Sunday, December 19, 2010

Reading a River - Part 1

As I learn to navigate the shallow, rocky, and swift water in the Snake River Canyon (the deepest rivers gorge in North America, by the way. Suck it, Grand Canyon!) I learn more and more about reading shallow moving water.

Quick history – I’ve been on the Columbia and Snake Rivers my entire life, skiing, fishing, and just generally enjoying them. I’ve run boats in sizes ranging from 6 foot paddle boats up to a 53 foot, twin-screw monster, all on inland waters of the Columbia and Snake River system. I’ve locked through dams, run shallow canals to the Chain Lakes off the Coeur d’Alene River through which most people wouldn’t dream of taking a power boat, and pretty much run boats non-stop since I was old enough to sit in Dad’s lap and steer. I think that I am a damned good boat operator.

One thing I’ve never really done, though, up until this Spring, is run in fast-moving shallow water. I’ve run moving water on the Hanford Reach and below dams, including Lower Granite and Bonneville, but it was deep. I’ve run shallow water all over the place, but it was typically pretty still. I can read a lake or river pretty well given the topography around it (steep shorelines typically mean deep water off shore, flat shorelines mean shallow water. Rocky shorelines mean rocky bottom, and so forth) but I’ve never run water that you have to actually read the water itself to see what is going on beneath. It is a trip.

The first thing that I learned about a river is that it will speak to you in three ways:

1.) In Vees. You can see vee-shaped formations in the current. Vees pointing downstream mean that the water at the center of the vee is moving faster than the water at the edges, because of obstructions at the edges. This means that a downstream vee shows you the location of the deeper channel, and is typically a safe zone that you want to aim for (typically, but not always). Vees pointing upstream are always created by obstructions. There is a rock or stump or something under there. Avoid upstream vees at all costs.

2.) In hydraulics. Hydraulics are often times mis-read as rocks or obstructions. The way to tell the difference is that a hydraulic is not constant. It will “flicker” in and out, and possibly even move around a bit. Rocks, on the other hand, are solid, steady, and never move. Hydraulics are caused by water flow, as it moves quickly around the odd shapes of the river bed, and even sometimes, obstructions. Usually, the obstructions creating the hydraulics are deep enough that you won’t hit them if you skate over the top, but be careful. Hydraulics are there for a reason, and they are trying to tell you something. They can be very hard to interpret.

3.) In the surrounding topography. I discussed this above, but I failed to mention that the overall shape of the river also means something here. The outside of a river bend is deepest (usually) whereas the inside of a river bend can be very shallow as the slower water there deposits silt, and the faster water outside digs it out.

I’m not claiming that you will be able to go run a river with these three things in mind. Don’t do it. I’ve been doing it since this spring, as often as possible, and I still don’t think I am very good at it.

That being said, there are some things about vees that I want to elaborate on.

1.) A downstream vee is often the “safest” route through a rapid as it relates to missing obstructions, but can be the swiftest, most turbulent, roughest part of the river. Sometimes you can read the vee and hang to the edge of the channel where the water is moving more slowly and is not as rough and get a smoother, more fuel-efficient trip through the rapid. Remember, though, that the reason that the water is moving more slowly on the edge is because of friction – caused by either obstructions in the water, or by the bottom itself, meaning that the water is shallower there than in the channel.

2.) A rapid that is hard to read can often be made easier by “connecting the dots” between obvious upstream vees. Remember, all you have to do is not hit the rock. It doesn’t matter how close you get to it if you don’t hit it, and if it has a clear upstream vee, whereas other areas in the rapid are not so clear, go to where you know for sure where the obstruction is and squeak through there, rather than risking an unclear section of river.

3.) The rock causing an upstream vee is normally upstream of the vee, itself, by quite a ways. Look for clear humps in the river in front of the vee, and there is your rock. You can often times motor directly over the vee, itself, without hitting a rock, but I wouldn’t recommend it unless you can clearly see the rock.

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