New Collaroy Seawall Underway
In mid-2021, construction began on a controversial 13 metre high by 100 metre long seawall at Collaroy on Sydney's Northern Beaches. The seawall spans the ten properties bound by Stuart Street and Wetherill Street.
When the wall was finished, one of those property owners, Bob Orth, told the Northern Beaches Review the seawall should inspire others to do likewise.
"Once this is up it'll be a momentum for others to do it too," said Orth.
Less than a year after the wall was finished Orth's prediction is coming to pass.
In May, a Development Application was approved for the next ten properties stretching south of Stuart Street to Ramsay Street, and yesterday work began on the wall.
The new wall will be built by Horton Coastal Engineering, who also built the original wall, and it'll match its dimensions and appearance. The cost of the wall is to be shared between Federal Goverment (10%), State Government (10%), and land owners (80%).
The delay in getting this section of wall built was reportedly caused by getting all home owners to pay their share. If one owner didn't want to pay then the whole scheme couldn't continue. Since 2016, two properties have been sold and bought.
Though costly, a seawall would undoubtedly add to the property values. The beach in front will come and go, however the properties behind the seawall are now protected, catastrophic failure notwithstanding.
Above and below, the expected appearance of the beach after the seawall is built (Horton Coastal Engineering)
When finished, the engineers foresee a dune system establishing itself in front of the wall which they'll plant with coastal wattle, banksia, and native rosemary.
However, ongoing sand recycling from Narrabeen Lagoon and sand nourishment from suitable building sites are both "strongly supported".
See also:
The Wicked Problem of the Collaroy Seawall
Comments
yeah good luck. coupla 1/100 year storms (more like 1/every couple of years) and we're back to square one. !remindme a couple of years.
Jaspo. Hope all the engineers involved in this project have read the outstanding book “Waves and Beaches -The Powerful Dynamics of Sea & Coast” by Willard Bascom (1963, 1979 & Kim McCoy (2020)
One of the best if not the best book on coastal dynamics, well worth the read and readily available to buy from Patagonia or good bookshops.
did they reveal who would pay for the maintenance & repair ? same breakdown as the purchase?
Not sure. Tough work trying to wade through the molasses of paperwork.
thanks
"Once this is up it'll be a momentum for others to do it too,"
Yeah, no shit! Because now the problem just magnifies and shifts to the sections of the beach directly adjacent the wall.
Johnson. Spot on, we all know that so called ‘fixing’ a problem in one place just diverts the issue to somewhere else on the coast. We know the dynamics of coastal behaviour, it’s just a ‘cut & fill’ process , unfortunately interrupted by humans. How planners and engineers convince parties to part with enormous sums of money for this (and it WILL be temporary) is beyond comprehension. The East Australia current will just continue on its merry way doing its normal cyclical processes.
The only problem that exists at Collaroy is purely the proximity of dwellings to the nearby waterline, nothing else. Construction at or near the interface of the littoral zone is always fraught with danger. Haven’t we learnt anything? Revegetation to dunes, don’t get me started. I had a revegetation company for 30 years and we never, ever planted into dune systems. For the better part most dunes are mobile with only a few examples of immobile ones. Dunes are always in a state of flux depending upon what meteorological system is in action at the time.
Very interesting Mr Wallace. You seem to have the knowledge base and have walked the walk. If one wanted to restore the dune systems of Australian beaches to pre-marram, how would you advise them to go about it?
Go on - all the way up to Palmy and down to Freshie.
Noosa needs one too - preferably on the Bruce just before Caloundra...
I love this: "When finished, the engineers foresee a dune system establishing itself in front of the wall which they'll plant with coastal wattle, banksia, and native rosemary"
Absolutely no chance of that happening but I'm sure there is an artists impression of how it might look.
"When finished, the engineers foresee a dune system establishing itself in front of the wall which they'll plant with coastal wattle, banksia, and native rosemary."
Ha! Good luck with that.
"The engineers foresee" comment shows how little these peanuts know about the ocean or dunes!
As has been pointed out here before (by others) the effort put into that tiny bit of coast may have a lot to deal with how narrow it is (ocean to lake) and that major services (transport power sewer water etc) probably run along that skinny bit of land to service the population further north.
If that is true, it does explain, or perhaps even justifies the madness somewhat.
Anyone with knowledge of this care to comment?
Collaroy has quite a bit of land behind it and an escarpment from memory (Collaroy Plateau); but you're right, it gets skinnier up toward North Narrabeen - will the wall extend up there ? Its flooded a few times but a sea wall wont stop that since the water will come from the lagoon on the other side of Pittwater road you'd think. It'd be an absolute tragedy to lay yet more concrete any further up that stretch; but property rules.
