July 2010: The Perils of Rock Fishing

Sorry, sorry, sorry....I don't update this often enough and keep saying I will, but don't! I think it's because I'm putting up more material on the Science of the Surf Facebook page. I actually never thought I'd be a convert to Facebook, but it's a great way to communicate information, including beach science. Please check it out and you'll find some good stuff on my page.

It's winter here and with winter often comes long, clean swell waves generated from distant storms. It's great for surfing, but too often extremely perilous for rock fishers. Back in May, there was a group drowning of 5 people just south of Newcastle, NSW  and just a week later, a solo fisherman was swept off the rocks at North Bondi, and drowned. Already 22 people have drowned this year rock fishing, which is way above the Australian average. So what's happening? Why is rock fishing so dangerous? 

Coastal rocks, headlands and rock platforms are wet, slippery, remote places exposed to the full brunt of wave energy so it’s easy to understand how people can get into trouble. Unfortunately the hazard often gets distorted by sensational and incorrect reports of ‘freak waves’ and ‘tsunamis’ washing people off of the rocks.  The reality is that a person can get washed off the rocks into the water by wave splash or runup under any conditions.  Obviously, it’s more dangerous during big, rough seas, but the most treacherous conditions seem to be clean swell days when waves are very ‘groupy’. In other words, every now and then a big set of 5-8 waves comes seemingly out of nowhere creating all sorts of sudden ‘freak’ conditions.  The problem is that the lulls between sets can often be long and deceptively calm giving fishers a false sense of security when looking for a place to set up.

The real problem is that once in the water, people often cannot get back onto the relative safety of the rocks because they either can’t swim or there is simply too much wave reflection going on.  When waves hit rocks, a lot of their energy is reflected back offshore and interacts with the next lot of incoming waves creating a big turbulent, sloshing mess. This process is called wave clapotis and occurs whether waves are big or small and makes it extremely hard to swim, even for good swimmers. Rocks are also hard and impact injuries are common. Put simply, rocks at the ocean boundary are not places where people are meant to be.

All that knowledge alone won’t help save drowning. People like rock fishing and people often do foolish things on rocks. Although a commendable new education campaign called ‘Don’t Put Your Life on the Line’ can be found on www.safefishing.com.au, I’m not sure that it will work. It’s not like beach safety education which is relevant for everyone who ever steps foot on a beach and can easily target school children and parents. At the risk of getting into trouble Wil Anderson style (see his Twitter comments at the recent Australian TV Logie awards), the vast majority of rock fishers who drown in Australia are adults from Asian backgrounds, often with poor English skills, and represent a small and difficult demographic group to target.

There’s an easy solution though. What about making the wearing of lifejackets compulsory for rock fishers? After all, it’s the law to wear helmets when riding bicycles and to keep a seatbelt on when driving. Seems like a no brainer to me. Staying afloat means staying alive.

March 2010: Bondi Mass Rescue and the Myth of the Collapsing Sand Bar

Everytime I give one of my Science of the Surf community talks I always get asked the same question “Do sand bars collapse?” and I always give the same answer “No, sand bars do not collapse unless you blow them up with explosives”.  Sand bars are big piles of sand that are pretty solid and heavy.  Sure, they shift around from time to time, but this takes days, weeks and even months.  They never, ever, ever implode on themselves. It just doesn’t happen. But you still hear stories of collapsing sand bars getting people into all sorts of strife. So where did this myth come from?  Well, if it’s wacky and related to the beach, it must come from….Bondi.

Sunday 6 February 1938 at Bondi Beach was a beautiful summer day and many of the 30 000 people at the beach were splashing around in the water standing safely on the shallow sand bars. According to eyewitness reports, everything was fine until three large waves approached the shore and broke. Soon after that, a bunch of swimmers suddenly found themselves in deep water being dragged into a deep channel and out to sea.  Approximately 60 surf lifesavers conducted a mass rescue during the ensuing hysteria and panic. In the next 30 minutes, 250 bathers required assistance, of which 35 were rescued unconscious and revived, while tragically five drowned.

Today this mass rescue is still often reported as being caused by a collapsing sand bar, which is unfortunate because that’s not what happened at all.  The report of three large waves and a deep channel tells an interesting story though. The deep channel was probably a rip channel and the larger waves were probably a wave set coming in. Waves in the ocean tend to travel in groups of 3 to 10 bigger waves with lulls in between. Surfers call them sets.  When the waves in the set at Bondi that day broke, the water level would have risen and swimmers standing on the sandbars near the rip would have lost their footing and floated or been carried into the rip by the water draining sideways off the sandbars. 

Then the rip would have pulsed. All rips have a nasty habit of suddenly doubling their speed for about 30 seconds before going back to normal. It usually happens after a wave set has broken.  All that extra water coming in has to get back out and it basically “pumps” the rip.   So all these people who were washed into the rip channel would then have been taken way offshore when the rip pulsed.

The stories of collapsing sand bars are not uncommon, but it’s almost guaranteed that in each case it was a rip pulse. However, although not proven, there is some evidence to suggest that the waves that came in at Bondi that day were not part of a wave set, but those of a small tsunami! But that’s a whole different story…

February 2010: How you can save lives at the beach

Sorry for not getting anything up lately. I’m going to put more stuff up this year, but then again, Facebook seems easier to get things up quickly and more often, so become a Fan of the Science of the Surf!

