Last month I mentioned the impact that sea level rise might have on our beaches and surf and suggested that the news might not be so good. It’s worth exploring that a little more as the reality is that it’s not all doom and gloom.
Sea level is rising, there’s no doubt about it, and it will continue to rise. The question is by how much and that’s the big unknown. We already know that sea level has risen about 20 centimetres in the last century and, for the most part, our beaches are doing just fine. They are remarkably resilient and adaptable features. But what would happen if sea level rose by a metre in the next 100 years, which is on the higher end of projected sea level rise scenarios?
The good news is that most beaches won’t disappear. They’ll just move. Beaches are dynamic features that are constantly adjusting to shifting wave and tidal action. They start hundreds of metres offshore where sand is first moved by the action of waves and extend inland to where sand is blown by wind, often forming dunes.
On a completely natural beach that has natural dunes and no urban infrastructure, if sea level rose by a metre, the beaches and dunes would simply shift further inland and would look exactly the same – just in a slightly different place. So the majority of our beaches will be just fine.
Unfortunately there are many locations where we have built buildings, car parks and roads too close to the ocean and this is where the story is different. Beaches would have nowhere to go to keep up with rising sea level. There are already numerous erosion ‘hotspots’ throughout New South Wales where properties and infrastructure are at risk and the Illawarra coast is not immune. If sea level rose by a metre, even more of these hotspots would occur and we would need to resort to coastal engineering responses, such as seawalls, to stabilise our shorelines, which will do the job, but won’t do our beaches any favours.
What about the quality of surf? On most beaches that have been able to migrate naturally with sea level rise, the behaviour of sand bars and the shape of the beach will be the same, so beach breaks will still be as plentiful as ever. The story is a little different for reef breaks, which rely on a fixed substrate and are ‘tuned’ to work best at certain water depths and wave conditions.
Yep, we’ll probably lose some of our favourite breaks, or they won’t provide as good a wave, but others will be created. The news isn’t always bad – there will always be good surf no matter what sea level is doing!
A new edition of Dr Rip’s Essential Beach Book is out now. Visit www.unsw.press/DrRip or Collins Booksellers Thirroul
