped reverse long-term erosion.

Researchers documented major shoreline and delta changes between 2011 and 2017 as waves and currents redistributed newly delivered sediment.

Studies also found that the sediment pulse created substantial new coastal wetland habitat within only a few years.

This is significant beyond the Elwha.

Across the world, many dams trap sediment that would otherwise replenish downstream deltas and coastlines.

As sea levels rise and erosion intensifies in many regions, restoring sediment connectivity could become an increasingly important component of coastal resilience.

Did All the Released Sediment Harm Marine Life?

Scientists expected disruption.

And there was disruption.

Large sediment pulses altered nearshore habitat and changed biological communities.

But longer-term studies found that the new sediment also created valuable habitat.

USGS research documented newly deposited areas supporting ecologically important organisms, including forage fish such as sand lance and shellfish such as geoducks.

Coastal vegetation expanded onto newly formed surfaces as well.

The important lesson is that disturbance and restoration are not opposites.

Healthy rivers naturally disturb landscapes.

Floods redistribute sediment.

Channels migrate.

Gravel bars appear and disappear.

Ecosystems evolved alongside those processes.

The dams had suppressed many of them.

What Makes the Elwha Such an Important Scientific Experiment?

Large dam removals are difficult to study because scientists rarely have comprehensive measurements from before, during and after the project.

The Elwha was different.

Researchers from the National Park Service, USGS, NOAA, universities and the Lower Elwha Klallam Tribe established extensive monitoring before demolition.

They then tracked:

• Sediment
• Water quality
• River channels
• Salmon
• Vegetation
• Wildlife
• Estuary conditions
• Nearshore ecosystems

USGS describes the project as a living laboratory whose lessons can guide future dam-removal and restoration decisions.

That makes the Elwha valuable even for rivers where removing a dam may not be appropriate.

It provides evidence about what happens when connectivity is restored at ecosystem scale.

Where Else Could Removing Barriers Make the Biggest Difference?

The Elwha does not demonstrate that every dam should be demolished.

Dams can provide essential services including:

• Drinking-water storage
• Flood protection
• Irrigation
• Navigation
• Hydropower

Removing an essential structure without replacement infrastructure could create serious social and economic harm.

The more useful question is:

Where do aging or obsolete barriers impose major ecological costs while providing relatively limited benefits that can be replaced?

The Elwha suggests several places where restoration may produce unusually large gains.

1. Rivers Where Migratory Fish Are Blocked From Large Areas of Good Habitat

The ecological return can be enormous when one barrier blocks access to dozens or hundreds of miles of otherwise suitable habitat.

That was the Elwha’s defining opportunity.

Once the dams disappeared, more than 70 miles became accessible again.

Similar logic applies not only to major dams but to smaller barriers.

Poorly designed road crossings and culverts can also obstruct fish migration, which is why NOAA maintains detailed fish-passage guidelines for stream infrastructure.

Sometimes the obstacle blocking an ecosystem is not a 200-foot dam.

It is one badly designed pipe beneath a road.

2. Sediment-Starved Rivers and Deltas

Where dams trap large quantities of sand and gravel, downstream consequences can extend all the way to the coast.

The Elwha showed that restoring sediment transport can:

• Rebuild beaches
• Expand deltas
• Create wetlands
• Restore estuarine habitat

The project provides unusually strong evidence that dam removal can reverse at least some forms of sediment-starvation-driven coastal erosion.

That makes sediment connectivity an important consideration when evaluating aging dams near vulnerable deltas.

3. Obsolete Dams That No Longer Provide Major Benefits

Dam removal is easiest to justify where a structure is old, expensive to maintain and no longer economically important enough to offset ecological damage.

The Elwha dams once contributed important electricity to regional development, but by the time restoration was seriously considered, the broader energy system had changed substantially.

The decision became not simply:

“Dams or no electricity?”

but:

“Do these particular dams still provide enough value to justify blocking an extraordinary river?”

That is the kind of calculation other communities can make.

4. Places Where Restoration Also Repairs Cultural Damage

The Elwha demonstrates that ecological restoration can also be cultural restoration.

For Indigenous communities whose fishing traditions, treaty rights or cultural landscapes were damaged by river barriers, restoration may have value that cannot be measured only through megawatts or fish counts.

The Lower Elwha Klallam Tribe’s decades of advocacy are inseparable from the river’s eventual restoration.

Similar decisions elsewhere should include Indigenous nations not simply as stakeholders consulted near the end, but as governments and knowledge holders involved from the beginning.

5. Watersheds Where Upstream Habitat Is Already Protected

The Elwha had another enormous advantage.

Much of the watershed above the dams lies inside Olympic National Park.

Once access was restored, salmon were not immediately entering a heavily industrialized or channelized upper river.

They were gaining access to extensive protected habitat.

That creates a powerful restoration equation:

Remove one barrier → reconnect an entire protected ecosystem.

