25 
On the Removal of Bars from the Entrances to 
our Rivers. 
By WALTER SHELLSHEAR, Assoc. M. Inst. C.E. 
[Read before the Royal Society of N.S.W., 4 June, 1884.] 
THE removal of bars from the entrances to our rivers is a work of 
national importance, directly affecting as it does the progress and 
trade of the whole group of Australian Colonies, and in New South 
| ape 
on this subject may not, therefore, be without interest to the 
members of this Society. 
The coast of New South Wales might not inaptly be described 
m 
but in some few instances they pass into rock-bound inlets of 
considerable depth, notably in the case of ~ Hawkesbury River. 
The formation of bars at the entrances to our rivers is mainly due 
to the action of the waves in lifting large cuahisties of sand as they 
pass into shallow water, the sand being carried up the estuary by 
the incoming tide, and is deposited as soon as it is beyond the 
i the 
when the tide and waves are left to themselves, the tendency is to 
close the entrance altogether. To this is to be attributed the 
oe state of our river mouths in time of prolonged drought. 
is point is very forcibly brought out in the notes on the 
Admiralty charts, where it is stated that certain entrances are only 
open after a heavy fresh. 
The opinion that bars are mainly formed by the action of the 
waves is held by many leading authorities on the subject. Mr. 
/ 
