Bass Strait and Swell Direction

Nick Bone's picture
Nick Bone started the topic in Thursday, 19 Jul 2018 at 5:50pm

Looking at the bathymetry maps on Navionics leads me to ask how can there really but difference in swell direction for the entire Bass Strait? Basically anywhere East of Portland.

Why I think this is because of the Bass Strait Ridge (dont think its called that but know it has a name as ive read about it before), the clearly defined curved part where the water depth goes from roughly on average 1300m to the Bass strait waters that average around 70 meters. That depth seems to be fairly consistent before becoming shallow not too far from the coast line.

Ive been wondering for a while now and it came too mind when Craig posted a article back in May regarding bathymetry and period. Ill cut n paste the key part to my question (Cheers Craig)

"Swells start to feel the ocean floor at a depth equal to half their wavelength, and this wavelength can be calculated by taking the swell period, squaring it and multiplying by 1.56.
Wavelength = 1.56*period^2
So for a 10 second swell it only starts to feel the ocean bottom at a depth of 78 metres.
When looking at a 16 second swell though, it starts to feel the ocean floor at 200 metres.
And a 20 second swell will start feeling the ocean floor at an incredible depth of 312 metres.

I read that and think that the answer is right there, that a due West swell or a due South swell of any significane will be steered back to a SW direction.

Heres the link again too the bathymetry maps and have a geeze for yourself, love to hear some feed back and as usual, i hope my question is understandable.


southey's picture
southey's picture
southey Thursday, 19 Jul 2018 at 10:41pm

This has been discussed atleast 4 times on this site . Email Ben if you want answers . Let’s just keep this place as an extension to Instagram

Nick Bone's picture
Nick Bone's picture
Nick Bone Friday, 20 Jul 2018 at 6:17am

Funny you say that Southey, was gonna email Ben but didn't really want to bother him with personal questions. I didn't ask in the comment section in the said article and ill admit my own selfish curiosity got the better of me by posting in forums.

Im happy to put my email down here if you would be happy to email me any feedback?

indo-dreaming's picture
indo-dreaming's picture
indo-dreaming Friday, 20 Jul 2018 at 4:35pm

Crazy Victoria (east of cape otway) gets the swell it does when you look at a map of Australia.