1. The Significance of Dam Removal in the United States and the Recovery of
Anadromous Species
Harrison Corbett
Fall 2015
ENSC 450 ProSeminar
For Dr. Terrianne Lavin
Abstract:
With the recent removal of multiple large-scale dams, it is clear that the breaching of barriers and
reopening of riverways will help recolonize anadromous and catadromous fish populations. Dam
removals in both the Pacific northwest and Atlantic northeast have set a precedent for the future
of dams in the US.

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Introduction:
There are approximately 75,000 dams in the United States, and of these dams
approximately 66,000 are located on rivers (American Rivers 2012). “Think about that number.
That means we have been building, on average, one large dam a day, every single day, since the
Declaration of Independence” (Babbitt 1998, n.p.). A study conducted by the US Energy
Information Administration in 2006 showed that hydroelectric power only accounted for 7.1% of
total energy used (USGS Water Science School 2015). In the early 20th
century, the construction
of dams became a way for America to boost its economy. The construction of dams was not
strictly for the production of hydropower, but for flood control, irrigation, and recreation as well.
In 1907, President Theodore Roosevelt created the Inland Waterways Commission in order to
further analyze the industrious use of river systems in the US. In the Commission’s initial report
to congress, Roosevelt stated,
It is poor business to develop a river for navigation in such a way as to prevent
its use for power, when by a little foresight it could be made to serve both
purposes. We cannot afford needlessly to sacrifice power to irrigation, or
irrigation to domestic water supply, when by taking thought we may have all
three. Every stream should be used to the utmost (Roosevelt 1908, 7).
While it may be true that the construction of dams was an asset to the US’s economy in
the early 1900s and contributed to the country’s manifest destiny mindset, currently, dams serve
little to no purpose and are far more harmful than they are beneficial.
The current existence of dams in the US is a controversial topic as many environmental
groups push for dam removal and the re-opening of riverways for anadromous and catadromous
species. Dams have become increasingly contentious recently due to the massive push for
alternative renewable energy sources, such as solar and wind power. It is difficult to view dams
and hydroelectricity as renewable forms of energy, as hydroelectric dams harm local species with

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unintentional consequences. Barriers can be detrimental to fish populations, as they alter the flow
of nutrients and sediments downstream, as well as cause increased water temperatures, all of
which are not suitable for many species of anadromous and catadromous fish.
Anadromous species are species that are born in fresh water, live in salt water, and return
to fresh water to spawn. Conversely, catadromous species are born in salt water, live in fresh
water, and return to salt water to spawn. Having barriers, such as dams in riverways, prevents
fish from efficiently navigating the river and spawning, which ultimately leads to a declination in
species population. Many methods have been invented over the past few decades to assist fish in
passage through these barriers, however none have proven useful. With the removal of barriers in
the US river systems, anadromous and catadromous species will see a massive increase in
population.
History:
The process of building a dam starts with finding the right location. A river system must
be found that is not too close, but not too far, from civilization or developing areas. Over the past
century, many of the US’s greatest treasures have met these criteria and, therefore, have been
subject to flooding. Hetch Hetchy Valley was flooded in 1923 with the completion of the
O’Shaughnessy Dam to provide San Francisco with drinking water. John Muir, founder of the
Sierra Club, stated in opposition, “Dam Hetch Hetchy! As well dam for water-tanks the people's
cathedrals and churches, for no holier temple has ever been consecrated by the heart of man”
(Muir 1912, Chapter 16, n.p.). Muir’s views on dam construction were not unwarranted, with
eight (8) dam failures between 1874 and 1916 accounting for approximately 2,500 fatalities,
along with creating immeasurable, longstanding ecological problems. In 1928, the St. Francis
Dam, located approximately 40 miles northwest of Los Angeles in the San Francisquito Canyon,

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failed resulting in 600 fatalities (Stansell 2012). William Mulholland, chief architect of the St.
Francis Dam, was quoted saying “Fasten it on me. If there was any error of judgment, human
judgment, I was the human” (Los Angeles Times 1928). Damming river systems in the US has
always been debated, but as we look toward a greener future, the construction of new barriers is
not appealing.
Dams work by being built on a river that has a large change in elevation. This allows the
water in the reservoir to increase its potential energy. Controlled passage of the water allows for
turbines to spin and generate power which can be stored and sold. However, just the presence of
a barrier, such as a dam, will alter the riverine habitat and greatly affect the populations of
species that navigate the river systems. The species that are most affected by the presence of
dams in the United States are Pacific salmon, most notably Chinook salmon in the northwest,
and Atlantic salmon in the northeast. Some known salmon species listed under the Federal
Endangered Species Act include bull trout, Chinook, chum, coho, sockeye, steelhead, and
Atlantic salmon (Washington State 2009).
A wide variety of devices have been invented in attempt to increase fish navigability
through barriers. The two most used devices are fish ladders, which allow the fish to travel past
the dam on their own by way of a pathway past the dam for the fish to navigate through (fig. 1
and 2), and fish elevators, which allow the fish to travel via a lock system (fig. 3). There are
multiple types of fish ladders. The two most common are the vertical-slot fishway and the Denil
fishway. The Biology Department at Concordia University conducted a study to quantify fish
passage in various US river systems; it showed the mean upstream passage efficiency of
anadromous species was only 41.7% (Noonan 2012).The project concluded that the vertical-slot
fishway, as seen in figure 1, is the most successful with fish passage, while the lock system and

