Clearing the channels with Bruce McLachlan

Stu Nettle
Swellnet Dispatch

In 2018, following two years of drought, the entrance to Brisbane Water on the NSW Central Coast began to silt up. Without flooding rain the boat channel narrowed to the point of being dangerous for ferries and recreational boats. Residents complained to council and NSW Maritime to dredge the channel; remove the sand accumulated between Umina and the eastern shoreline.

That sand, however, forms the basis to Box Head, one of the best waves on the Central Coast and one of the longest in Australia.

Bruce McLachlan, an independent Councillor from The Entrance, saw the dredging plans and was concerned the dredging would ruin The Box. So McLachlan injected himself into the debate, which at time was rife with party politics, cutting through the partisan charade with amendments focussed squarely on protection of the wave.

“In my amendments I wanted them to consider where they were going to put the spoil," McLachlan said to Coast Community News in July 2018. Part of the bank would have to be dredged, but rather than lose the sand altogether, McLachlan wanted it placed on the bank but further down the line.

“My amendments were about consideration and enhancement of the surf break at The Box."

Using the same rationale, McLachlan then broadened his scope across the whole council area, "I just want the surf break to be a consideration in all our future plans, whether it is rock groynes, or even artificial reefs and enhancements of what we have got. We build all sorts of other sporting arenas and I think surf breaks are our sleeping giants."

“It is a natural resource that we don’t want to muck up.”

The Entrance channel almost silted shut

Much of McLachlan's focus since then has been to train the channel at The Entrance, a tidal channel which connects three lakes - Tuggerah, Budgewoi, and Lake Munmorah - to the sea. Much like the opening to Brisbane Water, the Entrance channel has almost silted up and since 2017 a dredge has been clearing channels on the inland side of the spit.

For guidance, McLachlan looks at projects of similar size. Both Lake Illawarra and Wallis Lake (Forster, Tuncurry) are of similar size and both have training walls that provide safe transit of recreational craft, plus surfing options nearby.

Lake Illawarra entrance before the breakwalls were finished, above, and the photo below shows the channel as it is now

More recently, McLachlan has observed the erosion at Wamberal and insisted Central Coast Council look to the coastal works of the Gold Coast for assistance. At a council meeting last night, McLachlan moved a motion that council, amongst other things, noted the artifical reef at Narrowneck, which has helped widen the beach at the northern end of the Gold Coast, plus the recent Palm Beach artifical reef, installed to do the same thing. Theoretically, a Multi-Purpose Reef constructed off Wamberal could do the same thing, while also potentially creating a new surfing reef.

Also included in the motion was a movement for Central Coast Council to recognise the amenity provided by coastal works in Queensland, plus liase with Gold Coast City Council on their coastal works and share those findings with "relevant State and Federal agencies".

The last point is to enable the opportunity to seek funding for grants.

The wheels of bureaucracy turn painfully slow, and with a new Coastal Management Plan due in 2021, McLachlan is patiently getting his ducks in a row. Council can't go it alone, they'll need funding.

"The main aim of the Notice of Motion," McLachlan told Swellnet, "is to get the concept into the Coastal Management Plan, so they are then eligible for NSW grants funding. If they are not voted to go into the mix, then council can’t apply for grants."

For years, surfers have been outside the decision-making processes that effect the coast, when arguably we're the ones with most at stake. Fortunately, people like Councillor Bruce McLachlan are now inside the tent and making decisions on behalf of surfers.

Comments

savanova's picture
savanova's picture
savanova commented Tuesday, 11 Aug 2020 at 2:27pm

Training walls arnt the answer. The RMS have recently deposited over 7000 ton of rock to TEMPORARILY stabilise Windang bridge from collapsing due to erosion. The Tidal flow from lake through the narrowed channel resembles the snowy hydro outlet after rain and a big tide and is causing severe erosion and only dumps the sand at the end of the sea walls. Narooma entrance has training walls and is one of the top 5 most dangerous entrances in Australia, with 3 ft of swell and an outgoing tide the dang aint much safer.

