Posts Tagged ‘Caraway Creek’

Water Fences and Check Dams

February 14, 2009

Caraway Creek Dam

Caraway Creek Dam

Warren Dixon provided the photo above, which is of a dam on Caraway Creek he was called on to investigate by the property owner.

He was interested by the fact that it is virtually identical to another dam he’d recently seen on nearby Taylor’s Creek, and by the facts that, though both dams are intact, neither impounds a pond or lake due to the carefully-designed and engineered drain in the center of the stream bed, and that neither dam has an associated foundations of structures or a mill.

I told him they looked like what old timers used to describe to me as “water fences.”

A “Water Fence” as I understood the term is a stone structure that was built across a waterway to decrease the speed of stream flow and to allow sediments to drop from the water.

Caraway Creek Dam- view 2

I think the correct technical engineering term is a “check dam” or silt-retention dam.   Temporary ones are called “silt fences;” they are the ones built of logs or rocks or hay bales staked across ditches to trap soil particles in run-off water during construction.

I’ve always thought of them like sediment ponds that impound water so the silt drops out, but large permanent ones like this would also have a flood-control function to eliminate destructive floods that would scour out the stream channel. Everything but the center hole is exactly the same as a permanent dam.  The carefully engineered spillway doesn’t strike me as necessary for a check dam, but unless there is a head races coming off the dam somewhere, and a way to open and close the center hole, I don’t see how these dams could have functioned to power any kind of mill.

Unlike a regular dam, a check dam isn’t mean to impound water permanently.   I think the large hole in the center base of the dam is to insure that the stream channel remains open and doesn’t clog with silt behind the dam.    Even during floods, water would continue to come out the center hole, and even at times pour over the spillway on top.

At least, this is how it was explained it to me. But soil conservation and erosion prevention are legacies from the Great Depression, and I’m not sure how worried people were about it 100, 150, 200 years ago.

When it comes to the time, effort and expense of building a stone dam like these, did property owners really do all that just to fertilize the fields with the silt? The trapped silt would act like annual fertilizer, and the dam would allow it to spread across the bottom land instead of building up behind the dam.  Today we’d also recognize that it allows the water to stay long enough to recharge ground water. Maybe that would have made it worthwhile.

Caraway Creek Dam panorama

Caraway Creek Dam panorama

I know there are more dams like these around Randolph County. What did you all out there think?