This summer has been particularly depressing for rip drownings in Australia. Based on overwhelming positive feedback I’ve had about the rip education video on this website, I really believe that if everyone who went to the beach in Australia watched it, lives would be saved.

So lets do an experiment. Let’s make it viral.

Send the link to the video (http://tv.unsw.edu.au/video/don-t-get-sucked-in-by-the-rip- or www.scienceofthesurf.com ) to every single person on your email address book and every single friend on your Facebook page and tell them something along the lines:

If you go to the beach, watch this video, it may save you or your child’s life. It’s worth 4 minutes of your time.

People should NOT be drowning in rips.

To that extent, I wrote an opinion piece to the Sydney Morning Herald and I think they are going to put it in, but if not, here’s the gist of it:

A Blueprint for Reducing Rip Drownings

Despite the terrible drownings at our beaches and the headlines of a ‘horror’ summer for swimmers, the truth is that nothing is unusual about this summer. Our beaches are no more dangerous or safe than they have ever been. Each year anywhere from 80-90 people will drown along our coast and this value has not changed in decades. It seems worse this year because last summer experienced unusually calm wave conditions and rip current activity, the main factors related to beach drownings and rescues. There have also been several particularly emotional circumstances surrounding the recent rip drownings, but every drowning is tragic, regardless of who is involved. The real problem is that there seems to be no improvement in reducing the number of these tragedies.

A controversy has erupted this summer over a national rip current education campaign launched by Surf Life Saving Australia focussing on the key slogan ‘to escape a rip, swim parallel to the beach’. SLSA chose this message because all surf drownings occur on unpatrolled beaches or after patrol hours. Swimming out of a rip on your own is often the only option available when there is no help available.

Critics of the campaign, including professional lifeguards and surf safety educators, argue that not all people caught in rips are good swimmers, not all rips flow straight out to sea, and the best option is to stay afloat, conserve energy, signal for help and don’t panic. SLSA also acknowledges this on the campaign website. The only problem with the ‘stay afloat’ advice is that all rips have a nasty habit of suddenly shooting out well past the breakers now and then. If there’s no one around, what do you do then?

The reality is that neither approach is foolproof. ‘Don’t Panic’ comes close, but it’s easier said than done. The only perfect and obvious solution when it comes to rips is to not get in one in the first place. The best way to do this is to swim between the red and yellow flags on patrolled beaches. We all know we should swim between the flags, but too many of us chose not too. It’s unrealistic to think that this situation will ever change. It is also logistically impossible to have lifeguards and lifesavers on every single surf beach. Clearly the answer must lie in improved education and unfortunately, one line slogans such as ‘swim between the flags’ are not educational.

A recent study by the University of New South Wales found that 60% of Australian beachgoers could not identify a rip in a picture that showed an obvious example of one. A newspoll study by SLSA found that over 90% of respondents didn’t know what a rip current was. The only way to improve these woeful figures is to start educating people on what rip currents are, why they are dangerous and what they look like. The average beachgoer doesn’t have to be rip expert, but the more they understand and are aware of rips, the more motivation they will have for swimming between the flags, or not swimming in inappropriate locations and conditions.

Rip education is challenging, but not difficult. If we want to get serious about it, the following approach has to be adopted:

Step 1: Make surf and rip safety education compulsory for primary schools. Rips are very visual features and viewing a 15 minute DVD each year will have an enormous impact. Not only can kids pass on this knowledge to their parents, they become the parents of the future. If we want surf safety to become ingrained in our culture, it has to start in the schools.

Step 2: Start showing visual footage of rip currents on public service announcements on television. UNSW TV created a rip education video “Don’t Get Sucked in by the Rip” that has received both NSW and National Australian Safer Communities Awards. The feedback has been phenomenal, but very few know about it. Everyone in Australia who goes to the beach should watch this video. It needs to be promoted.

Step 3: Get some useful beach and surf safety information on the planes and in airports. This should be a federal requirement and can be informative rather than frightening.

Step 4: Some information about rips at beaches would be nice. Every public beach in the US has information signs about rips including diagrams. You can’t miss them. Signage is not always effective, but anything is better than nothing. When it comes to rips, Australia has nothing.

The Australian Water Safety Council has set a target of reducing drowning deaths by half by 2020. Dr Richard Franklin is the National Manager Research and Health Promotion for the Royal Life Saving Society and sounded like a defeated man in Monday’s Herald saying “I don’t think we will achieve it”. When it comes to rip current and surf drownings, I think he’s wrong. Follow the steps above and we will see improvements, but it won’t happen overnight and it won’t happen without increased funding from both the State and Federal governments.

November 2009 Rips 103 - The Rip Current Survival Guide.

I’ve already described in previous months how rip currents form and what the different types are. That’s all great, but is that information of any value to the average person who gets stuck in a rip? Errrr…probably not. So this month I’m going to stick to the basics and describe the best ways to survive getting caught in a rip current.

Part 1 – What Should You Do If You Get Caught in a Rip Current?

Rule #1: Don’t get in one in the first place.
This sounds simple and it is. If you don’t get in a rip, you aren’t going to drown in one are you? So how do you avoid rips? If you are aware of rips, but really don’t understand them and haven’t got a clue how to spot them, your best bet is to talk to a lifeguard. When you get to the beach, make sure you swim near a lifeguard patrolled area and ask them where the safest place to swim is. Also ask them to point out any rip currents. After a bit of practice and experience, your ability to spot rips will improve! However, in Australia, the best way to avoid rips is to ALWAYS SWIM BETWEEN THE RED AND YELLOW FLAGS. The flags are set up away from rip currents, so swimming between the flags takes all the guesswork and confusion out of having to spot rips and pick the safest place to swim. If there are no lifeguards or flags around, the golden rule is: if in doubt, don’t go out.

