Anatomy of a River

After the Flood —
When Rivers Rearrange the Dust

By Tamia Nelson
tamia@paddling.net

May 10, 2005

The Schoharie Creek ran high and fast, swollen with snowmelt and spring rains. The current surged against the trunks of partially submerged willows and sycamores. Looking up as I hurtled past, I spotted shopping carts, countless plastic bags, one seemingly intact Volkswagen Beetle, and a dead deer — all high in the trees, all ensnared in the tangle of naked branches. It was a salutary lesson in the force of moving water. The planet's surface bears witness to this power everywhere, displaying the scars of giant waves and surging floodwaters, from deluges both ancient and modern.

Moving water always leaves change in its wake. On a river, nothing lasts forever, but that's…

The Tao of Flowing Water

A rising river first fills its channel from one bank to the other and then spills out over the surrounding land. Even a bankfull river is fast and powerful, but the Force is really with a river in flood — abandoned cars and shopping carts don't end up in trees without some doing. There's a lot going on underneath the surface, too. From microscopic flecks of clay to boulders the size of cottages, sediments are plucked from their resting places and dumped somewhere else. And moving water doesn't just eat away at soft earthen banks. Armed with the cutting tools that suspended sediments provide, it erodes solid rock as well. A low, slow river also reshapes its channel, but this work is done at a measured, leisurely pace. A lazy river approaches the job with the laid-back attitude of a teen-ager, confident that there'll always be another day to do what needs to be done. A river in flood is something else. It's like an old man in a hurry. Change comes fast and furious. That's why the first paddling trips of the season are often voyages of discovery, even on familiar streams.

Hopefully, you won't be on many rivers while they're in flood. If nothing else, it's a little disconcerting to hear a distant rumble and realize — belatedly — that you're hearing boulders banging together on the river bottom. But you don't have to ride the flood to see what the water's been up to. You can read a river's history in the landscape, long after the floodwaters have receded. It's a new way to…

Read the Water

One frequently encountered relic of past floods is the sweeper, a toppled tree whose branches hang down into the water, while its roots still cling to the land. You'll most likely find sweepers at the outside of bends, where floodwaters have undercut a bank. I use the word "encountered" figuratively, by the way. Sweepers are best viewed from a downstream vantage point. The current passes easily through the submerged branches, but paddlers don't. An unlucky boater can be trapped in this vegetable snare like a moth on the grill of a speeding car, and in a worst-case scenario the boater's chances aren't a whole lot better than the moth's. Don't bet against the odds. The gentle susurration of water as it washes through a sweeper is the sound of whispering death.

Sweepers aren't confined to river bends, though. Nor are they always solitary pickets. Sometimes — especially on big rivers — many sweepers are…well…swept away from the land altogether, piling up in great drifts of dead wood in the shallows. These driftwood islands, too, are best avoided. Approach them, if you must, from downstream. R.M. Patterson, whose Dangerous River remains a paddling classic more than 50 years after it was written, speaks feelingly of watching whole trees speeding by in the grip of the muscular Nahanni current, now vanishing below the surface, now vaulting free of the water altogether. Later, while camping on a gravel bar in midriver, he clambered out onto a driftwood pile built up from many such wayward sweepers. The trunks of the grounded trees quivered and thrummed as the Nahanni swept relentlessly beneath them. Dangerous river, indeed! Had Patterson been unfortunate enough to dump upriver of that deadly trap, he'd probably never have lived to tell his story.

Moving water carries more than trees, of course. The gravel bar that Patterson camped on was itself a legacy of past floods. Rivers are always rearranging the dust, building new islands, raising new banks, extending sandy spits and bars, and making beaches. Look for these landmarks anywhere the current takes a breather: the insides of bends, say, or the gentler reaches between major drops. But beware. Not every river is a Nahanni. Streams in more "sivilized" latitudes transport almost as much trash as natural sediment. That attractive-looking beach you're eyeing for a lunch stop is likely to have broken beer bottles, strands of rusty barbed wire, and splintered wood from discarded shipping pallets embedded in the warm, inviting sands. The days of barefoot beachcombing are over. Be sure to go properly shod whenever you explore afoot.

