Two people drown in Wollangambe 1 (Mt Wilson)

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DaveJones
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Two people drown in Wollangambe 1 (Mt Wilson)

Post by DaveJones » 03 Jan 2021, 12:10

Still ongoing, they have not found them yet.
two women missing in the Wollangambe:
https://www.abc.net.au/news/2021-01-03/ ... N31Wwi941w

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Re: Two people drown in Wollangambe 1 (Mt Wilson)

Post by DaveJones » 03 Jan 2021, 13:02


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Re: Two people drown in Wollangambe 1 (Mt Wilson)

Post by DaveJones » 03 Jan 2021, 14:42

One of the victims was a local police officer from Lithgow station.
https://www.abc.net.au/news/2021-01-03/ ... s/13028364

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Re: Two people drown in Wollangambe 1 (Mt Wilson)

Post by T2 » 03 Jan 2021, 14:44

Yes, an extremely tragic outcome.

There are lots of questions that many people have about this accident, but I think it's best to let the dust settle before speculating.

The facts, as we know them, are that this was a trip run by a reputable bushwalking club. It was led by a very experienced leader. It was a simple lilo trip down Wollangambe One.

Knowing the club involved, I am sure they will provide further details when the time is right. I imagine the leader, and the rest of the group, are still in shock. This would have been an incredibly traumatic experience for all of them, and we need to give them time to heal and process what has happened before pushing for more information.

NPWS has closed Wollangambe One until further notice, in response to what they describe as a "dangerous whirlpool" that has formed mid-way through the canyon following recent rain. They have also issued a general safety alert regarding canyon water levels across the Blue Mountains.

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Re: Two people drown in Wollangambe 1 (Mt Wilson)

Post by Skinner » 03 Jan 2021, 15:03

thanks for the updates. Wollangambe is a beginner trip, but most of use have seen it can get pretty dangerous as it has such a large catchment. Well done to the police divers, that would have been pretty difficult. I feel for the group and especially the leader. It is easy to speculate but not that helpful.

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Re: Two people drown in Wollangambe 1 (Mt Wilson)

Post by DaveJones » 03 Jan 2021, 19:17

Thanks Tim
So glad that NPWS closed the canyon and provided a quick update. I was afraid that other groups would still go in there unaware given how popular the canyon is.

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Re: Two people drown in Wollangambe 1 (Mt Wilson)

Post by T2 » 07 Jan 2021, 12:35

The Blue Mountains Gazette has published the following article which provides a good summary of the accident.

Canyoning tragedy in Mt Wilson
B.C Lewis
https://www.bluemountainsgazette.com.au ... mt-wilson/

A social event with a local bushwalking club went horribly wrong on Saturday (January 2) when two women were sucked under a vortex in a canyon in Mount Wilson and died soon after.
The bodies of the two women, aged 24 and 39, were recovered by police divers a full day later a few metres down the river from where they went under. They had been swept into an unusual whirlpool in the Wollangambe Canyon and disappeared.
The 39-year-old was confirmed as serving NSW Police officer, Senior Constable Kelly Foster, from Lithgow station. The other woman is a 24-year-old international student from Chiswick. As of Monday her name had not been publicly released and police are waiting for confirmation that family members in China had been notified.
Initial reports from witnesses indicate the younger woman was tipped off her inflatable lilo and swept into a three-four metre deep whirlpool; Snr Cst Foster was swept into the underwater hole when she attempted to rescue her.
The pair was with eight others on a social trip with an established Mountains bushwalking club when they disappeared. Other members of the group were uninjured and some had already successfully navigated that part of the canyon - about a third of the way in from the start.
Two members of the group made the steep 90 minute climb from the river to get mobile phone reception, while attempts were made to retrieve them with a short length of rope. The emergency call went out at about 2.30pm.
Blue Mountains Police Rescue Sergeant Dallas Atkinson, who helped recover the bodies, said "in the context of Blue Mountains canyons it's an extremely unusual event", one he had not seen in 14 years working in the rescue area.
"It could have happened to anybody," he said. "It was an unfortunate tragedy."
"Despite some rain, the water levels were not unusually high, maybe slightly above normal. It wasn't running dirty and the rest of the canyon was normal."
Sgt Atkinson likened the force of the event to pulling an 800mm plug from one end of a 25 metre pool.
"In the very recent past, something's changed in that particular section of the canyon that's caused the bulk of the water volume to go underneath the rocks. As a result other ordinary flow points have stopped flowing. You don't see it virtually ever, but there's always the potential. You put moving water [and moving debris] through a space, it's got to go somewhere."
National Parks has closed the canyon to the public and are examining the site.
A spokesperson for the NSW National Parks and Wildlife Service (NPWS) said they had "closed Wollangambe One Canyon, effective immediately".
"Signage and barriers have been erected at major entry points to this area of the river and the closure has been notified on the NPWS website.
"While we understand this is an extremely popular canyoning location, we are asking the canyoning community to comply with the closure until further notice.
"NPWS will consider its options for managing the site into the future, including seeking available independent, expert advice."
The Wollangambe canyon has a large catchment area with many tributaries and the volume of water through Wollangambe River, unlike smaller slot canyons is considerable. Wollangambe One is classified as an introductory canyon and one often frequented by children.
But Sgt Atkinson stressed that "canyoning does have risks and canyons' behaviour is unpredictable."
During the recovery operation, Sgt Atkinson said the behaviour of the whirlpool was changing frequently.
Blue Mountains Police, Police Rescue and divers, NSW Ambulance and the Rural Fire Service assisted in the rescue. Due to poor weather conditions, the search was suspended about 6pm Saturday but recommenced Sunday.
Blue Mountains Police Chief Inspector Peter Scheinflug told media: "It's true traditions of the NSW Police that it's service above self and it's a common line we're quite often first responders [who] run towards danger as other people run from it."
NSW Police Acting Commissioner Mal Lanyon extended his condolences to the Foster family on behalf of NSW Police.
"It's a very sad time for the NSW Police Force and Kelly's death is a loss to the whole community," Acting Commissioner Lanyon said.
"To hear reports that Kelly was trying to help another woman when she died demonstrates her commitment to the community she served and the ability to put the needs of others before her own.
"Kelly was a highly regarded and dedicated officer who will be sorely missed by colleagues across the force. Police said "the family and friends of both women have requested privacy at this time".
Police Minister David Elliot said the officer had "sadly lost her life coming to the aid of another, a truly heroic act that will never be forgotten".
A report is being prepared for the Coroner which will also look into the heights of the water, water flow and causation.