Mistake #1: Getting caught in a rip current
Ok, lets assume you ignore Rule #1 and just swim anywhere. Lets face it, half the time it’s easier to swim closest to where you parked your car or entered the beach and geez, it’s a hot day and the flags are so far away and crowded and heck, the water looks nice and safe here. So in you go. Most of the time you’ll be absolutely fine, but since there’s about 18000 rips on Australian beaches on any given day, there’s also a good chance you’ll end up straight in a rip. Ooops. 

So what does it feel like to be caught in a rip current? Actually it feels quite pleasant. Because you are going with the flow you feel absolutely nothing at all. You certainly won’t be pulled under by the dreaded “undertow” because no such thing exists. Nope, most people only realise that something is wrong when they suddenly pay attention to where they are and notice the distance from the shoreline increasing rapidly. This generally leads to:

Mistake #2: Swimming against the rip current
Rips flow pretty fast. Faster in fact than the average person can swim. Unfortunately the main reaction when somebody realizes they are drifting offshore is to swim back to the beach….against the rip. An average swimmer hasn’t got a chance. You’ll just get tired, go backwards, swim harder, get more tired and then give up which leads to panic. Panicking is bad news. It affects your breathing and you can drown incredibly quickly once you lose the plot, so this leads directly to Rule #2:

Rule #2: Don’t Panic
Of course this is easier said than done when the safe confines of the beach are disappearing in front of your eyes and you feel utterly helpless to do anything about it. And hey….there could be sharks out there!!!! Relax. Lets think about REASONS WHY YOU SHOULDN’T PANIC:

1. Sorry to destroy your childhood fears, but you aren’t going to get bitten by a shark;
2. There is no such thing as undertow so you won’t get pulled under;
3. Rips will not take you across the ocean;
4. Most of the time rips take you in nice big circles back to the beach;
5. The human body has a natural tendency to float.

What this all means is that the main thing you should do when you realise you are caught in a rip is to :

Rule #3: Stay Afloat and Signal for Help
That’s it. That’s all you need to do to survive. How do you stay afloat? Well, you could tread water, but that can get tiring after a while. You’d be better off conserving your energy by lying on your back and gently moving your arms and legs. Even non-swimmers can do this. How do you signal for help? If there’s lifeguards or lifesavers around, just raise one arm straight in the air…that is the signal they are looking for. Or you could yell for help or raise the attention of nearby surfers.

The great thing about staying afloat is that it’s easy and conserves energy. Also, most rips really do travel in these great big circles about 80% of the time. It’s all part of a natural process called surf zone circulation. So if you do nothing at all but stay afloat, chances are you’ll end up back in nice shallow water in about 5 to 10 minutes.

Part 2 - How to Get Out of a Rip Yourself

People often ask me what you should do if you get caught in a rip in the middle of nowhere and there’s no lifeguard around. I usually tell them they shouldn’t have been swimming in the first place! In reality you really only have two options. You can chose to stay afloat and hope that the rip circulation eventually brings you back to the beach. Unfortunately that doesn’t happen all the time. Rips have a nasty tendency to pulse now and then and rip pulses can carry swimmers well outside the region of breaking waves. So in that case you need to be proactive and get out of the rip yourself. 

Many swimmers also chose to swim out of rips themselves on patrolled beaches. Usually this is to avoid getting rescued or they are experienced enough to realise that they are stuck in a rip and are strong enough swimmers to get out of one. The key word here is experienced. If you do not have a good understanding of rips and are not a good swimmer, your best chances for survival are to stay afloat and signal for help. However, if you do want to get out of a rip, here is how you do it:

Rule #4: Swim towards the breaking waves and white water
If you are a strong swimmer and are stuck in a rip, your best bet is to swim towards white water at the sides of the rip. Most rips are fairly narrow (usually 10-50 m wide) and are bound by shallower areas on either side where waves are breaking. Swimming towards white water is a good idea because it means you are swimming towards shallow areas outside the rip where you can possibly stand up. White water also brings you back to the beach which is what you want to do. So swimming towards white water on the sides of the rip is a no-brainer. However, it’s often hard to tell inexperienced swimmers that this is the smart thing to do because to them the white water looks dangerous!

Will it work?
Getting out of a rip always sounds easy in theory and most experienced surf swimmers can swim out of a rip. However, what about someone who isn’t a good swimmer? Consider the following scenario: an average swimmer suddenly realizes they are stuck in a rip and are rapidly moving offshore. While they look around trying to orient themselves to the beach, the sides of the rip and areas of white water, the rip continues to take them offshore. They finally start to try and swim out of the rip, but while they are doing this the rip is still moving them offshore. Before they know it the rip has spit them out the back before they even had a chance to get out of it! All they’ve really accomplished is to tire themselves out and get a bit scared. They would have been much better off staying afloat and signaling for help. What else can you do? Traditionally, the old advice has been to “swim parallel to the beach” to get out of a rip. That’s great if you are a good swimmer and the rip is flowing straight offshore. However, many rips flow at an angle to the beach. This is a problem because if you swim parallel to the beach, you might end up swimming in the direction that is actually AGAINST the flow of the rip. This is not good!

