42 Years Ago This Week The Teton Dam Broke And Changed America (Rexburg: living in, nicest)

[Rakin]

Good read Mike very interesting.

[mollysmiles]

Thanks so much for taking the time to post this! My husband and I are new to Idaho, and living in Teton Valley we passed the sign about the flood on our first drive to Rexburg. After stopping to read, my husband pulled up some info online, but it certainly doesn’t compare to your first hand account! I’m amazed that it wasn’t so much worse than it was! I’m sure your memories are deeply ingrained, and I hope you’ve taken time to write things down for your family. Thanks again!

[banjomike]

Originally Posted by mollysmiles

Thanks so much for taking the time to post this! My husband and I are new to Idaho, and living in Teton Valley we passed the sign about the flood on our first drive to Rexburg. After stopping to read, my husband pulled up some info online, but it certainly doesn’t compare to your first hand account! I’m amazed that it wasn’t so much worse than it was! I’m sure your memories are deeply ingrained, and I hope you’ve taken time to write things down for your family. Thanks again!

Idaho, Washington and Oregon got a very lucky break.

Once the floodwaters reached Idaho Falls, the river bed deepens and widens from there southward to the American Falls reservoir, so the water was mostly contained. The city of Blackfoot, 25 miles south of I.F. got some flooding, but past Blackfoot, the river held the water.

The American Falls dam is old, built during the 1930s, and is one of Idaho's largest reservoirs. The old townsite of American Falls was inundated, and the entire town was moved uphill. The reservoir site is very deep and wide, one of the few spots on the river that made an excellent natural spot for a containment dam. It is much larger than the Teton reservoir.

If the American Falls dam, which is downstream from the Teton dam by about 120 miles, had overtopped or broke, the flood would have become much worse. That the American Falls dam held allowed all the other dams downstream to open their headgates, so the floodwaters ran down riverbeds that were nearly dry downstream.

That stretched the flood over about 1200 miles of riverbed and robbed it of all it's velocity. The Snake and Columbia ran high down from American Falls, but not high enough to flood.

It nearly happened. If the watermaster had hesitated much longer before partially opening the floodgates at American Falls, the flood could have destroyed the dam, sending another, larger, lake's worth of water down the Snake.

The communications then were not like today.
The watermaster was receiving some conflicting reports about the flood, but when the watermaster of the Palisades Dam, far upstream from Teton, called him and told him he as closing all his head gates to stop the Snake flowing there, it convinced the American Falls watermaster the water that was coming his way was Big Water. Huge Water.

Even then, he didn't open his headgates all the way. He only opened them halfway up at first, but by the time the water was about 75 miles away, he opened them to 3/4. That was just enough to allow the dam to hold and stop the floodwaters there.

Since the dam was brand new, no one believed it had collapsed. Most folks didn't even believe the Teton reservoir had even filled up yet, but it had, to the tippy-top.

That disbelief was what caused the watermaster to hesitate for so long. Until the flood waters began to hit the towns closest to the Teton dam, everyone downstream thought the water wouldn't be bigger than the average spring run-off. The Snake always runs high in the spring.

Another lucky break was the time of summer. By July, the reservoirs are all being drained by irrigation, so American Falls wasn't full. If the dam had failed in May, nothing could have stopped the incredible destruction.

But it was a very close save. A few minutes difference could have caused another dam collapse.

If American Falls breached, it would have caused a cascade of dam failures downstream, with each escalating and building the power of the floodwaters, all the way to the Pacific ocean.

The Snake is the Columbia River's primary tributary, and at their convergence, the Snake is a much larger river than the Columbia; the Snake makes the Columbia River as big as it is.

The flood could have wiped out Boise, Portland, and every city between them if the American Falls dam had not held.

And all surrounding lands for miles on either side of the rivers. I think about half of Idaho's largest cities and about the same in Oregon would have been destroyed, along with all of the tri-city area of southeast Washington.

One of the unique things about both the Snake and Columbia rivers is how many deep gorges both have. These gorges don't allow flood waters to spread out and inundate the surrounding river banks, so when the water emerges from them, it's very, very high in a big flood like this, and has a lot of velocity. When the country flattens out, the flood would be both massive and very fast-flowing.

The gorges themselves were all cut by huge floods- so large they defy imagining- during the last ice age, and the gorges are all well over a mile deep.

They are also very narrow in some spots. The damage that would have been caused is unimaginable to us, but it certainly would have been the worst flood in our continent's human history. Imagine a big high-pressure hose nozzle shooting rocks the size of a car out of it, and you get an idea of the destructive power of that flood.

