Aquatic barriers like dams and culverts negatively impact natural stream flows and wildlife movement in the Hudson River watershed. There is growing interest in removing unnecessary barriers and upgrading culverts. While initial costs are high, the long term benefits to both ecosystems and communities are worth the investment. Benefits include restoring more natural environments, increasing recreational opportunities, and decreasing infrastructure maintenance costs over time. The DEC is working to identify and map barriers to determine where restoration would be most effective.

1. Aquatic Connectivity
For centuries, aquatic barriers, such as dams and culverts, have been negatively affecting natural stream flow, sediment deposition, and the movement of
fish and wildlife in the Hudson River Estuary watershed. In recent decades interest has grown for the removal of unwanted dams and the overhaul of
poorly installed and undersized culverts. There is especially high interest in taking action where rare or threatened species reside. Often the sizeable price
of removal or retrofitting existing structures is a major deterrent to restoration. While initial costs may be high, the benefits accrued are often well worth
the investment. Upgrading culverts to meet adequate size requirements can lead to decreased maintenance and less frequent replacement, both substantial
money savers. In addition to biodiversity benefits and more natural sediment regimes, human enjoyment of the watershed is amply boosted as well.
Other benefits include a restoration of the seasonal variability in water flow, and the removal of impediments to recreational boaters, all of which may re-
sult in a steady return of municipal funds through increased public recreation. The DEC’s Hudson River Estuary Program has been actively identifying
and mapping aquatic barriers over the past several years to determine the best ways to aid in ecological restoration. Through projects to identify biologi-
cally important barriers in the entire Estuary watershed and to survey culverts in focal watersheds, the Estuary Program is creating a list of locations
where aquatic barrier restoration could help human communities and ecosystems.
Dams and Culverts: Barriers and Aquatic Connectivity
The Hudson River Estuary: Before the Decline
At the very start of European colonization in New York, the Hudson River Estuary and the land surrounding it flourished with an unrivaled fecundity that
can hardly be imagined today. Before rampant pollution and zealous overfishing, the fisheries of the Hudson were some of the most productive on the
east coast. Massive oyster reefs in New York Harbor, measured in acres, commonly contained individuals larger than an outstretched hand. Moreover,
men from Henry Hudson’s own crew were recorded as catching “ten great mullets, of a foot and a half long a piece and a ray as great as four men could
haul into the ship” in little time while fishing from shore to restore diminished supplies (Folsom, 1841).
Incredible diversity was not solely restricted to the brackish portions of the south. Adriaen van der Donck, an early settler of the region, described how in
1647 he witnessed two whales journeying up the Hudson, one which ultimately became beached near the Albany area and was drained of its precious oil
by eager townsfolk. This occurrence was not as unusual as it may sound. Up until the 1800’s it was routine to see the occasional dolphin or porpoise in
the northern reaches of the river. Also in this area, the sturgeon stock was so abundant the species was referred to as “Albany beef,” and served as a staple
food source for centuries. Not until industrialization began did the Hudson’s prodigious bounty severely diminish (Groft et al., 2009).
Dams Culverts
Residents of Fort Orange (present day Albany) saw a white
whale swim up the Hudson in 1647.
Sturgeon, striped bass, and shad were caught in massive
quantities in the Hudson prior to overfishing and pollution.
Consequences of Dams
 Half of the dams within NYS were constructed prior to 1953, and often used as a power source for industries. Currently, most dams are
no longer serving this purpose and are falling into disrepair (Vedachalam & Riha, 2013).
 Barriers block the natural passage of wildlife, often upsetting the delicate balance of an ecosystem. Fish often cannot make the trek past
the dam to locations farther upstream. Important feeding, mating, and spawning opportunities may be missed. Additionally, rare species
that already have a limited range are further constricted, possibly leading to a decline in numbers that may result in local extirpation or
complete extinction.
 River herring return to the Hudson from the Atlantic Ocean in the spring and swim up tributaries to mate and spawn. If left unblocked,
these fish may journey up some tributaries for over a mile.
 Turtles, salamanders, and American eels greatly benefit from dam removal as well, reconnecting areas that were once open to them. Bar-
riers impede necessary movement; this may be especially harmful if these species become trapped in degraded environments. Various
contaminants and nutrients tend to accumulate behind the barriers causing levels to become dangerously high upstream (Gratwicke,
2008).
Why Remove Dams Where Appropriate?
When a dam becomes structurally damaged and there is a chance it could pose a threat to human life or seriously degrade important
ecosystems and/or rare species, it may be appropriate to remove the structure.
 Biological: Removing dams can reestablish wildlife passage and improve aquatic connectivity.
 Hydrological: Restore the shape of streams and rivers, along with the natural flow regime.
 Economic: Avoid costly maintenance and upkeep. Dam removal on average costs 3-5 times less than repairing aging or damaged
structures (Delaware Riverkeeper).