However, swimming parallel does work once the rip has brought you beyond the breaking waves. Then you can try and swim along the beach and then bodysurf back to shore with the breaking waves over the sand bars.

Ultimately though, you’re better off going with the flow, staying afloat and signaling for help.

October 2009, How do waves form?

You can’t avoid waves when you go to the beach. Unless of course it’s flat calm, but on most open ocean beaches, that’s pretty rare. There’s always waves coming from somewhere and it doesn’t matter whether it’s a surfer tucked into a barrel or someone out for a leisurely coastal stroll, we all appreciate them in some way. But have you ever wondered where waves come from and why they seem to change every day…and even during the day?

Waves are formed by wind. It’s as simple as that. When the wind blows over the ocean, the wind literally grabs onto little bumps on the water surface and energy is transferred from the wind to the water. As the bumps get bigger, the transfer increases, and the bumps turn into waves that keep growing…and moving.

Waves basically move in the same direction as the wind that formed them. What’s neat is that there are actually two totally different types of motion associated with a wave. One is the movement of energy through the wave which is what gives the wave its shape. The second is the movement of the water. Every water particle is caught up in these large circular motions underneath the wave. Think of the to-and fro motion you experience lying in the water as waves pass…the wave moves past you, but you basically stay in place. It’s the same as the Mexican Wave at the Sydney Cricket Ground before it was banned for being socially unacceptable and breeding criminal behaviour (for non-aussies…yes, the wave was actually banned!).

All waves can be described by 3 characteristics: wave height, period, and wavelength Wave height is simply the vertical distance from the crest of the wave to the trough. If you see someone surfing a wave that is about double their height and someone only calls it “4 foot” they have obviously been corrupted by the Hawaiian habit of calling wave height from the back of the
wave.   Wave period is the time it takes between two wave crests to pass the
same point and wavelength is the physical distance between wave crests.  Why do all 3 change? It comes back to the wind.  Basically, the stronger the wind blows, the longer it blows for, and the larger the distance over water that it can blow (a sailing term called fetch), the higher and longer the waves will be.

There are also different types of waves.  Think of what happens to the nice glassy morning conditions on hot summer days. The onshore seabreeze kicks in and the surf turns to mush. We call these wind waves because they are generated locally and are short, choppy and messy with periods of 2 to 7 seconds. Wind waves are pretty common in fetch restricted bodies of water such as Sydney Harbour, protected bays, and lakes. However, in the middle of the ocean, wind waves have room to grow and the further they travel, the more they sort themselves out into nice, clean lines of swell waves which have periods of 8 to 20 seconds. The longer the swell, the further the waves have traveled.
Generally we always experience swell coming from somewhere, usually the southeast, but if it’s a windy day, we’ll have wind waves superimposed on top.

September 2009 Fear, Loathing and a Lot of Geology on the Sydney Eastern Suburbs Coastal Walk

For those of you who haven’t visited Sydney (and you really should), the Eastern Suburbs beaches and coastline are connected by a number of stunning scenic coastal walks that are enjoyed by walkers, joggers, tourists, and dogs alike. In particular, the Bondi to Bronte walk has to be one of the most beautiful urban coastal walks in the world. Beautiful and hostile.  It’s pretty rare to get a friendly smile and “hello” or “good morning” from anyone. I once made the mistake of trying to wish people “Merry Christmas” on Christmas Day and was only greeted by shock, befuddlement and fear. I’d like to think it’s because everyone is blissed out by the best urban coastal scenery on the planet. Unfortunately, I think it’s got more to do with people desperately trying to squeeze in some precious coastal time and exercise amidst their busy work schedule in order to justify paying exorbitant mortgages and rents for wanting to have a coastal lifestyle in the first place.  This makes them fundamentally bitter. But I digress, because what I really wanted to talk about was the geology of the coast.

What does walking from Diamond Head to Watsons Bay, Bondi to Coogee and Coogee to Maroubra all have in common? They all involve walking across a massive deposit of rock called the Hawkesbury Sandstone whose origins can be traced back 300 million years ago when Australia was connected to Antarctica as part of a supercontinent called Gondwanaland.  The Eastern Suburbs landscape was already being shaped back then with lots of thrusting, bending and folding activity going on eventually creating a bowl-shaped depression that we now call the Sydney basin. Slowly, the basin started to fill up with layers of sediments carried by ancient river systems. Some of the material was organic and turned into coal layers, which explains why coal is found at the surface to the north, south and west of Sydney, but only at depths of 900 metres in Sydney itself. However, the dominant layer was a 300 m thick layer of sand that turned into what we now call the Hawkesbury sandstone, which is what we see today.

As dinosaurs ran amok, Australia broke away and started to move slowly northwards thanks to the conveyor belt-like movement of the earths crustal plates. Around 120 million years ago, New Zealand began to split from Australia creating the Tasman Sea and leaving our eastern coast with a steep and narrow continental shelf.  Now exposed to waves and salt spray, the Hawkesbury sandstone cliffs slowly eroded back creating a coastline full of nooks and crannies and leaving behind a wide, flat rock platform that got covered with sand delivered to the coast by more ancient rivers.

The last two million years of the earths history has been dominated by a series of ice ages which resulted in the sea-level going up and down like a yo-yo. In last month’s Beast, I described the last sea level rise which ended 6500 years ago and formed our beaches. Our beaches may have only been around that long, but much of the sand on them is millions of years old and originated from rocks in the vicinity of outback New South Wales.  This might not make for a hot topic of conversation amongst the grumpy power walkers, but it’s a cool story.

