There are approximately 75,000 dams greater than six feet high in the waterways of the United States. Many thousands of smaller dams also block our nation’s rivers1. Dams provide important benefits to society. They generate hydropower, provide water for crops and human consumption, help manage floods, create navigable waterways, and provide recreational opportunities. But dams, both large and small, come with significant costs. Dams have fundamentally changed the ecology of hundreds of thousands of river miles in our country, damaged habitat, disrupted native populations of fish and wildlife, and adversely affected some local economies and communities.
In recent years, several things have happened to cause many to take a second look at the value of some dams. First, we have learned a great deal about the adverse impacts of dams on river ecosystems and neighboring communities. Second, an increasing variety of non-structural alternatives to dams for flood management, irrigation, water storage, and power generation have been developed. And third, all dams across the country are continuing to age and an increasing number are in need of substantial repair.2 At the same time, there is an increased understanding and appreciation for the many societal values of healthy rivers and fisheries. As a result, many communities, dam owners, and agencies across the United States are finding that in some circumstances dam removal can serve as an effective river restoration tool and also provide economic and social benefits.
A 1999 report, Dam Removal Success Stories compiled by American Rivers, Friends of the Earth, and Trout Unlimited, identified over 4653 dams that have been removed in the United States. Professor Molly Pohl of San Diego State University has catalogued over 400 dams greater than six feet high or longer than 100 feet that have been removed since the 1920s.4 Many of these were removed because they were old, obsolete, or posed safety hazards. Many other dams were removed to restore river ecology and bring back fish and wildlife. Dams have also been removed to provide recreational benefits, enhance aesthetics, and improve water quality.
When appropriate, dam removal can benefit rivers, wildlife, and neighboring communities that reap the rewards of a healthy river. It can achieve environmental improvements by restoring natural flows to a river, removing blockages to fish migration, re-establishing healthy river habitat for fish and wildlife, returning river rapids and riverside lands, and improving water quality. Dam removal can lead to community revitalization through the generation of additional revenuesfrom improved fishing and boating opportunities in the restored river, and by creating riverfront revitalization opportunities, such as riverside parks, historical interpretive exhibits, and green spaces. And dam removal can result in the elimination of safety hazards posed by deteriorating, unsafe, or abandoned dams. Dam removal can also be the most fiscally prudent choice to meet river management and dam safety goals.
While hundreds of dams have been removed, that does not mean that all dams should be torn down. In fact, very few of all documented dams in the United States are even being considered for removal. The removal of 400 dams represents just over one-half of one percent of the more than 75,000 dams over six feet tall existing across the country. Many dams continue to serve important public or private functions such as flood control, irrigation, and hydropower generation. In some cases, changing the way a dam operates will provide enough ecological improvements to the river to justify the continued benefits of the dam. In other cases, removing a dam could have adverse ecological effects – such as the release of contaminated sediments – that are too costly to mitigate. And in some cases, dams are retained because they represent a significant aspect of the community’s history.
The concept of dam removal can arouse strong emotions, both from advocates of dam removal and from opponents.
However, a decision whether or not to remove a dam should not be based on emotions or entrenched positions, but on a balanced analysis of the pros and cons of both dam removal and dam retention. How can you tell if a dam is a good candidate for removal? How do you weigh a dam’s costs and benefits to the river, the dam owner, and to society? Because every river and dam is unique, there is no generic formula or quick checklist for determining if a dam should be removed. Not all benefits and costs can be quantified, nor do they apply to all dams and rivers. Judgment is required to balance and compare options. Exploring Dam Removal presents questions that will help sort out the many issues surrounding dam removal in order to increase the likelihood that an informed decision can be made.