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THINGS TO KNOW ABOUT THE TIDAL MOVEMENT TO LAKE ILLAWARRA

Lake Illawarra is not working the way it should be.

The picture is of he back channel (behind the PCYC) low tide, at high tide it is covered by about two to five inches of water.
It clearly shows what it is and what it should be. This area has minimal tidal influence. The 4 knot sign is high and dry.

Yes, we have an efficient double rock walled entrance and a good feeder channel, but that’s as far as it goes.

The tidal movement is good in the feeder channel, up to the main lake. That’s where the two islands Bull Island and Bevan’s Island are . These islands limit the flow of tidal water down to two narrow channels.

The channel between Bull and Bevan’s Islands is choking with sand. Since the entrance wall works finished, the extra tidal pressure has caused sand movement in the channel as far up as the lake drop-off.

When the sand reaches the main body of the lake, the flow pressure dissipates, which allows the sand to slow and settle on the channel floor. This is causing the depth of the channel to become shallower and being a boating hazard. This point is like the narrow neck of a sauce bottle, it limits the flow rate.

The second channel, called the back channel, is a total disaster. Back in the late thirties when the Windang Bridge was built, a causeway was built across the back feeder channel and this totally changed the flow and pressure of the water which went to the southern side of the lake. Over the years, the back channel has been silting up and is now almost totally blocked.

Lake Illawarra is being starved of a good tidal exchange rate. It is receiving only a fraction of a tide exchange movement.

We have been told by a professional fisherman who works Lake Illawarra , that the southern en of the lake is loaded with sea slugs. These are regarded as a reliable indicator as to the poor health of the water where they live.

In 2004 the Lake Illawarra Authority (LIA) formed the back channel advisory committee to find the best option for the back channel. The option which was adopted was for a channel 40 metres wide and 2 metres deep. That is as far as it got, the LIA has fallen into a four year plus coma. The state of the lake will spiral down in freefall, even though we are all aware of the regional growth around the lake in the future.

No Action Now means the lake will not be ready for the extra load in the future.