Why the Shape of Your Coastline Matters When Talking About Wave Quality

Tony Butt

by on

Updated 8d ago

In this fresh series of upcoming articles, forecaster Tony Butt will run you through the mechanics of how different types of waves work. From pounding beachies, to long, incredible pointbreaks, big waves and rivermouths and everything in between, we're going to get to the meat of it all. But before we dig in, it's important to understand how the shape of your coastline can impact the surf and wave quality. Here, Tony lays out exactly what that means.

A short while ago I wrote a few articles describing where swells come from and what happens to them as they propagate from the storm centre towards the coast, and then what happens to them as they hit shallow water. I described how the variation in depth (the bathymetry) is important for controlling the shape, quality, length and size of the waves when they break. In fact, it doesn’t matter how perfect the swell is just before it gets to the coast, if you don’t have the right bathymetry, you won’t get good waves for surfing.

But the bathymetry doesn’t have the last word. Even if there is some underwater feature that produces perfect A-frame peaks or magnifies the swell into one spot, the waves still need to have the right sort of platform to break over. The coastline has to be orientated in the right direction relative to the swell, and there must be a suitable bed of rock or sediment for the waves to peel down.

Check out the mechanics of Skeleton Bay: HERE

One of the world's most famous pointbreaks from an eye up high. Thanks, Google Earth.

One of the world's most famous pointbreaks from an eye up high. Thanks, Google Earth.

Pretty obvious stuff, I know. And with a bit of luck on Google Earth you might not need to think about any of this. If the satellite image was taken when there was a good swell, you might be able to spot a pointbreak running for 400 metres, or a beachbreak crammed with A-frame peaks. Also, if somebody took a photo of the wave from the ground, you might even be able to see how hollow and perfect it is.

However, if it turns out to be that easy, chances are somebody else has already been there, so you might as well just ask them. After all, there is still no substitute for actually being there and checking it out for yourself. And, even then, somewhere that looks like it might have great potential at first could turn out to be no good in the end, or vice-versa. You won’t know for sure until you see the place working under the right swell conditions.

I spent years meticulously searching for new surf spots on a forgotten section of coastline in northwest Spain. According to the charts, the offshore bathymetry contained a lot of promising features; but when I checked it out first-hand I found most of the coastline either devoid of good surf, or only containing the kind of setups I wasn’t looking for.

One part of that coast was full of spheroid-shaped granite boulders, which resulted in mutant slabs that mostly sucked dry and then backed off – perhaps okay for bodyboarding or towsurfing, but not what I was looking for. The other part contained high cliffs and giant plates of rock sticking out of the surface almost vertically. This resulted in uneven, bouncy waves that turned out to be virtually unsurfable.

Did you know that Skeleton Bay in Namibia was uncovered by the now defunct Surfing Magazine's (RIP) Google Earth challenge?

There was, however, an oasis of over 20 quality surf spots crammed into a short section of coastline, right in the middle of what I was beginning to think of as a waste of time. The waves were nothing like the rest of the coastline: they peeled right and left with clean faces, long walls and tubes that didn’t collapse on themselves, and there was no backwash, backing off or doubling up. Among them were a couple of previously-unsurfed big-wave spots, one of which I ended up surfing virtually alone for the next ten years. Call me a bit slow if you like, but it took me quite a while to realise what was going on. It was all to do with the coastal geology

Call me a bit slow if you like, but it took me quite a while to realise what was going on. It was all to do with the coastal geology.

To the west, the predominantly granite topography of the entire northwest corner of Spain meant that flat, user-friendly reefs were extremely few and far-between. To the east, the once-flat sedimentary rock had been folded over by a geological event which resulted in those giant vertical plates sticking up everywhere. It was only in that short middle section where the rock strata had remained horizontal.

I began to realise how important it was to consider the type of material over which the waves break, how that material had got there in the first place and how it had evolved over geological time.

In summary, when the waves come to the end of their journey – after they have been born in the storm centre, propagated over the ocean and steered by the coastal bathymetry – there is still one factor that can totally control the quality and surfability of the waves: the coastal geology. Apart from the simple example above, there are many other examples, including coral reefs, volcanic reefs, beachbreaks, rivermouths, sand points, cobblestone points and a whole number of sub-categories in between. In a few upcoming articles I’ll be having a closer look at a few of these, with typical examples of where in the world they occur.

Cover shot of Tony Butt by Andres Suarez.