Dislocated skeleton: The shifting position of Skeleton Bay

Craig Brokensha
Swellnet Analysis

As surfers, we tend to see the coastline through two different prisms: rapid change or timeless constancy. Think about beachbreaks, they're always in flux, the banks are good today and terrible next swell. We expect them to change, even hope that they do. While reef and rock breaks are immutable, they're the same today as they were last year, last decade, and last century. We accept their permanency.

Some waves, however, don't match either category. The change is slower than beachbreaks but fast enough to perceive when closely observed, and those changes give us an idea of deeper processes at work. The Mentawai Islands are a good example. Due to their location between two tectonic plates, the Mentawais are slowly sinking and the reefs are getting deeper by a few centimetres each year.

Another wave is Skeleton Bay, and like the Mentawais it lies on a very dynamic coastline, however it isn't plate tectonics changing the shape of the Namibian coast but a steadily migrating mass of sand.

Four years ago, almost to the day, we wrote an article detailing the rapid changes happening to the shoreline at Skeleton Bay. The premise of the article was simple: “the world's most perfect and thought provoking sand-bottom left hand point break may not exist in twenty years time”.

In the subsequent four years we've had multiple satellite and aerial photograph updates, the most recent being May this year. What is evident is a further build up of sand inside Donkey Bay, where the wave runs into, reducing the peel angle and speeding up what is already a challenging and super fast wave.

At Swellnet we looked at past satellite imagery of Donkey Bay and from 1973 through to 2012 the shoreline shifted 1km north. In the four years since, fresh satellite imagery has shown the wave shifting a further 120m to 150m further north, depending on where you measure the bank from.

Overlayed satellite imagery showing the shift in coastline from July 2009 to May 2016

The Namibian coast is in constant change due to strong persistent south-southeast winds blowing off the Namib Desert, transporting sand into the nearshore zone. This along with significant longshore drift - approximately 1 million cubic metres of sand reaches Donkey Bay every year, twice as much sand as passes the Superbank - makes for a coastline in considerable flux.

"It's always changing," says Shaun Loubser from nearby Swakopmund who first rode it in 2002. "My opinion is, yes, the wave has changed since I started surfing it, but every year the banks are different to the year before." However, Shaun cautions against relying too much on the satellite passes as the sand can move a great deal: "What time of the year the photo was taken? Was the photo taken during swell, before a swell or just after a swell? All these factors will have an influence on what the sand bank is looking like from sky at that specific time."

Another regular visitor to Skeleton Bay is photographer Alan van Gysen. He's travelled there many times since Surfing Magazine blew it open in 2008, including two trips this year. "I am very concerned and aware of a big bulge of sand midway down the point that is breaking up the point and a soccer field-sized deposit down near the bottom of the wave which on a more southerly direction is creating a closeout and/or righthander! Without a doubt it's a very different wave from 2008."

A critical aspect of the wave, in fact a critical aspect of any wave, is its 'peel angle'. The peel angle is the angle between the refracted swell line and the lined traced by the whitewater as the breaking curl peels along the coast. In our Coastal Creationism articles Chris Buyx described the peel angle of waves. Most surfers want a peel angle between 50 degrees - which provides slow but fun waves - to 30 degrees - which describes fast, down the line waves.

Slight reduction in 'peel angle' from 2009 to 2016, making the wave slightly faster

In 2008 the peel angle of Skeleton Bay was approximately 25 degrees, creating fast, challenging waves that could only be ridden by advanced surfers.

Since then the coast has shifted slightly more anti-clockwise, reducing the peel angle along some sections of the wave to below 25 degrees. This is getting close to being unmakable even by the best surfers on the planet, and if a further shift is seen, we may see Skeleton Bay turn into a glorified close-out - albeit one of the best closeouts in the world.

With the wave shifting hundreds of metres north in only four years, along with the coastline steadily rotating to create a faster, less makable wave, the question is how much longer will Skeleton Bay resemeble its current incarnation. How much change can it cope with before it becomes just another bend in the coast?

The other unknown is the lagoon which abuts the point. During big swells the waves can threaten to wash into the lagoon which would change the sandflow at the bottom of the point as the runoff would need to find an outlet. Both Shaun and Alan agree that if it were to happen it'd be very bad news for the wave.

While all of this may sound horribly pessimistic there is a very bright side to consider. Before the year 2000 Skeleton Bay barely resembled the wave we know now. It was transformed into something truly magnificent by the slowly migrating sand. So just as the coast at Skeleton Bay changed for the better, so too can other waves transform from ugly ducklings to beautiful swans - even beautiful Donkeys! - when the sand falls in just the right way. To plagiarise an all-too-familiar ad campaign, the search is endless. //CRAIG BROKENSHA and STU NETTLE

Comments

SurferSam's picture
SurferSam's picture
SurferSam commented Tuesday, 20 Sep 2016 at 2:44pm

Like my local beachy but on a grander scale - can be smokin in winter and one long closeouts in summer

davetherave's picture
davetherave's picture
davetherave commented Tuesday, 20 Sep 2016 at 4:02pm

Get out the dredge and shift the soccer field.

davetherave

zenagain's picture
zenagain's picture
zenagain commented Tuesday, 20 Sep 2016 at 4:25pm

Great article.

