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LNMagic t1_iwk7qck wrote

Reply to comment by unswsydney in Study indicates flood events at dams will significantly increase over next 80 years due to out of date rainfall modelling and climate change. by unswsydney

It looks like this study focuses mostly on the likelihood of flooding or reservoir overfilling events. Does this take into account various dam construction methods? The reason I ask is that one of Texas' largest artificial lakes is dammed by an earthworks construction which has become increasingly leaky over several decades. If it were to fail, potentially half a million people could be downstream, and the dam is 20 years older than its designed lifespan.

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admiralbundy t1_iwk848b wrote

How you mean construction methods? Dams generally are not supposed to overtop and the spillway prevents this. But if the rainfall is more intense the spillway may not be large enough, resulting in overtopping (which fails the dam).

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LNMagic t1_iwm3x31 wrote

With earthen dams, sometimes you get water leaking under or through the dam. If a bulge isn't handled (usually by stacking sand bags on it to counter the pressure), you could end up with a runaway erosion with catastrophic results - especially with half a million people living downstream.

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IdentityCrisisNeko t1_iwkwf1m wrote

I am a civil engineer and worked with dams for a bit (though I am by no means an expert). For what it’s worth, earthwork dams are always a bit leaky. You’ve got an enormous pressure difference on one side of the dam versus the other, and that pushes water through underneath the dam. That being said, that IS a design consideration. So I wouldn’t worry.

High profile dams like that usually have a lot of eyes on them, but if you’re worried I would find out which state department is responsible for handling dams (in Indiana, the department of natural resources handles dams for example) and shoot them a FOIA request! They should have some construction records and inspection records. In the past couple of years the dam community on the whole has opted to be more transparent about dams in general so I don’t expect the report to be useless.

There’s a chance that your dam is an army core one and then I wouldn’t worry about it. The army core does a pretty good job with their dam and levies.

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boopmouse t1_iwkq2dw wrote

It's not about leakage, we're having regular floods here all over the East coast of Australia bc of dams overflowing.
The dams we have are in good condition so far, but catchment and holding areas aren't large enough to hold the amount of rainfall we're getting with the increasing intensity of La Niña weather pattern.

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willowtr332020 t1_iwlbyg3 wrote

Just to clarify, we'd be getting floods with or without dams. Some (not many) of the dams are there to reduce (but not completely stop) flooding affects. Wivenhoe (QLD)is a flood protection dam. Warragamba (NSW) is not, it's a water storage dam (with a side benefit of some flood reduction).

The flooding is just happening because of the wet (LA Nina) period we are having as you've suggested.

We can't insulate ourselves from flooding due to the dangerous rainfall events in the report (like PMP events). In the PMP event you mainly want the dam to safely pass the water and stay structurally sound. Dan failure is worse than any natural flood event.

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[deleted] t1_iwl6fs1 wrote

[deleted]

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Dr_seven t1_iwogwar wrote

The real danger in the US is the ones FERC doesn't supervise. I'll actually politely contest your statement that most dams are federally regulated- most dams that are smaller are regulated at the state level (or at least, in my state they all are regulated that way) and those small ones are very common.

Of course, the small dams are in horrid shape and most haven't been adequately maintained in many years. They're not as catastrophic but we are still talking inundating thousands or tens of thousands of people sometimes depending on the location.

State agencies are much worse equipped to supervise such a vast field of infrastructure and so many don't, according to the correspondence and conversation I had with some engineers at my state's dam regulator. Those guys looked shell shocked and gave me like 12 hours of presentations and materials for free, saying I was the only owners representative in years to take any real interest in the dam on our property. Statewide. As in, they could not even reach live humans connected to any deeds or paperwork for most of their dams, and much of the rest was them getting stonewalled.

Silent and in the background, but terrifying.

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