Lake Mills Delta

Jumped on an opportunity to visit the Lake Mills delta with Tim Randle of the Bureau of Reclamation and Gary Smillie and Brian Cluer of the National Park Service. Relative to the Lake Aldwell delta, the Lake Mills delta is huge - maybe 3-4 times the area, and seems to be composed of coarser sediment in general. Given that it is the primary trap for most of the sediment production in the watershed this makes sense. Overall it is an astonishing feature to visit. Tim, who had visited a month earlier, was shocked by the amount of change - a shifted river channel, new delta lobes, and a rapidly prograding delta front. It is a landscape in motion, with bigger changes coming over the next year...

A series of photos from the morning...

Drawndown

The latest in a long list of steps to be taken in preparation for dam removal on the elwha river was taken a few weeks ago. the power-houses for both dams were turned off, and the water diverted out of the penstocks feeding the turbines, and through the spillways in the dams themselves. The spillways were also fully opened, lowering the levels of both reservoirs by 10-20 feet. These actions exposed even more of the impressive deltas that have built up at the up-stream ends of Lakes Aldwell and Mills, and, seeing as the sediment of the deltas is the beach building sediment of the coming decade I've taken a few opportunities over the last week or two to view those deltas.




The Lake Aldwell delta, 25 June 2011









The Lake Mills delta 25 June 2011













fine sediments (mostly mud) compressed onto the bedrock side of the reservoir. and check out the logs!














shear scarp at the former water level.













cool stratigraphy exposed by the lowered water level, Lake Aldwell delta