U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2018–3025 

April 2018 Printed on recycled paper

Glines Canyon (left) and the Elwha (right) dams before (top) and after (bottom) they 

were removed from the Elwha River. Photographs by John Gussman, private citizen.

Science Partnership Between U.S. Geological Survey and the Lower Elwha 

Klallam Tribe: Understanding the Elwha River Dam Removal Project 

The Elwha River Dam Removal and 

Ecosystem Restoration Project

After nearly a century of producing power, two large 

hydroelectric dams on the Elwha River in Washington State 

were removed during 2011 to 2014 to restore the river 

ecosystem and recover imperiled salmon populations. Roughly 

two-thirds of the 21 million cubic meters of sediment—enough 

to fill nearly 2 million dump trucks—contained behind the 

dams was released downstream, which restored natural 

processes and initiated important changes to the river, estuarine, 

and marine ecosystems. A multidisciplinary team of scientists 

from the Lower Elwha Klallam Tribe (LEKT), academia, nongovernmental organizations, Federal and state agencies, and 

the U.S. Geological Survey (USGS) collected key data before, 

during, and after dam removal to understand the outcomes of 

this historic project on the Elwha River ecosystem.

USGS — Lower Elwha Klallam Tribe 

Science Partnership

Since time immemorial, 

the Lower Elwha Klallam Tribe 

has depended on the Elwha 

River for spiritual, cultural, 

and economic sustenance.

Natural resources staff from the

Lower Elwha Klallam Tribe 

have partnered with scientists 

from USGS for decades, with 

a particular emphasis on monitoring the Elwha River and its 

coastal zone where the Tribal Reservation is located. This

ongoing and mutually beneficial science partnership created 

an information legacy that will help the Lower Elwha Klallam 

Tribe understand the changes resulting from dam removal and 

manage their coastal resources into the future.

Key Lessons Learned So Far

• The river adjusted to the sediment release faster than 

scientists anticipated.

• With restored hydrologic connectivity, the Elwha River now more 

closely resembles other wild rivers of the Olympic Peninsula.

• Salmon are returning to the main stem and tributaries upstream 

of the former dams.

• The estuary and coastal beaches are expanding, with 

communities of plants, aquatic organisms, and bird life using 

the new habitats. 

• Marine environments off the river mouth have 

fundamentally shifted toward a restored state.

Photographs (left to right): Measuring a juvenile salmon, a clown nudibranch

(Triopha catalinae), a candy striped shrimp (Lebbeus grandimana) with a sand 

rose anemone (Urticina columbiana), kelp (Pterygophora californica) in new 

sediment, and Tribal canoes. Tribal canoes photograph by John Gussman. All 

other photographs by U.S. Geological Survey.
>10,000

500 − 999

1,000 − 4,999

5,000 − 9,999

100 − 499

<100

Total suspendedsediment 

concentration (mg/L)

USGS water-quality 

monitoring 

station No. 12046260

Daily average 

discharge (m3

/s)

Annual percentage 

in each 

concentration bin

EXPLANATION

220 240 260

0

100

80

60

40

20

0 20 40 60 80 100 120 140 160 180 200

2012

Discharge (m3/s) Proportion of week (percent)

0

400

300

200

100

2011 2013 2014 2015 2016 Year

Week

Figure 1. River discharge (top) and suspended-sediment 

concentration at low to high concentration on weekly (middle) 

and annual (bottom) basis. Sediment concentration values 

based on turbidity measurements collected every 15 minutes 

and a series of suspended-sediment concentrations from 

across a range of streamflow conditions (photographs). Data 

based on Magirl and others (2015).

 2011 2012 2013 2014 2011 2012 2013 2014

Salinity (PSU) Depth (m) Temperature (°C) Turbidity (NTU)

East Elwha estuary West Elwha estuary

0

10

20

30

40

0

0.5

1

2 2

1.5

0

5

10

15

20

25

0

500

1,000

1,500

10

20

30

40

0

0.5

1

1.5

5

10

15

20

25

0

500

1,000

1,500

0

0

Figure 2. Water-quality samples collected from the east and west sides of the Elwha River estuary 

during dam removal. An increase in turbidity (bottom) and decrease in salinity (top) began when 

sediment load increased beginning in 2013. Images (left) and graphic from Foley and others (2015).

Estuary — Physical

The Elwha River efficiently transported more 

than 90 percent of the eroded sediment from the 

reservoirs to the coastal zone (Warrick and others, 

2015). Accumulation of sediment at the mouth of 

the river led to rapid and persistent changes to the 

estuary, as measured by water-quality instruments 

installed by USGS and Tribal scientists (fig. 2). 

Before dam removal, the river mouth routinely 

fluctuated as tidal and river flow conditions 

mixed fresh and salt water in the estuary. After 

dam removal, large sediment deposits formed, 

eliminating the tidal influence and turning most 

of the “old estuary” into freshwater-dominated 

habitat (Foley and others, 2015).

