Study finds big savings in removing dams over repairs

Study finds big savings in removing dams over repairs
Credit: Portland State University

A new study by Portland State University researchers finds billions of dollars could be saved if the nation's aging dams are removed rather than repaired, but also suggests that better data and analysis is needed on the factors driving dam-removal efforts.

The study, published online in May in the journal River Research and Applications, analyzed the best available national data to compare the trends and characteristics of dams that have been removed with those that remain standing.

The researchers expect that if trends continue, by 2050, between 4,000 and 36,000 dams will be removed.

The study found that a high-end cost estimate of removing 36,000 dams would be roughly $25.1 billion, a significant savings over the estimated rehabilitation costs.

The American Society of Civil Engineers estimates more than $45 billion would be needed to repair and upgrade roughly 2,170 high-hazard dams—those that pose the greatest threat to life and property if they fail. The Association of State Dam Safety Officials estimates it would cost $64 billion to rehabilitate all of the U.S. dams that need to be brought up to safe condition, according to the study.

"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 the study's lead author. "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 study found that hydroelectric and water-supply dams were the types most disproportionately removed, a finding that suggests more nuanced conversations about what drives the removal of dams is necessary.

Grabowski said the choice between removing or rehabilitating dams is often framed as a cost-benefit tradeoff between the ecological, social and economic impacts of dams.

"Yet we should also be looking at how including the public in dam safety decisions might increase the number of dams that don't make sense to rehabilitate," he said.

Among the study's recommendations:

  • More detailed data needs to be made public and data collection on removed and rehabilitated dams needs to be standardized to allow for more robust comparative research and better-informed decisions at the national, state and local levels
  • Dam policy officials and researchers need to take an interdisciplinary approach and draw knowledge from dam engineering, ecological restoration, social science and technology as well as the communities affected by dams and their removals

Explore further

Dam removal study reveals river resiliency

More information: Zbigniew J. Grabowski et al. 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
Citation: Study finds big savings in removing dams over repairs (2018, May 28) retrieved 17 August 2019 from
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May 28, 2018
Hydroelectric is perhaps the best form of renewable energy. Properly designed the dams have integrated fish ladders so they do not interfere with spawning fish and on the down stream they can be designed not to harm fish going that way too.

A dam has an ecosystem above it that has adapted to the presence of that water. Removing the dam destroys that ecosystem.

The water is falling from the mountains to the sea. Getting energy from it is almost free and very green. People aren't going to give up electricity for their phones, cars, homes, refrigerators, lights and more.

In my area we have enough old dams to generate all the electrical power of our state. This would make us totally free of fossil fuels for electric generation. No nukes needed. No wind which the NIMBYs complain about. No big solar farms.

Rather than destroying dams we should be fixing or replacing them and generating all the electricity we need.

Jun 20, 2018
Many of these structures act as flood control for down stream cities and properties. Would the cost of flooding in these areas or alternate forms of flood control be less than rehabilitation of the dam?

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