"leftylisa" wrote:

Pardon my ignorance -- I'm new to paddesports -- but what's a
"low-head" dam?

Otherwise known as a weir. It's a structure built all the way across a
river to control upstream levels (often to feed water into a diversion canal
for irrigation). The water flows over the top of the structure. If the
downstream side is uniform (as they typically are unless the person who
designed it was particularly smart), the hydraulic created by the water
flowing over it is incredibly uniform, and often very powerful. Unifrom
means there are no tongues crossing the hydraulic which can pull people or
boats out. To make things worse, they often have concrete walls at each
side, making it impossible for anyone stuck in it to get out at the edges.
Rescuing someone from a powerful low head dam can be very dangerous--many
rescuers have lost their lives over the years.

For pictures of one, look at
http://members.aol.com/RivierRatt/Trash/TrashUG.html This one, as the
author's disclaimer says, requires Class V skills to get out of. But it
does have a way out. Many do not--no matter how good you are, either in a
boat or as a swimmer.

-Paul