Yesterday Astral Goat said he was pinning this thread for emergency monitoring. Not sure what that entails, but it does need to stay pinned please.
Folks in California should read the article from Scientific American about the flooding that occurred during the winter of 1861 - 1862 and be aware that this could happen again.
Prayers that this situation with the dam and spillway does not become an emergency and a way to repair it is quickly found. Everyone stay aware and prepared!
Quoting: ItsaTwister I think the only possible emergency is that the inflow above the dam exceeds the release capacity of the powerhouse and the damaged spillway, causing the emergency overflow spillway to come into use.
This scenario was a possibility in 1997, when the inflow exceeded the release capacity by 100,000+ CFS. All of the downtown Oroville area was evacuated, as were Marysville and Yuba City downstream. Thankfully, the rain stopped, the
inflow slowed, and major disaster was averted for the area. A levee did fail south of Marysville, flooding what was then mostly farmland.
The scenario today, with the main spillway damaged, is a bit different. A short distance below the main dam is a structure known as the Diversion Dam. The river channel between the main dam and the Diversion Dam is known as the Diversion Pool. The Diversion Dam is used to divert water from the main river channel into a canal that feeds other resources of the system, such as the Thermalito Forebay and the Thermalito Afterbay. These are largely used to supply agricultural water at varying temperatures.
If the Emergency Spillway comes into play (uncontrolled overflow), the water coursing over it would erode the hillside beneath it, dumping debris and sediment into the Diversion Pool. If the debris fills the Diversion Pool to the level of the Diversion Dam, the Diversion Dam will become irrelevant, with the water choosing the easiest course, which would be through the main river channel and downtown Oroville.
This would be bad.
