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A number of people have asked for more time-lapse products related to the Condit Dam decommissioning.  Here (https://vimeo.com/85659994) is a very simple but interesting time-lapse video constructed from some 7,000 images taken over a 6 hour period (one image recorded every 2.5 seconds) on blast day (26Oct11).  The 6 hour time period is compressed into 11 minutes of video.  The camera was situated on the upper deck of Cabin 69 (Cyphers), 0.4 miles mile upstream of the dam on the west shoreline.  View is to the south, and toward the dam.

The video begins by showing a black dog wandering down to the shore for a drink, and then beating a fast retreat at the exact time of the explosion.  He may have even felt the shock wave of the explosion in his tongue, although nothing was visible to those of us along the lake.  The dog wore a surprisingly guilty expression during the remainder of the day, as he had wrongly assumed responsibility for a catastrophe.

The rest of the video speaks for itself.  The first several minutes of the flush were characterized by the movement of relatively clean reservoir water through the drain tunnel.  This was soon followed by large masses of non-suspended slurry derived from bank collapses moving forward and being discharged along with increasingly turbid erosional reservoir water.  Later, when most of the reservoir water was drained, the flushed material seemed to be dominated by river water carrying a full sediment load, plus a heavy non-suspended bed-load moving in dune-like fashion below the surface.  This form of bed-load movement was visible 2-3 hours into the flush (see about 4 minutes into the video) in the form of “sand waves” travelling upstream.  The slow upstream progression of sand wave dunes (actually the expression of downstream movement of sand and other particles) is visually accelerated using time-lapse.

During most of this period, I was standing on the west shore just upstream of the emerging Jaws canyon section (above the mouth of Little Buck Creek and ¼ mile above the dam).  Looking back to about 15 minutes into the breach, I noticed that the entire lower reservoir surface began flowing upstream for perhaps 5-10 minutes (beginning about 40 seconds into video).  This coincided with the appearance of the first turbid surface water.  This upstream surface flow was occurring despite the very steady and fast drawdown of reservoir level at the dam, and not what I would expect to see if the mechanics were as simple as unplugging a bathtub.  My best explanation is there may have been a layer of dense slurry moving fast along the reservoir bottom, which was displacing the lower-density and slower moving surface water, thus forcing surface water back upstream.  Perhaps someone has modelled this or similar situations, and can better scientifically explain the complex movements of water, bed-load and slurry happening that day.  Comments are welcomed.  We would also welcome guest posts, if anyone wants to jump in with meaningful information on this or other aspects of the Condit decommissioning.

Stampfli@gorge.net

https://vimeo.com/85659994

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