Places with similar conditions may offer exceptionally high ecological returns.

The Klamath Is Now Testing the Idea at an Even Larger Scale

The removal of four Klamath River dams in Oregon and California, completed in 2024, has become the next landmark experiment in restoring river connectivity.

The Klamath is substantially more complicated than the Elwha.

It crosses multiple jurisdictions.

It supports agriculture.

It contains competing water demands.

Several Tribal nations have deep cultural connections to its salmon.

Its restoration will unfold amid drought and climate pressures.

But the basic ecological question is familiar:

What happens when salmon encounter an open river where generations before them encountered concrete?

The answer will take years to emerge.

The Elwha tells us it is worth watching.

The Elwha Is Not a Story About Nature “Healing Itself” Without Humans

There is a romantic version of restoration in which humans simply walk away and nature immediately repairs everything.

The Elwha does not support that interpretation.

Humans had to:

• Pass legislation
• Acquire the dams
• Engineer their removal
• Manage sediment risk
• Protect vulnerable fish during demolition
• Raise native plants
• Remove invasive vegetation
• Monitor salmon
• Restore habitat
• Conduct decades of scientific research

The Lower Elwha Klallam Tribe, federal agencies, state agencies, scientists, volunteers and conservation organizations all contributed.

What makes the project remarkable is the relationship between those interventions and natural processes.

Humans removed the barriers.

The river moved the sediment.

Humans planted hundreds of thousands of plants.

Millions more seeds arrived through natural dispersal.

Humans reopened the migration corridor.

The salmon chose where to swim.

Restoration created the conditions.

The ecosystem performed much of the rebuilding.

Ten Years After Dam Removal, the River Is Still Becoming Something New

It is tempting to imagine restoration as rewinding a landscape.

The Elwha cannot literally return to the year 1900.

Climate has changed.

Species populations have changed.

The surrounding human landscape has changed.

Some salmon runs remain severely depleted.

River channels have been altered for generations.

The coastline has changed.

What is happening instead is the creation of a functioning post-dam ecosystem.

Researchers are watching natural river processes reassert themselves while human restoration helps guide particularly vulnerable components.

That may be a more realistic definition of ecological restoration.

Not recreating the past perfectly.

Restoring enough biological and physical processes that an ecosystem can once again evolve on its own.

The Elwha’s Most Powerful Lesson

Humans are extraordinarily good at changing rivers.

We straighten them.

Dredge them.

Divert them.

Dam them.

Line them with concrete.

Build cities beside them.

For much of the industrial era, engineering success often meant forcing rivers to behave according to human expectations.

The Elwha offers another vision.

There, engineering was eventually used to give control back to the river.

And the response was visible almost immediately.

Sediment moved.

A delta grew.

Plants emerged.

Fish migrated.

Animals occupied new land.

NASA could see the landscape changing from orbit.

Yet the most important evidence is probably not the satellite photographs.

It is a salmon swimming beyond a place where, for the previous hundred years, its ancestors could go no farther.

The concrete disappeared.

The river remembered the route.

Frequently Asked Questions About the Elwha River Dam Removal

Where is the Elwha River?

The Elwha River is on Washington State’s Olympic Peninsula and flows from the Olympic Mountains into the Strait of Juan de Fuca. Much of its watershed lies within Olympic National Park.

How many dams were removed from the Elwha River?

Two major hydroelectric dams were removed: the Elwha Dam and Glines Canyon Dam.

When was the Elwha Dam built?

Construction occurred from approximately 1910 to 1913.

When was Glines Canyon Dam built?

Glines Canyon Dam was constructed between 1925 and 1927.

Why were the dams originally built?

They were hydroelectric projects intended to provide electricity for local industrial and economic development around Port Angeles.

Did the Elwha dams have fish ladders?

No. Neither dam provided effective fish passage for migrating salmon and steelhead.

How much of the Elwha watershed did the dams block?

Together they blocked migrating fish from approximately 90% of the watershed.

Why were the Elwha dams removed?

Congress authorized restoration to recover the Elwha River ecosystem and native anadromous fish populations after decades of ecological damage and advocacy by the Lower Elwha Klallam Tribe and others.

When did Elwha dam removal begin?

Removal began in September 2011.

When was the Elwha Dam completely removed?

The lower Elwha Dam was removed in 2012, about six months after the broader demolition project began.

When was Glines Canyon Dam removed?

Removal was completed in the summer of 2014.

Was the Elwha project the largest dam removal in history?

At the time, it was the largest dam-removal project in U.S. history and became an internationally important restoration experiment. Larger-scale removal later occurred on the Klamath River, where four dams were removed by 2024.

How much sediment was trapped behind the Elwha dams?

Pre-removal estimates placed the amount around 19–21 million cubic meters, equivalent to roughly 30 million tonnes of reservoir sediment exposed during removal.

What happened to that sediment?