the_b's picture
the_b's picture
the_b commented Tuesday, 11 Aug 2020 at 2:44pm

Very different lake to Wallis Lake which is a lot deeper and can accomodate that trained entrance. Spend 30Mill or more on training walls at Tuggerah Lake and you'd still need to dredge periodically, max depth is currently only 2m.

savanova's picture
savanova's picture
savanova commented Tuesday, 11 Aug 2020 at 2:54pm

Best bang for buck would be east coast councils shot in an by a dredge between em selves, take turns to clear their own entrances and replenish their own beaches. Gotta be more cost effective then buying back multi million dollar real estate and building sea walls.

science's picture
science's picture
science commented Tuesday, 11 Aug 2020 at 3:50pm

Would the construction of breakwalls in The Entrance channel disrupt the South-to-North flow of sand, resulting in a Stockton-like scenario?

the_b's picture
the_b's picture
the_b commented Tuesday, 11 Aug 2020 at 4:48pm

It's reefy and rocky shoreline to the south, only a pocket beach just south of the entrance where Council constructed a groyne to trap sand at that beach (the beach used to wash away in big storms). No real sand transport from south of the entrance

science's picture
science's picture
science commented Tuesday, 11 Aug 2020 at 5:39pm

Fair point however the more I think about it Newy is not dissimilar: for eg south of the Enny channel you have rocks pretty much until Bluey and Toowoon, with the next significant open beach being North Shelly/Shelly then a lot more rocks, whereas south of Newy harbour you have Nobbys (artifical), rocks until Newy beach, more rocks until the next open beach Bar/Merewether stretch.
The scale's a bit off but each have a long sand catchment to the north (Stockon and North Entrance) with rocky points to the south

shoredump's picture
shoredump's picture
shoredump commented Tuesday, 11 Aug 2020 at 5:47pm

Sand movement is North to South at the channel

science's picture
science's picture
science commented Tuesday, 11 Aug 2020 at 6:12pm

I thought sand movement was governed by the prevailing swell direction i.e. south

I am making this up as I go though, not being in coastal management. Flying on the wings of intuition

shoredump's picture
shoredump's picture
shoredump commented Tuesday, 11 Aug 2020 at 7:06pm

Yeah, that makes all the sense in the world and is exactly what I thought. Only going off what a good friend tells me, who has lived 40 years of his life 3rd building from the opening. Keen fisherman / surfer

science's picture
science's picture
science commented Tuesday, 11 Aug 2020 at 7:18pm

might be something with bathymetry, swirling of currents or something weird kind of like how cold upwelling occurs via apposing forces. idk good luck to em, i live in newy now

the_b's picture
the_b's picture
the_b commented Tuesday, 11 Aug 2020 at 7:44pm

North to south because the enny channel is a sand sink

Nick Bone's picture
Nick Bone's picture
Nick Bone commented Tuesday, 11 Aug 2020 at 5:46pm

Excuse the ignorance i.e lack of knowledge but I cant make sense of the 1st image against Google earth?

D2-E0-F91-C-C0-FC-4-FE9-AD96-41-DCB4-C4-F866
29-D63-A20-DE75-4835-B5-E1-57-E1878-D7-B9-B

Am I just in the wrong sort or...? Uncertainsweatdrop emoji

I am the bone

Westofthelake's picture
Westofthelake's picture
Westofthelake commented Tuesday, 11 Aug 2020 at 6:41pm

Nicko, like Thingo says, they're 2 different locales entirely.
I remember getting mixed up when people mentioned The Entrance, I'd always think, the entrance to what?... I do have a bit of connection to the place though. Spent many hours exploring the coast in my pre-surf youth youth days when I used to regularly visit my grandparents who lived on the other side of Ocean Parade opposite the Pools. Magic little gem of a place.

Thingo's picture
Thingo's picture
Thingo commented Tuesday, 11 Aug 2020 at 6:13pm

The photo is from further up the coast at The Entrance.

Mac Snaps's picture
Mac Snaps's picture
Mac Snaps commented Tuesday, 11 Aug 2020 at 7:07pm

I live at The Entrance, the council are idiots.

