Official Site of The State of New Jersey
Dams are constructed barriers used to hold back the flow of water, causing it to raise and form an impoundment. Dams serve many purposes including hydropower generation, flood control, drinking water supply, navigation, irrigation and recreation. Many of the smaller impoundments across the state were created long ago to power saw and grist mills. The mills have since vanished, but the dams and impoundments created remain behind. However, dams come with the cost of severely reduced aquatic connectivity, altered flow regimes, and barriers to fish migration preventing species like River Herring, American Shad, Striped Bass, and American Eels from reaching historic spawning areas. Additionally, many dams are outdated and no longer serve their original purpose creating liability, public safety and maintenance concerns. Dam removal is an option to alleviate these problems and, in the process, improve overall watershed health. All potential removal projects are reviewed on a case-by-case basis as each dam comes with its own unique set of variables. The ecological conditions, such as surrounding habitat, water quality, and species composition must all be considered. Some dams may never be candidates for removal as the recreational, cultural, or infrastructure benefits are too great. In addition, high costs associated with removal can be limiting.
Benefits of Dam Removals
Restore free-flowing conditions – Allows for recovery of natural riverine processes responsible for creation and maintenance of habitat.
Improve water quality – Seasonal and weather induced flows, temperature and oxygen levels return to their natural variations and normally associated flora and fauna.
Enhance connectivity for movement of resident and migratory fish – Pathways for migratory fish species such as American Shad, Alewife, Blueback Herring, Striped Bass and American Eel may be restored.
Reconnected floodplains, habitats and aquatic habitats – When dams come down, upstream and downstream areas within and adjacent to rivers are reconnected.
Improved sediment release and transport – Water flow and turbulence revert to normal, distributing sediment naturally.
Enhanced public safety – Even a properly maintained dam can be a safety hazard, especially for recreational users likes anglers and boaters. Removal eradicates the risk of injury, loss of life and property destruction from dam failure.
Eliminated maintenance/repair costs – Over time, dam removal is less expensive.
Drawbacks of Dam Removals
Invasive Species – Dam removal allows for the free upstream migration of invasive species into new habitats that were previously inaccessible.
Ecologically Sensitive Species – Construction activities, along with sedimentation and changes to local hydrology, may result in local negative impacts to immobile species, such as mussels.
Other Impacts – Not everyone is pleased by dam removals, as shifts in recreational use and cultural significance may occur.
Recent New Jersey Dam Removals
- Columbia Lake Dam, Paulins Kill River
- Weston Mill Dam, Millstone River 8/2017
- Hughesville Dam, Musconetcong River 9/2016
- Nevius Street Dam, Raritan River 7/2013
- Roberts Street Dam, Raritan River 7-8/2012
- Calco Dam, Raritan River 7-8/2011
- Finesville Dam, Musconetcong River 11/2011
