Dam Failures and Infrastructure Damage in a Changing Environment

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Climate change is increasing stress on thousands of aging dams across the US
Published: July 13, 2023 8:37am EDT Updated: June 24, 2024 7:27pm EDT

Heavy rainfall generated widespread flooding. in the Upper Midwest in late June 2024, putting at least one aging dam at risk. In southern Minnesota, the Blue Earth River cut a path around the Rapidan Dam in Rapidan Township, about 15 miles south of Mankato, on June 24, putting the structure at imminent risk of failing. Officials warned local residents that if the dam burst, the river could rise by 2 feet, but said that evacuations were not needed.

This event comes a year after flooding in Vermont collapsed at least one dam and threatened others. Hiba Baroud, associate professor and associate chair in the department of civil and environmental engineering at Vanderbilt University, explains how flooding stresses dams in a changing climate.

How old are most US dams?

There are more than 91,000 dams across the U.S., in all 50 states, with diverse designs and purposes. The average dam age is 57 years, and more than 8,000 dams are over 90 years old.

Every four years, the American Society of Civil Engineers produces a report card for the nation’s infrastructure that assigns grades based on the condition of structures like roads, bridges and dams, and the investments that they need. The most recent report card estimates that 70% of U.S. dams will be more than 50 years old by 2030.
Overall, the report gave U.S. dams a “D” grade and estimated that more than 2,300 high hazard potential dams – those that could cause loss of life or serious property damage if they fail, based on the level of development around them – lacked emergency action plans.

Certainly there needs to be some consideration with respect to the changing environment and impact on older dams not designed for extreme weather.

Are there ways to strengthen older dams against flooding without completely replacing them?

Decommissioning or replacing dams can be complicated and cost-prohibitive. It also can have cascading effects on the surrounding community, and possibly on other infrastructure. Regularly maintaining and upgrading older dams can be a cost-effective way to strengthen them and make them resilient to natural hazards.

When dams no longer serve the purposes for which they were built, they may be partially breached or entirely removed to restore the river’s natural flow.

The Association of State Dam Safety Officials estimates that it would cost US$157.7 billion to rehabilitate all nonfederal dams in the U.S. Of this amount, about one-fifth ($34.1 billion) is for rehabilitating high-hazard potential dams. The 2021 Infrastructure Investment and Jobs Act includes approximately $3 billion for dam safety projects, focusing on rehabilitation, retrofitting and removal.

Extreme weather events associated with a changing climate are producing more frequent flooding events in various parts of the US and world in general.

Infrastructure designed for a cooler environment are now at risk.

More generally, cases studies of dam incidents and failures

For example - flooding of the Red River, border between North Dakota and Minnesota, the 2019 flooding of the Niobrara River in northern Nebraska, and the current flooding (June 2024) of the Big Sioux and Blue Earth Rivers affecting South Dakota, SW Minnesota and NW Iowa.

Red River and Valley - Prone to flooding
Major floods in historic times include those of 1826, 1897, 1950, 1997, 2009, 2011, and there has been significant flooding many years in between.

Nebraska Flooding on the Niobrara River: March 2019

Loss of the Spencer Dam (on Niobrara River)

During a multiple-day stretch centered from March 13-23, 2019 (but peaking in severity March 13th-17th), several Nebraska counties mainly along/north of Interstate 80 within the NWS Hastings coverage area endured widespread flooding, ranging in scope from minor/moderate to historical/catastrophic (the likes of which had not been observed in several decades). By far the worst flooding occurred along several primary rivers, including the Loup River system (including North and South branches), Cedar River and Wood River (among others, see record crest information below). Not only was this flooding characterized by high water levels (as is the case with all floods), but in many areas damage was also augmented by an unusually-severe break-up of thick river ice. Taking a back seat to the widespread flooding in terms of impacts/severity, much of the local area also endured a winter storm with high winds and blizzard conditions on the night of the 13th into the morning of the 14th.

Nebraska’s Spencer Dam will not be rebuilt in wake of historic 2019 flood

Rapidan Dam in southern Minnesota experiences partial failure; no plans for mass evacuation

The Dam Store, known for its homemade pies, has been in business since 1910 and owned by Barnes’ family since 1972.

Chart Shows Big Sioux River's Record-Breaking Flooding Spike

The Big Sioux River experienced record-breaking flooding during the 2019 Midwestern U.S. floods.

And now, the Big Sioux River is having record flooding in 2024.



