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June 9, 2023

Coastal expert warns of rock wall dangers

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A section of the gallery at a recent council meeting discussing rock walls. Photo Eve Jeffery
A section of the gallery at a recent council meeting discussing rock walls. Photo Eve Jeffery

Hans Lovejoy

Bored with the Belongil rock wall yabber yabber? You bet – but part of the reason it’s dragged on for so long has been the lack of authority within the debate.

The pros and cons have largely been dominated by politically driven, non-expert councillors.

But a qualified scientific opinion has now been voiced, with the chair of the NSW Coastal Panel telling The Echo he and his colleagues have ‘significant reservations’ about the project, including the use of temporary walls, which can dislodge during large storm events.

Angus Gordon also explained why the panel has only been able to make a limited contribution to the Belongil rock wall project.

The NSW Coastal Panel are possibly the most authoritative voice on all coastal matters, and provide advice to Councils and the state government, specifically on ‘impacts of rock revetments on beaches and public beach amenity’.

Mr Gordon’s comments came in response to a press release last week by The Byron Preservation Association (BPA) – who have accused the Greens of publishing inaccurate information on flyers.

Specifically BPA say MP Tamara Smith inexplicably withdrew an online petition after being queried about its claims.

So who are BPA? They are headed by chairman of Ramsay Health Care, Michael Siddle. Ramsay is ‘one of the top five private hospital operators in the world,’ according to its website.

Mr Siddle says BPA are a ‘not-for-profit organisation concerned about coastal issues in the Byron Shire who object to the principle of planned retreat in urban areas.’

He says, ‘These rock walls will protect a majority of public land, not private land as the petition and flyer said, and will not cause further erosion or the loss of beach.

‘The community need to know the facts, not the misinformation are pushing as it may have long-term ramifications for other beaches in the Shire which may also need to be protected.’

Mr Siddle went on to say that the review into environmental factors of the project by consultants UMWELT paints a different picture to what the Greens are saying.

He claims the, ‘Coastal Panel’s concerns were relatively minor in nature,’ and quoted the report’s statement: ‘Scenic amenity not adversely affected.’

Mr Siddle added, ‘There is no evidence at all that the proposed interim rock wall accelerates the erosion of the beach… the evidence is the opposite conclusion. Only the Jonson Street structure is accelerating erosion.’

Siddle ‘incorrect’

While the office of Ms Smith declined to comment, the NSW coastal panel’s Angus Gordon gave a detailed explanation to of issues raised by Mr Siddle.

Mr Gordon told The Echo, ‘The statement that, “the NSW Coastal Panel’s concerns over the Belongil rock wall proposal were relatively minor in nature” is incorrect.

‘The panel includes three specialists, each with over 40 years’ experience in coastal issues and in particular the impact of rock revetments on beaches and the public beach amenity.

‘Because Byron Council decided to use the Infrastructure SEPP, and thereby make itself the approval authority, the only role the NSW Coastal Panel can play under the Coastal Protection Act is to provide “Matters For Consideration” for the Council in its decision making.

‘This role significantly limits the NSW panel’s ability to make its views known.

‘After the NSW Panel provided the “Matters for Consideration” clearly Byron Council did not consider them “relatively minor in nature,” as Council specifically requested a meeting with the panel so that the panel could “explain” its position.

‘That meeting occurred and the panel certainly did “explain” to Council the significant reservations the panel had in regard to the proposed wall; reservations which continue.

Panel’s concern

‘One of the matters the panel specifically addressed with Council was the panel’s concern about the amenity being adversely affected.

‘A matter of concern brought to the attention of Council, that appears to be overlooked by what, based on your [correspondence], appears to be the UMWELT assessment, is the fact that a “temporary” wall with a lower design standard than a permanent wall can result in rocks being dislodged (as has already occurred with some of the existing walls), thereby creating a hazard for beach users and particularly for surfers.

‘To treat the “amenity” simply from a visual perspective suggest a limited experience with the impacts of rocks on beaches.’

Nourishment seen as important

Regarding the expected loss of beach owing to rock walls, Mr Gordon said, ‘The technical literature abounds with papers and articles regarding the adverse impacts of artificial walls on beaches.

‘The basic explanation is that a beach absorbs the breaking wave energy whereas a wall reflects at least some of that energy thereby increasing the energy available to promote erosion in front of the wall.

‘That is why appropriate beach nourishment is seen as an important adjunct to the construction of such walls.

