Apr
01
2010

The Sisyphean sediment experiment

A dam is removed from a mountain waterway. What happens to the 750,000m3 of sediment that has accumulated behind that dam? Chuck Podolak, a Ph.D. student with the National Center for Earth-surface Dynamics (NCED), is using a flume experiment at the U of M's Saint Anthony Falls Laboratory (SAFL) to help him understand just that question.

In 2007, the Marmot Dam was removed from the Sandy River in Oregon, releasing 750,000m3 of sand and gravel that had accumulated behind the dam. At the time, the breach represented the greatest release of sediment from any U.S. dam removal. Chuck's goal is to understand how all that sediment will affect the river’s bottom.

Chuck’s work will help predict how bed topography in mountain rivers like the Sandy will respond to dam removal, or how large-scale gravel additions that are occasionally employed downstream of dams will affect bed forms that are beneficial for fish spawning and habitat.

One arm of Chuck’s Ph.D. research endeavor is his recent flume experiment at SAFL. Peter Wilcock, Chuck’s adviser, described the work to me as a Sisyphean task, and he did so with good reason. With help from SAFL staff and researchers, Chuck spent several weeks removing sediment from the bottom of an indoor 9 ft x 250 ft x 6 ft flume (SAFL’s “main channel” facility), shoveling tons (literally) of it back into the flume, collecting it at the flume’s mouth, and adding it to the channel again.

Chuck is using a customized instrument set-up to take laser scans and make centimeter-scale maps of the flume bottom. The measurements will give him an extremely detailed look at the flume bed, tracking down where the added sediment ended up: in pools, on top of bars, or in new bars. After the experiment’s conclusion, Podolak will combine its revelations with data gathered from field studies to run computer experiments that will shed new light on bed topography dynamics in gravel-bedded rivers.

Here is a movie I made about Chuck's experiment:

Chuck also created time series renderings of the topography in the main channel flume at SAFL during his Feb-Mar 2010 sediment addition experiment. Orange background indicates times of sediment additions:

Your Comments, Thoughts, Questions, Ideas

KelsiDayle's picture
KelsiDayle says:

I'm a little rusty on my high school English lit, so I looked up the Greek myth of Sisphyus. Basically, the guy was punished in Hades by having to continually roll a boulder up and down a hill. For all eternity. (Yikes!)

Therefore, a "Sisphyean task" is a challenging, frustrating, or maddening job that doesn't end.

posted on Thu, 04/01/2010 - 1:22pm
dhudles's picture
dhudles says:

I think what Peter Wilcock was alluding to, and therefore what I was alluding to in the title is the fact that Chuck's experiment involved the fairly onerous and challenging task of shoveling tons of sediment out of the flume, shoveling it back in, collecting it, and adding it in again... being repetitiously involved in a burdensome task.

Sill doesn't work?

posted on Thu, 04/01/2010 - 5:40pm
KelsiDayle's picture
KelsiDayle says:

I think the title is fabulously creative if you know what "Sisphean task" means. I simply took the time to look it up and was hoping to pass on the wealth to other readers.

Nice job, dhuddles -- on both posts. :)

posted on Thu, 04/01/2010 - 6:43pm

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