Disappearing sand from the North Coast

I was interested to read an article in my areas 'local rag' The Northern Star. It was a thoughtful piece by someone who loves the regions beaches. It was also a controversial one as it implied a man-made cause for the erosion of many of the regions beaches. You can read the article here: http://www.northernstar.com.au/story/2012/08/24/is-our-sand-on-goldy-beaches/. It actually, provides a good follow on from my last post on the matter.

Waves, wind, currents and a thin strip of sandy beach
One of the regions typical beaches near Ballina

In this article the author (Ben Bennick) suggests that although the mechanism of northward long-shore drift of sand is recognised as a significant driver for the erosion of many beaches, it raises the question of whether the Tweed River sand bypass scheme actually affects beaches further to the south. It is suggested that this is as far south at beaches such as Kingscliff or even those at Byron Bay. The Tweed River sand bypass scheme was introduced to stop the mouth of the Tweed river from being constantly dammed by sand deposited at the mouth. The closing of the mouth of the river would adversely affect water quality in the esturine reaches of the river. It has been operating for more than a decade now and Ben is worried that this might be affecting more than the Tweed River. The bypass scheme has been active since approximately 2001.

Ben suggests that during some times of the year sand would actually migrate to the south, contrary to the potentially simplistic concept of inexorable northward sand migration. As discussed in my previous post about long-shore sand drift, the action of the East Australia Current travelling south actually does not have the effect of causing sand to drift along the coast instead currents generated by the prevailing wind direction means that there are smaller coastal currents which tend to travel in a northward direction.

But Ben does raise an interesting question and rightfully this questions the absolute nature of the eastern Australian coastal currents. Maybe the situation does arise where sand can actually be transported from north to south from time to time. I wonder if such a phenomenon would be great enough to transport sand from the Tweed as far as Byron Bay and beyond? This would find a culprit in the Tweed River sand bypass scheme and would show us that the coastal strip is even more fragile than is already assumed.

In addition to the above comments I also suggest that local knowledge is very important to reconstruct the recent history of our area. Sometimes it is the bloke who has visited the holiday camp at Broken Head for the last 40 years who has some important observations to share. Local knowledge might be pointing to something we are missing. But, and a big but, there are also times where local knowledge is actually completely flawed! Tibby et al. (2007) demonstrated that the recollection of the behaviour of the sand bar at Lake Ainsworth near Ballina was often quite different to what was revealed in aerial photographs, indeed many anecdotal observations which were considered high reliability were in fact impossible when compared with historical photographs.

So, what does this mean? I think it requires someone with a good coastal management background to put us straight. Southern Cross University, despite its shortcomings has an excellent coastal management school. Maybe the answer is not known at the moment, in which case maybe this knowledge gap can be filled. It might just be that Frazer Island is indeed made from 100% Kingscliff and Byron Bay sand, and that is the way it always was. The sand dunes along the coast hide many a change to the coastline in the last 100 000 years, we can't claim to know what caused more than one or two of the many changes during this period and they are generally natural things like extended storm systems... but you never know.

References/Bibliography:

*Tibby, J., Lane, M.B. & Gell, P.A. 2007. Local knowledge and environmental management: a cautionary tale from Lake Ainsworth, New South Wales, Australia. Environmental Conservation V34.
*White, M. E., 2000. Running Down, Water in a Changing Land. Kangaroo Press.