 Tourism: Create new habitat to fish, like native brook trout, can bring increased fishing and related businesses.
 Hazard Mitigation: Lower risk to people (even if they are kept in good shape there is the possibility of failure during large
storms).
 Liability: When dam failure results, the owner may be responsible for damages and liabilities (this may include criminal charges).
Improperly maintained dams could fail at any time—large storm events and high flow events are becoming more common as the cli-
mate changes.
Silver Lake Dam, Woodridge, NYDaniel Case
Successful Dam Removal: Cuddebackville Dam Removal
In 1903, the 125 foot long Cuddebackville Dam was constructed on the Neversink
River to divert water into electrical turbines for the production of cheap and accessible
power. By 1945, progress had introduced a modern network of power lines that im-
ported electricity from farther away. No longer needed, the plant shut its doors. The
property was then transferred over to Orange County, who retained ownership of it until
2004, when the Nature Conservancy, concerned with its impact on rare species, advo-
cated for its complete removal.
Standing at 6 feet high this structure blocked upstream access to virtually all aquatic or-
ganisms. Large schools of trout and anadromous American shad containing hundreds of
individuals were noticed trying to migrate farther upriver by DEC officials, but due to
the dam’s presence, formed an impenetrable barrier. The endangered dwarf wedgemus-
sel was also affected similarly. The mussels, all located above the dam, were trapped
from disbursing downstream. Mussel surveys were unable to document a single individ-
ual in the southern portion of the river. Most were discovered concentrated just above
the dam, a dangerous scenario that could result in extirpation if this localized area be-
came degraded.
The total cost for demolition was $2.2 million, and was covered jointly by The Nature
Conservancy and Army Corps of Engineers. After removal, the ecology of the
Neversink substantially improved, with an influx of aquatic organisms being seen mov-
ing back and forth past where the barrier once stood (Nature Conservancy).
The endangered Dwarf Wedgemussel
Wood Turtle (Species of Special Concern) Glass eels ( juvenile form of the American eel)
Dams and Larger Storms
Hurricanes, tropical storms, and other damaging weather phenomena,
while infrequent in New York, should be considered when making deci-
sions about the fate of a dam. As Hurricane Irene and Tropical Storm
Lee have shown, even dams thought of as structurally stable, can be
overwhelmed and fail when inundated by these colossal storms which
will appear with greater regularity in the future as the climate continues
to shift (see climate change section of this poster).
Hurricane Irene in 2011 was especially damaging, with certain parts of
the Catskills receiving 12-18 inches of rain, most of which fell within
12 hours. Throughout New York, over 20 dams received significant
damage, leading 3
low-hazard dams to
fail, along with a
single intermediate-
hazard dam (NYS
DEC, Dam Safety).
References
Delaware Riverkeeper. Background on Dam Removal and River Restoration. 300 Pond Street,
Second Floor, Bristol, PA 19007. accessed 5/5/2014 http://bit.ly/Q71CGT
Folsom, G (ed.). 1841. Collections of the New York Historical Society. (Vol. 1) New York, NY:
H. Ludwig.
Gratwicke, B (ed.). 2008. Proceedings of the Appalachian Salamander Conservation Work-
shop. IUCN/SSC Conservation Breeding Specialist Group: Apple Valley, MN.
Groft, T.K., McCombs, W.D., & Greene-McNally, R. 2009. Hudson River Panorama: A Pas-
sage through Time. Albany, NY: SUNY Press Albany.
Meyer, A. 2013. Barriers to Aquatic Connectivity in the Hudson River Estuary Watershed.
NYS Department of Environmental Conservation Hudson River Estuary Program, presentation
at the 2013 Black Rock Forest Symposium http://bit.ly/1kFSYsH
The Nature Conservancy. Neversink Preserve. accessed 5/6/2014. http://bit.ly/1oki8zt
NYS Department of Environmental Conservation. Dam Safety in the Northeast: Response to
Hurricane Irene & Tropical Storm Lee Flood Events. accessed 5/6/2014. http://
www.dec.ny.gov/chemical/81891.html
NYS Department of Environmental Conservation Hudson River Estuary Program. 2013. Cli-
mate Summary, A Summary Prepared for the Town of Germantown. pp.10 http://bit.ly/Q72lba
Rosenzweig, C., Solecki, W., DeGaetano, A., O’Grady, M., Hassol, S., & Grabhorn, P. 2011.
Responding to climate change in New York State: the ClimAID integrated assessment for effec-
tive climate change adaptation. Annals of the New York Academy of Sciences, 1244(1), 2–
649.
University of Wisconsin-Extension. Fish Friendly Culverts. pp.8 http://bit.ly/1ijpKwR
Vedachalam, S., & Riha, S.J. 2013. Small is Beautiful? State of the Dams and Management Im-
plications for the Future. River Research and Applications. pp.11.
