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#42
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07-15-2022, 12:19 AM
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 My Rank: MAJOR Poster Rank:193 male Join Date: Mar 2021 Posts: 7,766 Mentioned: 2 Post(s) Quoted: 1466 Post(s)
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Re: Water Rescue Ends Badly
The hydraulics explanations so far are close, but not dead on. The trap at the end of the vid is a hydraulic jump, also known as a "standing wave" or "hydraulic" in whitewater circles. Yes, it is the same type of wave that can grab people downstream of low-head dams. The standing wave is caused by water transitioning from supercritical velocity to subcritical velocity. The water goes supercritical at steep angles (spillways) and changes to subcritical at shallow angles. The water depth is much smaller at supercritical velocity, and that change in depth is what causes the standing wave. This graphic shows how the wave is formed and how the currents trap people.  In this screenshot, look at how the wall drops down at an angle, then levels off again. The bottom of the channel does the same thing. These angles are creating the same standing wave as the above diagram.  |
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#43
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07-15-2022, 12:35 AM
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| My Rank: MAJOR Poster Rank:193 male Join Date: Mar 2021 Posts: 7,766 Mentioned: 2 Post(s) Quoted: 1466 Post(s)
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Re: Water Rescue Ends Badly
In another post, it was advised to roll up like a ball to escape a standing wave. I don't know about that. I would dive underwater and swim powerfully downstream, skimming the bed, to escape a standing wave. The current is going to be moving downstream at the base of the channel, and that is a good way to regain your orientation after being shloshed around in a hydraulic: Dive to the bottom and follow the current out. Swim like hell.
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#44
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07-15-2022, 12:45 AM
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| My Rank: MAJOR Poster Rank:193 male Join Date: Mar 2021 Posts: 7,766 Mentioned: 2 Post(s) Quoted: 1466 Post(s)
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Re: Water Rescue Ends Badly
IMO, those "rescuers" hurling themselves into the channel were absolute idiots. Whatever their profession, they clearly had no training in the danger of moving water. The last thing that a rescuer should do is turn themselves into another victim that needs rescued. Awesome video though.  |
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#45
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07-15-2022, 12:57 AM
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| My Rank: MAJOR Poster Rank:193 male Join Date: Mar 2021 Posts: 7,766 Mentioned: 2 Post(s) Quoted: 1466 Post(s)
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Re: Water Rescue Ends Badly
What the hell - one more post. Standing waves are not entirely evil. Whitewater paddlers love standing waves and seek them out. Surfing standing waves is probably my favorite whitewater activity.  |
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#46
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07-15-2022, 01:06 AM
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| My Rank: LANCE CORPORAL Poster Rank:2809 Join Date: Jun 2021 Posts: 144 Mentioned: 1 Post(s) Quoted: 26 Post(s)
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Re: Water Rescue Ends Badly
I like how the dude filming is just like "la la la rather get this than literally even throw a fucking stick" did someone scream put the fucking phone down at the end or is my subconscious acting up again
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#48
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07-16-2022, 02:28 AM
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 My Rank: MAJOR Poster Rank:161 SCARY BLACK. BOO BITCH! Join Date: Mar 2010 Posts: 9,672 Mentioned: 45 Post(s) Quoted: 2426 Post(s)
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Re: Water Rescue Ends Badly
Saw this on Reddit. Included a clip of at least one officer alive and well. OP said both cops survived.
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#50
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07-16-2022, 02:46 AM
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 My Rank: PRIVATE Poster Rank:5734 Join Date: Jan 2010 Posts: 42 Mentioned: 0 Post(s) Quoted: 10 Post(s)
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Re: Water Rescue Ends Badly
The article says that the one police officer who kept fooatibg helplessly down the canal had been injured by underwater rocks, that’s why he he was unable to stand and try to get out like the other one that tried to save him. They both survived.
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