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Old 17th Feb 2017, 01:12   #41 (permalink)
 
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Originally Posted by Hydromet View Post
David, interesting that you mention Wivenhoe. The arrangement of flood mitigation storage above full supply level in not uncommon, but it's unusual (in NSW where most of my work was) for flood mit. to be so big. Am I correct in thinking the flood mit. was increased after the 2011 floods?
I've done a few flood op. procedures for dams, but none so complicated as Wivenhoe - large dam, large flood-prone area downstream, tide-affected levels downstream, and a huge amount of political pressure.
No, Wivenhoe flood mit capacity wasn't increased after 2011 floods, but the operating procedures were rigorously overhauled in the aftermath. There was a lot of justified criticism of the dam operators in 2011 and hopefully better decisions will be made more quickly in the future.

Another SE Qld dam that did have capacity added is the Hinze Dam but this was in 2011 providing water and flood mitigation for the Gold Coast. https://en.wikipedia.org/wiki/Hinze_Dam
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Old 17th Feb 2017, 01:18   #42 (permalink)
 
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Twelve Years ago.....the dangers was brought up to State and Federal Authorities....and were dismissed.

Since then....Governor Moonbeam and the California State Government which owns the Dam have diverted money that should have been used to address known deficiencies with the Dam to other areas of State spending....social welfare programs and programs for Illegal Aliens.


Oroville Dam: Feds and state officials ignored warnings 12 years ago
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Old 17th Feb 2017, 01:30   #43 (permalink)
 
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The Brisbane floods was avoidable but the inquiry into it was neatly steered to blame protocols and systems . The operational management staff were not available over the critical holiday period when they should have been do make the flood management decisions early.
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Old 17th Feb 2017, 02:13   #44 (permalink)
 
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SASless - REPUBLICAN Arnold Schwarzenegger was Gov. in 2005, and for six years afterwards. And did equally nothing for the dam.
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Old 17th Feb 2017, 02:47   #45 (permalink)
 
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whataboutery isn't a defense.
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Old 17th Feb 2017, 02:56   #46 (permalink)
 
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Arnold was married to a Kennedy....how Republican was he really?

Not withstanding that.....Brown has had Five Years and he too did nothing to prevent the problem unfolding before our eyes.

I fault everyone since the faults were made known....Arnold included.

But....Arnold was not squandering money like Moonbeam and did not just recently spout off about making California a Sanctuary State and Federal money be damned. At least until the Dam began to fail and then he begged for that same Federal Money he scoffed at the week before.

Spin your way out of that if you want to try.....care to try?
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Old 17th Feb 2017, 03:05   #47 (permalink)
 
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Don't give them a penny, not one, from the Feds. Cali needs to learn their silly, infantile politics will only lead to recurring disasters. The pension underfunding is starving essential services of money.

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Old 17th Feb 2017, 03:10   #48 (permalink)
 
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I'd say selectively fund by county. Many parts of the state are red.
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Old 17th Feb 2017, 10:14   #49 (permalink)
 
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Things have changed more than a little since 2014.

Oroville Dam - dramatic photos of Californias historic drought

Interesting story below, of a train wreck during the construction of the Oroville Dam.
To give you some idea of the size of the earthworks, trains hauling 4000 tons of earth and rock at a time ran for 24 hrs a day, 6 days a week, for years - and it took 41,315 train loads of earth and rock to construct the dam wall!
The wall comprises 80 million cubic yards (61.164 million cu metres) of earth and rock fill.

Oroville Dam Train - Tunnel Wreck

It's quite possible the extended drought period seriously shrank the underlying clays under the spillway, which resulted in movement of the concrete slabs, thus allowing cracks to form, and thereby allowing spillway water to access the underside of the concrete in the spillway, when the spillway started carrying huge volumes of water.

Last edited by onetrack; 17th Feb 2017 at 10:25.
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Old 17th Feb 2017, 17:04   #50 (permalink)
 
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one track,

Concrete performs as well as the substrate allows. Clay is an expansive soil, and the worst on which to pour concrete. You are on the money....

By the way, the local Dam managers have released a statement about the proximate cause of the initial damage to the main spillway.

"The damage that caused the original spillway failure was rainfall...."

I am not kidding.
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Old 17th Feb 2017, 19:12   #51 (permalink)
 
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Quote:
"The damage that caused the original spillway failure was rainfall...."
And there I was...thinking it was millions of Ton/Feet (or Buckets/Barrels/Shed Loads)) roaring over the top of the spillway and cascading downhill at a high rate of fuel consumption causing erosion that was doing it.

Dang...them Rain Drops must be something to see out in Prune Picker Land.
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Old 18th Feb 2017, 13:55   #52 (permalink)
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California 'bombogenesis', biggest storm in years, kills two.


‘Mass chaos’ of Oroville evacuation prompts worry over exit strategy.
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Old 18th Feb 2017, 14:06   #53 (permalink)
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Local emergency officials "do not believe there is enough time to perform evacuations in the communities immediately downstream of the dam during a sudden failure".
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Old 18th Feb 2017, 15:09   #54 (permalink)
 
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Keeping the level of the lake below the insertion of the emergency spillway's foundation is a no-brainer, if the damcrew does just a few correct things. At 850 feet, the lake depth would have to rise fifty feet to overtop the ES.

That would take a downpour of two inches per day for three weeks, without any spillage!...(drainage) no monsoons in the forecast...
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Old 18th Feb 2017, 15:45   #55 (permalink)
 
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That would take a downpour of two inches per day for three weeks, without any spillage!...(drainage) no monsoons in the forecast...
Can I ask where that number comes from? That would suggest the lake acts as catchment for only about 350 square miles, which sounds rather low (barely more than a 10 mile radius).

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Old 18th Feb 2017, 16:41   #56 (permalink)
 
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Don't let prior damage affect the reality. The dam was too full, because the "owners" (Los Angeles Metro, etc.) saw a payday. In Cali, water is money. Bottom line. Without rainfall, the net flow was negative one foot of elevation per three hours. Roughly 70kcfs out, average of 30kcfs in. With the generating plant outflow (max 15kcfs) and no Aux spillway available, that leaves 100kcfs available down the main spillway. The max inflow in the last storm was uowards of 200kcfs. So. My numbers are based on flows, not watershed. Worst case: a rise of one foot per six hours. That leaves seven days of contained inlet, plus an available 30 vertical feet if the Aux Spillway is included. Call it two weeks before overtopping the default spillway.....

Last edited by Concours77; 18th Feb 2017 at 17:03. Reason: My terrible geometry, and worse maths.
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Old 18th Feb 2017, 16:57   #57 (permalink)
 
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350 square miles would be a radius of fifty miles
I make r about 10.5 miles.
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Old 18th Feb 2017, 17:02   #58 (permalink)
 
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Arnold was married to a Kennedy....how Republican was he really?
My father was Left Wing, my mother Right. They seemed to manage.
My wife thinks David Cameron's fundament houses a fusion device; I rather less so
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Old 18th Feb 2017, 17:04   #59 (permalink)
 
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The actual area I put at about eight thousand square miles of watershed. I got ahead of myself....that's why for me, flow is easier to contemplate than the intricacies of drainage....
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Old 18th Feb 2017, 17:21   #60 (permalink)
 
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The Mosul Dam is another worry. Built on water soluble gypsum, the inevitable has happened.
From Wiki:
Quote:
In January 2016, U.S. General Sean MacFarland warned that the dam might undergo a "catastrophic" collapse. He added, “What we do know is this—if this dam were in the United States, we would have drained the lake behind it."
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