Oroville Emergency Spillway: Does this Look Like Bedrock to You?

February 13th, 2017 by Roy W. Spencer, Ph. D.

I’ve had a little criticism here and on Facebook that I’m not a geologist, so I shouldn’t be second-guessing the Oroville Dam engineers. They called for evacuations last evening out of an abundance of caution. That the emergency spillway is no doubt built on bedrock, and so it is safe.

Well, if it was only out of an abundance of caution that evacuations were ordered, why did emergency officials claim that there might be only one hour until the concrete weir topping the emergency spillway would fail? Hmmm?

And take a look at one of the ravines that eroded from only a little over 24 hours of flow over the emergency spillway

One of two major eroded areas just below the emergency spillway of Oroville Dam (Feb. 13, 2017). The little yellow spots are people.

Does that erosion feature look like it’s cutting into bedrock? Even though the spillway is supposed to handle 250-350,000 CFS, it was only ~10,000 CFS total flow across the 1,700 ft. long weir that caused this.

The latest press conference held shortly after noon today suggested that officials are avoiding hard questions. At one point a reporter asked, “With two parts of the system compromised (the main spillway and emergency spillway), how secure can people be?“. The speaker was not allowed to answer the question.

I honestly don’t know what’s going on, but if I lived in the flood plain (and now one of the near-200,000 people evacuated), I’d be wanting some more definitive information.

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