Bulldozers And Beaches
Maybe it’s just me, but I reckon there’s something a little unsettling about seeing bulldozers on beaches. There they are though, pushing the sand around and turning the beach into a construction zone, usually about once or twice a year.
What exactly are they doing? Good question. Most of the time, they’re simply cleaning or grading the beach. After storms, or strong onshore winds, the sand gets blown to the back of the beach and the esplanade where it piles up. Some of it blows onto the pedestrian walkway where it becomes a bit of a nuisance and a slip hazard. Flattening out the beach resolves this issue. It also makes it possible to erect beach volleyball courts and tents for functions and events.
Fair enough, but what is the logic behind where they dump the sand and can it damage the beach?
I used to go up to the bulldozer drivers during their ‘smoko’ breaks and ask them what they were doing. Aside from being asked to do something anatomically impossible to myself, I was often told that they were under orders to ‘fill in the rip’. The idea was that rips are dangerous so if you push the sand from the back of the beach into the rip channel it will fill it up, and presto, no more rip. Sounds great, except that it doesn’t work. Rips flow pretty fast so if you dump sand into them it will be swiftly swept offshore, thus leaving the beach with less sand!
The ‘filling in the rip’ philosophy is still doing the rounds but mostly these days the sand gets bulldozed towards the high tide mark and just dumped there. However, it’s impossible to spread it around evenly so there are often mounds and dips along the beach.
As it turns out, this has some important consequences. Recently, I was talking to Bruce ‘Hoppo’ Hopkins, Waverley Council’s head lifeguard, who has a theory that not long after they bulldoze the beach a bunch of incredibly strong rips tend to develop. He reckoned the waves would come up and find the dips in the bulldozed sand, which would start to scour a channel and create a rip.
He’s bang on the money, because all it takes is a little adjustment to the beach shape to trigger all sorts of domino effects, rip formation being one of them. This year Bondi had some ferocious rips after they bulldozed the beach in preparation for the City 2 Surf tents. Ultimately though, bulldozing is only a short-term issue as the beaches eventually re-adjust and get back to normal.
The message here is that when it comes to beaches, everything is connected: the shape of the beach, the waves, and the way sand moves. Any time humans alter the beach, we mess with the system and the beach will respond, sometimes in a good way, sometimes in a bad way. This, of course, is a major theme of my new book, which is selling like hotcakes (in my dreams) and is equally (if not more) engrossing than Ricky Ponting’s 2010 Captain’s Diary – cheaper too!
‘Dr Rip’s Essential Beach Book’ is the perfect Christmas gift for everyone you know and it’s available from all good bookstores or online at www.scienceofthesurf.com.