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Denil fishways are less efficient. This indicated that downstream efficiency was slightly higher at
68.5%, but that fishways were not successful in facilitating fish through dam systems. The
results also suggested that certain fishways were more successful for salmonids as opposed to
non-salmonids. Another study conducted by the University Of Maine; Department Of Wildlife
Ecology, United States Geological Survey (USGS), and the National Oceanic and Atmospheric
Administration (NOAA), focused on the Mill Dam on the Sedgeunkedunk Stream located in
mid-coast Maine. This indicated “the presence of a dam disrupted the natural longitudinal
gradients in fish density, biomass, diversity and richness such that these metrics were maximized
in the reach downstream of the dam [and] minimized in the reach upstream of the dam…”
(Gardner et al. 2012). These two studies showed that dam removal is a better choice over fish
ladders when it comes to navigation of riverine habitats by anadromous and catadromous
species.
Figure 1. A vertical slot fishway is the most used fish pathway in the US. Fish enter the ladder and are forced
forward as there is a barrier behind them (Department of Primary Industry, NSW 2015).

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Figure 2. A Denil fishway which is not widely used in the US. Fish enter and swim forward as it seems the walls
close in behind them (Department of Primary Industry, NSW 2015).
Figure 3. A fish elevator, which is not as preferred as the fish ladder approaches. Fish enter the elevator and travel
upward via a series of locks (Department of Primary Industry, NSW 2015).

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Dam Removal:
The American Rivers Organization named 2011the Year of the River as multiple dam
removal projects began that year. There have been 1257 dams removed since 1912, with 971 of
them occurring in the past 2 decades (American Rivers 2014). Prior to the 1990s, the idea of dam
removal was seen as radical. Bruce Babbitt served as Secretary of the Interior under President
Bill Clinton. While in office, Babbitt started to introduce dam removal projects in the northwest.
His plans were met with lots of opposition and the public consensus was, “It won’t work. The
salmon have been gone for a hundred years. What makes you think they’ll return?” (Babbitt
2012, n.p.). Babbitt went on to prove the public opinion wrong when he pushed for the removal
of the Quaker Neck Dam on the Neuse River in North Carolina. It was a small dam removal
project that succeeded in restoring the local populations and riverine habitats. The Quaker Neck
Dam removal helped to show the public how the benefits of dam removal are far greater than the
benefits of dam construction. Babbitt went on to say,
In the space of two decades, dam removal has evolved from a novelty to an
accepted means of river restoration. Most importantly, the concept has taken
root in hundreds of local communities as residents rediscover their rivers, their
history, and the potential not only to restore natural systems, but, in the process,
to renew their communities as well (Babbitt 2012, n.p.).
Many studies and projects have been conducted by various governmental and private
agencies assessing the different ways dams and other barriers affect riverine ecosystems.
Ultimately, it can be concluded that the best way to increase anadromous and catadromous fish
species in dammed river systems is through complete barrier removal.
The Columbia River system in the northwest Pacific was once one of the most abundant
salmon runs in the world. This watershed includes many rivers in Washington that have been

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home to a plethora of anadromous and catadromous species; the most notable rivers being the
Snake, Elwha, White Salmon, and Columbia. All of these rivers have dams that created a
detrimental effect on the populations of fish in the northwest Pacific, particularly the Chinook
salmon, the sockeye salmon, and the steelhead trout salmon. All of these fish have been listed as
endangered by Washington State’s Department of Recreation and Conservation (Washington
State 2009). As with most other rivers in the US, fish passage techniques have been used and
proved a failure for fish traveling to spawn. In the Pacific northwest, people are coming together
to give aid to these fish species. They are voicing their opposition to the operations of
hydroelectric dams in the area and are doing everything possible to remove dams from their once
diverse rivers in hope of recolonization by Pacific salmonids.
The Elwha River has been the center of controversy over the past decade as protestors
from all over the country voiced their discontentment with the two large, hydroelectric dams
(Glines Canyon Dam and Elwha Dam) that caused the endangerment of local fish species
populations. “The dams were built to supply hydropower to a timber and paper mill operation;
neither reservoir provided significant flood control or water supply benefits” (East et al. 2014).
The Glines Canyon Dam, which had a height of 32 meters, and the Elwha Dam, which had a
height of 64 meters (Brenkman et al. 2012) were responsible for the rapid decline of Chinook
and other local species by not only preventing passage upstream and downstream, but also by
completely changing the chemistry of the water and the sediment and nutrient movement
downstream. George Pess, a specialist in fish ecology and restoration at NOAA, stated that,
“Populations of all Pacific salmon species and steelhead in the Elwha became critically low,
habitat complexity decreased below the dams, and downstream coastal habitats became sediment