Personally i would like to see a similar approach to what was taken over at Mandurah with the Dawesville Cut, that will never happen though.

Distracted's picture
Distracted's picture
Distracted commented Tuesday, 11 Aug 2020 at 7:56pm

There is already beach erosion at North Entrance so even if there is a localised south eddy there would be a risk that the walls may increase beach erosion to the north.

groovie's picture
groovie's picture
groovie commented Wednesday, 12 Aug 2020 at 6:27am

Wallis lake used to be dredged up until Premier Bob Carr shut down the dredges in 1996 due to fish habitats being destroyed. The large East nor East facing bay in front of the lake now suffers from a lack of sand which has compromised several surfing breaks, with one premier surfing break disappearing ( The infamous Bar) altogether! Without the dredges running the lake system is predicted to totally silt up within 100 years therefore destroying most of the marine life in the lake system. We also have a dune care group who are stabilizing the dune systems which has also had an adverse impact upon sand flow on local beaches. Maybe the answer is a sand pump similar to the Gold Coast model to replenish the sand on the beaches & prevent the lake system from totally silting up.

stunet's picture
stunet's picture
stunet commented Wednesday, 12 Aug 2020 at 7:45am

I know how the Bar has disappeared but the claim it's linked to dredging appears counter-intuitive. Wouldn't an undredged lake provide more sand for the Bar?

When it's dredged the channels are deeper, and sand that would otherwise end up on the bar through tidal movements, gets taken out of the system altogether.

the_b's picture
the_b's picture
the_b commented Wednesday, 12 Aug 2020 at 3:11pm

Maybe the dredge spoil was dumped outside, hence feeding sand to said breaks at the time

Distracted's picture
Distracted's picture
Distracted commented Wednesday, 12 Aug 2020 at 6:08pm

There has been dredging in Wallis Lake several times since 96. One of the issues with dredging though is the silt impacts the oysters, whatever is done there are always winners and losers.
The issue with breakwalls keeping the entrances open is that there is a net inflow of marine sand as discussed in the Littoral drift thread which then builds up and needs dredging to maintain navigation.

cd's picture
cd's picture
cd commented Wednesday, 12 Aug 2020 at 5:36pm

There was some modifications made to the training wall on the Forster side ( approx 2004/5). Including a small extension. Although only minor alterations were made in my opinion, the deposition of sand has since been affected.

heals's picture
heals's picture
heals commented Wednesday, 12 Aug 2020 at 8:31am

FWIW Bruce has also been suggesting solutions other than training walls. Sand bypass being one of them. Being a proud Central Coaster he sees the natural environment being mismanaged and is pointing to success stories elsewhere in the belief it can be done there too.

Justonemore's picture
Justonemore's picture
Justonemore commented Wednesday, 12 Aug 2020 at 10:48am

I agree with Sav coastal councils should communicate with each other on silting of ocean entrances for what works with similar situations .

t-diddy's picture
t-diddy's picture
t-diddy commented Wednesday, 12 Aug 2020 at 2:20pm

Humanities coastal interventions rarely go as planned (or any other environmental intervention for that matter)

theblacksheep's picture
theblacksheep's picture
theblacksheep commented Wednesday, 12 Aug 2020 at 3:47pm

Far better to follow the wise Northern beaches council and pour the money into an expensive scultputre as a memorial of COVID (the old version, not the current outbreak which is pending a 2nd memorial), maybe even stick it in the middle of the entrance to block annoying waterflow and create more sand for the local retirees to socially distance on, thereby killing two birds with one statue.
Fuck I'm running for council....

cd's picture
cd's picture
cd commented Wednesday, 12 Aug 2020 at 5:47pm

Will be interesting to see how the beach immediately to the north of the Lake Illawarra breakwalls will be regarding erosion in the future.

tango's picture
tango's picture
tango commented Wednesday, 12 Aug 2020 at 5:57pm

What a can of worms.

It's great that the councillor is looking to have surf quality considered as part of the process, as it has all too often been neglected. There's been some progress, particularly on the gold coast and it's also been helped along by the economic value work done by a range of people like Neil Lazarow and Dan Ware among others.

