Good points Mazdon, and to some degree I do agree, however,
The sand for both snapper and d,bah is pumped from Letita spit, this is not natural sand movement, prior to the comps and after big storms the sand will be pumped continuously for days, this is actually a bit of a kicker to assist my philosophy.... the location the sand is pumped is comprised of river sand and coastal dune sand , all of which drifts up the coast much of it from sand dunes.
Additionally as displayed in the below photo it can be seen that on the southern side of tweed river there is limited coastal development for several kilometres so I don't think that you can utilise snapper and d,bah as a normal coastal situation as it has been heavily tampered by man..
The fact 99% of the sand that is pumped there is from non developed coast and how the banks there are quite resilient to storms probably only adds further weight to my point?
not so sure about the wedge set up you are referring to Mandurah? California but neither of these places in my opinion are considered a "a class beachies" they are both refracted waves off breakwalls and again man made,,
I am more picturing myself standing on a beach down south or up north looking at dunes,,,,

Your storm surge points do hold a lot of validity and as can be seen on your supplied chart it is the predicted surge, this is where it gets tricky and I don't really know how it happens but....below pic is Claremont jetty from sat night, whilst a terrible photo this boat on a normal night would be sitting at least a metre below the jetty, (on a high tide) there is at least a metre above to the gunwhales also you can see the jetty is wet this is from the water underneath slapping up.
at least two metres of storm surge....I actually had to do a calculation to get under the first bridge in the river coming upstream. My calc with the surge and tide as displayed in the chart left me with 3.8 metres above my roof, in reality it was no more than 1.2-1.5 this is why I was so perplexed that not one website had any info in regards to the "actual"