River Sedimentation

Dam removal on the Elwha River released a 

massive amount of sediment into the river, similar 

to observations of rivers following the eruption 

of a moderately sized volcano (Foley and others, 

2015). In the first 3 years after dam removal, the 

river was choked with sediment that filled pools 

and, at times, created a sand-bedded channel (East 

and others, 2015) that was much different from the 

more typical cobble-gravel river bottoms in natural 

sections of the river upstream. After passage of 

the large sediment pulse, the shape and character 

of the riverbed downstream of the dams started 

to resemble pre-dam conditions. Monitoring 

of the river upstream and downstream of the 

dam removal projects (Magirl and others, 2015) 

indicated high suspended-sediment concentrations 

during dam removal, with progressively decreased 

sediment concentration in later years (fig. 1).

June 2013

October 2013
Estuary — Biological

New habitat and landforms were created in the estuary, 

reversing decades of erosion and habitat loss (fig. 3). This 

shifting habitat mosaic, caused by the changing landforms and 

a new water regime, has prompted responses in estuarine plant 

and animal species. Although total plant species richness and 

relative density was stable, the amount of pioneer vegetation 

increased in response to the newly forming habitat. Benthic 

invertebrates declined due to dam removal across seasons, 

likely due to sediment deposition. The estuarine fish community 

changed in the former estuary, favoring freshwater adapted 

species, while still functioning as a nursery for juvenile salmon. 

As the river mouth delta expanded seaward, new estuarine 

habitat was created and used by salmon, shorebirds, and their 

invertebrate prey.

Vegetation

Geomorphology

Mixed riparian forest

Willow-alder forest

Riparian shrub

Emergent marsh transition

Dunegrass

Mixed pioneer vegetation

Roads and residental

Aquatic

Beach 

River bar 

River mouth bar 

Coastal waters

N

2009 2011

2012 2013 2014

Before dam removal

During dam removal

Difference

2011–14

(percent)

-3

-10

8

15

-3

63

140

173

480

567

0

0 500 1,000 1,500 feet

250 500 meters

Figure 3. Time series of coastal habitat change of the Elwha River estuary during dam removal. Modified from Foley and others (2017). 

Seafloor mapping.

Coastal — Physical

Before the dam removal project, 

the beaches around the Elwha River 

mouth—including those fronting 

the Lower Elwha Klallam Tribal 

Reservation—had been eroding 

at more than 1 foot per year, a 

rate that was increasing with time 

(Warrick and others, 2009). This 

coastal erosion resulted in the loss of 

Reservation lands, including coastal 

wetlands. Dam removal changed 

this erosional trend and resulted in the creation of broad, new beaches 

and a new estuary complex near the river mouth (fig. 4; Gelfenbaum and 

others, 2015). Although the coastal waters remained turbid, or cloudy 

with sediment, during the dam removal project, this condition has 

improved considerably in the years following dam removal.

Figure 4. Time series of beach and seafloor mapping of the Elwha River mouth 

before, during, and after dam removal. For detailed methods, see Gelfenbaum and 

others (2015). Image courtesy of Andrew Stevens, U.S. Geological Survey.

Before During

After

-5 0 5

Elevation, in meters

0

0 500 1,000 1,500 feet

250 500 meters

Aug 2011

Mar 2013

Sep 2014

Feb 2016 Jul 2016 Jul 2017

Jan 2015 Jul 2015

Sep 2013 Apr 2014

May 2012 Aug 2012
Coastal — Biological

 For 10 years, scuba divers from USGS, LEKT, and other 

partners monitored the ecosystem responses on the seafloor of the 

Strait of Juan de Fuca near the Elwha River (Rubin and others, 

2017). The response of biological communities to dam removal 

varied with distance from the river mouth. In most places near the 

river mouth (sediment source), the increased turbidity decreased 

light availability to kelp and algae, which led to a significant decline 

in abundance. For other taxa like clams, tubeworms and some fish, 

significant changes were seen only when the sediment accumulated 

on the seafloor, and in some cases the changes attracted species such 

as the Pacific sand lance (Ammodytes hexapterus), which increased 

in abundance (fig. 5) in newly deposited sand after dam removal. 

Importantly for the Tribe, the return of abundant Dungeness crab 

along the new Elwha River delta allowed a productive fishery to 

resume for the first time in the memory of many Tribal fishers.

References Cited

East, A.E., Pess, G.R., Bountry, J.A., Magirl, C.S., Ritchie, A.C., 

Logan, J.B., Randle, T.J., Mastin, M.C., Minear, J.T., Duda, J.J., 

and Liermann, M.C., 2015, Large-scale dam removal on the Elwha 

River, Washington, USA—River channel and floodplain geomorphic 

change: Geomorphology, v. 228, p. 765–786.

