What would really be cool would be to have the 3d geometry of the river, and run it through water simulation software ; put a rag-doll in and see how the current would pull you down.
Constructing the 3d geometry is probably an interesting engineering challenge. Although there exists some off the shelf underwater lidar solutions https://www.youtube.com/watch?v=YevvMcc6Zu4 and underwater drones, it's likely to be too turbulent (and with air bubble) for them to stay in place at a known position to work properly out of the box (but maybe not because it seems to be possible to scuba dive the strid https://www.youtube.com/watch?v=kUamSryCUK4).
(referencing Ken Liu's Dandelion Dynasty, which I just finished. Liu is the American translator for Liu Cixin's Three Body Problem, which has been discussed on HN, so other HN readers might be interested to learn that he also has his own fiction)
Anyone know differently?
EDIT: More at https://www.youtube.com/watch?v=kUamSryCUK4, but sadly without progess as reported at https://www.youtube.com/watch?v=wDskXBfyNes#t=179.
So as if an elephant were pulling you down beneath the water and you only had your strength to grip against it. Can’t be done.
<s>I looked but was not able to find CFM/CMM for the input and output</s>; but that would give a reasonable idea of what the volume of the canyon must be because what goes in must come out. So the volume of the flow at the outlet and inlet gives a very good idea of just how crazy it can be.
In an incompressible flow (e.g. water under anything resembling normal circumstances), there is no net flow into or out of any given volume, i.e. a 3-D box or other shape. But the surface is 2-D! So you can look at a little box with its top at the surface and its bottom slightly below the surface. If there is downward flow out the bottom (and zero flow out the top, of course), there must be net inward flow in the sides. Nothing wrong with that.
This could happen if the river has constant speed and constant cross-sectional area everywhere but gets progressively narrower and deeper. The water moves inward because it has to get away from the encroaching banks and moves down to fill the deepening channel. If this is abrupt enough even in the absence of turbulence, the downward current a foot or so below the surface will be substantial.
Loads of fatalities in turbulent water occur because the victim rapidly becomes unconscious in the water.
It's an underground tunnel with a small exposed strip at the top.
the water can be circulating around the tunnel, flowing back and forth under the rocks. It can be pulling sideways or down at the exposed strip with the water circulating back up in the underground areas out at the sides.
Under the water is turbulence that just traps a person and keeps them tumbling underwater.
In addition the article points out that there are numerous rock outcroppings underwater against which an unfortunate person's head would likely get bashed, reducing or eliminating consciousness.
I also notice that the water is quite frothy and full of air bubbles. This reduces it's net density and thus reduces the buoyancy available to any objects that would otherwise float. It can be enough to sink ships .
So, basically, the turbulent water will pull you under, bash you hard against the rocks, give you less-than-normal buoyancy, and hold you under. It's kind of a toss-up whether you lose consciousness first from the head injuries or the lack of air, and after a few minutes of that, you're dead. Have a nice afterlife
There's a few spots near me that are well known danger spots for kayakers due to this phenomenon.
> The Strid (grade 5-) is a long thin section of river where the Wharfe narrows to 5-6 feet in places. The main problems are beneath surface in form of ledges which if you're swept under - you can forget it! At a higher level as seen in pictures, it's runnable. The pictures show med-high water and most of the ledges were covered. I'd have graded it at 5- this day. At lower levels it runs at class 5+ and many would portage, the ledges that trap you need divers to get to you and even good safety cover would be of little use in an entrapment situation. (2 tourists fell in at the Strid last year and one didn't emerge for nearly a week)
Portage in this context means get out and carry your kayak past it. From https://www.ukriversguidebook.co.uk/rivers/england/north-eas...
You're not coming out alive.
> The reason for the dangerous network of caves is just further up above the mouth of the Bolton Strid the river flows 30ft wide and a lot easier giving a more idyllic, romantic and tranquil flow before being disrupted by a geological formation that abruptly funnels hundreds of gallons of water through a tiny six-foot channel.
So, the surface appears tranquil, but under the surface is a swift turbulent undercurrent.
Looks absolutely brutal.
Of course, there also might not be a sign, sometimes it comes down to “don’t do stupid crap”. Again, on you.
Regardless, seems like never a more suitable description could be made.
That water is not fathomable, literally.
As an American it's always startling to casually see a date that far back in history, and know a specific event such as the death of a child was recorded, and has been remembered for nearly a thousand years.
We get passed on the highway when we're doing 120km/h. I don't imagine you can maintain those kinds of speeds on account of speed limits and winding roads. Possibly takes an hour or three?
You can guess where I live.
My European relatives can't even believe it when I tell them. They think driving that long is some superhuman ability.
I'm quite content listening to my history podcast for 10 hours.
Either visiting family in Cornwall (400 mile, 12 hour trip when we were young kids before the roads were improved, 8 hours when we were older) or camping holidays in France (usually two weeks.)
There are videos of people swimming it (not deliberately: it's a rapids, and they've fallen out of boats).
> To save a click: the "100% mortality" thing is a local legend.
Middlebrow dismissal, given that there's no proof that it's not 100% and obviously there's no way to prove that it is. It's very easy to imagine a design that would kill 100% of swimmers, it would actually be surprising if there isn't somewhere in the world that would do it.