August 2009 Beaches: Stuck between a rock and a hard place
(apologies to international readers, apologies for the emphasis on the Sydney coastline)

Last month I was going to talk about where the sand on our beaches has come from, but got distracted by the recent beach erosion. Now that the beaches are slowly recovering, it’s obvious that in the short term the sand comes from the ocean and is brought onshore by wave action, but how did it get there in the first place? Next time you are standing on one of the local beaches, look down at the sand and then up at the sandstone headlands. Same colour right? So the obvious answer is that the sand must be coming from the erosion of the rocks? Not so fast. Those sandstone rocks are over 100 million years old and are more resistant to erosion than you may think. There is actually only a tiny amount of sand being added to our beaches from the rocks at the present time. The beaches are youngsters in comparison and the sand that’s sitting on Bondi or Maroubra is actually the same sand that’s been sitting there for the last 6500 years or so. So if it’s not coming from the rocks, how did it get there?

Cast your imagination back 18,000 years. The earth was in the grip of it’s last ice age and so much of the oceans water volume was wrapped up in ice that sea levels were about 120 metres lower than they are today. Bondi would have been a vegetated lowland valley and the coastline was about 25 kilometres offshore of where it is now and was inhabited by Aboriginals rather than hostile joggers and power walkers. As the earth started to heat up, the ice melted, and sea level started to rise. Fast. More rapidly, in fact, than most of the predictions of sea level rise for the next 100 years. Did the beaches disappear? Nope. Instead, a massive landward migration of the shoreline, beach and dune systems took place and only stopped about 6500 years ago when sea level stabilised and our present day coastline was formed.

Our local beaches are where they are because the beaches and sand literally got pushed into old river valleys where they got stuck between the ocean and the rocks. It’s important to remember that geology is the main control on what our coastline looks like. For example, Wedding Cake Island is an old remnant ridge line that would have been bounded by rivers on both sides. If it wasn’t there, Coogee would receive bigger waves and would have sand bars and rips and decent surf. Sydney Harbour is the perfect harbour because it once was a deeper valley that was essentially drowned during the last major sea level rise.

So when it comes to our beaches, what you see is what you get. Not much sand is being added at the moment so the next time you empty out your towel and bathers when you get home and the sand pours out, maybe you should bring it back!

July 2009  Beaches: Here today, gone tomorrow?

Last month I described what the sand on our beaches is made of. This month, a good question would be to ask "Where's it all gone?". I walked along Coogee Beach in Sydney's Eastern suburbs the last week of May and saw something I'd never seen before: the remains of concrete pilings sticking out of the sand in the intertidal zone. Presumably these were the pilings for the old pier that used to extend out 180 metres into the sea from 1928 to 1934. The pilings were sticking so far out that kids were jumping off them. This got me thinking. First, there was a lawsuit just waiting to happen. Second, was the original demolition job dodgy or were the pilings buried so far under the sand at the time that nobody ever thought they'd never be exposed? Probably a bit of both, but beaches are more dynamic than you might think and the volume of sand can change quite rapidly.

Beaches on the east coast of Australia have lost a lot of sand since the summer. One simple rule to remember is that big waves take sand offshore and small waves bring it back. I surveyed Tamarama Beach in Sydney every month from August 2000 to December 2005 and during that time, the position of the shoreline fluctuated an amazing 120 metres. At it’s worst just before the Olympics, the shoreline was about 10 metres behind the storm drain. At it’s best, during the summer of 06/07, you could almost walk around to Bronte at low tide. In fact, there was more sand on our beaches that summer than in the previous 15 years and even the beach at Mackenzies appeared again. Then we got hit by the massive East Coast Cyclone storm in early June 2007. Not only did the 10 m + waves wash the Pasha Bulker freighter onto Nobby’s Beach in Newcastle, all of our beaches got hammered and lost huge amounts of sand. They have yet to fully recover from this storm and in April and May this year, a number of big wave events occurred so frequently that the beach erosion was exacerbated.

Sand volumes on our beaches are probably at a ten year low right now.  Is this something to worry about? Not really. It’s been a lot worse. 1974 was a terrible year for storms and many beaches, including Tamarama and Bronte, were virtually stripped bare of sand exposing the rock platform underneath. Yet they recovered.  The sand doesn’t disappear, it sits just a little ways offshore and provides some good banks for surfers as it starts its journey back to the beach. There are also climatic forces at work. We tend to get smaller waves and phases of beach recovery during El Nina cycles and more storms and erosion during La Nina periods. Summers also tend to have smaller waves leading to healthier beaches.  Forget about the grim tidings of climate change for the moment. Beach change and erosion are completely natural so don’t panic. Our beaches won’t disappear anytime soon.

May 2009 Rip currents 102: What are the different types of rips?

We recently did a survey at UNSW as part of a research project that showed that about 60% of beachgoing Australians couldn’t spot a rip when shown a pretty obvious picture of one. I would imagine this would be closer to 90% for international tourists. One of the difficulties in spotting rips is that there are actually different types of rips and the different types not only look different, they can behave differently and can differ depending on what type of beach or coastline you are on in the first place!