Much of it was eroded from the former reservoirs and transported downstream. Research found approximately 20.5 million tonnes moved during the early post-removal period.

Did the sediment reach the ocean?

Yes. Large quantities reached the Strait of Juan de Fuca and were redistributed around the Elwha River mouth by waves and currents.

Did dam removal help reverse coastal erosion?

Yes. USGS reports that renewed sand deposition after dam removal helped reverse long-term erosion along sediment-starved coastal habitats near the river mouth.

How much did the Elwha delta expand?

National Park Service monitoring reports more than 400 meters of expansion of the river-mouth delta landform after renewed sediment delivery.

Did the dam removal create new land?

Yes. Research found approximately 26.8 hectares of new delta surfaces created through sediment deposition.

Did vegetation grow on the new land?

Yes. Researchers documented vegetation colonizing about 16.4 hectares of newly created delta surfaces, while hundreds of acres of former reservoir beds also began revegetating.

How much reservoir land was exposed?

Approximately 290 hectares, or more than 700 acres, of previously unvegetated reservoir sediment was exposed.

Did restoration crews plant the former reservoirs?

Yes. Olympic National Park produced approximately 320,000 native plants and 7,000 pounds of seed while also relying heavily on natural recolonization.

What plants returned?

Restoration included native species such as Douglas fir, red alder, black cottonwood, western red cedar, willow, salmonberry and riverbank lupine.

Did salmon return after the dams were removed?

Yes. Salmon began recolonizing habitat upstream of the former dams within months.

How much salmon habitat was reopened?

More than 70 miles of mainstem river and tributary habitat became accessible to migratory fish.

Which salmon species have returned upstream?

Monitoring has documented several anadromous species above former dam sites, with Chinook and coho among the most widely distributed. Steelhead have also shown strong signs of recovery.

Have Chinook salmon fully recovered?

No. NOAA reported increasing abundance and distribution but adult productivity remained below recovery targets as of its 2024 assessment.

Which fish appear to be recovering fastest?

Steelhead have shown particularly encouraging progress and advanced further in NOAA’s adaptive recovery framework than Chinook.

Are any salmon populations still doing badly?

Yes. National Park Service monitoring reports that pink and chum salmon remain critically low.

Did NASA photograph the Elwha dam removal?

Yes. NASA published satellite imagery from the Landsat program showing the reservoirs draining and the river landscape changing during and after dam removal.

Can you actually see the reservoirs disappear from space?

Yes. NASA comparisons clearly show Lake Aldwell and Lake Mills before removal and the exposed river valleys afterward.

Did wildlife return to the former reservoirs?

Yes. Camera studies recorded at least 15 mammal species using the recovering reservoir landscapes, including bear, elk, deer, cougar, coyote and bobcat.

Why are salmon important to the wider ecosystem?

Salmon transport marine-derived nutrients upstream and provide food for a large range of wildlife. Olympic National Park notes that more than 130 species can benefit from salmon during their life cycle.

Did the Lower Elwha Klallam Tribe support dam removal?

Yes. The Tribe spent decades advocating for restoration of the river and salmon and remains deeply involved in fisheries, ecological restoration and scientific monitoring.

Was dam removal good in every possible way?

No. Releasing large amounts of sediment caused major short-term disturbance, and the newly dynamic river has affected infrastructure including roads and former campground areas.

Does the Elwha prove all dams should be removed?

No. Many dams provide essential services. The Elwha demonstrates what may be possible where ecological damage is high, replacement options exist and removing a barrier can reconnect extensive high-quality habitat.

What is the biggest dam-removal project now?

The four-dam removal on the Klamath River in Oregon and California surpassed the Elwha project in scale. The final targeted dam was removed in October 2024.

Did the Elwha influence later dam-removal projects?

Yes. USGS and NOAA researchers explicitly use lessons from the Elwha to inform dam-removal science and restoration work elsewhere, including the Klamath.

Has the Elwha River completely recovered?

No. Recovery is ongoing and may take generations. Some salmon populations remain below desired levels, forests are still developing and the river continues adjusting physically.

What is the most important lesson from the Elwha River restoration?

The Elwha demonstrates that removing a major ecological barrier can restart processes that engineering had suppressed for almost a century.

Humans did not manually rebuild every beach.

They restored sediment movement.

They did not place every salmon in its historical spawning ground.

They reopened the river.

They did not design every future forest.

They exposed the land, planted native species and allowed natural succession to continue.

The transformation is therefore not simply a story about demolishing two dams.

It is a story about connectivity.

A river connected to its sediment.

A coastline connected to its mountains.

Salmon connected to spawning habitat.

Forests connected again to nutrients carried from the ocean.

And a Tribal community reconnecting with a river whose salmon had been blocked for generations.

The Elwha reminds us that ecosystems can retain an extraordinary capacity for recovery.

Sometimes the most consequential thing humans can build is a dam.

And sometimes the most consequential thing we can do is take one away.