IN a natural environment, changes to coastal waterways tend to happen over geological scales of time, in systems that are more or less at equilibrium.
But once we start altering the geography of a river inlet, the usual results are corresponding changes elsewhere in the vicinity, as nature tries to find its balance once again.
The Hunter coast has three notable hot-spots as far as sand movement is concerned, and all of them bear the mark of human influence.
The south end of Stockton Beach is eroding like no other on our coast because the dredging of Newcastle Harbour, and the breakwalls at its entrance, have altered the usual northern flow of ocean sands.
At Port Stephens, the repeated erosion of Jimmys Beach is almost certainly linked to human changes along the narrow Winda Woppa peninsula, even if debate remains as to the exact cause and effect.
The third example is Swansea Channel, where sporadic dredging efforts have been no match for the rate of sand buildup at "the drop-over" into the deeper water of Lake Macquarie.
As the colour photograph above shows, various shoals of sand are pushing well out into the lake, beyond the cluster of islands - some of them artificial - at the end of the channel.
The buildup of these islands over the past 50 or 60 years is clearly apparent when comparing time-scale aerial images.
On one hand, the buildup of sand may not be having an appreciable effect on the overall ecological health of the lake, and the high-tide depth is enough to safely navigate motor vessels.
However, the same can not be said for fixed-keel yachts, and so this season, as in previous years, there are calls from the yachting fraternity and the tourism sector to expand the existing piece-meal dredging program or replace it with a permanent sand-shifting operation.
Environmentally, a case could be made for leaving things as they are, and allowing the channel to find something close to a new balance.
But if maintaining a yacht-navigable way through the drop-over is a priority - and the tourism and recreational arguments are strong - then it would seem better to devise a larger, more effective way of dealing with the problem than the "just-enough" dredging programs that have already cost taxpayers $4 million since 2011.
Once again, we are left to observe that finding the money to deal with the problem comprehensively wouldn't be a problem if Swansea was in Sydney.
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