I am reasonably confident of these values as the Focus geologists took this picture yesterday of the spillway:
The circled boulder is the crest of the spillway, so water flow will start when this point is reached. Of course the one potential problem is a slope failure on the spillway walls, which could block the channel. This is a real possibility, but we won't know until tomorrow.
Close up the channel at this point looks like this:
Unfortunately the large boulder will resist lateral cutting, initially at least, which is likely to increase the rate of down-cutting. This is unfortunate. Once the water reaches the top it will initially flow down this channel, crossing the summit of the dam:
And then will flow down here:
The disturbance here is from collapse of the banks induced by the seepage. Finally, it will flow down the main river channel:
Any estimates of seepage?
ReplyDeleteI tried plotting the seepage/depth on a loglog plot. It was not very linear, as might be possibly expected from Darcy's law, which would (very roughly) predict seepage proportional to the square of the depth [(area)*(dP) or (L*W)*(gH)*K]. In fact, the seepage appeared to increase faster than expected, perhaps due to fines washing out and increasing permeability. I'm not sure what the water depth is now (114 m?) but extrapolating from the previous data, 114 m depth would predict a substantially greater flow (anywhere from 10 to 30 m3, depending on whether all points or the last ones are used). Then again, Darcy's law might be completely inappropriate.
Thanks David for up to hour information. its really interesting to see the pic it might take another week if the banks of the spill way collapse, hope so it will take a smooth passage but things are really concerning once the summit is down.
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