I've heard that said before, and I don't really have the expertise to answer with conviction, however by my reckoning the road is behind the foredune and hence protected - it's the houses that are upon it and vulnerable.
Everything being equal, beaches find their own equilibrium, they don't keep retreating inland. So I think protection of public assets on the road are both an irrational fear, and a furphy used to justify this seawall.
Of course, rising sea levels, if they were to happen, could throw a spanner in those works.
I know this is a bit off topic but a mate of mine sent me footage of a groin and some big earthworks at the end of the main Sanur break! It’s very worrying what could come of that
Here is an article from Sydney Uni that states "Rising sea level does not mean the end of sandy beaches". The caveat being the beaches require space to retreat landward. Seawalls such as Collaroy and Wamberal interrupt that process - “As sea level rises, shoreline retreat must, and will, happen but beaches will survive. The biggest threat to the continued existence of beaches is coastal defence structures that limit their ability to migrate.”
https://www.sydney.edu.au/news-opinion/news/2020/10/28/rising-sea-level…
Poseidon: I'll see you and raise you
they could at least build them to become future A-frame slabs.
Poseidon Vs puny humans
Fabulous plan! (Aka, The Cane Toad solution.)
1. Plant Coastal Wattle etc.
2. Trap sand and form dunes unnaturally close to the water.
3. Establish steep beach faces which encourage backwash which erodes sand from the inshore area.
4. Form a wave power highway during storms along the disappearing beach towards the sides of the wall.
5. Plan another wall to protect the houses that are under threat from the mechanics of the existing wall.
6. See point 1.
How does the “expected appearance” image relate to the 5m high concrete tank trap that was built down the beach.?!
The local ratepayers will be paying for the sand to be taken from Narrabeen back down to replenish in front of the concrete every time there is a major storm so that they still have a public beach to walk on.
the headline had my internal monologue put on its best Australian drawl - "your farkkeeennn kiddinn"
I do hope Mr Wallace is pausing for thought (or gone or gone for a surf) as I’d love to hear some positive news about the future of our dunes. Maybe we could all have a little think on johnos question. I’m guessing it would have to be a gentle transition of weed eradication followed seeding in sections that would need carefull scheduling to the seasons.
I too would like to hear from Alfred!
If you leave it to me, it will be massed dune buggys and V8 4x4s tearing the dunes up Lord Humungous style combined with continual burns to eradicate the non-native dune species, huge blowout, lots of sand blowing offshore, lots of A frame barrels in landscapes of desolation
then the planting of the spinifex
however, you might be surprised to learn I'm not trained in the field
VJ. Reply is coming, looking after a sick one at present. You and i had a great discussion about 13th Beach dunes about two years ago, from memory it was good. Look forward to putting input into into this discussion. You’ve pleased me already, i think of saw the word Spinifex in your text, youve got my motor running.
Good stuff, I will await an informed answer!
In my wide ranging travels of Oz and reading about how it's landscapes, flora and fauna came to be, I discovered one spot relevant to the marram/non-marram subject that blew my mind. I sent the pic to Stu some years ago - perhaps you could work out a PM and I'll show you the lot of that location, never seen so perfect little waves, it's like I've seen paradise lost, and am keen to engineer paradise again (all Australian landscapes are man-made).
This shit is actual delusional. What a waste of time, money and, energy.
Feels that way doesn't it?
Yet yesterday I went and killed an hour or two reading the council DA, including online submissions supporting the wall. All of them were written by people with outside addresses (i.e not the land owners), and I got the sense that, while surfers and beach users understand hard barriers in the surf are foolish, it's still a niche insight. The greater population simply sees no problem with it.
All ocean pools & and man made wave pools get closed and drained annually for repairs due repeated wave action damage. How they gonna close the Pacific Ocean?
I think the greater population simply a) isn't aware of it b) too exhausted by daily shitfuckery or c) has a vested interest either financially or watching nervously from a similar position.
Lets face it humans really can turn back the tide. We have been doing it since we begun. Our engineering feats are incredible. If we really wanted to protect these properties we could. If we can tunnel a canal through Panama and built islands in months from nothing in the south china sea protecting the NB properties is a piece of piss. I think the collaroy thing is a just a case of oiling the squeaky wheel and keeping it as hush as possible and thus why its such a piss poor job. As SN have pointed out in previous articles this issue is only going to get more and more prominent - both coastal and riverine. e.g. Lismore and region currently in a deer headlight situation. There's going to become a point when we simply can't ignore it and we will want to know where the money is going. Meanwhile its make hay while the sun shine for a select greasy few.
pave paradise and put up a parking lot... F$ck wits
Such a poor decision.
