A Study that was recently conducted by researchers from Portland State University has found that removing aging Dams across the country instead of repairing them could save billions of dollars, but cautions that more research is needed surrounding the factors that are driving efforts to remove dams across the country.

The study, which was recently published online in the scientific journal River Research and Applications, assessed currently available nation-wide data on dams and compared characteristics and trends of dams which have been demolished to those which have been left standing.

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If the current trend in dam demolition continues, the researchers estimate that anywhere between 4,000 - 36,000 dams will have been demolished by 2050.

According to the study, the maximum cost of demolishing 36,000 dams is estimated to be around US$25.1 billion, which is significantly cheaper than the estimated cost of repairing these dams.

According to estimates proposed by The American Society of Civil Engineers, it will cost more than US$45 billion to upgrade and repair around 2,170 dams considered high-risk to life and property should they fail. However, the cost of rehabilitating all the derelict dams in the US to bring them up to a condition deemed safe is higher still, estimated to be around US$64 billion.

"I think it's time for a re-invigorated public process around managing the risks dams and aging dam infrastructure pose to public safety throughout the U.S.," said Zbigniew Grabowski, a Ph.D. candidate in PSU College of Liberal Arts and Science's Earth, Environment & Society program and lead author author of the study. "It's difficult to assess the actual public safety hazards and the most cost-effective ways of mitigating those hazards because the data on dams and dam removals has not been systematically compiled in a way that allows for robust analysis by government agencies or independent researchers."

The researchers found that a disproportionately higher number of hydropower and water-supply dams were removed, suggesting more discussion is needed over the factors that drive dam removal.

According to Grabowski, the decision to remove or rehabilitate a dam often hinges on cost-benefit tradeoffs between the environmental, social and economic impact of the dam in question. But, he says that we should also focus on public safety when making these decisions, as from a safety perspective it simply may not make sense to repair many of these dams.

The study suggests several recommendations to improve the decision-making process, including:

1.  Data collection methods used to track records of dams that are rehabilitated or removed need to be standardized and made available to the public to allow researchers to undertake more effective comparative research and for decision-makers at local, state and national levels to be able to make more informed management decisions.

2.  Researchers and officials responsible for dam policy need to look at the broader picture when making decisions regarding the future of dams by taking a multi-disciplinary approach that draws knowledge from disciplines such as ecological restoration, dam safety engineering, technology and social science, while also considering communities that are affected by the presence or removal of dams.

Journal Reference

1. Zbigniew J. Grabowski, Heejun Chang, Elise L. Granek. Fracturing dams, fractured data: Empirical trends and characteristics of existing and removed dams in the United States. River Research and Applications, 2018; DOI: 10.1002/rra.3283