‘Interestingly, one of the reasons accelerated erosion occurs when an erosion escarpment forms is again the reflected waves from that vertical wall.

‘That is, although the escarpment is in itself eroding back, the reflected wave off its face helps remove the sand in the swash zone and takes it offshore. If this mechanism were not present the escarpment would simply collapse and the erosion stop.

‘Any person who has observed wave attack on a vertical erosion escarpment would have witnessed this phenomenon; it doesn’t require any specific expertise to see the adverse impacts of any structure that reflects waves.

‘As far as the Jonson Street wall is concerned, my 1978 report, Byron Bay-Hastings Point Erosion Study, clearly pointed out that the Jonson Street wall was having an adverse impact on erosion along Belongil, but was not the only reason for the erosion.

‘The Jonson Street Wall was constructed to stabilise Main Beach because of the natural sediment deficiency at this point in history along this section of the north coast.

‘The 1978 report put forward a number of management options for Belongil, including rock walls and/or a groyne field as well as retreat and in 1986 – I believe this is the correct date – it is my understanding that Council resolved to adopt a policy of retreat for Belongil and therefore the DCP called for demountable/relocatable housing. I am not aware whether Council has ever rescinded this resolution.


‘It is inappropriate for me, as chair of the NSW Panel, to have a view on the type of coastal management the people of Byron wish to have at Belongil; however, it is important that whatever decision is made, the full ramifications of that decision need to be understood.’

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  1. great read! Quite informative to have Angus Gordon explain more about the workings of rock walls.

    A little more info: Gordon mentions his 1978 report about the impact of the Jonson St works. The update on that issue is found in a report on the council website by Worley Parson (2013)

    “there has been very little recession of the 4 m contour immediately downdrift of
    Jonson St Protection Works between 1999 and 2011 implying that while the initial
    impact of the seawall construction in the mid 1960s was significant the Jonson St
    Protection Works are now almost fully bypassed by longshore sediment transport and may
    have a reduced impact on the shoreline recession downdrift (fig 15)”

    from pdf which is linked to the words in the second the last paragraph on this page

    Worth looking at the report for the excellent photos showing the changes on the shore over time.
    Of special interest is that while the Jonson St public works have stabilized, the remaining works all labelled “private” have not and appear to add to existing erosion.

  2. This argument has now raged for well over a decade, more, yet the fundamental question remains unsettled:’who is liable when houses fall into the ocean?’. I would imagine that’s what those people who have bought in at Belongil in the last few years want to know, as do their insurance companies no doubt. As was observed regarding the rock walls, there’s been a lot of (hopeful) speculation by non expert vested interests but nothing concrete from the experts.

    • Under the current regime, the landowners must remove their houses if the erosion line comes too close. Buildings there are supposed to be demountable. It would be surprising if they were able to get insurance.
      The argument has raged for so long because some people cannot accept that when they made the decision to buy land in Belongil, they did it under the Council’s policy of nearly 30 years – planned retreat. That should be the end of it. Those people who bought from the mid 80s onward did so with the full knowledge that (Council) ratepayers would not be bailing them out. It is an impossible situation that Council has put themselves in with this latest rock wall debacle – it is not only in Belongil that they are expecting Council to protect their properties. There are houses at risk in New Brighton and Suffolk Park. Are we going to spend millions on all these too? Crazy.

  3. With the greatest respect to coastal engineer Angus Gordon whose comments and understanding of local coastal processes are based on his 1970s work. The understanding of the coastal dynamics and processes are now more complete Patterson 2010 Goodwin 2006. The expert currently working in the field reiled on by Council for the “Design of Interim Beach Access Stabilisation Works – Belongil, Byron Bay WRL Technical Report 2013/08 October 2013 J T Carley and I R Coghlan” State in their report
    P36 8.7.2 Off Site Impacts of Proposed Interim Beach Access Stabilisation Works
    “It is well accepted that hard structures cause increased erosion/recession where they end
    (Figure 8.5). It can be seen in Figure 8.5 that a functioning seawall can fail through erosion at
    its end – a “flanking failure”. At Belongil, the increased recession is likely to occur
    predominantly on the northern side of structures due to the predominant northward littoral drift,
    and is evident on Belongil Spit beyond the northernmost limit of protection works.”
    In relation to the proposed works at they say P 46
    “These proposed structures would replace existing structures on a coast with predominantly hard
    foreshore protection. Therefore, they would not cause an incremental increase in off-site
    impacts. Without these structures in place (whether the existing or proposed), neighbouring
    structures are vulnerable to flanking failure.”

