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