Watashi wa metabo oyagi desu.

benski's picture
benski's picture
benski commented Tuesday, 20 Sep 2016 at 4:40pm

Yep. Great read.

tonybarber's picture
tonybarber's picture
tonybarber commented Tuesday, 20 Sep 2016 at 4:41pm

Interesting - as given the swell direction is relatively predictable year in year out, I would have thought there would be a strong equilibrium to keep the peel angle much the same. The time frames mentioned are relatively short. Or are we just seeing a 'temporary bulge of sand' due to a season different swell directions.

Craig's picture
Craig's picture
Craig commented Tuesday, 20 Sep 2016 at 4:52pm

Good question TB, some techinical info I left out answers this.

The way the coast handles incoming waves depends on its incoming angle. If the angle is fairly straight on (like east swell on the East Coast), any small disturbance/kink in the coast is gradually smoothed out and lessened.

If the incoming angle of the swell is greater than 45 to the coast though, the disturbance is amplified and increased, that being Donkey Bay in this case. Climate studies also have found that the mean swell direction has tended more south in the last half-century, and this is resulting in the coast angle tending more anti-clockwise and to the west.

tonybarber's picture
tonybarber's picture
tonybarber commented Tuesday, 20 Sep 2016 at 6:16pm

Thanks, it's interesting to hear that swell direction is tending more west - other forces at play.

Craig's picture
Craig's picture
Craig commented Tuesday, 20 Sep 2016 at 6:22pm

Ah, no it's swinging more south, but the coast alignment is swinging more west.

mibs-oner's picture
mibs-oner's picture
mibs-oner commented Tuesday, 20 Sep 2016 at 6:08pm

best be booking that plane ticket now rather then later then ay

mibs-oner's picture
mibs-oner's picture
mibs-oner commented Tuesday, 20 Sep 2016 at 6:08pm

fuck maybe we can start a gofundme campaign to get mibs proper pitted at skeleton bay

udo's picture
udo's picture
udo commented Tuesday, 20 Sep 2016 at 6:17pm

The 'OutSider' is long overdue for a trip.

surfstarved's picture
surfstarved's picture
surfstarved commented Tuesday, 20 Sep 2016 at 8:39pm

Aren't we all?

Don't let the bastards grind you down

t-diddy's picture
t-diddy's picture
t-diddy commented Tuesday, 20 Sep 2016 at 9:32pm

Great article! Stu, imagine the coastline is perfectly perpendicular to the swell direction (a swell angle of 90o I believe?) this tends to create closeouts as well (not slow waves). How does the character of the wave change as the peel angle gets closer to 90 and 0? Apologies if this was addressed in Chris's articles.

Chris Buykx's picture
Chris Buykx's picture
Chris Buykx commented Wednesday, 21 Sep 2016 at 3:07pm

Good question tdiddy. A peel angle of 90 degree would be best referred to as the 'not peeling angle'! That is a wave breaks with a shoulder with no face, existing for a moment before it would disappear.
I reckon a 90 degree peel angle cannot be sustained as a swell invariably wraps on to a reef due to refraction, changing the angles (see Coastal Creationism #2).

t-diddy's picture
t-diddy's picture
t-diddy commented Thursday, 22 Sep 2016 at 11:09pm

Thanks Chris!

andrew-pitt's picture
andrew-pitt's picture
andrew-pitt commented Wednesday, 21 Sep 2016 at 11:15pm

Great article Craig. Yep I reckon you will be correct. Donkey bay infills with sand. Peel angle becomes too acute. Wave peels too fast. And blokes will walk around saying it's not as good as it used to be.

joe-taylor's picture
joe-taylor's picture
joe-taylor commented Thursday, 22 Sep 2016 at 11:04am

feels westy

Craig's picture
Craig's picture
Craig commented Tuesday, 9 Oct 2018 at 2:31pm

We've got some fresh data from the last two months and it looks like during August it took on an outer bank setup..

The angle or coastline hasn't changed much since 2016, though has considerably since 2005.

pinky_bits's picture
pinky_bits's picture
pinky_bits commented Monday, 23 Mar 2020 at 10:45pm

Hi Craig, I just saw this post, so a pretty random question this late.
I was there for a swell in late August 2018 and that outerbank scenario wasn't good. It was like a fat, breaking out to sea Chicama-esque wave down the bottom half of the spit.
There was only 1 swell between that one in August and the real swells that all came in June, but it was decimated by NE winds. Super strong NE winds also blew for a reasonable amount of time (there's satellite imagery out there of sand being blown 50km out to sea) in July.
Could those winds (and as a result, potential wind swell going out to sea) of caused the bottom half of the bank to be 'ripped' away and form the outerbank?

I focus's picture
I focus's picture
I focus commented Tuesday, 9 Oct 2018 at 2:53pm

Hey Craig, thanks for the article.

"Due to their location between two tectonic plates, the Mentawais are slowly sinking and the reefs are getting deeper by a few centimetres each year."

On a different note isn't the fall in the Mentawai islands an indication of possible measure of the size of the impending tsunami to come?

Which will end up being a major rise afterwards?

Craig's picture
Craig's picture
Craig commented Tuesday, 9 Oct 2018 at 2:57pm

Yeah for sure, we wrote an article about this back in 2012..

The Mentawai Islands: The rise and fall of a surfing wonderland

I focus's picture
I focus's picture
I focus commented Tuesday, 9 Oct 2018 at 4:45pm

Excellent article Craig

Craig's picture
Craig's picture
Craig commented Tuesday, 9 Oct 2018 at 4:48pm

Cheers, would love to get the data from those sensors.