    Mr Gordon posed concern about displace rock impacting surfers. I guess this is remotely possible but given the proposed interim wall is landward of existing rock walls outside the active surf zone and the current walls inclusive of the Jonson St structure have been in place for 40 years without incidence this was factored into Council’s decision making process.
    I agree with Mr Gordon when he said ,‘It is inappropriate for me, as chair of the NSW Panel, to have a view on the type of coastal management the people of Byron wish to have at Belongil; however, it is important that whatever decision is made, the full ramifications of that decision need to be understood.’

    It appears Council has taken all concerns into consideration and an interim rock wall leaves ” the type of coastal management the people of Byron wish to have at Belongil” open and avoids the potential disaster left open by an inadequate geo-bag wall that “real experts” as far back as 2000 said would fail.
    This is what expert Coastal Engineering firm MHL stated in 2000 about the then proposed geobag wall:
    “Clearly such a design condition is not intended to provide any engineering protection and this should be clearly understood by the community. As MHL has advised previously (MHL Report MHL 1052): “It is not acceptable engineering practice to design and construct a protection structure ín the fuIl knowledge that the
    structure will not withstand even a moderate design condition. To implement protection measures (such as sand-filled geotextíle bags) that are not capable of withstanding even these lesser events, runs a high risk of damage to the structure and the development ít is supposedly protecting. This type of structure is prone to sudden or catastrophic failure in an exposed location. This risk is generally judged by practicing engineers as being unacceptable,”
    It appears the current Council have also taken the earlier expert comment on geobags into consideration!

  4. Hmmm. The J T Carley and I R Coghlan report is actually commissioned to design rock walls, not further understanding of coastal processes. The passages quoted above echo exactly what Angus Gordon says in the article above: rock walls encourage erosion. They replace hard structures and continue the erosion already underway.

    But the next passage quoted above is not what appears in the document. Esp worrying are the lines “Therefore, they would not cause an incremental increase in off-site impacts..” I cannot locate these exact words on p 46. (which is actually a list of references).

    But on p 38 I do find this ” They (the rock walls) are a replacement for an existing protection structure, so they would have no incremental (additional) impact beyond the status quo.”

    Again, this says erosion is underway and another hard structure will continue as much (but not additional) erosion as is already underway.

    In his extensive work on the coastal panel, Angus Gordon would be up to date about coastal processes and widely experienced with the impacts of engineering. That is why he mentions sand nourishment, which in other places goes hand in hand with rock wall construction.

  5. Well sorry Mary the quote repeated below is really not too difficult to find it’s on Page 44 of the WRL’s report not Page 46.
    “These proposed structures would replace existing structures on a coast with predominantly hard
    foreshore protection. Therefore, they would not cause an incremental increase in off-site
    impacts. Without these structures in place (whether the existing or proposed), neighbouring
    structures are vulnerable to flanking failure.” p44

    One can understand Council’s decision to replace the geobags when the expert report also says at page 38.

    “8.7.3 Likely Impacts if Proposed Interim Beach Access Stabilisation Works are not
    If the proposed interim beach access works are not undertaken (and the existing sandbag walls
    are removed and/or fail), and the surrounding protection works are retained, deeply embayed
    beaches would form between the protection works on either side in a similar manner to Figure
    8.5 (northern side only for Border Street).
    Flanking failure of the works at each end of the local embayment (northern side only for Border
    Street) would be likely under a “do nothing: scenario. A breach of Belongil Spit would also be
    possible, particularly at Manfred Street.”

    Pretty much like the advice given by the PWD’s Coastal Engineer Anthony Moratti to Council in 1990 @ Page 23
    “A land survey profile was taken through the dune fronting Manfred Street on 8 February 1990 to align with a photogrammetric profile taken from aerial photography dated 23 June 1987.
    Application of a short-term storm demand figure of 200m3/m run of beach above AHD at this location shows that the entire dunal system could be removed during a severe storm event (see Figure 16). Without a dunal buffer, oceanic inundation across Manfred Street is likely under combined conditions of severe wave attack and elevated ocean levels”.
    Mary Council has never been short on expert advice, at least this Council recognized the danger at this point and is acting on the best advice available.

