Quote:
Originally Posted by Dig68
JP-There is a low head dam to be carried? Newbie question. Read what a low head dam is. Exactly what are you saying? You have to stop, get out and carry past the dam? Trying to learn some of the lingo.
Thanks, Donna
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Donna,
Low head dams (usually only a few feet high) pose a serious hazard to boaters. Although they can appear innocuous or even placid, those looks can be very deceiving. NEVER APPROACH A LOW HEAD DAM ON THE WATER FROM UPSTREAM OR DOWNSTREAM.
Water pouring over the dam creates a depression in the pool of water below the dam. This causes the water in the pool to slope (and therefore flow) back toward the dam for a short distance. These dynamics create a more or less circular circulation pattern know as a hydraulic from the water surface to somewhere near the bottom. Objects (like people and boats) that get caught in these hydraulics can easily become trapped and circulated over and over and over. This can be especially serious in the spring when the water is cold.
To illustrate the danger of a low head dam when I was learning to paddle, the instructor showed a video of two individuals trapped in a low head dam's hydraulic in upstate New York and the subsequent rescue efforts. Firefighters in two separate john-boat type vessels tried to reach the two victims, approaching them from downstream. Both rescue boats crossed the boil line (where upwelling water from the hydraulic reaches the surface) sending all would be rescuers into the hydraulic. The net result was, I believe, five drownings. Two individuals survived. It left an impression on me that I will never forget.
So, yes, in general, we get out of the boat and carry around low head dams.
The web will be full of explanations and illustrations. It's a good idea to check out a few of them.
Hope this helps.