Friday, 24 August 2012

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: 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.


*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.


  1. Hi Rod,

    Interesting post, particularly since I have been studying coastal geomorphology and climate change with Robert Baker and Bob Haworth for the last few years. If Bennink thinks sand can move all the way back to Byron from the Tweed, he is off his rocker and is ignoring some very salient points.
    ~ changes in river discharge due to dams and other man made structures
    ~ changes in river discharge due to El Nino and La Nina effects
    ~ industrial sand extraction
    ~ sand locked away by beach capping and development
    ~ sand loss to shelf sediments due to SL rise

    This last point is the most controversial because it is at the heart of the current climate change debate. Patrick Nunn has written some amazing papers regarding the Lapita Peoples response to oscillating SL, such as the mid Holocene warming and the ascent out of the Little Ice Age. Both of these events have been generally pooh-poohed by the IPCC and ANU, but not for much longer because there is too much supporting evidence.
    You made a good point with Lake Ainsworth.
    Sorry to babble on but this is one of my pet subjects.

    1. Hi Dylan,

      Somehow I knew you'd comment on this one. And I'm glad you have and a wonderfully detailed comment too.

      As you may be able to tell from my post, I was hesitant to agree with the author of the newspaper article. I thought it possible that there could be some local influences... maybe as far as Kingscliff????, but then again you'd think the beach south of Fingal Head would be in a worse state if this was the case. I would have been surprised that such a scheme would have such a regional influence. As you rightly point out there are many more explanations which explain the situation better.

      Bob and Robert know sea levels that is for sure. They've got some very good published work in many journals. I have heard of Patrick Nunn but never read any of his work. It'd be great to get a post on Holocene sea levels in the region, it is an area which I am weak on... but maybe I can ask someone... such as yourself to do one? I know you are very busy at the moment but It'd be great to get your local knowledge and strong educational background on this one.

  2. The Sand comes and goes. I also don't believe that the sand travels south unless it is a very local and short term event.
    I was at Yamba on the weekend and at least 2 feet of sand had come back on the beach within 5 weeks.
    Re my post today on The Gorge, it is such an interesting spot geologically, do you know anything about it?

    1. Wow, 2 foot of sand in just over a month! I knew that beaches could disappear over a such a period, it is amazing that they can come back over such a period too!

      Sadly, again, I don't know much about the geology of that area though I suspect that the rocks are part of the New England accretionary complex which is composed mainly of regionally metamorphosed marine sediments. Maybe there is some granites in the area too which have intruded through those meta-sediments. Could also be Clarence-Moreton basin sedimenary rocks too but this is the least likely. I'd love to go there and have a look.