Further complicating the matter is that different people, different brochures and different websites will give you different names for different rips. Then, just to be different, some information out there is different to the point of being incorrect. It can get very confusing. The following is an attempt to make some sort of sense of the most common types of rips you may come across when swimming at the beach. It might help to look at the Fact Sheet on rips found on this website which has pictures of some of these different types and to watch the “Don’t Get Sucked in by the Rip” YouTube video which also explains the differences between them.

Fixed Rips
As the name implies, these rips are fixed in place with their deep channels snuggled in between shallow sand bars. They may stay in the same place for days, weeks and even months depending on the wave conditions and are often called low-energy rips because they tend to occur when waves are relatively small or haven’t changed much for a while. Don’t be fooled though, because they can flow extremely fast and lifeguards will tell you that most rescues happen in these rips. They are the easiest to spot because they look like dark gaps between breaking waves and they are also the most common type of rip. Another way to spot them is to look for large embayments along the shoreline because fixed rips will erode the beach back over time.

Flash Rips
Flash rips are also known as high-energy or traveling rips because they occur when waves are big and the rips have a habit of suddenly forming in one location for a minute or so, only to disappear and suddenly reappear somewhere else along the beach. This is partially due to the old rip channels not being big enough to transport all the extra water brought in by the bigger waves, but flash rips can also pop up when a large set of waves breaks, or when several big waves break close together. Flash rips are extremely dangerous as it is difficult to predict when and where they will form and they they also flow very fast. They also look different than fixed rips and can appear as a turbulent, chopped, up and streaky water surface, often carrying suspended sand and can sometimes appear lighter in colour than the surrounding water.

Permanent Rips
Permanent rips exist in the same location virtually all the time and should not be confused with fixed rips, which only occupy the same location for shorter periods of time. They are often called headland rips because many beaches are often bounded by headlands at both ends and depending on the wave direction, water will be transported along the beach where it eventually reaches a headland, and has nowhere to go but offshore. Rock reefs and structures such as groynes, jetties and piers can also have the same effect. Because these rips also sit in a deep channel, they also look like darker gaps through the surf and can also flow quite quickly. Since they are so permanent in location, they are often given names by locals such as the famous “Backpackers Express” at the southern headland at Bondi Beach in Sydney, which is famous for taking a lot of backpacker tourists for a free ride.

April 2009 : Rip currents 101: Why do we get rips?

It suddenly occurred to me that while this website is focussed on rips, there isn't a lot of information that actually explains what rips are and how they behave! There's a little bit on my rip fact sheet on this site and I have a rip poster that I give out to schools (that I will eventually load up here so everyone can download it), but for now, here's a bit of a refresher on what rips are and I've taken the liberty of using an article I gave to the guys at www.frothers.com.au last year:

One of the first things I did when I arrived in Australia from Canada was to head for Bronte for a swim and my Aussie friend (actually Dr Ian Turner from UNSW who is now a colleague as well) politely pointed out the rip current that I needed to avoid. The only problem was, I couldn’t see it. Even when he kept pointing it out, I just couldn’t see it. I had an excuse…I was from Canada, but what really disturbed me was that during my undergraduate degree studying coastal geomorphology (a field that no-one has heard of, but every surfer would love) we actually studied rip currents. How was it possible that I could study something out of a textbook and not be able to spot it? This started a lifelong interest in rips and now it’s hard for me to imagine what it’s like not being able to spot one, but I would bet that 99% of international tourists don’t have a clue and we’ve just done a study that shows that 60% of Australians can’t spot one either. So it’s no surprise that most of the 80-90 surf drownings and 90% of the 20,000 or so rescues every year are rip related. Just watch any episode of Bondi Rescue for a demonstration. However, to surfers, rips are a good friend and represent a free ride out the back.

But how many of us actually know how they work and why they’re there?

The simple definition is that rips are “rivers of the sea” and transport water built up at the shoreline by breaking waves, back offshore through narrow, constricted channels. For this to happen though, you need waves, and more importantly a lot of wave breaking. No wave breaking, no rips and the best thing that promotes wave breaking are sand bars. That means that most beaches with waves and sand bars will have rips from time to time.

When waves break, the whitewater is physically transported towards the beach. Obviously this can’t happen indefinitely as the water needs to get back offshore to maintain a water balance. At the same time, when waves break the elevation of the water surface rises, a phenomenon known as wave set-up. Wave set up is about 10% of the wave height so a 1 m breaking wave will cause a rise in water level of 10 cm, which is virtually impossible to observe with the naked eye. If you’ve got a shallow bar with a deep section (i.e. a gutter/trough/channel) next to it, the waves will break over the bar, but not so much in the deeper water. That means that the water level is higher across the bar than it is in the deeper section, so water will literally flow downhill towards the deep section and you’ve got the beginning of a rip. As waves also break close to shore, the water level there is always a little higher than further offshore and this also tends to cause water to flow offshore. Throw in a deep channel between some banks and all this water flow gets squeezed and you’ve got a classic rip.

The link to wave breaking also explains why rips flow fastest around low tide and can sometimes stop at high tide. At low tide, water depths are shallower and there’s more wave breaking and therefore more wave set-up that drives the rips. Sometimes at high tide, the water depths over the bars is so great, that no waves break so there’s no wave set-up and no rips. However, this is no excuse to call rips “rip tides” which is just WRONG. Rips are NOT RIP TIDES!!!! Tides happen slowly over 6-12 hours. Rips flow almost continuously.

So that’s it, rips exist because of spatial variations in wave breaking caused by spatial variations in water depth caused by different patterns and locations of sand banks and channels. There’s a lot more to it than that, including different types of rips and different flow behaviour, but that’s best left for another month….

