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Alongshore

Surf's Up! Exploring the Place Where the Sea Meets the Land

By Tamia Nelson
tamia@paddling.net

Stand stable here
And silent be,
That through the channels of the ear
May wander like a river
The swaying sound of the sea.

    W. H. Auden, "On This Island"

November 16, 2004

The "swaying sound of the sea." The gentle swoosh and hiss of spent waves washing rhythmically over a sandy beach, minute after minute, hour after hour, year after year. It's a pleasing image, especially when the window over my desk frames nothing except bare trees and gray skies. But the sea is changeable. One day, the beach is a placid paradise. On the next, towering waves totter and collapse, gnawing away at the land where they fall.

This drama plays out in a rough-and-tumble strip of seacoast called the surf zone. It's a fluid boundary at best, bracketed between the outermost line of breakers and the most recent high-water mark. Fluid or not, though, it's where the action is, where waves wash or crash ashore, and where beaches are born, grow old, and die. If the bleak November days have got you thinking about sea kayaking, then the surf zone is where you'll first wet your blade in salt water.

Sounds good, doesn't it? But don't just shove off and hope for the best. Experienced river paddlers know it pays to scout any water that's new to them. And the same applies to sea kayakers. There's simply no substitute for local knowledge. But it's not easy to scout the surf zone from shore. So let's head down the pier and see if we can find an old salt who'll help us make sense of the surf.

We're in luck. Pelé's heading out for a little fishing, and he'll be happy to take us along. What's that? You don't see anyone else on the pier? Just a pelican? Right on! That's our bird — and don't let him hear you dissing pelicans. What Pelé doesn't know about the waters hereabouts isn't worth knowing, and when he's airborne he's got the best seat in the house for the show.

OK. Ready to fly? Good. It's a great day for it, too. Visibility's unlimited, and gentle swells are rolling in toward the beach. Let's follow one and see what happens to it when it first "feels the bottom." There! See that? The crest of the roller is rising as it climbs the gradual slope of the foreshore. Soon the wave is standing tall, and the crest is starting to collapse. Now white water is spilling down the face. A minute later, and all that's left of the wave is a sheet of water and foam washing up onto the beach. But by the time this wash drains away, another wave is already rolling in.

Pelé's going farther out to grab a bite to eat now, so let's land on the beach and see what we can see from shore. You could call this studying surf-zone processes if you wanted to impress your friends, but we'll leave the equations and wave-tank experiments to the pros. What matters most to both pelicans and paddlers is what we can understand with no other tools than the Mark I eyeball. And that means going eyeball to eyeball with…

Breakers

This beach would be a good place to launch or land, and today would be a good day. A gently-sloping shore, not too much wind, and no storms far out at sea — all these add up to moderate surf. The waves are breaking, sure, but they're not hammering down. They're "spillers," in other words. As each wave comes ashore, its crest spills down its face. Spillers can get big, but however big they get, they still break easy. That's why they're welcomed by both kayakers and novice surfers alike.

Of course, not all waves are so accommodating. Storm swells driving against a steeply-shelving shore often break hard. The crest curls over in a hurry, trapping an air pocket that extends along the entire face of the breaker. Then, as the crest topples shoreward, this "tube" is caught between the tumbling mass of water and the unyielding bottom. Squeezed between a wave and a hard place, the air in the tube has to do something, and it does. It explodes skyward. Kayakers call these waves "dumpers" for good reason. More prosaic folks call them plunging breakers. Whatever you call them, they're no place for a small boat.

While we're talking about eyeballing the surf, let's see if we can't answer one of the most-asked questions on any beach: How big are the waves, anyway? No, you don't need doppler radar to figure this out. Simply walk up the beach until the tops of the breakers touch the horizon. Now estimate the height of your eye above the swash line (the highest place on the beach reached by water surging forward from the surf). That's how high the waves are. Try it yourself. And don't just measure one wave. Take several minutes and size up each wave that comes along. No two waves will be the same height. It seems chaotic. After a while, though, a pattern often emerges. Ten or more small waves will be followed by three or four really big ones, only to be followed by another comparatively quiet interlude. This alternation is known as the beat of the surf, and a kayaker who takes the time to get in sync with the beat can spare herself a lot of grief in launching and landing.

