Hurricanes Pose Increasing Threat to Dams

A new study from Upmanu Lall, a leading researcher in water resource management and climate risk analysis, and Jeongwoo Hwang, a former postdoctoral research scientist with Lall at Columbia Engineering and now at North Carolina State University; sounds the alarm on dam infrastructure throughout the U.S. The paper, published October 10 in Nature Natural Hazards, explores how our changing climate, with intensifying clusters of rainfall, is likely contributing to increasing failures of dams. With the catastrophic damage recently caused by Hurricanes Helene and Milton, we wanted to learn more about the threat to dams and asked Lall, director of the Columbia Water Center and visiting professor of earth and environmental engineering at Columbia, to help us understand what’s going on.

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Can you tell us a bit more about compound rain clusters and why is this happening?

An open question has been whether the climate will become “stickier” or more random as it warms - stickier meaning that the wind patterns just persist for longer periods of time, random meaning things get disorganized. It seems that there are modest but detectable changes -- at least over the United States -- where the incidence of persistent patterns in which waves of moisture are repeatedly directed to the same places is increasing. Each wave brings rain that starts to fill up dams and then, if a bigger rain event happens and the reservoir is vulnerable, there is the potential for failure.

Our study is the first analysis of rainfall sequences and events associated with recent

hydrologic failures of 552 dams in the U.S. We found that persistent atmospheric circulation patterns that lead to recurrent rainfall events, rather than just more moisture in the atmosphere, are a possible reason. The probability of these compound precipitation risks has increased across part of the country. With over 90,000 aging dams still in service, the increasing likelihood of intense rainfall sequences raises urgent concerns about future dam failures.

What are the near-term solutions?

We need to visit the portfolio of more than 90,000 dams in the U.S. and check not just their state of maintenance but also how they are being operated to decide which ones should be demolished, which ones repaired, and which ones given better strategies to hold on to water they already contain while we improve our predictions of floods or droughts. We need to improve the near-term prediction of persistent rainfall patterns. It’s urgent that we do a portfolio risk analysis that considers the climate, fragility, and operational risk factors with a mapping to potential impacts from dam failure so that we can better understand the collective risk of cascading failure of critical infrastructure that would be triggered by dam failure and its socio-economic impacts.

Is this happening across the globe, not just in the U.S.?

Yes, we see similar behavior in the data in many places around the world, especially in the higher latitudes (>30), where the storm tracks organize and then persist. But a more comprehensive study is needed.

What have been some of the successes out of this collaboration to date? 

Our work has generated the first air pollution data from highly populated cities such as Kinshasa, Democratic Republic of the Congo. We are leading the state of the science in low-cost sensor applications, building relationships with local decision makers and informing policy in India, and increasing capacity among thousands of local practitioners on air quality management and air pollution science. 

Dams in which areas of the U.S. are more prone to collapsing and why?

We have concerns with older dams that are not being maintained; these are primarily concentrated in the Northeast, Upper Midwest, and Southeast. And while Western dams tend to be newer and larger, in 2017 the tallest U.S. dam operated by the State of California -- Oroville -- nearly failed, and 200,000 people had to be evacuated. Persistently high, but not extraordinarily high, rainfall was implicated. The reservoir was full because the operators wanted to hang on to the water in case they lapsed back into drought, and a modest amount of rain forced them to use the overflow spillway (which was in poor repair), and it failed - the concrete just ripped off as the water went over it. They switched to the emergency spillway, which also failed.

Are hurricanes playing a major role in these scenarios? 

Hurricanes are really concerning since the amount of water that they can drop could easily overwhelm the capacity of local reservoir managers to cope with. In 2015, 52 dams failed in South Carolina in just one hurricane event–Hurricane Joaquin. With Hurricane Harvey, the Addicks and Barker Reservoirs in Houston were very vulnerable to failure, and a last-ditch effort to release water from them and flood downstream areas– in the middle of the night–prevented a more catastrophic failure. 

There has been a concern that hurricanes will be more frequent and stronger with global warming, and evidence has been presented in favor of and against this argument. Harvey persisted in place and kept on raining longer than any prior hurricane in the region, so the emerging question is whether we will see more of that. If we do, the vulnerability of dams may go way up since they may not be able to handle the resulting deluge.

What do you think about all this?

This seems to be a silent crisis so far. Since 2000, we’ve had a dam failure due to overtopping, on average every two weeks in the U.S. Luckily, most of these have been small dams, and the loss of life and immediate impact have not been catastrophic. But if a large dam were to fail above a major population center or a power plant or a super fund site or a bridge, the impacts could be devastating and long-lasting. The silence would be broken with a bang.

Lead Photo Credit: Kirk Fisher/Shutterstock