632 SAND-MOVEMENT ON THE NEW SOUTH WALES COAST, 



headland was reached. Unable to move further south, the 

 impounded waters force their way through a narrow channel, 

 which is being continually filled in by sand drifted from the 

 north. 



When dry weather prevails for a lengthened period, the sand 

 accumulates until the entrance is completely blocked, and the 

 sheet of water becomes a saltwater lagoon, but when rain at 

 length falls, and the water-level of the lagoon is raised, the sand 

 dam gives way (helped perhaps by the exertions of the fishermen) 

 and another channel is formed, which in its turn is filled up, and 

 so the cycle runs. About a mile to the north of the entrance to 

 Tuggerah Lake the sand spit is about 700 feet wide, and the 

 sand dunes about 30-40 high; and here a remarkable bank of 

 white sand is visible for many miles. A violent gale made a 

 break in the line of sand dunes about 10 years ago, and exposed 

 a surface of sand for the southerly winds to play upon. Since 

 that time the sand has been moving northwards, and now presents 

 a face 35 feet high at its northern end at a distance of 600 feet 

 from the break. 



On the southern side of the break very little movement has 

 taken place, although the prevailing JST.E. winds have been blow- 

 ing against it for 10 years. The sand is now encroaching on the 

 lake at the rate of about 60 feet per year. Advantage has been 

 taken of this well known influence of the predominant winds in 

 moving dune sand to construct a roadway across the wind-blown 

 sand at Bondi.* This work was designed and carried out by Mr. 

 W. A. Smith, M. Inst. C.E., of the Public Works Department, 

 and is an object lesson on the results to be obtained by utilising 

 the forces of nature intelligently. 



In this case the dominant wind, so far as the material above 

 high water is concerned, is the southerly; but the fact of the 

 beach-sand moving to the south proves that these winds have no 

 effect, so far as the movement of the material below high water 



* Smith, W. A., M. Inst. C.E., " Treatment of Drift Sand, as applied to 

 Bondi .Sand Dunes," Sydney University Engineering Soc, Oct. 27th, 1902. 



