American Rivers, an organization dedicated to protecting and restoring national rivers, has released its annual list of dam removals for 2012. There were 65 dams removed across the country last year in order to restore rivers, conserve wildlife and alleviate safety risks. Pennsylvania led with 13 dams removed across the state, followed my Massachusetts with nine and Oregon with eight.
The reasons behind these removals vary, but they generally have two common themes: restoring the ecosystems in these rivers and increasing public safety. For the Curtis Pond Dam that was removed from Massachusetts' Boston Brook, some results were immediate.
"The dam had created a pond, which instantly drained into a free-flowing river," said Beth Lambert, River Restoration Program Coordinator for the Massachusetts Department of Fish and Game. "In only three months the flood plain area grew back with beautiful plants, including cardinal flowers."
This next year will be spent doing follow ups to monitor water changes and to see how these changes will impact the species that live there. Two of the species that this removal will benefit, the river herring and the American eel, are currently being considered for inclusion on the endangered species list. The restoration of the river means a new spawning habitat for the herring, as well as an improved water quality to help them thrive. The American eel will now have the freedom to move more freely through the river now that the basin is gone.
Other species, such as the sea lamprey, are returning to the area to spawn. It will take a few years for the full effects of the dam removal to be realized, but the changes so far look promising. There are more plans for dam removals in the river, which should open up 38 miles of the waterway to greatly improve the local ecosystem.
In August the Rutan Dam of Anguilla Brook in Connecticut was removed. This particular dam was built in the 1800s as part of a mink farm that has been vacant since the 1970s. The removal of this 120-feet wide dam has opened 11 miles of river habitat for many aquatic species. Mussel populations are already showing an increase. Removing this structure has also helped to subside some localized flooding risks, an especially important concern as spring nears.
Likewise, the Darby Creek restoration in Pennsylvania has shown marked improvements for both wildlife and for people who live near the floodplain. This project was managed by Dr. Laura Craig, Associate Director of River Restoration Program. There were three dams removed from this area, Hoffman Park Dam, Kent Park Dam and the Darby Borough Dam, which will result in the lower 9.7 miles of the Darby Creek opening. Like the Curtis Dam removal, these restorations will greatly benefit a variety of fish species, included the near-endangered river herring and American eel.
"Removing the dams eliminates a barrier to upstream-downstream movement and a direct cause of impaired habitat," Craig said. "The impounded area upstream of the dams was poor habitat for riverine fishes - slow-moving water, high temperatures, low dissolved oxygen, and a lack of typical riverine streambed features."
While some of the changes are seen immediately, it will take a few years for the river's ecosystem to fully adjust to the removal of the dams. The physical changes to these habitats were visible immediately, but the migratory fish in the river, including bass, suckers and multiple species of shad, will need to be monitored to see how much the river's opening will improve their numbers.
For the Darby Creek project, a big goal of the removals was to help alleviate flooding issues.
"Darby Creek is notorious for flooding," Craig said. "And the Darby Creek watershed is heavily urbanized."
The flooding in the watershed was so severe from 1999's Hurricane Floyd that many lost their homes to a federal buyout. As spring approaches, snowpack will begin to melt, rains will increase, and flooding risks will rise. With the dam removed, some of that flooding will be reduced.
"Removing the dams eliminates a location for debris to become trapped, which often contributes to flooding and local over-topping of banks. Dam removal also lowers the water level above the former dam locations and increases the capacity of the channel in the former impoundment," Craig said.
While this will help with local flooding concerns, Craig said that there are more steps to be taken to address the problem. Improved storm-water management will also be needed to protect the homes in the area.
To see a complete list of the dams removed last year visit the American Rivers website. There you can also read about the progress of these and past projects in your area, as well as learning what you can do to help these efforts.