“The controlled spillway was designed for 250k cfs. Only yesterday did they bump the outflow from 60k to 100k.”
Really? Judging from the stadium sized crater in the spillway, I’d say some calculations were off. That spillway fell apart at half capacity?
I do agree that the real culprit are those managing the outflows. I bet I know what’s happening today at every other dam in California - drawing down.
In 1993 they had a similar problem at a reservoir (Tuttle Creek) in Kansas. The Corps of Engineers refused to release water, because it might damage St Louis (500 miles away). By the time they figure out their mistake, they were opening up the emergency gates...for the first time (sound familiar)...and wiping out some houses downstream.
They knew that spillway would fail if they ever had to use it because concrete in the section that failed was a mess and tons of water would break it apart if it ever had to be used. There was never any doubt what would happen if they every had to use it. They had years of great dry conditions to harden this structure and the problem areas. This was just criminal.
I had a close family member that was part of TVA dam safety and thus FEMA. There are several dams in the US built on the wrong type of rock and many that have not been maintained well and they all know which ones....this is no surprise.
As someone with plenty of experience noted recently that the earth (dirt) moves around for all sorts of reasons (water saturation to bone dry cycling) over the years. The spillway has been there for a while and its subsoil foundation apparently developed some problems that made some of the weighted slabs drop into a void.
It would be interesting to know what the downstream flood stage water flow capacity (including the irrigation diversion channels) is. I'll bet that it is less than 100k cfs.