Dams and Culverts Factsheet

What are Dams and Culverts?
A dam is a barrier to stop or slow down the flow of rivers or streams. They are created often to suppress floods but can also be harnessed to provide water for irrigation, human consumption, industrial use, or hydropower.

A culvert is a structure that allows water to pass under a road, trail, or railroad. It is often constructed from a pipe or reinforced concrete.

What problems do they present?
Poorly placed or constructed culverts can pose significant problems to water quality and aquatic organisms. If designed incorrectly, culverts can erode and damage the water quality in the area. When placed poorly, they can become an obstacle to organisms that need to pass through and move from different habitats. Culverts can also become clogged with sediment and debris during rain events. This may cause erosion, overflow into roads, or damage to surrounding species.

Dams severely alter the natural flow of the waterway they are built in. Dams can obstruct the normal movement of fish as they pass through the waterway. In the Saw Kill, near where it opens into Tivoli Bays, dams obstruct the movement of American Eels.

How can these problems be mitigated?
Currently, the Hudson Valley has many culverts that are blocked or alter water flow, however, by constructing culverts efficiently, the stream habitat can be resilient to changes in climate and land use. By planning and researching the construction and by using materials that are less likely to erode, one can increase the likelihood of a culverts’ success and minimize environmental damages.

Dams can also be managed in environmentally safe ways. Some places are removing their dams in order to restore natural stream systems, but in places where that is not possible, fish and eel ladders can be constructed to lessen the barrier they present to aquatic populations.

Known Barriers to Aquatic Connectivity in the Saw KillSawKill_KnownAquaticBarriers

“Aquatic Connectivity and Barrier Removal: Restoring Free-Flowing Rivers in the Hudson River Watershed for Human and Fish Communities.” New York State Department of Environmental Conservation. Web. http://www.dec.ny.gov/lands/99489.html

More information can be found in the New York State Department of Environmental Conservation’s Dam Removal and Barrier Mitigation In New York State, here.