I think there's a great need to hurry slowly with any proposals to train estuary entrances, though. I can't think of a single one in Australia which has had benefits across environment, society and economy though. I certainly can't think of one river entrance in the lee of a headland which has been trained and resulted in better surf - the only one I can think of with good waves is Rodiles in Spain and for all I know it might have been another Mundaka before the walls. There are always impacts and they often create more trouble than they're worth.

By the way, Justonemore, there are existing arrangements for experts and managers to discuss these kind of issues and share info. There are professional development activities for all sorts of professionals focussed directly at estuary entrance issues, such as the Engineers Australia event last year. There are also a whole range of formal processes which would accompany a proposal of this kind.

It's not clear why the Cr would want the sand dumped down the line, either, as usually the sand moves down the bank and so all it would do is extend the bank shoreward - and if nature provided conditions for that to happen it would have been in place already.

If the right studies aren't done, there's also a significant risk that the Box could get wrecked rather than enhanced. The 2010 estuary dredging study identifies the issue of entrance access as a problem but it doesn't seem like the 2012 Mgt Plan covered the nearshore sand deposits from the figures in it.

Groper's picture
Groper's picture
Groper commented Wednesday, 12 Aug 2020 at 7:12pm

Shark Alley @ The Box has been previously dredged with the spoil being deposited on Ettalong Beach. The sand would then slowly work its way back out. The Box is a dynamic wave and was never ruined by this process. The only things that have ruined The Box are an incoming tide (spaghetti arms) and the presence of Nat Young.

Lanky Dean's picture
Lanky Dean's picture
Lanky Dean commented Wednesday, 12 Aug 2020 at 10:30pm

Mark Warren?

Groper's picture
Groper's picture
Groper commented Thursday, 13 Aug 2020 at 5:25am

Surfing atlas???

bbbird's picture
bbbird's picture
bbbird commented Wednesday, 12 Aug 2020 at 10:31pm

RMS; NSW Maritime is responsible for the harbours, estuaries, rivers & these projects;
https://www.rms.nsw.gov.au/maritime/projects/index.html

* project Ettalong Channel (the Box); description: In 2017 and 2018, emergency navigational dredging by State government (over $1 million... of your taxes) to improve boating access . ferry operations.

* project: The Entrance Rock Groyne . Channel Dredging
project description: Construct 100m long rock groyne and dredge 7,000 cum sand

Title to the bed of all other tidal waters (unless the subject of a Crown grant) is vested in the Crown, i.e. 'The State of NSW', under the control of Crown Lands on behalf of the Minister Administering the Crown Lands Act 1989.
https://rg-guidelines.nswlrs.com.au/deposited_plans/natural_boundaries/t...

The “time to act is now”, as stated in the 2009 House of Representatives Inquiry on managing our coastal zone in a changing climate. Sea level will continue to rise well into the future and coastal recession will become more prevalent,... Proff. Bruce Thom
https://theconversation.com/who-owns-the-beach-when-the-sea-is-rising-24767

bbbird

zawl's picture
zawl's picture
zawl commented Friday, 14 Aug 2020 at 6:12am

There is also these obstacles in the channel

https://www.youtube.com/watch?v=I_BkW0nxxtE

marcus's picture
marcus's picture
marcus commented Friday, 14 Aug 2020 at 11:30am

stockton needs an artificial reef / and or bombora
Stockton has never had (in many recent years) anything but closeouts.

here is a chance to make a world class wave in newcastle. something that is lacking in the area.

you could even have a deep water big wave bombora out the back with easy harbour access

if they built a reef and it was done properly you would have sand build up on the lee side of the reef. just like nobies spit.

i remember the internet when it was just for intelligent people but.

Stupitt's picture
Stupitt's picture
Stupitt commented Saturday, 15 Aug 2020 at 9:07am

Always fucken with nature. Tear the damns down upstream.

stunet's picture
stunet's picture
stunet commented Monday, 17 Aug 2020 at 8:30am

Last week, Central Coast Council voted to consider Bruce McLachlan's suggestions - RE beach erosoion - for their forthcoming Coastal Management Plan. While it may not sound like much, this allows the NSW State govt to consider grant applications from the Council.