Foley, M.M., Duda, J.J., Beirne, M., Paradis, R., and Warrick, J.A., 

2015, Rapid physical change in the Elwha River estuary complex 

during dam decommissioning: Limnology and Oceanography, v. 60, 

p. 1719–1732. 

Foley, M., and Warrick, J.A., 2017, Ephemeral seafloor sedimentation 

during dam removal—Elwha River, Washington: Continental Shelf 

Research, v. 150, p. 36–47.

Foley, M.M., Warrick, J.A., Ritchie, A., Stevens, A.W., Shafroth, P.B.,

Beirne, M.M., Paradis, R., Duda, J.J., Gelfenbaum, G., McCoy, R., 

and Cubley, E.S., 2017, Coastal habitat and biological community 

response to dam removal on the Elwha River: Ecological 

Monographs, v. 87, p. 552–577.

Gelfenbaum, G., Stevens, A.W., Miller, I.M., Warrick, J.A., Ogston, 

A.S., and Eidam, E., 2015, Large-scale dam removal on the 

Elwha River, Washington, USA—Coastal geomorphic change: 

Geomorphology, v. 228, p. 649–688.

Magirl, C.S., Hilldale, R.C., Curran, C.A., Duda, J.J., Straub, T.D., 

Domanski, M., and Foreman, J.R., 2015, Large-scale dam removal 

on the Elwha River, Washington, USA—Fluvial sediment load: 

Geomorphology, v. 246, p. 669–686.

Rubin, S.P., Miller, I.M., Foley, M.M., Berry, H.D., Duda, J.J., Hudson, B.,

Elder, N.E., Beirne, M.M., Warrick, J.A., McHenry, M.L., Stevens, 

A.W., Eidam, E.F., Ogston, A.S., Gelfenbaum, G., and Pedersen, 

R., 2017, Increased sediment load during large-scale dam removal 

changes nearshore subtidal communities: PLoS ONE, v. 12, no. 12, 

p. e0187742.

Warrick, J.A., Bountry, J.A., East, A.E., Magirl, C.S., Randle, T.J., 

Gelfenbaum, G., Pess, G.R., Leung, V., and Duda, J.J., 2015, Largescale dam removal on the Elwha River, Washington, USA—Sourceto-sink sediment budget and synthesis: Geomorphology, v. 246, 

p. 729–750.

Warrick, J.A., George, D.A., Gelfenbaum, G., Kaminsky, G., and 

Beirne, M., 2009, Beach morphology and change along the mixed 

grain-size delta of the Elwha River, Washington: Geomorphology, 

v. 111, p. 136–148.

West Mouth East Control

EXPLANATION

Brown algae Invertebrates Fish

0 0.0

2

4

6

8

Density (number/m2

)

0

2

4

6

8

0.1

0.2

0.3

0.4

0.5

 Pre 2012 2013 2014 Pre 2012 2013 2014 Pre 2012 2013 2014

Figure 5. Response of seafloor biological communities to dam removal, 

Strait of Juan de Fuca near the Elwha River. Data represent average density 

of brown algae, invertebrates, and fish counted on permanently located 

seafloor transects over a 10-year period. Control location at Green Point is 21 

kilometers east of the Elwha River. Data from Rubin and others (2017).

Partners

We gratefully acknowledge the contributions and 

collaborations that benefited this work from the National Park 

Service, National Oceanographic and Atmospheric Administration, 

Washington Sea Grant, University of Washington, Bureau of 

Reclamation, U.S. Fish and Wildlife Service, and other members 

of the Elwha Research Consortium. The U.S. Environmental 

Protection Agency, the Puget Sound Partnership, the Lower Elwha 

Klallam Tribe, and USGS provided key funding for the science and 

the USGS Office of Tribal Relations provided publishing support.

Photograph by Tom Roorda, private citizen, 2012.

Authors: 

Jeffrey J. Duda - jduda@usgs.gov

Matt M. Beirne - beirne@elwha.org 

Jonathan A. Warrick - jwarrick@usgs.gov

Christopher S. Magirl - magirl@usgs.gov

For more information:

Regional Executive, U.S. Geolocical Survey Northwest Area

909 First Ave., Suite 800, Seattle, WA 98104

Email: nwa_dropbox@usgs.gov/northwest / Phone: 206-220-4600

U.S. Geological Survey Elwha River science portfolio

http://www.usgs.gov/elwha

Lower Elwha Klallam Tribe - http://www.elwha.org

All photographs used with permission.

Publishing support provided by the U.S. Geological Survey,

Tacoma Publishing Service Center

Design: William Gibbs ISSN 2327-6916 (print)

ISSN 2327-6932 (online)

https://doi.org/10.3133/fs20183025