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Re: Two people drown in Wollangambe 1 (Mt Wilson)

Post by T2 » 07 Jan 2021, 13:16

I’ve given this a few days, because this tragedy is still very raw and hard for a lot of us to process.

In that time there has been some very good, very respectful discussion among canyoners on social media and elsewhere. I wanted to bring together some of the key points to help people better understand what has occurred.

Where the accident occurred:

The accident occurred about a third of the way down Wollangambe 1 (Upper Tourist Section). This is a popular liloing trip. There are thousands — if not tens of thousands — of people who safely descend this section of the Wollangambe River each year. Most people would consider it a beginner friendly trip.

The exact location is marked here: https://goo.gl/maps/ZC8XA4sbmTAvHux67

The accident occurred at a point where a pool ends with a boulder section. The river drops under these boulders to a lower section of the river. This is a point where people dismount from their lilos / floatation and walk down to the next pool.

The below photo shows the location of the accident, with the “whirlpool” circled.

syphon2.jpg
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The hydraulic feature involved:

While media reports talked about a “whirlpool”, the technical name for the feature involved is a syphon.

A syphon occurs where the water flows under / through obstacles. In more aquatic canyons, they are considered one of the more dangerous water hazards. Syphons are not always visible and can be fully submerged. Narrow siphons are dangerous because they funnel the water, rapidly increasing its speed. Because Blue Mountains canyons generally have low water flows, we usually see minor features where the water disappears underground, but rarely features capable of causing harm to people.

Some good information about syphons (and other aquatic canyon features) is available here: https://canyonmag.net/technical/safety/ ... y/#Siphons

Other people report seeing this syphon in low water levels as far back as February 2020. In those conditions it did not appear concerning, and was simply a hole that the river drained into. The hydrology of this feature may have been altered by the large rain event in February 2020 that followed last summer’s bushfires, bringing large quantities of ash, soil, and debris into the canyon. It may also have been influenced by recent rain.

The following photo shows the syphon in low water. Below that is a video of the same feature, again showing it in low flow.

syphon-low-water.jpg
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Conditions on the day of the accident:

While there had been recent rain, other groups had been down the Wollangambe the day before and reported water levels being only slightly elevated.

On the day of the accident the river was running clear (not dirty, as it does following heavy rain).

The below video shows the syphon the day after the accident. While the water level in the pool is higher than normal — perhaps 30 or 40 cms — the flow of water does not appear to be much above normal. The syphon also appears very benign and many people would not even notice it.



The day after the accident the syphon was observed fluctuating in power quite a lot. Some have speculated that something may be happening underground that is causing the water flow to vary, changing the intensity / strength of the syphon.

Things to consider:

A syphon works a lot like the plug hole in your bath or sink. When water levels are higher, it can be very difficult to see the water draining. The classic whirlpool effect often only occurs once the water level gets lower. In the same way, in certain water levels it can be extremely difficult or even impossible to identify a dangerous syphon because nothing is visible on the surface.

The last 12 months have seen major bushfires followed by periods of intense rain. This combination can result in significant changes to canyon hydrology. New, unseen risks may be present. For Blue Mountains canyoners, who are generally not experienced with flowing water canyons, these hydrological features may not be obvious. When canyoning this summer, it is important to be extra cautious about these potential changes.

Next steps:

The accident is being investigated by NSW Police, and a report will be provided to the coroner. Depending on this process, there may also be a Coronial Inquest at some future point.

Blue Mountains Police have requested anyone with further information, including footage of the hydraulic feature involved at any time prior to the accident, to get in touch. This will assist with their investigation.

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Re: Two people drown in Wollangambe 1 (Mt Wilson)

Post by T2 » 07 Jan 2021, 15:52

@DaveJones I've edited the subject from your original post. I hope that's okay. I just want to ensure it's easy to find going forward, especially as there are likely to be further posts following the Police investigation, etc.

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