SAND-DRIFT PROBLEM IN NEW SOUTH WALES. 85 
4. The three stages in the reclamation of a sand-dune., 
—Sand-dune reclamation consists of three stages :— 
a. Cutting off the further supply of sand from the ocean. 
b. Fixing the sand by means of vegetation. 
ce. Maintenance of such vegetation. 
The sand is of course primarily brought from the sea by 
the action of winds and waves. The deposit on the beach 
is dried and is then blown by the prevailing winds, forming 
dunes. Our most violent gales, in the Sydney district, 
come from the south-east. Let us consider the above three 
points in detail: 
a. Cutting off the further supply of sand from the ocean. 
—To do this, what is called the ‘‘ dune littorale’’ is formed. 
The old official system of constructing the protecting dune 
may briefly be described as follows :— 
Ata distance of from 150 to 200 yards from high water mark 
a wattle fence,’ some 40 inches in height is erected, parallel to the 
general coast line, and at right angles to the direction of the pre- 
vailing wind. The drifting sand is arrested by this fence, and 
mounting up to windward forms a gradual slope towards the sea. 
After some little time this fence is overtopped, and a second is 
put up some 63 feet from the base of the steep leeward slope 
formed partly by the sand which has been forced through the 
interstices of the first fence, and partly by the sand which has 
blown over the top, and parallel to the first fence. The space 
between these two fences is soon filled up, and the embryo dune 
assumes a certain profile. Midway between the two fences a 
palisade is erected. This palisade is formed of pine planks sharp- 
ened at one end, 5 feet long, 7 inches to 8 inches wide, and 1} 
inches thick. The planks are driven into the ground some 20 
inches, and 3 of an inch apart, their breadth being at right angles 
to the direction of the wind. As the sand drifts up the windward 
or west slope of the dune, it is again arrested by the palisade, 
1 Tea-tree (Leptospermum, etc.) would be used in coastal N. S. Wales. 
