I’ve been getting a lot of questions lately about the impacts that the proposed offshore wind farm will have on our surf and beaches. There’s a lot of concerns about the issue floating around out there (pun intended!) and while it’s important to ask these questions, the good news is that the wind farms will have absolutely no impact on our surf, or on our beaches. All thanks to our wave climate and fundamental wave behaviour.

‘Wave climate’ describes the characteristics of waves for a region. Ours is dominated by swell waves that are formed by wind hundreds and thousands of kilometres away.

‘Swell’ is defined as waves with wave periods – the time it takes successive wave crests to pass the same point – of between 8 and 20 seconds and our swell comes from the south-east, east and north-east directions. Swell waves can propagate thousands of kilometres without losing their energy, until they hit shallow water and the coast. Swell is what gives us good surf.

If the turbines are floating structures, they’ll either go up and down with the swell, or the swell waves will simply wrap around and quickly reform thanks to the process of wave diffraction.

It wouldn’t matter if the turbines were only 1km offshore, there would still be no impact on the swell reaching our beaches.

We also get wind waves, which are locally generated waves caused by strong wind and these have periods of between 3 to 8 seconds. Most of our wind waves are associated with the strong summer north-easters and storms – usually not the best surfing conditions. There is some research that shows that in wave climates (such as the English Channel and North Sea) dominated by locally generated wind waves, there can be a reduction in the height of downwind wind wave formation, but it’s minimal. But that’s not our wave climate and those are not waves that you would normally surf.

Our beaches are dynamic features that constantly adjust with changing wave conditions. If the turbines aren’t going to affect the waves, they’re not going to affect the beaches.

There’s also a concept called ‘depth of closure’ which is the furthest offshore distance that the seabed is altered by wave action. At most, even during the most severe east coast cyclones, ours is probably about a kilometre offshore, which is nowhere near where the closest wind turbines will be.

So at least we don’t have to worry about what the wind farms (if they happen) will do to our surf and beaches! What we should be worrying about is what climate change will do to them with rising sea levels and potentially more damaging storms.

Then we’ll see major impacts and the news won’t be so good.

About the writer

Rob Brander – aka ‘Dr Rip’ – is a coastal geomorphologist and professor at the University of New South Wales in Sydney. A resident of Coalcliff, he’s been studying beaches for more than 30 years, starting in Canada where water temperatures convinced him to come to Australia. He is an international expert on rip currents and beach safety and runs The Science of the Surf, an award-winning community beach safety education program for all ages.

A new edition of Dr Rip’s Essential Beach Book is out now. Visit www.unsw.press/DrRip or Collins Booksellers Thirroul