Estuary Program Partnering with The Nature Conservancy and UMass Amherst
The Hudson River Estuary Program, in conjunction with The Nature Conservancy, has recently completed identifying 139 biologically important aquatic
barriers in the Hudson River Estuary watershed. These barriers were highlighted due to their possible situation in biologically important areas. Basic
measurements were taken of each structure and the surrounding stream, along with noting the condition of the barrier and its exact location. Through this
inventory a database was set up and information was placed online to make it easily accessible to the public.
We have recently changed our data collection methods to match up with the protocol used by the University of Massachusetts Amherst (UMass). Their
River and Stream Continuity Project collects information on aquatic barriers in the Northeast, with a useful website. By syncing up with the UMass pro-
tocol all data will be presented in a single format, thus allowing for a comprehensive database to emerge that will result in a greater understanding of the
region’s fragmented waterways and ensuring easier interstate cooperation.
An Aquatic Circulatory System
With the Hudson River Estuary having over 20 major tributaries, each getting fed by their own smaller streams and rivers, and every one of those also
having numerous tiny rivulets branching off, a complex network emerges across the landscape. A significant percentage of the thousands of streams that
are scattered throughout the Hudson Valley have at least one barrier. The sheer volume of dams and culverts makes checking each barrier unfeasible. To
utilize time and resources most efficiently, the Estuary Program has been documenting barriers mostly on streams that have a considerable known eco-
logical significance, such as those that harbor rare species, or is utilized as an important mating locale and/or nursery.
“Albany Beef” (Sturgeon)
The Hudson River Estuary Program’s Culvert Sizing Project
The program’s main agenda to document, assess, and remediate culverts:
 Field work identifies culverts
 Model current and future stream flow
 Prioritize culvert replacements for the town
 Address costs
 Work with municipalities to fund replacement of top priorities
Climate Adaptation
While it is sometimes believed that climate change will bring about a profuse increase in precipitation in the coming years, total rainfall
has only increased slightly over the past few decades and will likely follow a similar course in the future (NYS DEC, Climate Summary).
An important issue for municipalities relates to the size and severity of the storms. Storms are predicted to become fewer in number, but
the ones that do emerge will be significantly larger, dumping high amounts of rain in a short time span. This will result in higher flows in
streams, which could lead to the damage or destruction of undersized culverts. Aging road crossing structures might have been adequate to
deal with most storms when originally built. Today however, with the effects of climate change already being felt, they often cannot prop-
erly handle stream flows seen relatively often; in the past these storms would occur perhaps but once or twice per year and were considered
severe. Records show that between 1980-2009 heavy downpours on land east of the Hudson increased by 74% (Rosenzweig et al., 2011).
Perched Culverts and Open-bottomed Structures
Narrow culverts constrict and funnel runoff, thereby increasing the current in the “choke point.” Apart from the obvious negative effects to
wildlife, culverts can lead to higher rates of erosion and stream turbidity. Negative effects are greatly amplified if the culvert happens to be
perched, meaning that instead of lying level with the stream, it is suspended above it, allowing water to cascade out, similarly to a water-
fall. Perched culverts effectively restrict nearly all wildlife passage, no matter the size of the opening. Whenever possible, culverts should
be placed level with the stream, have an adequately large opening, and where economically feasible, replace a standard culvert with an
open-bottomed structure to allow for a natural stream bottom.
 Open-bottomed culverts are preferable for usage due to their ability to preserve the substrate of the stream.
 Rocks and debris on the bottom serve as important habitat for fish, and especially macroinvertebrates, which cling on or
under substrate.
 Culverts lacking a substrate layer are typically a “biologically dead zone.”
 Stream debris helps to slow down water flow, create ripples and eddies, and other areas fish find attractive.
If implemented correctly wildlife will have difficulty in realizing anything is amiss. The only drawback to an open-bottomed structure is
that it can cost up to 50% more than a standard circular culvert. In certain instances it may be preferable to construct a bridge when the
stream in question is large enough. Department of Transportation (DOT) funding may be available in such a case to help offset the cost
(University of Wisconsin-Extension).
Perched culverts form impassable barriers that aid in stream ero-
sion. This set-up is poorly designed.
This is a properly designed open-bottomed culvert that preserves
the natural stream bottom and refrains from funneling water.
Culvert data collected from previous years is now getting
placed online. Pertinent information regarding culverts and
a display of their location can be viewed in a set of interac-
tive GoogleMaps.
Online Data for Public Access
Duck Hole Dam Failure in the Adirondacks
Hurricane Irene over New York
NOAA
Michael Adamovic
Watershed Specialist
mjadamov@gw.dec.state.ny.us
Andrew Meyer
Shoreline Conservation Specialist
axmeyer@gw.dec.state.ny.us