The Michigan Dam Failures Are a Warning

Many need repairs. Let’s fix them before climate-related flooding gets worse.

Two dams down, a few thousand more to go.

Luckily, no one died last week when rain-swollen flooding breached two dams in Central Michigan. But thousands were evacuated, homes and businesses were inundated, and floodwaters spilled into a chemical plant and Superfund site.

Appropriately, President Trump signed an emergency declaration. But once again, there has been little serious discussion since about what to do to address the looming national hazard of aging dams like those that failed in Michigan.

In November 2019, The Associated Press reported that 19 dams in Michigan, including the first of the dams to breach, were in unsatisfactory condition and presented high hazards, meaning their failure can cause loss of life. The events of last week should not have come as a surprise, and it is only a matter of time before a catastrophic dam collapse will occur somewhere in the United States. The combination of aging and poorly maintained dams and extreme, climate-caused flooding presents potentially deadly risks for people downstream.

We won’t be able to say we weren’t warned. The federal government offered a stark message in its national climate assessment in 2018, cautioning that aging and deteriorating dams and levees “represent an increasing hazard when exposed to extreme or, in some cases, even moderate rainfall.” The report noted that heavy rainfalls led to widespread dam or levee failures in 2005, 2015, 2016 and 2017. “The national exposure to this risk,” the report said, “has not yet been fully assessed.”

But here is what we do know. A majority of the roughly 90,000 dams in the United States are older than their nominal design life of 50 years, the point when they become increasingly more difficult and expensive to keep safe, assuming they’ve been properly maintained in the first place. The National Inventory of Dams includes about 25,000 dams considered high or significant hazards if they failed.

We recently wrote a report assessing the risks of climate-induced dam failures. We found that much critical infrastructure — other dams, electricity-generating plants, highways, bridges, toxic Superfund sites, water treatment and wastewater treatment plants — lie in a path of potential destruction below aging dams. The Michigan dam failures are an example of a cascading failure — the breach of the Edenville Dam, which was rated by the state in 2018 as being in unsatisfactory condition, led to floodwaters overflowing the downstream Sanford Dam, which was rated as being in only fair condition.

A presidential disaster declaration certainly makes sense after a dam fails. But wouldn’t it be better to prioritize which ones to fix or remove before disaster strikes? We recommend an approach that assesses the potential for climate extremes, the probability of a dam failure, and resulting direct and indirect financial losses. This would enable regulators to expeditiously screen and identify the subset of dams that need urgent attention and investment.

There is no doubt that climate change is increasing the frequency of extreme rainfalls and the risk of floodwaters overtopping dams, the main reason a dam fails. But while climate change may not be so easily fixable, making sure dams can withstand flooding is, and it is much cheaper than the consequences.

The Oroville Dam in the foothills of California’s Sierra Nevada illustrates the point. In 2005, three environmental groups urged the repair of an emergency spillway on the dam, which at 770 feet is the tallest in the United States. At the time, the work would have cost roughly $100 million, according to one of those groups. In 2017, the spillway failed. Some 185,000 people were evacuated downstream because of the potential of catastrophic flooding. The cost of repairs following the near catastrophe was $1.1 billion.

In Michigan, Gov. Gretchen Whitmer said experts characterized the flooding that led to the recent dam failures as a 500-year event — something that would have a one in 500 chance of occurring in any given year. If we consider dams in the eight-state Great Lakes region older than 60 years (most have a design life of 50 years) that are in counties with a population larger than 500,000, 317 dams are classified as having a high potential for hazard in a failure. The chances of one or more of these dams experiencing a 500- or 1,000-year flooding event in a year would be 47 percent and 27 percent — which strikes us as pretty high.

The Great Lakes region exhibits approximately 10-year cycles of rainfall and is currently near record high levels. Extreme rainfalls are happening much more frequently in the region than in the past 100 years. What is being done to prepare with potential flooding and dam failures?

The state and the federal government have multiple offices that assess dam safety. What we lack is an overall strategy to fix the problem and the requisite financial resources. Rehabilitating dams with high hazard potential will cost an estimated $3 billion for federal impoundments and another $19 billion for nonfederal ones — a cost that vastly exceeds current spending.

We need a real plan and real money, and we need them soon. The coronavirus pandemic, which we are spending billions to battle, should at least remind us that a little bit of prevention can avert an enormous amount of anguish.

Upmanu Lall is the chairman of the department of earth and environmental engineering and the director of the Columbia Water Center at Columbia University. Paulina Concha Larrauri is a researcher at the water center.

The Times is committed to publishing a diversity of letters to the editor. We’d like to hear what you think about this or any of our articles. Here are some tips. And here’s our email: letters@nytimes.com.

Follow The New York Times Opinion section on Facebook, Twitter (@NYTopinion) and Instagram.