February 10, 20179 yr California is out of its drought. Now there is too much water. The nation's tallest dam has had it's primary spillway break apart. The 'backup' is not a real spillway and probably has not been used or used much. The lake being held back is rising with rains hitting Northern California. http://www.water.ca.gov/news/newsreleases/2017/020917spillwayflow.pdf Video:
February 10, 20179 yr Author Video of spillway and erosion around it as the damage worsens. The dam is a earthen dam. Its not a concrete dam like Hoover. Erosion of any level is not good.
February 10, 20179 yr Author Potential scenario - overtopped dam erodes out and collapse occurs. Estimates were at current level and raise of rise there was about 15 hours before the dam is over-topped. The graphic for the level of the dam has been removed from this state-wide monitoring reporting system for reservoirs: Major Reservoir Current Conditions Graphs
February 10, 20179 yr I no expert but why wouldn't the emergency spillway be concrete also? With that much rushing water erosion would be very,very quick.
February 10, 20179 yr Author Some more graphics and pictures here: Oroville Dam Spillway Failure | Metabunk Here is a view of the level rising. CDEC - Data Application 7 feet rise in last 12 hours. Level at 893.5. 900 is considered maximum. I think at that level the 'backup spillway' starts routing overflow down that embankment to keep it from topping the actual dam.
February 10, 20179 yr Some more graphics and pictures here: Oroville Dam Spillway Failure | Metabunk Here is a view of the level rising. CDEC - Data Application 7 feet rise in last 12 hours. Level at 893.5. 900 is considered maximum. I think at that level the 'backup spillway' starts routing overflow down that embankment to keep it from topping the actual dam. Thanks, great pictures of what is taking place.
February 10, 20179 yr Author Some more pictures and vids in one place. Gaping hole grows in the spillway of Oroville dam | Daily Mail Online Lake / reservoir was at 895 feet and at 901 water will crest the emergency spillway. So outlets make it sound like officials can control the 'use' of the emergency spillway. But there is nothing to control. If the level gets that high - and it will shortly if it has not already - water will run down the 'spillway' - which is really just natural path to the river below with no concrete or control mechanisms. This will be a serious situation in Cali today and for a while.
February 10, 20179 yr I no expert but why wouldn't the emergency spillway be concrete also? With that much rushing water erosion would be very,very quick. I'm also no expert but I think the purpose of the earth portion of the emergency spillway is that it will fail intentionally. The thinking being that if the pressure gets too high, it's better to have a small rupture to relieve pressure than chancing the entire dam bursting. But I don't know if that was the intended design for this dam or not.
February 10, 20179 yr I'm also no expert but I think the purpose of the earth portion of the emergency spillway is that it will fail intentionally. The thinking being that if the pressure gets too high, it's better to have a small rupture to relieve pressure than chancing the entire dam bursting. But I don't know if that was the intended design for this dam or not. Your ideal seems pretty reasonable to me. Though I would hope that there is some type of reinforcement in the upper section of the emergency spillway. Otherwise, I could see that ground eroding quickly (especially if it's already saturated from the heavy rains) and creating a much larger spillway than they intended. If the upper portion of that emergency spillway starts to give, the next thing you know the whole damn lake will be draining at whatever speed gravity allows. Erosion can happen really quick when dealing with that much water, hopefully the natural spillway is at least lined with something natural, large boulders for instance, to slow down the erosion process.
February 10, 20179 yr Your ideal seems pretty reasonable to me. Though I would hope that there is some type of reinforcement in the upper section of the emergency spillway. Otherwise, I could see that ground eroding quickly (especially if it's already saturated from the heavy rains) and creating a much larger spillway than they intended. If the upper portion of that emergency spillway starts to give, the next thing you know the whole damn lake will be draining at whatever speed gravity allows. Erosion can happen really quick when dealing with that much water, hopefully the natural spillway is at least lined with something natural, large boulders for instance, to slow down the erosion process. True, but it would only drain down as far as the depth of the lake behind that portion. Hopefully nearing the left edge of the lake in the diagram the bottom is quite a bit shallower than the rest of the lake.
February 10, 20179 yr True, but it would only drain down as far as the depth of the lake behind that portion. Hopefully nearing the left edge of the lake in the diagram the bottom is quite a bit shallower than the rest of the lake. Hopefully that's the case, I can't tell how much water would be able to flow into the emergency spillway from the photo above. But if that's the case and the lake keeps rising at just over 6 inches per hour, that's probably going to be more than the emergency spillway can handle regardless. The engineers that build the dam certainly know more about what they did than I do, but if water keeps rising at that rate, I'm not sure it's going to matter.
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