I'm wondering why they don't start draping a few hundred big ass pipes over the dam and start a siphon. That is how they drained the lake made by the Thisle mud slide in Utah back in 1984.

The downhill side of the dam looks to be a bend in the river, and Oroville's just on the other side of that bend. They'd need some awfully long pipes to get the water to move in any other direction.

quote:

They'd need some awfully long pipes to get the water to move in any other direction.

I think the idea is just to move as much water off the reservoir as quickly as possible. The current options are failing, a bunch of truckloads of pipes would help. Sure all the water's going into the same downstream river but that's the intent.

Honestly though, seems like the emphasis would be on "big ass" and "few hundred" to make any meaningful difference.

^ 1080p

f_book video linked: KCRA helicopter over the dam with live shots

River valve damaged in 2009 could have been fourth way to release excess water




^ 720p

pdf slide show

^^^^^ Seems like such a futile effort, like the water won't cut a new path

Yeah, it hardly seems likely that they can get enough material in there to even partially reconstruct what's been washed away before the next storm comes through. And even if they do, if the dam overtops again the erosion will just happen again. I don't get how the possibility of this event wasn't foreseen when the dam was being designed. I mean, didn't they understand water and erosion in 1960? Maybe somebody just blew it off - "Oh hell, this reservoir will never get that high!"

Lake Oroville Webcam



f-book: a few minutes ago

Due to lower lake levels, further inspections, ongoing work to shore-up the Oroville Dam emergency spillway and updated weather forecasts, effective at 1:00 p.m. today, the Evacuation Order for the Oroville Dam Spillway Incident has been reduced to an Evacuation Warning. Any resident displaced by the evacuation may return home at 1:00 p.m.; however all residents are advised to remain vigilant and prepared as conditions can rapidly change. People who have special needs or require extended time to evacuate should consider remaining evacuated...

- Butte County Sheriff



4 hours ago from Cal Fire:

The Department of Water Resources continues to reinforce the emergency spillway. Crews worked through the night, adding rock and material to areas of erosion. These activities are being undertaken 24 hours a day and are supported by helicopters and heavy construction equipment. There is no water flowing over the emergency spillway. DWR continues to regulate outflow in an effort to reduce water levels in the reservoir, support construction activities and protect the Hyatt Power Plant. The level of the reservoir continues to decrease and at current rates, is projected to possess the capacity to absorb anticipated inflows due to forecasted inclement weather. A Temporary Flight Restriction has been enacted for the area of the Oroville Dam as crews conduct continual surveys. This restriction includes recreational drones.

Mother nature will alway wins.

Here's some good maps, images and graphics to provide perspective
http://www.latimes.com/project...e-oroville-flooding/

quote:

Originally posted by Expert308:
Yeah, it hardly seems likely that they can get enough material in there to even partially reconstruct what's been washed away before the next storm comes through. And even if they do, if the dam overtops again the erosion will just happen again. I don't get how the possibility of this event wasn't foreseen when the dam was being designed. I mean, didn't they understand water and erosion in 1960? Maybe somebody just blew it off - "Oh hell, this reservoir will never get that high!"

Using those helicopter delivered sandbags to repair the dam is like ants trying to plug up a firehose with ryegrass seed.

A lot of photos here and some very heartbreaking.
See the lake just a few years ago dry 2014

http://www.dailymail.co.uk/new...am-12-years-ago.html

As of the last hourly system update, it appears that the water level is down to 884.76' - just under 18' lower than when water was pouring over the spillway.

This means that they are just over a third of the way to the level they are trying to accomplish. There are still flows into the lake from upstream, but those are lower than the output by a good amount.

The latest forecast suggests that rain won't be moving into the area for about 36 hours. The indications are that there may be up to 1" of rain on Thursday, maybe 0.5" to 0.75" on Friday. Some forecasts indicate another 0.5" to 0.75" through about Sunday or Monday. We have to wait and see what temperature is in the storm - if cold, some may stick in the mountains. As a practical point, we should consider it all to be water.

As has been stated earlier, the evacuation has been lifted, but they are still under an advisory to be ready to move out again if the weather really sets in.

Also, it was just announced that the Feds have approved the request for emergency assistance.

Stay safe, everyone!

We flew in over the Oroville reservoir last night (Tuesday) just at sunset descending towards San Francisco. We could see the mist from the spillways. Quite impressive.

There was a lot of water downstream all the way past Sacramento. It looked like the river has flooded a wide area already.

So the emergency spillway was just window dressing and not actually designed to be used? How else to you explain failure the 1st time it is actually used?

Being a civil engineer for a major southeastern power company I would love to see the HEC-RAS and HEC-1 studies that were used to generate their inundation mapping. If these calculations have not been updated in a few years the loss of life could be even greater than predicted. Its obviously listed as a high hazard dam by the Army Corps.
We continually manage and retrofit our dams to protect against uplift via grouting, tendons, and the like out of the necessity of meeting FERC regulations. I dont know if that has been the case here or not. I would hope that it would be but given California's propensity to over protect the environment I wouldn't doubt that something is amiss. Either that or the HEC-1 drainage studies (potential stormwater volume and peak runoff) have not been updated recently which can make the inundation mapping and dam stability moot.

Hopefully cooler heads over there will prevail and the good Lord will be watching over these folks.

Water is an amazing and beautiful thing but has a power in certain situations that should not be treated lightly.

As of the noon update, they have achieved over 50% of the drop in water level they were hoping to achieve - 877.39'

Forecast for rain
- Wednesday evening 1-2"
- Thursday about 0.5"
- Friday - 1" or more, then about 0.5" that night

Cautiously optimistic that they have the worst behind them unless outflows change.

The bigger situation is that almost all of the reservoirs are near capacity. Several have increased releases now to make room - it should allow them to reduce outflow during the storm to keep all downstream areas within limits.

Again, my family in the area is all high enough to be OK. My office is in the lower parts of the Sacramento area - we can only hope that all the work after the events in the 80's and 90's are up to the challenge.

And, as I said earlier - Stay safe, everyone!

quote:

Originally posted by Jelly:
So the emergency spillway was just window dressing and not actually designed to be used? How else to you explain failure the 1st time it is actually used?

This type of dam design is pretty common, reinforced concrete with a soft-core; there are very little all-concrete dams around, Hetch Hetchy and Hoover are the most well known. I'm not an engineer and it would be very interesting to see how/why the emergency spillway design couldn't have foreseen the undermining action of all the water pouring over such a short lip.

I'm curious to know how much water is added to the reservoir for each 1" of rain that falls in the area.

quote:

Originally posted by 4x5:
I'm curious to know how much water is added to the reservoir for each 1" of rain that falls in the area.

The watershed is 3611 sq. miles per Wikipedia, so using KenS' math on page 5 I think that works out to about 62.7 billion gallons. Of course it doesn't all flow in at once, but still in Alabama terms "a lot".

quote:

Originally posted by corsair:

quote:

Originally posted by Jelly:
So the emergency spillway was just window dressing and not actually designed to be used? How else to you explain failure the 1st time it is actually used?

This type of dam design is pretty common, reinforced concrete with a soft-core; there are very little all-concrete dams around, Hetch Hetchy and Hoover are the most well known. I'm not an engineer and it would be very interesting to see how/why the emergency spillway design couldn't have foreseen the undermining action of all the water pouring over such a short lip.

The dam where I was born (Bartlett, NE of Phoenix) is all concrete. My dad helped build the Spillway:

PHX_0065.jpg by David Casteel, on Flickr
And here's the whole dam (it's almost 300' high)

Bartlett Dam.jpg by David Casteel, on Flickr

flashguy