One of the things not being mentioned here is exactly what the dangers with
low head dams are.
For ANYONE not familiar with reading whitewater and understanding the forces
and physics involved with moving water, the next sentence could very well save
your life: LOW HEAD DAMS KILL MORE PADDLERS THAN ANY OTHER RIVER
why? well its pretty simple. To the average joe, they look pretty harmless. A
quick little drop, and you paddle on down an otherwise pretty tame section of river.
A lot of people actually go out and pick a low head dam to run as a precursor to
actual whitewater experience.
What about them, makes them so dangerous?
Okay here we go:
Most people can figure out the basic danger of a natural hyraulic. "Its below the
drop that is going to suck me backwards and pull me towards the actual water curtain.
" Think of low head dams, as a treadmill on water. If it is moving faster and more
powerfully than you can paddle, you are in real trouble. Oh ya, and nature’s treadmill
doesn’t get tired. Plenty of paddlers make it over the drop with no problems,
only to get stuck in the hydraulic paddling as hard as they can, going nowhere, until
the’ve burned up all the juice left in their arms and completely spent themselves.
Eventually you will give up … then you get pulled back. When you hit the curtain,
water fills and usually swamps the boat. This is when you are upside down, rotating end
over end, all the while being pushed backwards into the curtain of falling water or worse ,down
and backwards. How many front or back flips can you do underwater before you lose all
sense of direction. Thats a game we played in the pool as kids. Personally Im totally
disoriented after 3 or 4 rotations.
In a natural hydraulic you have 3 ways out - overpower it physically by paddling or swimming,
move parallel to the hydraulic until it gets weaker and you can break free, and / or luck or
some irregularity of flow it spits you out when its good and ready.
With a low head damn there are 3 big killers that naturally formed hydraulics don’t have.
The dam is almost always a uniform flat concrete or steel retaining wall that spans the
entire river. This means that the hydraulic formed also spans the entire river and
exerts an equal force across the entire river. So if you can’t overpower it physically,
moving parallel towards either shore isn’t going to be any easier, if you can move at
all. Man-made river features are too perfect. The second deadly feature is that
the wall of the dam is usually a perfectly flat and vertical or near vertical surface.
No major irregularities across the face of the concrete or steel damn. If your body is
thrown back and against the wall, you are stuck worse than in a naturally occuring water
fall that usually has enough irregular surfaces that you can claw, push off of, and otherwise
get yourself free and moving parallel and out of the hydraulic. (except for caves, but thats
another discussion entirely). Low head dams are just smooth walled death traps with
nothing to grab, and nowhere to move to even if there was.
Lastly, low head dams are almost always in areas of some built up civilization and that
means “Townies”… “No city or urban development has ever done any good to an
innocent river nearby”. Low head dams with their uniform in-escapable river wide
hydraulic are like giant rotating garbage mounds. Every piece of garbage, shopping
cart, spare tire, plastic bag, beer can and snarled knot of fishling line from miles and
miles upstream, eventually ends up in the churning, unforgiving hydraulic at the base
of a low head dam. just … yummy. Just one more added element to make a life and
death situation that much more interesting.
And the last element of danger… misreading the danger level. Because the hydraulic
is so uniformly perfect, even accomplished class V paddlers can miss-read the sheer
strength of the currents they produce. Generally speaking and this is VERY general .
… look at the width of the band of water that is flowing back towards the curtain
against the current. The wider the band, the more powerful the rotational force of
the hydraulic. If the band is wider than your boat is long … you are tossing the dice
with your life. Irregular flows or breaks in the perfect band usually means large foreign
objects that have come down river and been pinned in the hydraulic.
That is not to say that all low head dams are waiting to catch and kill you. Its extremely
dependent the actual flow of water going over the dam. Most river gauges are located
right on low head dams because its so easy to take accurate readings. If you’re not into
metric yet - (get with the rest of the world America ) I will provide a translation here
from Canadian/restoftheworldese to Imperial here: A cubic foot of water weighs 62.5lbs.
A 5ft x 30" standard steel bathtub holds almost exactly a cubic foot of water. River gauges
often have two scales on them. One of which is cubic feet per second. There are all kinds
of ‘rules of thumb’ to aproximate flows, but actual river gauges never lie and are
always precise, instead of ‘close’ The more cubic feet of water per second spilling over
the dam, the more weight and total force driving the hydraulic at the bottom. A measly little
10cubic foot flow is equal to 625lbs of force, pushing your body in a direction opposite to where
you want to go.
SO ya … thats whats dangerous about low head dams. They look like nothing… and thats how
they get so many people. There is a reason you don’t see any world class kayakers or videos on
youtube of pro paddlers messing around in low head dams. Experienced people know to avoid them.
Inexperienced people continue to take on low head dams ever year looking for a quick thrill, and
sometimes paying the ultimate price.
Sorry that was so winded. I just think its important that anyone thinking about running low head
dams, KNOW beforehand how dangerous they are.
Personally, I would rather run a C-5 concrete fishladder in full ‘rag-doll’ position than take a gamble and
bail in a high volume low head dam.