Research: Removing Outdated Dams Benefits Communities Adapting to Increasingly Extreme Weather

A newly released research paper from Utah State University, “Barrier Removal is a Strategy for Climate Resilience,” highlights how removing outdated or unsafe dams and barriers can make communities safer and stronger in the face of extreme weather.

There are more than 550,000 dams and over 298,000 road-related barriers, such as culverts, that fragment rivers across the United States. Many dams are aging and in disrepair at the same time they are being impacted by changing climate conditions.

“Our review of recent research suggests that removing dangerous and obsolete dams and barriers improves resilience to flooding, drought, increasing temperatures, sea level rise and changing rivers,” said Sarah Null, professor of Watershed Sciences at Utah State University and the paper’s lead author. “Many dams provide useful services and should not be removed. But for those structures that are outdated or unsafe, removal can be a smart decision for communities.”

Null and co-authors Gregory Goodrum, who just finished his Ph.D., and undergraduate researcher William Bosen conducted an extensive review of scientific reports and publications on this topic. They identified 50 studies, published between 2009 and 2024, that examined dam removal in relation to climate change, resilience or adaptation. The paper’s authors found that communities are removing dams for a variety of reasons, including safety, economics, cultural benefits and environmental protection. The research was supported by American Rivers and Resources Legacy Fund.

“Many of the dams we built decades ago are not equipped to handle today’s extreme weather,” said Ann Willis, regional California director for American Rivers.“Our aging infrastructure is increasingly challenged by more intense storms and catastrophic flooding. In a lot of cases, aging dams and dams that are not adequately designed or maintained are ticking time bombs, putting people at risk.”

NASA researchers recently reported that extreme weather events — including droughts and flooding — are more frequent, last longer and are more severe. Data show twice the number of severe weather events in 2024 than the average from 2003-2020.

According to the National Inventory of Dams, maintained by the U.S. Army Corps of Engineers, 70% of dams have outlived the average design life for a dam, with 16,700 dams considered high-hazard and a risk to people living downstream. In addition, the average age of U.S. dams is 64 years old, and the number of dams that pose a high risk to human life is rising.

Null said a surprising finding was that removing aging dams can protect people and communities, especially as intensifying storms lead to streamflows that exceed dam design specifications. In many cases, she added, it is also more cost-effective to remove aging, obsolete, and unsafe dams than to retrofit them.

The authors reiterate throughout the study that many dams and their reservoirs provide resilience to climate change and do not suggest that removing all dams is a promising adaptation for the future.

Dam failures and near misses that endangered communities have occurred throughout the country, including in Vermont, California, Michigan and North Carolina. Proactive removal of obsolete dams helps prevent catastrophic failures and reduces or avoids higher costs associated with emergency responses.

Dam and barrier removal can be a powerful way to strengthen communities in the face of extreme weather — given the benefits to public safety, culture, economy and environmental restoration. Key findings from the paper on the benefits of removing outdated dams include:

• Economic Benefits: While dam and barrier removal has upfront costs, it's often more affordable than repairing and maintaining aging infrastructure or dealing with disaster recovery. In many cases, increasingly frequent and severe droughts and floods are making dams less economically viable. In addition, dam removal can cost far less than rehabilitation and long-term maintenance expenses, making it a practical option.

• Cultural Benefits: Removing barriers is also a means for preserving cultural practices, including fish harvests. Dams were frequently built in and flooded areas that are culturally important for Native Americans, including gathering sites, celebration sites and ancestral community sites. Dams have severely impaired native fish populations that Native Americans have depended on for millennia. Barrier removals are necessary for preserving and respecting traditions and ancestral lands.

• Clean Water and Environmental Health: Dam and barrier removal can restore river health, improve water quality and bring back fish and wildlife habitats. It helps re-establish cooler, free-flowing waters essential for native fish, wildlife and healthy ecosystems. Without barriers, fish can access upstream habitats and escape high temperatures and drought conditions.

Read the full white paper from Utah State University here.