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starved” (Pess 2015).These two dams, in Olympic National Park, were doing far more
destruction than they were production.
Simultaneous removal of both the Glines Canyon and Elwha Dams on the Elwha River
began in September 2011.The dams were officially labeled breached as of September 2014 and
are officially the largest dam removal projects to date (Pess 2015).Many factors must be
considered when deciding to breach a dam. First, there is an immediate, massive release of stored
sediment downstream along with an immense amount of debris that is carried and eventually
deposited in an estuary, leading out into the ocean. Initially, this sharp increase in sediment has
the ability to kill or harm many species in the riverway, but a study conducted by Quinones et al.
(2014) on salmonid conservation in California indicated, “In exchange for the short-term
negative impacts of sediment flushing, there could be long-term benefits to both endangered
southern steelhead and to local beach-based economies.” Grant and Lewis (2015) stated,
“Estimated amounts of reservoir sediment stored behind recently removed dams range from
1000m3
to over 21,000,000 m3
.” Once the barrier is removed, the river will find the path of least
resistance and through the continual process of downcutting, create a new river bed and estuary
habitat, as shown in (fig. 4). It is also shown that, due to the influx of sediment downstream,
there becomes an influx of sediment-derived nutrients. Jim O’Connor, a USGS Geologist
specified that, “Rivers quickly erode sediment accumulated in former reservoirs and redistribute
it downstream, commonly returning the river to conditions similar to those prior to
impoundment” (Duda 2015).The increase of sedimentary nutrients to river systems directly leads
to an increase in native populations. Tonra et al. (2015) stated, “Marine-derived nutrients have
already made their return to the Elwha River as demonstrated by spawning salmon stable isotope
ratios, which were greater than in other consumers measured.”Their study focused on the

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percentages of dissolved N15
and C13
in Chinook, coho, and pink salmon that come from certain
microalgae ingesting the marine derived nutrients. Microalgae consume the readily-available
nutrients and are then eaten by fish. The marine nutrients necessary for sustainable riverine life,
which are consumed by the microalgae, accumulate in the muscle tissues of fish, making it easy
to observe nutrient increase in fish, over time, for documentation. With an abundance of
nutrients, and a sufficient water depth and gradient, anadromous and catadromous species have
the ability to rapidly recolonize post-dam removal as long as the species are not too far away to
be able to reach their target habitat and spawn within their lifetime (Tonra et al. 2015).
Figure 4. Photos showing the evolution of the Elwha River mouth and estuary complex during dam removal. (A)
19 March 2012 (tide height 1.5 m; river discharge 1930 ft 3
/ s) (dam removal had started but Elwha Dam was not yet
completely removed); (B) 08 November 2012 (tide height 1.3 m; river discharge 1260 ft3
/s); (C) 26 August 2013
(tide height 1.6 m; river discharge 431 ft3
/s); (D) 15 January 2014 (tide height 1.4 m; river discharge 1360 ft 3
/s); (E)
14 May 2014 (tide height 1.3 m; river discharge 2420 ft3
/s); (F) 12 August 2014 (tide height 1.5 m; river discharge
569 ft 3
/s) (Foley et al. 2015).

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A study on age structure and hatchery fraction of Elwha River Chinook salmon in 2014
completed by Weinheimer et al. (2015) indicated, “The fall of 2014 was the third spawning
season since 1913 that Chinook salmon were able to access the watershed between Glines Dam
and the former Elwha Dam (21.7 km to mouth).” With the full removal of barriers on the Elwha,
it is clear that the salmon will run again. Their study concluded, “It appears smaller Chinook
were able to negotiate the former Elwha Dam site and access the upper watershed during the
2014 season [which they previously had not been able to do]” (Weinheimer et al. 2015).The
removal of the Elwha and Glines Canyon dams on the Elwha River showed that a project of this
size is possible, and the outcomes are immediate and beneficial.
In 2011, the Condit Dam was removed from the White Salmon River in southeastern
Washington. The dam was breached and, as expected, decade’s worth of sediment were released
downstream. An effort by the US Fish & Wildlife service to translocate Chinook salmon was
initiated in order to save the species from the influx of sediment that would make the
downstream habitat inhabitable. The project sampled approximately 500 female fall Chinook
salmon and translocated them upstream above the dam breaching site. Engle et al. claimed, “The
distribution of spawning fall Chinook salmon adults in 2012 suggests a suitable lower White
Salmon River for spawning in addition to a new, useable area of spawning habitat in the exposed
river section of the former Northwestern Reservoir” (Engle 2013, n.p.). The study showed that
the beneficial effects of dam removal are observable within a year of breaching. The removal of
the Condit Dam is another example of how barrier removal in the US will benefit riverine
systems.
The idea of barrier removal in US river systems is no longer seen as revolutionary. The
Edwards Dam, which was removed from Maine’s Kennebec River in 1999, was the first major

