Somewhere (now I can’t relocate the darn article!) DWR people said the flow over the emergency spillway only reached about 12,600 cfs, when it is supposedly able to handle 250,000 cfs. They also claimed the lower flow would do more damage than a greater flow.
The explanations don’t, however, hold water. The once proposed gates for the emergency spillway were never built, therefor, in order to get to the higher flow rate, the lake would gradually rise and the flow would pass through that 12,000 cfs region, perhaps VERY gradually depending on what else was going on. Most likely, you’d get the damage we see, and then if the water ever did get to 250,000 cfs, it’d take out what remained quickly.
Sadly, what DWR is really doing is trying to bamboozle people away from the real issues of bad planning, questionable construction (of the emergency spillway) and worst of all, poor maintenance of the two spillways. If it’s not concrete, one at least wants an emergency spillway apron to be well-sodded grass. Instead, trees were still being cleared off it, almost up to the point it went into operation.
250,000 cfs, BTW, is an enormous amount of water, nearly equal to the average flow of the Ohio River @ Cairo, IL. (Ok, that’s a trickle compared to the Amazon River, but, still, 250,000 cfs is a LOT of water.)
That 100,000 plus cfs coming down the main spillway is nothing to sneeze at, either. If I have calculated & assumed correctly, the power available in the “drop” is in the neighborhood of 5,000 megawatts.
For comparison, the maximum propulsion of a modern “supercarrier” is somewhere around 200 megawatts.
I also read an article that said “slurry” (concrete) will be added to the rock fill, to solidify the fill. That may help a little, but if one has ever watched water erosion in progress, they know the water will simply find a new spot to carve out.
I would not jump to conclusions about the original designers and builders of Oroville dam. 50 years of drought and wet years it did its job. But I agree that the sooner researchers capture historical data before it's deleted is essential to laying blame where I suspect it ought to be.