Wednesday, August 13, 2008

Sand bar camping

As the last post explains, we had plenty of sand bar camping and only small amounts of Teva sucking mud on our Geology of the Green River class. The flow of the river had dropped to its not-runoff-minimum just the week before and we were expecting to see lots of stagnant mosquito filled back water eddies behind the best camping sand bars... but no. The camping was awesome.

It was interesting to look for changes in sand bar location and size after a banner snow year across the west. The Green River, although dam controlled, still boasted a larger than normal spring discharge that we hoped would translate into lots of sand transport, at least from the channel centers to the river's edge. The upper stretches of the river (between Green River UT and the start of Labyrinth Canyon proper) saw just that, a healthy crop of not new, but certainly beefier sand bars than the year before. However, once we were in the narrower portions of the canyon, the sand bars were certainly just as numerous as other years but also all showed evidence of terrain loss. The focus on the class did not allow any quantitative measurements so this is all anecdotal.

One fun exercise was that we examined the sorting of particles across each sand bar to see how the flow of water changed as the discharge dropped and the sand bar was exposed above water. Mostly however, the class seemed to find a need to memorize each formation name as we floated by and they were less enthralled with studying the energy regime that created the rock they are looking at.

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