Ben Hiron's picture
Ben Hiron's picture
Ben Hiron commented Monday, 17 Aug 2020 at 2:46pm

I wonder what the result of a breakwall on the brisbane water opening would be? how about a wall between the north end of ocean beach and the current takeoff zone at box head, where the far channel mark sits? The wall could reinforce a channel between tlopbster beach and the breakwall. Such a wall may encourage a left hand superbank type arrangement for ocean beach at Umina?
With an optimistic vision, I would expect that the bank would fill in against the wall and provide a long left hand bank which would likley continue to be a killer wave.
Pros and cons would be that you could now walk out to the take off spot via the breakwall, so acces sto teh break would be easier, but that would mean more crowds.... It would likely solve the marine access issue and support surfing amenity.

Ben Hiron's picture
Ben Hiron's picture
Ben Hiron commented Monday, 17 Aug 2020 at 2:53pm

Are there any other examples of a navigable entrance on the north end of an east facing beach on the Australian coast? Have any of these had a breakwall installed and what has been the results?
Are there any other similar setups anywhere else in the world?

bruce.mclachlan's picture
bruce.mclachlan's picture
bruce.mclachlan commented Tuesday, 18 Aug 2020 at 7:05pm

Thanks Stu for editorial coverage. Its a complex issue, and requires coastal engineers, but sometimes new ways have to be trialed. Thankfully Public Works engineers did take into consideration the surf break at the Box in their dredge plans, dumped the spoil at the back and allowed the natural wave action to nourish the beach. Good to see the surf break a consideration in infrastructure design works.

Wamberal is one of NSW erosion hotspots, and could possibly benefit from a Palm Beach or Narrowneck reef to help dissapate storm wave energy and help sand accretion. If a new quality reef break / dive spot was created by a multi facet approach to beach erosion control, as opposed to the single approach of a buried revetment wall then that would be welcomed by the local surf community.

Tuggerah Lakes and The Entrance Channel have been deteriorating for decades, with major siltation, water quality and flooding issues from urbanization, and it now requires man made intervention to assist revitalization efforts.. The shallow channel entry will still require regular dredging for flood mitigation, however according to one of Australia's leading coastal engineers Angus Jackson, increased scouring and therefore maintaining a longer opening period, and improved sea water exchange rate, could be assisted cost effectively with geo bag trial walls, similar to Noosa and Maroochydore, as opposed to major rock training walls. Sand build up in the Channel is from reportedly from Northeasters washing it back it, and to maintain flood mitigation will still require ongoing dredging, but could be at lesser intervals if managed.

When flood events do open the The Entrance Channel, it produces an amazing river mouth wave, at North Entrance and with some correct placement of dredge sand, this natural occurring wave could be recreated, by placing the spoil further into the break rather than dumping it on the sand berm and building up the sand barrier, as has been done in the past. Allow the natural wave action to nourish the receding North Entrance beach. Locals will recall the amazing waves in the mid 80s following a flood event, and that sand bar remained for a number of years. Why not emulate nature and make a permanent Super Bank like Kirra ?

Appreciate any coastal design concept must be done by qualified coastal engineers, however sometimes new concepts need to be trialed, rather than just procrastinate a or continue down the same old path that has proven in effective over past decades.

Surfing is one of Australia's most popular and successful international sports, and we put major investment into mega stadiums. Maybe its time to look at infrastructure spend on surfing, as we do other sports, and start building it into our future coastal management plans.

If sea levels rise, then urbanized areas will see more coastal management works, so this may well be the chance for the surfing community to gain enhanced surf breaks, just like at they have at the recently completed Palm Beach reef Gold Coast.

heals's picture
heals's picture
heals commented Wednesday, 19 Aug 2020 at 10:57am

That was a thorough assessment of the problems on the Central Coast and a prudent approach to fixing them. You won't get far in politics with an approach like that!

DjML's picture
DjML's picture
DjML commented Wednesday, 19 Aug 2020 at 4:09am

IMG_7555.jpg