It's Finally Raining in California!

The news I read is that the dam itself is not at risk but only the overflow channel and emergency overflow channel.

I see lots of erosion there, but has there been any news that the dam itself is in danger?

Mike

The dam itself is fine. It’s the emergency spillway that is in danger at this point. The emergency spillway is basically a 60-80ft tall mini dam. If that were to fail, you could imagine the devastation

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My understanding of the issue is that the flow over the emergency spillway is eating back towards the emergency spillway (see the picture in the LA Times article). If the erosion starts to take out the concrete of the emergency spillway, it may fail. If the emergency spillway were to fail there will be an uncontrolled release of 30ft of water. That doesn’t mean the whole dam will fail. But there would be a massive flood and loss of further control of the lake.

I have yet to see a geologist weigh in on the competency of the bedrock there. To me the stuff being eroded looks heavily weathered, as the rock is heavily rust-colored (evidence of weathering). The strength of that weathered rock is probably not too high, as there will be all sorts of joints/cracks in it that water can get into and pluck off big chunks.

Well, at least in the north. 700 miles to the south we could still use rain at the end of this week. Yesterday I had to water my outdoor potted plants.

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Interesting article Levers. It’s weird this erosion under the wall holding water back was the same issue which caused failure of the wall holding the storm surge back during hurricane Katrina. You’d have thought we learned something from that.

You mentioned the failure of the emergency spillway wouldn’t necessarily mean the whole dam would fail. Is there I possibility the whole dam could fail? I thought they mentioned that possibility on the news.

I hope things hold, otherwise I wonder if parts of CA would come under a water shortage again, if this huge reservoir drained?

Here is the best picture I could find. This is the eroision after a little over a day of about 2ft of water going over the emergency spillway. Those little yellow dots are people.

Imagine the erosion that a 30+ft “wall” of water would cause if this were to give way…You don’t want to imagine it.

Some news agencies over-stated the situation in titles of articles. However, as someone mentioned earlier in this thread: losing 30 feet of water from this lake would be a catastrophe downstream.

I just can’t understand how you wouldn’t take into account erosion forces (easily estimable) on the spillway. How could this be missed by competent engineers? Why was the spillway not tested?

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Hopefully they don’t have the same crew who did the Millennium Tower in SF.

I think people like to look at history and predict what will happen. We all want to know what the weather is going to be next week or next month. We talk about what it was last year at this time. I suspect that the spill way was designed for a worse case scenario. Well now here we are and it rained more than anyone thought it would and I don’t think it’s done yet. I feel sorry for the displaced people, I’m sure it is a complete mess for them.

Yes and no on the dam failure. The dam itself is supposed to be fine. But if the emergency spillway fails and there is a massive uncontrolled release of water, no one knows what erosion would follow. You could destroy enough of the hill that the entire reservoir could drain. The dam could still be there, but the lake wouldn’t be. Again, a low probability scenario – but so was the emergency spillway failing.

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Ya’'ll grow grapefruits out there? That must be a heavy load on a tree I’d imagine. Do you graft those also?

I’m off of work for at least the rest of this week due to the evacuations. Who knows what I’ll come back to, I’m assuming many of our families won’t return to the area.

Is this due to lack of confidence in the dam itself? Because I don’t believe there has actually been any flooding reported.

The evacuation order has just been lifted! It looks like they have it under control for now!

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That’s great news Steve, thanks for the heads up! Hope we can get buy this winter without anymore problems up there! We are about a 2 miles from folsom lake and it has come from 42% to 84% in just a few days. Outflows have been about 85000cfs on American river. This next storm looks to be smaller and colder, but still bringing a good amount of water! I hope you all avoid any more problems! I enjoy reading your posts as you are pretty close to me and have a good looking orchard with very good varieties!

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Another beautiful day for a walk in the park :slight_smile:

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Biggest rain in yrs for Socal.

https://weather.com/news/weather/video/los-angeles-will-see-heaviest-rain-in-years?pl=pl-editor-picks

Maybe they’ll scare it away with that forecast.

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GFS pumps out over 5 inches of liquid…plus it has rain next Tues/Weds…Insane stuff…

http://wxweb.meteostar.com/sample/sample.shtml?text=klax