Beachfront Erosion and Vetiver Grass

Slowly the foreshore project is generating waves. We're still without good rain but with a major El Nina event predicted -- with a likely run of cyclones -- the next few months should be interesting.
In the new year we meet with council -- local government -- to discuss these plantings.
Ironically we are still to harvest and divide in quantity from our nursery... so we cannot move quickly forward.

What's current practice?

Variation of a slope using rock this image at right.
when, my guess is it should be no more than 20 degrees. But that's more expensive to build and requires more land to run down. 
This is high tide in the photo. Low tide goes out a long way with around a 2 metre variance. 
Our 'bay' here is very shallow. That's our coastline we are planting on in the background. But the rock walls are moving thru it -- heading north. The shore faces approx due east into the prevailing south and north easterlies but protected, of course, by offshore sand islands and with mangroves patches to the north in the shadow of Bribie and to the south at the river mouth.
Not so much rip rap as the fact that the incoming tide and waves hit the sharp incline -- then as they dissipate back and drop their volume, the collective force pulls the sand from the base of the rock wall -- whereas a softer gradient and rockily uneven slope would absorb more of the sea's force. 
If you've ever paddled along a rock wall, the turbulence is quite strong as wave action moves back and forth to toss you about.
Sheer vertical walls here, built from landscaping timbers, are very quickly undermined despite footings and build quality. At least rocks roll and sink into any ditch.
A popular solution has been to layer green mulches -- branches, palm leaves -- along the foreshore edge to protect the sand and offer a surface that will absorb some of the sea's force and protect trees on the edge. That works until the trees fall over -- as Coastal Sheoaks are almost designed to do.  Laying logs don't work, as they float away in storms and King Tides. 
Most Australian foreshore species(aka 'Indigenous Fauna') that I am familiar with, are shallow rooted. They may suit suppression of wind erosion and later colonise with Banksias, Melaleucas and Sheoaks (and Hakeas in Victoria)-- but the ecology is not evolved to hold the land in place -- as mangroves do. Here too we have an advantage as the aquifer which skirts the foreshore is only 1.8 metres below the surface. If we can tap that soon enough we're all good.