It seems every generation makes mistakes. Then sometime in the near future, a massive legal case award costs for damages. Think asbestos, thalidomide and the catholic church.
The motivation of the litigants is not always money, it's usually to force change.
How to determine the value of a beach? A lost beach. By sqm? Width x length?
I see a future legal class action for loss of beach as a direct result of the sea wall.
At least we know split of the bill will be 80-10-10.
Still not seeing any issue with Narra's banks.
It does feel dirty having a wall constructed on a beach though, and I think that is where a lot of the hate comes from. Especially when it seems like it should be buyer-beware for the owners of property so close to the beach.
What is the backwash like at high tide - can you surf it ?
Collaroy had a longboard wave from memory - is that still working, same Q for South Narra - has the surf changed at all yet or too soon to know ? Might improve it ?
PS. Those walls really need some decent graffiti.
Collaroy is stuffed atm. The last few swells have dug a huge hole off the pool and there's hardly any sand in the beach corner.
The common sense of artificial reefs will never get past by any Council anywhere unfortunately.
As I wrote last year (link below with map):
I'm not entirely sure, but one of the reasons why an offshore reef structure hasn't been considered for Narrabeen may be because it's part of the Northern Sydney Protection Zone, hosting submarine cables that connect Australia to various parts of the Pacific (including Japan).
Amongst other things, it is illegal to "establish, maintain or use a spoil ground or other ocean disposal point (including dumping materials at sea)".
https://www.swellnet.com/comment/772908#comment-772908
I was advised in 1980's that only an offshore seawall would stop an ocean invasion (think Dutch Dykes)
https://dutchdikes.net/history/
The only difference beween the Dutch model & current planning is that wealthy Councils & beachfront landowners have some adhoc protection, rather than the majority of the community, the nation & future generations facing sea level rises, flooding, etc.
Some insight into the NSW Govt coastal protection program
https://www.environment.nsw.gov.au/topics/water/coasts/coastal-manageme…
review of NSW funding arrangements for Local Councils & residents at ri$k
https://www.environment.nsw.gov.au/research-and-publications/publicatio…
Fact: 50% of engineers graduate in the bottom half of their class. Obviously found them for this project.
The engineering school motto was "51% wasted effort, 49% wasted year."
I was living on Stuart St when the storm hit in 2016.
From memory there's a study somewhere done around 2018 for the Council where the conclusion was basically... that's a pretty important road there and there's a bunch of services etc along that alignment so that alignment is probably worth protecting... might as well get a wall in there. There's already a sectoin to the south. Of course, this means the erosion will be made worse to the north, and so the argument for extending the walls north gets strong....etc.....
This approach means the landowners have to pay for it. Though it remains to be seen how the maintenance and repairs costs (including for the beach, not just the wall) are distributed. I hope it's built into the land title and comes out of their rates. Would need to ensure it's enough though. Perhaps if they levy those properties via rates, building a fund to pay for "unexpected" costs, with something like "coastal protection levy" of $10k on your bi-annual rates notice. 12 ratepayers x $20k/yr for 5 years is a good chunk of coin. Some might baulk but then again the to kind of people that can afford to buy here (especially since 2016!) that might be worth it.
In addition to broader public ignorance or apathy about these things, another reason as to why these things get through that's often missed is planning law has historically been unsupportive of DA refusal. Meaning either the Council might want to refuse but there's no point because the applicant will just take them to court and win, and then the Court grants approval. Or, if the Council are dodgy, better regs would allow community groups to take the Council to court to have the approval decision overturned.
Good point about the DA refusal. 100% agree.
Hard to believe this is going ahead! This will lead to nothing but disaster. Seawalls will continue to result in the beach downstream of them being completely eroded, as the first collaroy seawall has proven. Extending the seawall will only result in more aggressive downstream scour, which will then start impacting Narrabeen beaches. The best solutions here are sand renourishment (eg Noosa & Snapper) or Groynes (Apollo Bay, Kirra, Point Lonsdale). Groynes dont look as good, but are a cost effective long term solution, and will bring back sand to not only protect the beach but also create waves. We have been fighting this battle at Pt Lonsdale for a few years now and can put you in touch with experts to advise if required. Seawalls are NOT the answer!