BNSF Railroad bridge collapses into Big Sioux River

KTIV-TV reports that the level of the Big Sioux River was at 44.25 feet as of 7:30 p.m. Sunday, surpassing its record of 37.7, but is believed to have crested.

The bridge, on a former Milwaukee Road line that is part of BNSF’s Aberdeen Subdivision, is also used by the D&I Railroad through trackage rights on BNSF between Elk Point, S.D., and Sioux City.


The North Sioux City railroad bridge has an interesting and long history. Originally, the trusses were built for the Cedar River Bridge: Cedar Rapids, Iowa. The trusses were moved and installed at the North Sioux City location in 1905 by the Chicago, Milwaukee St. Paul & Pacific Railway (aka The Milwaukee Road). So the bridge has been standing there for 119 years. The truss works were fabricated by Lassig Bridge & Iron Works of Chicago.
http://johnmarvigbridges.org/North Sioux City Rail Bridge.html

Upstream of the North Sious City bridge is the Elk Point Rail Bridge between Westlfied, Iowa and Elk Point, South Dakota
http://johnmarvigbridges.org/Elk Point Rail Bridge.html

The D&I Railroad (reporting marks DAIR) is a Class III shortline and wholly-owned subsidiary of L. G. Everist, Inc., owners of one of the largest privately-owned fleets of railroad equipment of any aggregate producer in North America.
https://iowadot.gov/iowarail/pdfs/diar.pdf (the filename is mis-spelled; it should be dair.pdf)
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I believe the take-away message is that dam design emphasises holding back water, but when that water flow exceeds the design capacity, it is the spillway that must protect the structure.

Spillways are designed to withstand a maximum flow. When that maximum is exceeded, all that extra energy must go somewhere, so it goes into eroding the foot of the spillway structure, which often cuts back upstream, undermining the dam wall.
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I think bringing "climate change" into it is a mistake, as it a) instantly politicizes things in an unhelpful manner, and b) is IMHO unnecessary and irrelevant. To my mind, the problem is 57 years. If they are designed to withstand a once in a century event, you have a problem.

Saying the same thing more numerically, 91000 dams x 57 years = 5 million dam-years. That's the MTBF we need if we don't want to see one go. That's tough. It's tougher still with old dams instead of new dams.
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  • #4
Vanadium 50 said:
That's the MTBF we need if we don't want to see one go. That's tough. It's tougher still with old dams instead of new dams.
We know some dams will fail, and that it will probably be a failure of the lower spillway during a flood event, as the spillway cannot be properly tested without that event. Water energy will search out the weakest rock available and exploit that path to find another path to escape.

Dams and spillways should therefore be designed with an expectation of failure. That should include the protection of downstream infrastructure such as roads, bridges, and villages. If that cannot be done, don't build the dam.

Rivers develop a natural grade or profile that can dissipate the potential energy of the flow during a flood. Steep rapids normally end in still pools, but during floods those pools are turbulent and catch loose rock dislodged from the rapid. In flood, the entrance to the pool is marked by a massive stopper wave where the water surface changes slope.

The steepest falls dissipate the greatest energy at their foot, so, like rapids, waterfalls that undermine their base, collapse and migrate upstream.

While water flows down the river, the rapids migrate up the river, until they catch up with another rapid, or reach your spillway.
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  • #5
Baluncore said:
We know some dams will fail, and that it will probably be a failure of the lower spillway during a flood event, as the spillway cannot be properly tested without that event. Water energy will search out the weakest rock available and exploit that path to find another path to escape.
Case in point: the Oroville Dam spillway failure in … One sec, searching… 2017. (Has it really been that long?) Lots of lessons learned the hard and expensive way.

On the other hand: Rapidan Dam “failed” because the river found an easier path and bypassed around it. Or the Edenville Dam in 2020, which was a structural failure due to a fairly extensive list of poor decisions and mismanagement over the life of the dam, all the way back to the design and construction of the dam.

Political hot button issue that it is, climate change is a valid point to bring up, imo, as it is causing changes to the precipitation patterns and cycles, changes that can significantly alter how the dam needs to be managed, operated, and maintained. Failure to acknowledge the changes and revise the operational plan, and even the structure of the dam if warranted, is borderline negligence.
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  • #6
Flyboy said:
On the other hand: Rapidan Dam “failed” because the river found an easier path and bypassed around it.
Due to the flooding, the Rapidan Dam spillways were choked with logs, which caused the water level to rise until it spilled over the shoulder of the dam. That then cut back under the roadway and captured the river flow, draining the reservoir.
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Eastern Wisconsin community evacuated after floodwaters breach dam

it looks like an earthen structure to the side of the dam, which apparently collpased.
MANAWA, Wis. (AP) — A dam in an eastern Wisconsin community has been breached, prompting people living downriver to be evacuated, the National Weather Service said Friday.

