"In other words, those living anywhere near a river, a slough, a levee, a creek or a canal need to be ready to flee floodwaters at a moment’s notice."
That is bad enough.
The state flood control system operators have done a great job so far. The system is close to overload so this present storm might put it over the edge. Any big warm rain in the next month might melt enough snow pack to do the same.
At that point the flood control operators will triage some areas by opening levees to save as much as possible of the rest. They won't wait until large areas flood simultaneously from widespread levee failures. That may happen anyway, but I'm sure the system operators have updated the triage plan and are ready to open levees as necessary to avoid avoidable flooding.
We're just at the point that major unavoidable flooding may happen by next weekend.
The Oroville Dam spillway break compounds the problem. The flood control operators must assume now that its emergency spillway will fail the next time it is used, and make a worst case plan for that. This means adding a sudden surge of several hundred thousand acre feet of water over several hours to their planning.
Which will mean opening levees downstream as soon as the Oroville Reservoir level goes over a certain level - maybe 895 feet above sea level (it's about 850' now and the emergency spillway top is at 901' above sea level). It will take several hours for the flow from an Oroville emergency spillway breach to get far down river, and a breach would take several hours to unfold. But it will also take hours for intentional levees breaches to minimize any dam breach spill pulse enough to avoid widespread damage to the downriver flood control system.
None of this can save Oroville, Yuba City, Marysville, etc, from an Oroville Reservoir breach.
Pay real close attention to intentional levee breaches by California flood control system operators. That will give us a few hours warning of how scared they are, particularly of the Oroville Dam.
O/T: I *just* saw evidence of counter-lock in this thread. FR’s seizing up because the code, when someone is filling out a reply, runs out and increments the counter and locks the thread_comment_key even though nobody’s hit post yet. I’ve seen this a few times over the years. Change the write to the counter to happen after hitting post and the bottleneck should clear up.
Do you think there is any way for the dam itself at Oroville to fail? Nobody says that there is a chance of that publically, and looking at the way the spillways are separated from the dam by the hillside, it doesn’t look like it could happen. I don’t think it could happen from erosion coming from the spillways. I do think that there will be tremendous erosion from the spillways which will continue, especially if the water continues around the emergency spillway and goes over the parking lot.
Good analysis. This is much like the “blowing” of the Birds Point levee back in 2015. (I was close enough that the explosions sounded like heavy thunder.) Unfortunately, the media construed that as a “Cairo vs. the farmers” (racial) issue, when the real issue was “the whole flood control system” vs. the farmers. Places far upstream and downstream were saved, including industrial plants @ Calvert City, KY, the new convention center @ Paducah, much other farmland, etc.
One has to feel bad for the farmers flooded out in the “relief” area, but, they KNEW they were operating in a floodway.
Good article on the (Birds Point) floodway:
https://en.wikipedia.org/wiki/Birds_Point-New_Madrid_Floodway
Having lived very near (but not actually on) flood prone land most of my life, I can really feel for those in CA...