Vetiver and Coastal Erosion: some lessons.

Source :plan-verde
The first time we planted Vetiver along the coast we did the 10/15 cm distancing and the waves came in during a surge and washed the hedge away. 
Vetiver slips were scattered all up the beach.
Now we plant with that in mind as the hypothesis is that the water comes in (and you really don't want to stop it as you can't) and then drags out whatever it can as it recedes.
What we want is the roots to hold onto the foreshore.
The process is different from erosion intervention on land as the flow is both ways.
We are now planting slips around 30cm apart and in staggered lines.
We also plant the first hedge back from the high tide mark, establish that hedge, then plant another in front of it -- moving the Vetiver 'forest' forward towards the sea.
That means the planting process continues over time. Not just a one off session.
We are not as yet anywhere near full growth and maturity of the shoreline Vetiver so it is all maybe landscaping. 
But we'd like to
  • protect the foreshore as best we can AND 
  • move it forward IF the sand is deposited in front.
So we're looking forward to seeing the beach incline rising in front of the Vetiver.In effect, getting the tide and currents to do the heavy lifting for us.
I'm not skilled up with supplementary interventions like sand bags and coconut coil matting, nor are we about to move in heavy machinery to reshape the shoreline.
This is a house by house process without any government support.
But if it works....The video below you'll find of interest.
 There is no shortage of sand here in South East Queensland, Our sand islands are huge. Fraser Island (K'gari) is 123 kilometres long and approximately 22 kilometres wide. And the whole magnificent ecology is built on and with sand.
Where we are losing sand from the foreshore, local councils and pumping sand from under the water to spread along eroded beaches.
Then planting native species(like casuarina ,and shallow rooted ground covers like Coastal Morning Glory) to hold it in place.
The sand here moves around not only because of human traffic but the seagrass beds are diminishing primarily because there is so much mud, nitrates and other pollutants washed into the bay.
Moreton Bay used to support tens of thousands of Dugong. Imagine the American Bison herds before white inavasion. Now there are (last census) maybe 650 resident dugongs with their food, seagrass, limited to isolated patches. Turtles are similarly diminished for the same reason.
It is common to reference Vetiver in association with erosion and rural activities, but if you look at this map below, this is what urban development does to an aquatic environment.
And when we have a major flood event --like we did in 2011/12 the dugong starved because the seagrass was buried under the mud the catchments washed into the bay.