The dam in Manawa along the Little Wolf River was breached about 1:45 p.m. by floodwaters, meteorologist Scott Cultice said. The town has a population of about 1,200. It was not immediately clear how many people were evacuated.

Manawa Police Chief Jason Severson estimated that a 50-foot-wide (15.2-meter-wide) area around the dam had eroded.

Gates on the dam eventually were opened to release water and relieve pressure on the structure, officials said.
The concrete dam structure may be intact. The dam faces west.
“It looks like the dam is intact, but there is quite a bit of erosion on the north side,” Severson told reporters Friday afternoon. ”We think the worst of it is over, so now we’re going to start assessing things and see where we go from here.”

The rains started about 8:30 a.m. Friday and about 5 inches (12.7 centimeters) fell in a few hours. A flash flood warning was issued for Manawa and other parts of Waupaca County
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The dam in Manawa on the Little Wolf River is a smaller example of an obstructed spillway. Google Earth (44.465997°, -88.919976°) street view, from the bridge downstream, shows that the right bank of the river (on your left) is lower than the walkway rail and obstructions above the spillway. Once the spillway choked with logs, the river level rose and overflowed the earthen bank, where it could more easily erode and undermine the end structure of the dam.

The mode of failure is the same as the Rapidan Dam, that had a road along the top of the dam, above the several narrower spillways. In that case, the road support columns trapped flood debris, raised the reservoir level, then overflowed the bank to one side.

Where the spillways are obstructed above, and could choke during floods, with logs, barges or houses, the dam shoulder should be built higher than the top of the possible obstruction.

It seems to be a false economy using the crest of a dam as a support for a bridge. It would be safer to place the bridge downstream from the dam, where it can catch the debris and be washed away, without risk to the dam structure, or of the reservoir volume being added to the flood.
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  • #9
I read recently while researching the Kariba Dam (Zim) and Cahora Bassa (Mocambique) that there are about 220 dams in Africa many of which are late colonial/decolon period and coming up for major renovations. Not looked at the Aswan yet.

In addition there is the Mosul dam, I've just been interviewed by AECOM, who were contractors for 'stabilizing' this. It's chronically unviable as it was constructed on gypsum by special request of the Iraqi govt.

Many of these dams hydroelectric capacity are also threatened by the effects of the recent climatic 'drying out' going on in California, Southern Africa, and Australia- (being the golden bits on Google Earth)! This raises the issue of what happens when dried out ground becomes rapidly waterlogged when (or if) the rains make a copious return. Surprisingly the Chinese Gorges dam is already presenting a NOW case of this; as the upstream water surface has expanded drastically, changing the local climate to far more humid, and increasing rain fall considerably. While gypsum in the Mosul dam is an obvious failure issue, the cavitation occurring in the Gorges dam because of over rapid concrete pouring effectively produced a similar issue. Tofu engineering at its best.

In my own work I identified a wall collapse in a Cornish church to c.1315 AD +/-2 years a direct result of water logged ground support immediately after that walls' construction. This date marks the historic Great Famine in Northern Europe and climatically the beginning of the Medieval Mini Ice Age in Europe. Typically in Britain this ended up being 3 years rain, and contemporary accounts describe bridges being washed away and crops being destroyed by lack of sun germination and mass flooding.

I got curious about dams fairly recently- initially watching UTube vids on Lake Mead's level dropping, and then noting the drying out in similar places across the world. This wet period 1300-2000 also accords almost exactly with the Colonialisation period both European globally outside and inside Africa- with the larger scale Bantu migration south- presumably now across a wet lush Central African savannah. It presents the interesting picture that human activity has not only been enhanced drastically by the Holocene inter glacial, but affects entire population movements/history in the more minor climatic variation peaks during this period.

Kariba dam is my favourite! Its undergoing renovations at the moment, with a bizarre solar panel hybrid Chinese project on the immediate Lake upstream. The project also includes a dramatic spillway renovation, where the overflow has eroded the outflow base rock significantly in 60 years, and it was creeping up on the dam base.
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