And that's not all. Nothing comes from nothing. For every new island or beach, there's a new channel, eroded bank, or deeper cut somewhere upstream. If the sandy spit you remember from last year is now an island, chances are good that a flood is responsible. Each spring, rivers grind deeper into their banks at the outside of every bend. Contractors and homeowners do their best to armor "their" stretches of shoreline against the floodwater's annual assault, to be sure, but it's a holding action at best, and doomed to failure. Whatever it may say in the deeds registered at the courthouse, a river retains title to all the land along its banks.

Sweepers. New islands. New channels. The ancient Greeks were right: you'll never find a river the same as you left it. That's where scouting comes in, and scouting puts us right…

On the Riverbank

In some places — the great rivers of the James Bay lowlands come to mind, as do the coastal bayous of the American South — and at some times, it isn't always easy to tell where the water ends and the land begins. Yet most rivers flow between well-defined banks, at least after the spring floods subside. In the High Peaks of the Adirondack Mountains, for example, many streams are constrained by rock walls for at least a part of their journey. But even mountain torrents have to slow down eventually, and as they spill out onto the plains, these lively streams dig deep into glacial till, sand, and clay. Here they have a free hand to remodel the landscape. As we've already noted, a river's appetite is most easily satisfied at the outside of bends. Even when it's not in flood, it gnaws away at the bank, undermining the overlying earth. To get a handle on what happens next, think back to the time before siege howitzers and bunker-buster bombs, when stone walls were the ultimate in fortification. If you wanted to bring a stone fort down in those days, there was just one way to do it: dig tunnels under the walls and then blow the shoring timbers out. The all but inevitable result? The walls came a-tumbling down.

A river attacks the banks at the outside of its bends in the same way, tearing at the underlying props. And sooner or later the riverbank, too, comes a-tumbling down. You don't want to be standing on it when it does. Whenever you scout a river, therefore, avoid the temptation to walk right out to the very edge of a high cutbank in order to get a better view. You just might take more of a trip than you bargained on.

However you look at them, undercut banks can be dangerous, and the danger lingers long after the spring floodwaters recede. Even if you never scout too near the edge, the exposed beach under a cutbank can make an attractive low-water summer campsite. Bad idea. Resist the temptation. Before staking out your tent, look up. Is there a dramatic overhang just about you? Are runoff channels and deep cracks everywhere? Do clods of earth litter the beach at your feet? Don't wait for the rangers to put up warning signs. Believe your eyes. And then look for another campsite.

Or maybe the bank above you is solid rock. No problem, you think? Don't believe it. Look at the base of the cliff. Do you see a pile of sharp-edged rock fragments? This is talus. Every time water and rock go head to head, water always wins. The talus is proof of that. Better not hang around to see the doomed contender hit your canvas.

Of course, spring rains and snowmelt make their presence felt away from the riverbank, too — as you'll find out when the time comes to portage. To see what I mean, let's…

Hit the Trail

Water has to get to the river somehow, and feeder streams crisscross the landscape throughout canoe country. These little rills may gurgle pleasantly enough during the dog days, but their gurgle rises to a roar in the spring and early summer. Footbridges and stepping stones are often swept away, and what would otherwise be a walk in the park becomes an exhausting expedition. During years when the rains come early and last long, the portage trails themselves are sometimes transformed into little rivers, complete with miniature rapids and waterfalls. You can't count on running them, though.

There's more. The storms that bring winter snows and spring rains — not to mention summer squalls — travel on the wind. Like water, wind also reshapes the landscape, bringing down limbs and knocking over trees. If the trail-maintenance crews haven't been through lately, you'll be glad you brought an ax or saw. Better check local regulations before you shift into Paul Bunyan mode, however. Many authorities frown on do-it-yourself trail improvements. You better know what you're doing, too. An ax, in particular, is a wonderfully efficient tool for cutting a holiday short, not to mention a leg.

Animals can also modify landscapes. Even if you paddle in one of the increasingly rare places where bulldozers and skidders aren't busy reshaping watersheds, there are other engineers at work, and they've been at it a lot longer. Beavers have their own ideas about how to manage the land, and it's not uncommon to find previously high and dry portage trails under water when a beaver's on the job. Wellies will sometimes see you through, but at other times you'll find yourself wading. Be prepared.

We all long for stability, but nature seldom obliges. And that's a good thing. Stability can be downright dull. But rivers are never boring, are they? Moving water is always rearranging the dust. Nothing lasts forever without changing. After each flood, the world along the riverbank has a fresh, new look. And that suits me just fine.

Copyright © 2005 by Verloren Hoop Productions. All rights reserved.

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