Oroville Dam emergency spillway may be used for first time ever
Jason Green
San Jose Mercury News
Feb 9, 2017
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[snip]

Photo credit: California Department of Water Resources

OROVILLE — Water could pour over an emergency spillway at Lake Oroville for the first time ever Saturday if the California Department of Water Resources does not ramp up discharges through the rapidly eroding main spillway, officials said Thursday.

A cavity opened in the main spillway Tuesday as 55,000 cubic feet per second of water coursed down it into the Feather River. Flows were halted so that engineers could assess the damage and determine how much the spillway could handle going forward...

And here's commentary about the Oroville situation that was posted on George Ure's Urban Survival website this morning.

Dinnertime TV? Oroville Dam Failure Looms
Posted on February 10, 2017
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Phone rang at 6:37 AM. My consigliere was on the horn. He got up early to run the numbers:

“Latest rate-of-rise calculations I’ve run for the Oroville dam is that it is likely pass capacity before dinnertime tonight in California. 12 to 14 hours from now. Looks like the emergency spillway will be eaten-back, too…because the downhill slope is not covered with anything. Just bare soil, so when the emergency spillway fails, it will eat down to bedrock and work back toward the lake.”

“Flip over to the San Jose Mercury News and look at the water being dumped.”

Whew! Breathtaking.

The second picture shows the downhill side of the emergency spillway.