3:20 of this video shows a well-prepared kayaker w/ a ton of PPE get quite the experience. https://www.youtube.com/watch?v=MkPUPxPfFHw
I don't think there's any way someone without a life jacket survives 3:40, or someone pulling them to safety at 3:54. The extremely bouyant kayak itself struggles at 3:54 to not go down. A ~neutrally bouyant human in that aerated water would be toast.
Edit: fixed the accidentally reversed cliché
(Or, I guess relevant here, you're not going to find much correlation between, say, getting guillotined and being dead 150 years in the future, even though getting guillotined absolutely does count as a cause of death in the conventional sense.)
correlation implies a linear relationship.
"a connection or relationship between two or more facts, numbers, etc." https://dictionary.cambridge.org/dictionary/english/correlat...
edit: Ah, Wikipedia intro suggests that yes it's specific within statistics (though still seems to not be a hard requirement to call something a correlation?): "In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. Although in the broadest sense, "correlation" may indicate any type of association, in statistics it normally refers to the degree to which a pair of variables are linearly related." https://en.wikipedia.org/wiki/Correlation
You can easily view cos(x) as causing the value of sin(x) to change - if cos(x) starts going down, sin(x) will too soon afterward. If cos(x) starts going up, so will sin(x), soon afterward.
In fact, if you allow for a time lag between your data series, you will find that sin(x) and cos(x) are perfectly correlated.
Not if you count kayaking. In general I doubt that this is more dangerous than other whitewater creeks. They are all death traps that people can't normally survive swimming in, especially if it's hard to get out. The article seems to be based more on local legend than actual facts.
edit: different video, there are really lots of them folks
The geology of the river that got my BIL is very similar to the Strid - swift deep waters cutting through a limestone bed, creating shelves that currents and buoyancy can trap you under, eroding through to natural caves, or in the case of the Māwhera, eroding into the old coal mining tunnels that burrowed beneath the riverbed in the 1800s.
End result is a highly treacherous waterway. The Police Dive Squad refused to search for my BIL's body due to the shelves and tunnels, and the current.
So, yeah, this is more dangerous than your whitewater creeks, mainly because it doesn't look dangerous, but also because of the additional hydrological dangers that a sweet whitewater run doesn't have.
The article is indeed of very low quality, though, and claims of it being "the most dangerous stretch of water in the world" are hyperbole at best.
Trees, on the other hand, are scary.
> most of the circulation he's stuck in looks to be horizontal
This section has up to 60m depth, the underwater currents are extremely turbulent and will you pull you under the rock on the sides (the whitewater is just a 'slit' on the surface, there's a whole river running underneath). If he didn't have someone ready to pull him out in two seconds like in the video, it's a good bet he wouldn't make it out.
It's possible that the man depicted could have been dragged under an undercut if he'd swum the full rapids, but the video doesn't show evidence of that. Rather, he's pulled out of an eddy without much drama.
(Whilst anyone unprepared, or a daredevil, wouldn't have had a life jacket, and then maybe 100%)
They're also less predictable than a lot of other river hazards. It's possible to come around the bend and be faced with a big strainer that wasn't there the last time you ran the river.
Here's a good video showing a rescue from one: https://www.reddit.com/r/whitewater/comments/cn6k8k/nasty_st...
Thanks for the explanation and link
How exactly do you plan to survive when falling off the kayak?
Call it the "sub-marine" or something such
Translation for pedants: Lots of people die - especially know-it-all idiots, thrill-seekers, and show-offs. We locals - whose taxes pay for the paperwork & such after each death, by the way - are utterly sick of it. Go earn your bloody Darwin Award somewhere else, arsehole.
What about with life jackets?
To me the whole idea of attempting this is like picking a fist fight with a polar bear; complete hubris.
I think they're both technically correct, but there's a nuance in their meaning.
In this case they have identical meaning in context, but there's frequently unpredictable semantic drift in these pairs, if both do end up in English.
> The passive past participle of this noun
> The perfect passive participle of this verb
Why was he infamous? I'm not finding much information on him at all.
I’ve seen many demonstrations since iPhone 12 of people just recording video in their fish tank.
You could chuck hundreds of iphones into the river along the airtag. I hear they're waterproof to some decent depth
Official statics, anyone?
I imagine there's some political challenges to that, but from an engineering perspective it's old hat. High likelihood of being sued and shut down by the local government, but low likelihood of anyone dying.
"Looks can be deceiving" is an extremely common idiom that means basically what I wrote in the title.
The meaning being understandable isn't an effective criterion for good writing, because even egregiously poor writing with multiple errors of grammar, spelling and word usage can often be understood.
Am I going mad? Is the surveillance state so deep in my subconscious that I fail to notice it’s observations? This article isn’t even tech related, why is it here?
This is just the regurgitation of the internet causing a deja vu effect
Now, just relax. The HN interface to your brain waves is a little noisy right now, and it works better when you are relaxed... /s
For starters how many thoughts does a typical human have in a day?
A similar thing happened to me the last time the Strid popped up on Reddit and HN. It was only a day after I had just returned from a popular walking route which passes alongside it and the Abbey.