March 2009 - Dead in the Water: Why beach safety is stalled by ignorance

Note: I originally submitted this to the Sydney Morning Herald as an Opinion Piece and it eventually formed the basis for an article by journalist John Huxley called “Dead Calm: Dangerous Rips” which appeared on the front cover of the Saturday December 20, 2008 Sydney Morning Herald.  The picture discussed below is shown in the February 2009 “Rip of the Month” on this website.

I have a picture taken at Hot Water Beach on New Zealand’s Coromandel Peninsula that I use to educate people on how to spot a rip current. It’s a stunning day, the water is seemingly placid, but to the left of some rocks the water surface is rippled and disturbed, a clear sign of a subtle rip. Almost unnoticed in the foreground, a man walks waist deep in the water, sifting the sand with his feet to find the hot springs the beach is famous for.  I took the picture at the time to show that rips can form even when waves are small.  Now I show it to illustrate the importance of understanding surf conditions because 30 minutes later the man in the picture was dead, another drowning victim of the most dangerous and poorly understood hazard on our beaches: rip currents.

Although this tragedy happened in New Zealand, it might as well have been Bondi.  During the summer months someone drowns in a rip on an Australian beach every three to four days.  If someone were killed by a shark at the same rate, the situation would undoubtedly be different. The response would be mass hysteria¹, beach closures, airborne surveillance and funding to address the shark “problem”. Yet none of this happens with rips. We rarely hear about rip drownings and as far as most us are concerned, there is no rip “problem”. The reason for this is that most Australians don’t really know what a rip is and couldn’t spot one to save their life.

Rip currents are strong, narrow, offshore currents that flow like “rivers of the sea” from the shoreline seaward to the extent of breaking waves at speeds faster than the average person can swim.  They are best identified as gaps of dark, calmer water between breaking waves.  Contrary to popular belief rips are not an “undertow” because they don’t pull swimmers under the surface and there is no such thing as an undertow. While most beachgoers are vaguely aware of rips, a recent study by the University of New South Wales and Surf Life Saving Australia has shown that 60% of beachgoers don’t know what they are.  It’s probably safe to assume that this value is over 90% when it comes to overseas tourists.

This represents a frightening lack of knowledge particularly when the vast majority of the 80 surf drownings and more than 20,000 rescues that occur on Australian beaches each year are rip related.  It should therefore be of some concern that the yearly number of surf drownings has not changed over the last 10 years and appears to be increasing. So how safe are you when you go to the beach? It’s a good question.

Australians have an unhealthy degree of complacency when it comes to beach hazards as it’s assumed we’re well looked after. And we are. You only have to watch an episode of Bondi Rescue or Surf Patrol, full of dramatic rescues in rips made by lifeguards and lifesavers to know that our beaches are in good hands. But which beaches? There are over 11,000 mainland beaches in Australia, but only 3% of these are actually patrolled. Even worse, most of these are only patrolled seasonally and the flags only cover a small section of beach so the “well looked after” assumption becomes somewhat tenuous. There’s a lot of beach out there to get in trouble, lifesavers and lifeguards can’t be everywhere, and it only takes a minute to drown.

The last point is crucial. Drownings can occur in a blink of an eye. Calls for more lifesavers and lifesaving equipment may sound like a solution, but not only is this logistically impractical, it arguably won’t have a significant impact. When it comes to rip currents, it must be recognised that prevention is the best medicine and at the core of prevention lies improved knowledge through education. If a swimmer doesn’t get in a rip in the first place, they aren’t going to drown in one.

The “Swim Between the Flags” campaign has worked as the message is ingrained in our psyche, but the flags themselves have no educational value of the hazards swimmers should be trying to avoid. Similarly, the effectiveness of warning signage is extremely limited.  Although a plethora of beach safety education programs exist in Australia they are ad hoc as the delivery is inconsistent in terms of target audience, content and the organizations and individuals who administer them.

Australia has an unacceptably high rate of drownings and rescues related to rip currents that involves significant emotional and economic costs.   A consistent and organized national rip education program is urgently needed and can only be achieved through improved collaboration between existing beach safety practitioners and greater engagement with the coastal scientific community. Just as we all know to look both ways before crossing a street, every Australian should know to look for rips when they go to the beach. Tourists must also be targeted for rip education.

However, none of this will ever be achieved without funding. At present, funding for rip education and research is extremely limited which is incredible given that rips are responsible for more deaths each year than bushfires, floods, cyclones, tsunami, and sharks combined². The reality is that it wouldn’t take much to fix the problem, but until rip and beach safety education and awareness is accepted as the best method to save lives at the beach, another 80 people will continue to drown needlessly in the surf each year and in a country that prides itself on our beaches, that is shameful.

¹Look at the media hysteria surrounding the 3 recent shark attacks on Sydney beaches and the harbour this summer. Awful and tragic yes, but fatal no. On average, there is only 1 shark attack fatality each year in Australia whereas 30-40 people drown in rips. So what’s more dangerous? Why is it that you have to look hard to find a very small paragraph discussing the latest rip drowning.

²Following the fatalities resulting from the tragic Victorian bushfires this year, this statement is no longer true. However, even including the recent fires, in the last 10 years rips are responsible for more deaths than bushfires. And the response to rips has been negligible.