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hydropower dam removal project in the US. A study conducted by Brown et al. on failed fishery
policies along the Atlantic coast stated,
A multi-partner trust was established to purchase three dams, remove the two
lower-most dams, construct a fish bypass around the third dam, and give the dam
owner the opportunity to increase generation at six existing sites. Theresult is
maintenance of more than 90% of current energy generation while allowing
unobstructed access to 100% of historical downriver habitat for sturgeon and
striped bass and greatly improved access to nearly 1,600 km of upriver habitat for
Atlantic salmon and alosines (Brown et al. 2015, n.p.).
The removal of the Edwards Dam on the Kennebec in 1999 proved beneficial for many
anadromous and catadromous species, as well as for the local economy. It also helped establish
the Penobscot River Restoration Trust, a non-profit with the purpose of freeing thousands of
miles of river in the Penobscot Watershed. The Edwards Dam set a precedent and, between 2012
and 2013, the Great Works Dam and the Veazie Dam were both removed from the Kennebec,
freeing nearly 1000 miles of riverine habitat for threatened shad and salmonid species
(Penobscot 2015). “The removal led to rapid recovery of anadromous fish populations in the
Kennebec and increased the value of recreational fisheries” (Robbins and Lewis, 2008). Trinko
Lake et al. conducted a study where 11 local fish species were monitored and observed closely in
the Penobscot Watershed. The study predicted a massive increase in accessibility of freed rivers
to these 11 species in the watershed following the Penobscot River Restoration Project. Their
results showed that the American shad has the ability to recover 522 km of river habitat (Trinko
Lake et al. 2012) (Table 1). Maine’s Penobscot River Restoration Trust is setting an example for
the rest of the country managing inadequate dams.

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Table 1.Historical, current, and predicted accessible river kilometers for 11 species of catadromous fish
following the Penobscot River Restoration Project (PRRP). Asterisks denote alewife habitat (ha) from
lakes >4ha (Trinko Lake et al. 2012).
*Atlantic salmon were not included in the habitat gain calculations due to stocking throughout the
watershed. American eel and sea lamprey were also omitted because of current passage at existing project
dams and current distribution throughout the watershed.
Conclusion:
Removing dams in river systems across the US will free thousands of miles of river for
anadromous and catadromous species to spawn. Breaching a dam appears to be the only sensible
option for a threatened species that depends on riverine habitat to survive. Fish ladders and
elevators, as well as translocation efforts, have proven inefficient over time. The destruction of
riverine habitats, and ultimately the destruction of species that depend on these habitats, cannot
be justified by only 7.1% of the US’s energy consumption (USGS Water Science School 2015).
Removal of dams in the US will not only benefit the riverine species that depend on the
habitat, it will benefit humans as well. Gordon Grant, a US Forest Service hydrologist, was
quoted, “As existing dams age and outlive usefulness, dam removal is becoming more common,
particularly where it can benefit riverine ecosystems” (Duda 2015). By removing a dam or a

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series of dams in a river system, rivers become multifaceted. They supply recreation and
navigation and save the taxpayer money. “Removal eliminates the expenses associated with
maintenance and safety repairs, as well as direct and indirect expenses associated with fish and
wildlife protection…” (American Rivers 2012). The breaching of dams in the US also has the
ability to seriously minimize the issue of food security in the US. Anadromous species come
back to spawn in freshwater and ultimately die. Their survival tactic is to sacrifice half of the
population in order to give life to the new population. Atlantic and Pacific salmon populations
could potentially be one type of solution to feeding those with food insecurity. As the US looks
toward the future of dam removal projects, it is clear they are the best option to restore riverine
habitats. Jim O’Connor, with USGS, stated, “The apparent success of dam removal as a means of
river restoration is reflected in the increasing number of dams coming down, more than 1,000 in
the last 40 years” (Duda 2015). Countless studies in the US indicate barrier removal as the key to
large increases of anadromous and catadromous species, as well as increased ecological
restoration in US river systems.

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