Are you wondering what causes the surf to beat? To begin answering that question we'll have to go back…

Offshore

But Pelé's still on his lunch break, and a lot of the action's underwater, in any case. So let's swim along with a real-life ancient mariner — a sea turtle. Verda may be the last of a vanishing breed, but she's not ready to give up. In fact, she's just laid a clutch of eggs in the beach sand. Now she's ready to go home. First, though, she has to make it out through the surf zone. And we're going with her. Hope you're ready. There's not a minute to lose. Verda's already wading into the swash.

We're through the surf before we know it, but it's hard to see much, isn't it? Even though the breakers are spilling, the constant beat of the waves still scours sand from the bottom. Happily, the water clears as we move away from shore. Soon we're approaching an undersea dune — a longshore bar, in fact. It runs parallel to the coastline, and if the incoming rollers were much bigger, there'd be a heavy surf over the bar, too. Today, though, there's only an occasional breaker.

What'd you say? You think Verda's slowing down? That's no surprise. She's had a hard night. Now she could use a little help getting over the bar and out to sea. And she's in luck. Look over there on our right. See the cut through the bar? It's a channel, and it's there for a reason. Verda's seen it, too — she was looking for it, in fact — and she's already heading toward it. We'll tag along. Watch what happens.

Wow! It's sort of like being on an escalator, isn't it? We've caught a…

Rip Current

The bar acts like a dam. Water piles up inshore, and it wants to get out. So, sooner or later, it cuts a channel through the bar and flows back out to sea. And we're going along for the ride. Once we're past the narrow cut in the bar, the current will slow down. But by then we'll be out of the surf zone.

That's it. Verda's on her way home. And we ought to be getting back to the beach. There's no need for us to buck the rip current, however. All we need to do is swim parallel to shore for a while. Once we've put a little distance between ourselves and the cut in the bar, we'll turn our backs on the sea and ride the waves in — without having to fight the rip.

 

It's good to be back on land. Now I'm going to get some shut-eye in the shade of the tarp.…

Damn! Is that the time? The beach sure is a lot wider than it was when I dozed off. And where'd that low ridge just offshore come from? Of course. It's the crest of the bar that we crossed earlier, when we were following Verda. The tides gone out. Now it's easy to see the channel cut by the rip current. No point in posting it to warn unwary swimmers, though, is there? The only thing that's constant in the surf zone is change. By next week the cut may have moved. By next year, the bar itself could be gone. Some things last, though. Like…

The Beat of the Surf

Think back to what we noticed earlier. Remember how three or four big waves came along after every ten or twelve small ones? Look at the breakers. It's still happening. And what's the explanation? It's easy, really. The ocean's a big place. Wind makes waves, and wave trains move at different speeds. When one wave train overtakes another, and crest overlaps crest, they add up. The waves grow. (If crest meets trough, however, the opposite happens: they cancel each other out.) The surf zone is where it all comes together. Each swell rolling inshore is the product of thousands of mid-ocean encounters. The result is the beat of the surf. Geography plays a part in setting the tempo, too. Gentle slopes make for extended surf zones, like those along the coast of Java, say, or even Hudson Bay. A kayaker may have to do battle with spilling waves for a good part of an hour before breaking free into open water. On the other hand, steep foreshores concentrate all the action in a narrow band. Then, when the surf's up, it can be impossible for paddlers to break through at all.

Whether the foreshore is steep or gentle, though, the beat goes on.

The message is plain to anyone whose ears are open to the "swaying sound of the sea." The only thing constant in the surf zone is change. Each shift in the wind and every turn of the tide remixes the music. Walk a mile down the beach. Conjure up a storm. Whatever you do, the surf zone will be different than it is here and now. That's the enduring challenge of the place where the sea meets the land.

Copyright 2004 by Verloren Hoop Productions. All rights reserved.
















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