Historic floods in the Midwest put spotlight on America's aging dams

Across the country, new weather extremes are testing aging dams. According to the federal government’s most recent climate assessment, the number of extreme precipitation days in the Midwest has increased 45 percent since the 1950s. Del Shannon, former president of the United States Society on Dams, joins John Yang to discuss.

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John Yang : Flood warnings are likely to remain in effect this week from Wisconsin and Minnesota to Missouri as more heavy rain is forecast. There’s already been historic flooding inundating parts of Nebraska bringing down a bridge in South Dakota.

The lasting image of the week is for Minnesota. Water surging around the west side of the 114-year old Rapidan dam on the Blue Earth River carrying away a home on a bank just downstream. Across the country, new weather extremes are testing aging dams. According to the federal government’s most recent climate assessment, the number of extreme precipitation days in the Midwest has gone up 45 percent Since the 1950s.

Del Shannon is the former president of the United States Society on Dams. It’s an organization of professionals who design build and operate dams, and they focus on dam safety.

Del, are the dams that exist now where they built and designed to withstand the sort of extreme weather we’re seeing now?

Del Shannon, Former President, United States Society of Dams : Well, John, the average age of a dam in the U.S. and their 92,000 dams in the U.S. is 60 years old. And so the majority of these dams were designed to a standard 60 years or older. And often, that is insufficient to withstand many of the floods that we’re now starting to see.

John Yang : Can dam somehow be retrofitted to bring them up to standard?

Del Shannon : Yes, of course, it’s a tall task at times because of the immense size of these structures. But absolutely, and they shouldn’t be because water is an irreplaceable resource that we have, there’s no plan B for anything other than water. So these structures must be upgraded if we want to maintain them as assets in our water portfolio.

John Yang : As I understand that the Rapidan dam was damaged by flooding in 2019 and 2020. And since then, there’s been a debate over whether to repair it or remove. It is enough being done to monitor the state of dams across the country?

Del Shannon : You know, it’s a complex problem, John. Each state is responsible for the oversight and the regulation and the inspection of dams, with the exception of the federal government dams, so the federal government is responsible for overseeing their dams.

So we have 50 individual entities charged with overseeing and maintaining them. And again, with 92,000 dams in our portfolio, it’s — it can be an overwhelming problem and often is.

John Yang : There are maintenance schedules and replacement schedules for highways and bridges are the things do we know enough about the lifecycle of dams?

Del Shannon : That’s an excellent question, John, we’re just starting to delve into that. We’re starting some research later on this year with federally funded research. But the answer your question is no, we have never gone through a full replacement cycle of our dams, and we don’t have a good understanding of the lifecycle. And that’s a much needed area of research and investigation.

John Yang : You know, whenever politicians talk about the need to fix the infrastructure, they talk about bridges, they talk about sewer systems, because these are things that people see and deal with every day. Is enough attention being paid to dams, do you think?

Del Shannon : Well, in my opinion, no. I’m quite passionate about the topic. But they’re these structures that just silently go about their business day in and day out without a lot of people thinking about them. But again, as I said earlier, there is no plan B for water, and we’re actually from a per capita standpoint, we’re declining.

We haven’t built new reservoirs, our population is growing, the age of these structures is increasing and the reservoirs and filling the sediment. All that adds up to a declining per capita storage volume of our reservoirs, both in the U.S. and throughout the world.

John Yang : Is there money in the infrastructure bill for dams? And is it enough?

Del Shannon : There is there is money in there, it’s a several billion. That’s a fantastic first step, and I don’t want to speak ill of that it’s wonderful. It is a downpayment on additional funding that is needed. And we need to continue to maintain these structures. The current estimate of upgrading our existing dams is in the 150 to $160 billion range. So it is a significant lift that we’ll need.

John Yang : Overall, what needs to be done to think to make dam safe and what ought to be done?

Del Shannon : So we need more resources, both in funding and in people. We need to establish a greater workforce focused on specifically on these structures. That includes increasing funding at the state level, and at the federal level as well. So all of these things need to be understood and invested in both people and the funding to upgrade these structures.

John Yang : It seems like we hear more frequently these days is about dam failures or overtopping is that the fact or is it just that once one happens we pay attention to the others?

Del Shannon : Well, it’s actually a complex problem when dams were built. In the heyday, after World War II, our understanding of hydrology and design was 60 years old. And so now as we’ve advanced, we have a better understanding of what the structures, the loading that they need to take the flood designs of that they’re designed to withstand, and so that’s improved.

The other thing that’s gone on is we’ve had an increase in population. So once were we had very rural dams that were designed for smaller floods. Now we have large populations downstream of them, and larger floods are happening and they’re overwhelming these dams.

Lastly, we’ve have a shifting climate and a warmer atmosphere can hold more water and I, and that we’re just starting to delve into this and understand it but we believe the size of the floods will continue to increase as our atmosphere temperature also increases.

John Yang : Del Shannon, thank you very much.

Del Shannon : Thank you John.