February 2009 - Steamers in Summer: When the Water Gets Cold!
This was originally written for the Frothers Mag

It’s the middle of summer, it’s stinking hot, so you head to the beach for a swim, jump in and the water is….freezing. Yet the week before it was magic, so what’s going on? Quite a lot as it turns out. Between December and April, the surface water temperatures around Sydney are usually between 19°- 23°, which is perfect for swimming. At water depths of 30-50 m the temperatures are significantly colder, but this doesn’t affect swimmers or surfers. Just as it takes a while for water in the pot to boil, it also takes a while for the ocean to heat up. For this reason, the ocean shows a steady increase in temperature from September onwards, finally peaking in March. What these long term trends don’t explain is why the water can suddenly drop several degrees seemingly overnight and in January 2007 dipped down to an icy and record cold 14°. Several swimmers suffered hypothermia, which is hard to believe when it was 30° on the beach. Is this normal? Yes and no.

It’s mostly about the wind. On hot days, the surface of the land heats up faster than the surface of the ocean, air rises over the land and onshore winds rush in from across the ocean to replace it. On most of the east coast of Australia these sea breezes blow onshore from the northeast, usually kicking in around noon and lasting into the evening. While they ruin the surfing conditions for the day, they have little effect on how warm the water is. However, summer is also prone to persistent periods of northeast winds, related to the strengthening of equatorial low pressure systems, and these can last for several days.

You would think that coming from the north, these warm winds would also bring warmer surface water to the beach, but the opposite is true, the water actually drops a few degrees! As my european oceanography professor once explained to me, this phenomenon is caused by “ze Ekman spirrell”. I think he meant spiral. Anything that moves in a constant direction on the planet is affected by the Coriolis force which acts to deflect moving objects to the left in the Southern Hemisphere and to the right in the Northern Hemisphere. This is the reason why water supposedly spins down the toilet in different directions depending on what side of the equator you’re on. This isn’t true of course, since the moving object has to be much larger to be noticeably affected by the Coriolis, but as the persistent northeasters move large amounts of warm surface water towards the shore, this water gets deflected to the left…offshore and away from the beach. It has to be replaced by something and large scale upwelling of deeper, colder water occurs which is then drawn towards the shore. It’s a little bit more complicated than this, but this whole process is termed Ekman transport and is referred to as a spiral because the resulting water movement literally spirals up from the bottom so that at the surface it is moving 90 degrees to the direction of the wind.

The good news is that when the prevailing southeasterly wind and wave conditions kick back in, the warm surface water offshore is also deflected to the left, which in this case is back to the beach. And it’s back into the boardies for most. Upwelling, therefore explains why water temperatures can suddenly drop a few degrees and the same thing happens if we have strong offshore westerlies that last for a few days and push the warm surface water offshore. However, it doesn’t fully explain why we had such freezing water in the summer of 2007! This was caused by a giant eddy the size of Tasmania situated about 100 km offshore of Sydney that was swirling around like a whirlpool with a full rotation of 10 days. At its centre, the eddy caused upwelling of very cold water from depths of almost 1000 m that spun around, eventually hitting the coast. All of a sudden it was like swimming in New Zealand in the winter, never a pleasant experience. You may even remember that the water was noticeably greenish and cloudy, a result of the rich nutrients brought up from the depths. Although these eddies are not uncommon, they are difficult to predict and scientists are not sure how or where they develop, but when in place they can last for several weeks. The good news is that they don’t impact on the quality of the waves. So maybe before you run to the beach in your boardies this summer, check the weather reports for winds over the last week and maybe even look up some satellite ocean temperature maps on the internet. You might need to grab a steamer.

January 2009: What are wave sets?

One of the most important characteristics of waves to surfers is the presence of wave sets. Scientists refer to sets as wave groups, but they are essentially the same thing. Defined simply, a wave set is a group of several large waves that seemingly appears out of nowhere. It’s a bit more complex than that as the length of time between sets is not always constant, neither is the number of waves in each set, or the height of each wave in a set. For surfers, this information is important as it helps in choosing the right wave, where to position yourself, and determines how long you have to wait for the next big wave and how long you’re going to get pounded when caught inside. So why do we get wave sets?

Waves are formed by wind and most swell comes from deep ocean storm events. However, the ocean is pretty big and there can be multiple storms occurring in different locations at different times creating waves of different heights and wavelengths (distance between crests). In other words, there’s a lot of different waves out there moving in different directions. If you get two waves traveling in the same direction, but having different wavelengths, the waves can physically join and add together. If the crests coincide, you get bigger crests. If the troughs coincide you get bigger troughs. This process is called constructive interference, but if the peak and troughs of the two waves overlap, the whole thing gets cancelled out and you’ll get a flat spot. This is called destructive interference. If you start to add more waves in the equation the patterns get more complex. Once the waves get locked in with each other, they travel as a new and coherent wave train. The odds are that the new wave train is going to have some sections of constructive interference (the large waves of the wave set) and some sections of destructive interference (the lulls between sets).

Believe it or not, this is a highly simplified explanation, but it explains why sets are so varied and seemingly random in so many ways…it’s because they were created by the interaction of waves traveling from different sources. The science behind sets involves fairly complex wave physics, but the bottom line is that we still don’t fully understand why the timing and characteristics of sets change every day. Basically, you get what you get on the day! We do know that the further you are away from the storm where the swell was generated, the more likely you’ll get sets. It is also thought that the longer the fetch length for wave formation (i.e. the distance that wind blows over the water), the more waves you are likely to get in a set.