  6. While the debate around whether to build rock walls or not continues to rage, the reportage of the issue leaves much to be desired.
    Most of the articles written through this outlet and others seem to carry a level of bias towards the construction of the wall’s opponents, and in many cases crosses the line between news and opinion without any clear delineation.
    In the case of this most recent article I would point out:
    1. Angus Gordon is an engineer, not a scientist, so this is not scientific evidence. Please ensure your readers are aware of this.
    2. Pointing out Mr Siddle’s role with Ramsay Healthcare adds no news value to the story, rather it seems to try and paint Mr Siddle in a particular light that could influence the reader towards a negative view of him given the rhetoric opponent groups continually push (i.e. supporters of the rock walls are pro development etc.)
    3. Mr Gordon states towards the end of your article that his 1978 report put forward a number of management options for Belongil, including rock walls and/or a groyne field – so why is the article seemingly biased towards not building the walls, and why is this fact buried at the bottom of the article when it in fact supports Mr Siddle’s comments? Shouldn’t your article read Coastal expert supports rock wall?
    Unbiased and factual reporting is what is required in this debate so that people have the ability to make up their own minds, and not be swayed by the editorialisation of what could be well-written news articles.

    • Felix Summerfield the debate is being had in the pages of the Echo because it has been stifled by Council – they decided to evade community input and proper public discussion by deliberately using the infrastructure SEPP to get this rock wall done in a hurry – and also evading the need to have the approval of the NSW Coastal Panel (of which Angus Gordon is a member and who should know a thing or two) to build the Belongil rock wall.
      They also are trying to hurry it through before a Coastal Zone Management Plan is in place – which would likely not support the “interim” rock wall. By doing this they leave Council unprotected legally — a CZMP is underwritten by the state government. The debate becomes more than just one of whether a rock wall is a good or bad thing but whether it is fiscally or legally responsible to take this step spending ratepayers’ money and leaving Council with a potential future of litigation that will drain the coffers into the future undefinitely. This is just plain poor management and highly irresponsible. The fact that the community was quite deliberately cut out of the process is also a sign of a Council that is doing what it likes without any mandate from the residents.

  7. Plato would be proud of your rhetoric Ms Coorey.
    The last time I looked the NSW local government act provided for a process that allows the residents of the Byron Shire (and all other shires and councils throughout NSW) the opportunity to elect representatives to get on with the job of running their local government. This happens every 4 years. The same process is in place for state and federal governments (albeit every 3 years in their cases) – that’s called democracy if you weren’t aware.
    To say the debate has been stifled by council is somewhat perplexing – aren’t they just doing the job we elected them to do? That’s called a mandate.
    As far as the issue being payed out in the Echo, the fine media outlet that it is, it also has to sell newspapers. As a long-term observer of journalism and the media in general, it’s no surprise they push an agenda – Mr Murdoch et. al. are often accused of the same thing – that’s called a business.
    In regards to the CZMP – I’m no long term resident – but I understand that old chestnut has been floating around for 20 plus years, with it’s last reiteration voted down by the then council – that’s called frustrating.
    And the fiscal and legal issues you raise by allowing council to get on with their job is also a tad bewildering – fiscally as I understand it 3 of the residents directly affected by erosion issues are contributing $100,000 each towards the wall – and legally as I understand it there is a court order to get the job done.
    No matter Ms Corey, given there are many other issues that also need resolving around the shire such as potholes, facilities like hospitals, schools and social services, and the long-term responsible management for a town that is continually under the strain of tourists and ideologists looking for a spiritual home, I’m sure you’ll dig deep into your own pockets to make a contribution to the coffers of the council you’re so concerned will become broke if they do what they were elected to do.

  8. Let’s be frank, there are vested interests on both sides, land owners wish to avoid loss, however the Coastal Panel ( soon to be an all empowered Coastal Council ) is staffed by hard line Greens who fundamentally oppose any coastal protection.
    Have readers considered that home owners in NSW including coastal owners contribute via home insurance to the $380 Million per year cost of the Rural Fire Service, the RFS protects private property against loss from bush fire – Why? Why not follow the coastal management lead and let all those houses burn? Why not institute forced planned retreat from bush fire prone areas?, surely it is lunacy to allow people to rebuild and continue to habitate these dangerous areas?

    Anyone beginning to see the paradox in management of bush fire vs coastal management yet?

    Bush fire management receives over $380 Million every year – NSW coastal management receives $3million which is regularly underspent due to ideological road blocks from the Green lobby.


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