90 SUNKLANDS OF PORT PHILLIP BAY AND BASS STRAIT 
The hole referred to here as the 17-fathom scour hole (Fig. 7) 
is in the Inner Basin near the toe of the inner scarp of the Bay 
Bar and about 1;^ miles N.N.E. of the inner outlet of an unnamed 
tideway that extends E.N.B. from the South Channel; it branches 
off from it about 4 miles west of that channel’s outlet into the 
Inner Basin. For the greater part of its length, this unnamed 
channel is 20 feet deep, but narrow ; near its outlet into the Inner 
Basin, it has been blocked by a sand bar over which there is only 
4 feet of water. The 17-fathom scour hole, which is being rapidly 
silted up, was apparently formed in the Inner Basin by in-going 
tidal streams that flowed through a tideway of some width, and 
not the narrow unnamed tideway. To the south-west extremity 
of Capel Sound, there is evidence of an older scour hole that 
appears to have been connected with a former tideway that 
had an outlet (Fig. 7) into King Bay, and is disclosed by the 
bathymetrical contours at 20 fathoms on the profile (Fig. 7) of 
that Bay. Gregory (1903) suggests that this outlet may be a 
river outlet from Port Phillip Bay, but the alignment of the 
three suggests that they have been connected by a tideway, not 
a river channel. 
There are large, but relatively shallow, scour holes at the inner 
entrance to Symonds Channel, but closer soundings are necessary 
to enable one to comment on them. 
It has been stated that tideways are ephemeral. Due to the 
encroachment of dunes, they are constantly altering their courses, 
and move at different times throughout the length of a bay bar. 
Thus, the Tootgarook Tideway previously referred to was an 
earlier tideway than any of those now converging on The Heads ; 
it was formed along Selwyn’s Fault on its downthrow side, and 
entered King Bay on the submature portion of the coastline 
near where the Fault crosses it. Scoured out of the consolidated 
dune-rock, its former course can be clearly discerned from a 
view point such as Arthur’s Seat. 
(Ill) King Bay Profile 
The slope of the profile (Fig. 7) shown by the bathymetrical 
contours of King Bay south of the Nepean Peninsula down to 
the 35 fathom (210 feet) platform is taken to be the outer or 
southern face of the Upper Dune Series. Eight outlets, some 
of tideways, others of river channels, are revealed by the 
bathymetrical contours (Fig. 7). They are referred to here by 
the fathom line at which they occur, and given in order of their 
priority in functioning as outlets. All are outlets of the Upper 
Pleistocene Yarra. 
