BURSTEliminating obsolete or unsafe dams could help bolster community safety amid climate-induced weather extremes, watershed experts are recommending.
Storms and floods have intensified in both frequency and severity, since the construction of the dams — many of which are now in a state of disrepair, according to a new white paper, published by Utah State University.
“Removing dangerous and obsolete dams and barriers improves resilience to flooding, drought, increasing temperatures, sea level rise, and changing rivers,” said lead author Sarah Null, a professor of watershed sciences at Utah State University, in a statement.
“Many dams provide useful services and should not be removed,” Null acknowledged. “But for those structures that are outdated or unsafe, removal can be a smart decision for communities.”
Crossing the nation’s rivers today are more than 550,000 dams and 298,000 transportation-related barriers, such as culverts, structures that enable water to flow underneath a road or railway.
About 70 percent of U.S. dams have exceeded their designed lifespan, with 16,700 deemed high-hazard and a risk to people downstream, the authors explained, citing data from the National Inventory of Dams. The average age of American dams is 64, and the number of structures that are jeopardizing communities is surging, the researchers warned.
“Many of the dams we built decades ago are not equipped to handle today’s extreme weather,” said co-author Ann Willis, regional California director of American Rivers, in a statement.
“In a lot of cases, aging dams and dams that are not adequately designed or maintained are ticking time bombs, putting people at risk,” Willis added.
Removing obsolete dams rather than renovating them requires just a fraction of the expense associated with the latter — typically amounting to just 30 percent to 40 percent of the cost of a retrofit, according to the report.
Dam and barrier elimination also provides a means for preserving cultural practices, by facilitating fish harvests in areas where the natural flow of native species has long been impaired, the authors noted.
Restored river health and improvements in water quality can thereby help bring fish and wildlife back to their former habitats, while establishing cooler, free-flowing waters that are more capable of withstanding drought, per the report.
The researchers acknowledge that dams can provide climate resilience benefits when they are well-maintained and offer cost-effective services. In places where removal would not be practical, the authors suggested creating additional storage and coordinating surface and groundwater management as promising strategies for reducing flood risk.
But in so many cases over the past several years, communities have endured extreme weather conditions that have compromised dams — often when storm flow has surpassed dam design specifications, according to the report.
“Removing unsafe, outdated dams is a proven approach to restoring rivers and strengthening communities,” said co-author Shara Sparks, senior program officer for the Open Rivers Fund, in a statement.
“For communities challenged by extreme weather, restoring their rivers via dam and barrier removal can deliver a host of benefits,” Sparks added.