Monday, June 29, 2009

White Rock/Sediment Experiment

A little while back I learned of an experiment one can do involving placing painted rocks in a river or stream and tracking their movement from high water flows. That idea gave me the inspiration for a way to try to see how much silt/sediment settles out of the water in Little Swamp Creek after a good rain. (Truth be told, I know my idea was influenced by my interest in the environmental sculptor Andy Goldsworthy) I purchased a bag of white marble "chips" and made a circle of them in the stream about 15-18" in diameter:

These starting pictures were taken on June 4th. You may be able to tell from this closer picture that at this location the bottom of the stream is covered with a bit of silt already - about 1/4-1/2". I chose this day to place the rocks in the stream because it hadn't rained for a couple of weeks and there was rain in the weather forecast - the perfect conditions for some particularly silty water to come downstream.

I was very surprised to see that after just 3 hours in the stream, on a clear day, the white rocks looked like this:

After 18 hours, the rocks looked like this (and we did not have the forecasted rain):

This is 24 hours after the rocks were placed in the stream:

48 hours in the stream:

5 days after placing the rocks in the stream:

And today, after 25 days in the stream, and not much rain, the rocks are almost buried:

At this point, instead of anxiously awaiting a big rain flow to see what sediment covers up the rocks, I am now very curious to see if a good flow clears off the sediment. And I wonder what kind of flow it will take to move the white rocks. Check back for updates on this ongoing experiment!

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