Reading the River

Eddies, Up Close and Personal

By Tamia Nelson
tamia@paddling.net

September 16, 2003

Reading water is Job #1 for all river paddlers, from the canoeist who's happy drifting lazily through Class I riffles to the kayaker itching to challenge steep Class V drops. No river is a featureless sluiceway, and no two rivers are alike. The Battenkill of my youth was an intimate, meandering pool-and-drop stream, very different in character from the big rivers of the American West. Despite their obvious differences, however, the Battenkill and the Colorado have many things in common. One of these is the eddy.

What is an eddy? In simplest terms, it's a place where the current of a river slackens suddenly, or even reverses itself. Eddies are characterized by circular flow patterns. A whirlpool is a kind of eddy, but the eddies that most paddlers know best are the ones that form on the downstream side of obstructions in a river.

Examples abound. Midstream boulders create eddies, whether or not the boulders are visible above the surface. So do downed trees, bridge piers, and projecting rock ledges. Eddies also form at the inside of every bend in a river. And even when the channel runs straight as a die, there are weak eddies along the bank on either side, where friction robs the rushing water of some of its force and speed.

In short, expect eddies anytime something gets in a river's way, slows it down, or forces it to make a turn.

Want a demonstration? You can find one as close as the nearest culvert, parking lot, or drainage ditch. The next time a rainstorm sweeps through your area, look for a thread of running water. It doesn't matter how small it is. Just follow the main current with your eye. See how grass clippings and other debris collect in tiny swirling pools below every pebble, and on the inside of every bend? Those are eddies.

Let's get back to the river. Check out the big boulder in midchannel. The river flows around it, right? But water piles up against the upstream side, too. That's the cushion. True to its name, you can sometimes rely on it to soften the blow if you misjudge your line of descent and slam into the boulder. But don't count on it. The cushion is stuffed with rock, after all!

And what happens downstream? The boulder splits the river into two parts, but the filaments of water are reunited almost immediately. Then, impelled by gravity, some of the flow surges back to fill the "hole" in the river. The result? An eddy is born.

Of course, no two eddies are exactly alike. If a river is lazy and slow-moving, its eddies will be equally languid, their ill-defined margins marked only by minute, almost imperceptible whirlpools. Such eddies are easy to drift into on lazy summer paddles. This isn't the case when a river rushes pell-mell down a steep valley, though. Here the eddies take on a more muscular character. They're now maelstroms of sloshing spume, and their boundaries ("eddy-lines") form heaving barriers. There's often a pronounced drop or "step" at the edges of the larger eddies, too. You won't drift into these eddies unaware! You'll have to drive hard to cross the eddy-line, leaning your boat as you enter to avoid being flipped by the powerful reverse flow. And you'd better watch out for a rough landing. If you're not prepared, the eddy will thrust your boat up against the boulder at its head — and send you sprawling forward into the bargain.

Still, a rock doesn't have to stand tall to have an eddy below it. Submerged rocks can also play the game. It's "invisible" eddies like these that most often take summer paddlers by surprise on easy water. "Why have we stopped?" they ask themselves, as they spin slowly around in midchannel, their paddles on their knees, going nowhere. And then they catch sight of a sunken rock just a few feet upstream. The mystery is solved. They've blundered into a "slick." It's not a big deal. There's no better place to take a picture or two, drink some water, or have a bite to eat. Once they've tired of going nowhere, they just pick up their paddles and move on.

When big, fast rivers wash over submerged boulders, however, it's a whole 'nother scene. Such wash-overs produce huge, boat-eating "souse holes," with powerful vertical currents. Experts find them exhilarating playgrounds, but most beginners would rather face rush-hour traffic than deliberately enter one of these midriver Maytags.

Happily, there's a broad middle ground between placid slicks and churning souse holes. That's where you'll find the "friendly eddies," welcome refuges amidst the swift currents of whitewater rivers. They're good places to stop and scout, or bail, or catch your breath. Let's take a closer look at one example, made a little more complicated by the presence of a second rock in the eddy, with an eddy all its own. This is a common occurrence, but you needn't lose any sleep over it. If the main eddy is large enough, the second rock won't cause any problems for alert paddlers. In fact, if the parent eddy is really big, it's simply another opportunity to play the river.

Eddies are more than just parking places and play spots, though. Heading upstream? Eddies can make your job easier. Pushing hard against a stiff current, you'll want to "work the eddies," catching the tail of one, riding the counterflow upstream as far as it will take you, then ferrying across to catch the next — and keeping it up till you run out of river (or eddies). As long as the current isn't too strong or the water too shallow, you can eddy-hop your way upriver for miles, leaving your tracking line and pole untouched in the bottom of your boat..

But suppose you're strictly a lake paddler or sea kayaker? Eddies can still be your friends. Many lakes (and almost all reservoirs) have well-defined currents. These currents create eddies, and canny paddlers soon learn to exploit them. Sea kayakers, too, practice working the tides — making the best use of tidal currents and the eddies associated with such coastal features as sea cliffs and headlands.

That's a subject for another day, however. For now, let's return to the river and see how one expert waterman makes use of an eddy.

Our expert is looking for a place to preen. (It's not vanity. Dirty feathers aren't waterproof. A duck's gotta float, after all.) So he rides the river till he catches sight of a suitable rock just ahead of him and angles toward it. The faster the current, the higher he aims. If the river's running really fast, he'll aim right at the rock. Then he paddles vigorously through the eddy-line. He also leans into the turn a little, so that he's not rolled over by the sudden change in the direction of flow. The stronger the current, the more he'll lean. "Bottoms up!" is his rule. It should be yours, too. (Just remember that the current that matters is the current you're entering. When turning into an eddy, lean into the turn — toward the rock — so your bottom's lifted up to meet the current in the eddy.) Back on the water, the main current spins our expert's tail around, but he's already got his head in the eddy. In less time than it takes to tell about it, he's parked behind the rock. Just ducky!

But suppose our expert was headed upstream and wanted a breather. What then? No problem. He'd simply take the ferry.

He spots a rock in the right place, so he turns his head to face it, paddling hard. The current shoves him sideways, toward the eddy. If he starts dropping downriver, he angles upstream a bit more and paddles harder. On the other hand, if it looks like he'll overshoot, he eases up and falls off. He's an expert, remember. He's done this many times before. It's second nature by now. Once he's in the eddy, he can relax. Whew!

Later, if he decides to continue upriver, our expert will paddle out of the eddy and look for another eddy to climb. But suppose he's decided to head downstream. What then? Piece of cake! He approaches the eddy-line, his head facing upriver. Now he paddles hard, out into the main current. The river catches him and whirls him around. He leans downstream this time, into the turn but away from the rock. Once again, his bottom's lifted up to take the force of the current he's entering. He's on his way.

Our expert has it easier than we do, of course. He's a born waterman. He has no need of sweeps and braces. We canoeists and kayakers aren't that lucky. We have to learn to use our paddles to do what a duck does naturally. The exact stroke choreography will vary from boat to boat and paddler to paddler. Folks paddling solo kayaks will approach things differently than those in solo or tandem canoes, for example. It's something best learned by doing — exactly the same way a duck learns, come to think of it. Once you know how, though, you'll be well on your way to becoming a qwacker…er…crackerjack waterman. It's worth the trouble. Just ask the expert!

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