Steve Hansen
Erosion in Byron Bay appears out of control and may have the potential to threaten the welfare of the town.
Solutions proposed over the years have included building a rock seawall and importing large amounts of sand from elsewhere.
A Council release from April 2021 indicates plans to restore sand dunes by beach scraping, sand trapping, fence restoration and dune revegetation. It is suggested that these approaches will be implemented ‘once the sand rebuilds’.
The rebuilding of the sand appears to be the core of the problem. This may be impeded by the phenomenon of ‘headland bypassing’, which occurs when sand is transported from one beach to another around an obstacle, such as a headland, and, in the absence of the appropriate conditions in terms of wave direction and strength, fails to deposit sand in the area directly behind the obstacle.
Sand mining
A study from 1991 identified a pattern of sand movement that sees sand removed by summer storms, and redistributed by winter conditions, typically resulting in a build up at Little Wategos and The Pass, and a removal of sand at Wategos and Clarkes/Main beach.
But the vegetation currently growing on the Clarkes/Main Beach foreshore may be part of the problem. After sand mining finished on the beach and in the dunes of that area in 1968, the area was left a barren wasteland until 1973, after which the dunes were reformed and revegetated.
In a healthy dune system several vegetation zones should succeed each other: a hind dune with tall trees like melaleucas should sit behind a foredune with medium-sized plants like banksias, which should sit behind a primary dune with low colonising species like spinifex.
In front of that should be a beach berm with open sand and a swash zone where waves roll up and down. It is crucial that this berm and swash zone present a low, flat profile to the sea, so that when waves surge, as they do after storms, their energy can be dissipated without doing any damage. Then as they peter out, the sand they contain can be deposited, aiding in the reinforcement of the beach structure. Loose sand can then be redistributed by the wind, further flattening the beach profile.
However, when vegetation grows too close to the water’s edge, wave energy is reflected by the obstacle of root-bound sand, rather than dissipated by open flat sand. This results in the removal of sand, and the development of an escarpment, as is currently the case. That escarpment then becomes self-perpetuating.
This would indicate that removing the vegetation and flattening the escarpment would be the solution.
In 2014 the council of Woonona, in southern NSW, did exactly that. Faced with deteriorating erosion, as an experiment they cleared a part of their foreshore of all vegetation, while leaving other, erosion-affected parts as they were.
The cleared area was then flattened out. When the storms came the cleared area was able to absorb the impact of surging waves, and natural processes repaired any damage done. The control areas continued to erode, and to develop larger escarpments.
Therefore the solution to our current erosion problem may well be the removal of those banksias and pandanuses still standing, and a flattening of the escarpment, rather than a reinforcing of it.
While this would be a radical remodelling of what’s left of the area between Lawson Street and the beach, this process is currently undertaken by the sea already, whether we like it or not.
The removal of vegetation goes against all our environmental conservation instincts. Would we be able to do it?
♦ Steve Hansen is a former bush regenerator and Parks and Wildlife Service ranger.
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