The collapse of two Michigan dams on Tuesday following heavy rainfall has triggered concerns over how precarious dam infrastructure in the U.S. is inadequate to handle severe weather.
Aging dams will increasingly fail as climate change makes extreme precipitation and storms more frequent and intense, scientists warn.
“A lot of the country’s infrastructure systems were built during a time when these kind of weather events were considered rare and didn’t present a significant threat,” said Hiba Baroud, a professor of civil and environmental engineering at Vanderbilt University.
“But things have changed. The climate has changed. These dams are aging and need to be maintained, upgraded and in the most extreme cases, the entire design must be revisited,” Baroud continued. “Otherwise, the situation like in Michigan will become more frequent in the future.”
The Edenville dam is seen after breaking in Edenville, Michigan, U.S., on Wednesday, May 20, 2020.Sean Procter | Bloomberg | Getty Images
The 91,000 dams in the U.S. earned a “D” for safety in a 2017 report from the American Society of Civil Engineers. The ASCE estimated the cost of fixing up the dams whose failure would threaten lives at roughly $45 billion, and the cost of fixing all aging dams at over $64 billion.
In Michigan, which is under a state of emergency after the two dam breaches, the average age of the state’s total 1,059 dams is 74 years old, older than the typical 50-year designed life span. Just over 170 of those dams are labeled as high hazard potential — meaning a collapse will result in a loss of life.
“The combination of aging infrastructure, older design guidelines and an increasing probability of extreme events from global warming is increasing the overall risk of these events,” said Noah Diffenbaugh, a Stanford University climate scientist.
A man walks across a washed out West Saginaw Road in Sanford, Michigan, on May 21,2020, after the area saw heavy flooding and damage from heavy rains throughout central Michigan.Seth Herald | AFP | Getty Images
The most common form of dam failure is over-topping of inadequate spillway design, which accounts for roughly 34% of all dam failures. The water levels behind the dam become too high and break through the entire structure rather than passing through the spillway.
Regarding the two dams that broke on Tuesday, the Edenville Dam that was built in 1924 was rated in unsatisfactory condition in 2018 by the state. And the Sanford Dam that was built a year later was rated in fair condition.
Federal regulators since 2014 were warning the Edenville Dam’s owner, Boyce Hydro Power, that the dam could not handle a “probable” heavy flooding event. The Federal Energy Regulatory Commission eventually revoked the dam’s license in 2018 due to a failure to increase the dam’s spillway capacity to safely allow flood water to pass through.
Residents in boats inspect the floodwaters flowing from the Tittabawassee River into the lower part of downtown on May 20, 2020 in Midland, Michigan.Gregory Shamus | Getty Images
The commission on Wednesday ordered the company, which also owns Sanford Dam, to investigate the Michigan dam failures. The last inspections of the two dams were done in June 2018.
“There must be investigations to understand what measures need to be taken to fix the dams,” Baroud said.
Regular inspections of the dams could have provided warning signs of maintenance and upkeep that needed to be completed to avoid a failure, according to Baroud.
“If it costs a lot of money and you can’t fix it now, the dam should be operated at a lower than normal level to provide a buffer to allow for a great influx of water during heavy precipitation,” she said.
Operating a dam at a lower level can be done through conducting a reservoir drawdown, where the water level in the dam is slowly drained through gated openings or valves to avoid future flooding during an emergency.