Here's a good map that shows just how big the Snake/Columbia rivers really are. It is the largest river drainage to the Pacific ocean in North America.

As you can see in this map, the American Falls reservoir is the largest in the Snake's water management system. If you spot Rexburg on this map, you will see the Teton river. The Teton dam was due north of Rexburg.

https://upload.wikimedia.org/wikiped...erNicerMap.jpg

[mollysmiles]

Wow! Just amazing... thanks again Mike!

[ScottStielow]

Thank you Mike for the message, and passing the story on in amazing detail, as one who was there.

[Nevada2012]

Love your stories !!!!!

[banjomike]

Thanks, Nevada.
I've always loved history. It, to me, is nothing but stories, most often good ones. The problem with history as a school subject as I see it is it isn't taught well. When a kid learns about the times and the places that important folks in history did what they did, it becomes a lot easier to understand and the stories all become much more colorful.

I was helped a lot by my Grandmother, who was a school teacher for decades. She taught me how to read when I was very young, and would always give me any book she had to read, whether I understood it or not. If I didn't, she would answer my questions and point me in the right direction so I could learn my answers on my own.

One thing about history is we all make it every day. Where a person lives really has a huge effect on how they live, what they think, and what they do.
Our home territory is how we all define the wider world; it's the only place most of us are really familiar with and are comfortable in, so it's natural to presume the rest of the world must be like our home place, even if we can vaguely understand other places are different.

We Americans live in a huge nation that spans an entire continent. It's our differences as much as our similarities than makes us all Americans, and the places we live create many of those differences. Our similarities are often harder to understand, but they are both subjects that are endlessly fascinating for me.

Every once in a while, if anyone lives long enough, they become witnesses to something important to our country and the world. I just try to remember the my times as a witness, and I like to learn about earlier times here in Idaho too.

My entire family is a big bunch of story-tellers, so stuff like the flood is easy for me to write and something I enjoy doing.

[aclappine]

I work as a Geotechnical Engineer out of New York City, working on foundations for very large structures and occasionally, dams. The same type of Civil Engineer responsible for designing and supervising the grouting of the bedrock and placement of the earth-backfill at the Teton Dam site. I have long been fascinated with the failure of the dam, and have visited the site several times. You can climb to the top of the dam and see the highly fractured rock in the canyon slope. Upon seeing it for the first time, my first thought was to wonder how any engineer could have believed the rock could be successfully sealed by grouting. In engineering circles, the Teton Dam failure was attributed to political and engineering hubris in picking such an unsuitable site for a dam, and the result of federal dam design practice not keeping pace with the changes which had occurred in earth dam design outside the federal agencies.

One small correction, I believe it was the US Bureau of Reclamation which oversaw construction of the dam, not the Corps of Engineers. And you are correct, the Teton Dam failure essentially marked the end of federal dam construction in the west, as it demonstrated all the good dam sites had already been utilized, and the agencies were now just trying to keep their people employed.

[MondoTime]

Speaking of “history”, the mentioned flood was nothing on the scale of that which resulted from Glacial Lake Missoula.

That’s the (repetitive trend) you want to read about.

[banjomike]

Originally Posted by MondoTime

Speaking of “history”, the mentioned flood was nothing on the scale of that which resulted from Glacial Lake Missoula.

That’s the (repetitive trend) you want to read about.

That's very true. Those floods were so much larger they defy the powers of description.
And we won't see anything like them until another miles-deep ice sheet reforms over Canada and the northern US again, and then melts.;

The most amazing thing to me is how fast and how incredibly powerful the floods were. The only thing that compares to them in the least is the Snake River canyon in the Twin Falls area, where the Lake Bonneville drainage cut the canyon a mile deep in less than 2 days.

We always tend to think nature changes slowly. But sometimes, it doesn't, and some incredible events happened very fast once they began.

The capper to me is the Mediterranean Sea.
It's the basin that an entire region of earth drains into, and then the water goes on to join the Atlantic Ocean's waters, through the very narrow Straights of Gibraltar- only a couple of miles wide.

At one time, an earthquake closed the Straits of Gibraltar. The earth went through a warming period shortly afterward, and all the rivers that emptied into the Med could not replace the waters lost through evaporation.

The Mediterranean dried up, down to the seabed. Like the Colorado in Baja, the big rivers drained into the basin floor and then just trickled out into nothing as they evaporated. If a human existed, he could have walked across the bottom if he could have withstood the heat.

And then, after the warming period stopped and the earth began to cool again, another earthquake opened the Straits again, and the Pacific Ocean re-filled the entire basin in less than a week. A scientist said the volume of water pouring through the Straits was so great it caused a continuous sonic boom that lasted for days.

Imagine that!