Wave vs Hole ?

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Neilo
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Wave vs Hole ?

Post by Neilo » Wed Feb 04, 2009 3:30 pm

Hi,

can someone, in the most simple terms as possible, describe the difference between a 'hole' and a 'wave'. I have tried searching out an answer but, in relation to river flow, I am still none the wiser. I hear (and read) about how 'such and such' weir is forming a wave or hole, but even when I've been there, I cannot work out which I am on. I think I 'surf' a wave, but then am I not also 'surfing' when in a hole?

Diagrams, photos or pictures would help and be greatly appreciated. Please no mathematical explanations, Wikipedia completely lost me !

Many thanks, let's hope we have a consensus of opinion ? ?

Neil.

Moneill
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Re: Wave vs Hole ?

Post by Moneill » Wed Feb 04, 2009 3:49 pm

A hole in essence is a breaking wave.

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Re: Wave vs Hole ?

Post by Poke » Wed Feb 04, 2009 3:55 pm

Moneill wrote:A hole in essence is a breaking wave.
Yet the middle gate at hurley, or Hawaii-sur-rhone, or the Tryweryn cafe wave, are all considered waves, yet all are breaking...
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RVabdn
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Re: Wave vs Hole ?

Post by RVabdn » Wed Feb 04, 2009 3:56 pm

I always think that it's to do with the angle of the water as it enters.

Steep -> hole
Shallow -> wave
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DaveWortley
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Re: Wave vs Hole ?

Post by DaveWortley » Wed Feb 04, 2009 4:10 pm

If you can front surf it without too much difficulty it's a wave, if it's hard to front surf without spinning or flipping then it's a hole.

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RichA
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Re: Wave vs Hole ?

Post by RichA » Wed Feb 04, 2009 4:46 pm

Stopper - Side pour over at Shepperton, typical of nasty weirs. Flat towback.
Hole - Shepperton when it's too high and starts handing out beatings. Big fluffy towback.
Broken Wave - Shepperton at a nicer level! Big fluffy stopper with a green wave underneath it.
(Green) Wave - When Shepperton's a bit too high. Just the wave on it's own!

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mark Hirst
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Re: Wave vs Hole ?

Post by mark Hirst » Wed Feb 04, 2009 5:16 pm

Try Thinking of it this way in simple terms

Hole = something you fall into that is hard to get out of

Wave= Something that waves you through

or

Try to remeber you always fall down into a hole
A wave will be waving straight at you in your face at eye level

Hope this helps
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ol
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Re: Wave vs Hole ?

Post by ol » Wed Feb 04, 2009 5:39 pm

The below photo of Steve Fisher on the Zambezi I think demonstrates the transition between the two quite well. On the left you have a green(unbroken) wave, curling over and 'tubing' but essentially providing a shallow approach angle of the water. You could sit on this, your bow would be clear of the water and not digging under, you would be surfing. This I would call a classic 'wave' shape.

On the right you have a steep and violently recirculating mess of whitewater. If you surfed to the front of this whitewater, or foampile as its called, you would find your bow would most likely bury, you may be side-surfed and you would flip forward and probably be repeatedly flipped(windowshaded). The steepness of the entry angle of the water and the resultant foampile would more likely hold you in the point where the incoming water and foampile meet(the Seam). This I would call a classic 'hole' shape.

Image

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waverley610
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Re: Wave vs Hole ?

Post by waverley610 » Wed Feb 04, 2009 6:12 pm

A wave is something you try hard to stay on, a hole is something you try hard to get off?

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Re: Wave vs Hole ?

Post by ChrisBainbridge » Wed Feb 04, 2009 7:08 pm

Surely it has to do with what the water is doing. A wave has the water coming up against an underwater obstruction, rearing up into a wave face but the water continues down stream. If the wave face is steep enough and the top of the wave breaks then the water will fall back on top of itself but it is still always running downstream and you will always be flushed out whether on the surface or deeper.

A hole has water hitting an underwater obstruction just like a wave, and rearing up from the pressure BUT a layer of water at the surface is always rolling back into the pit of the hole. Therefore something floating on the surface will not escape but will always be pulled back in to the wave. How deep the layer that is recirculating is and how far down stream the recirculation extends is a matter of the river, water level, barometric pressure, etc.

Thus for a big hole such as on the nile or Zambezi people describe tucking up as you hit the bottom of the ramp and trying to go with the bottom water which will suck you down and under the recirculating water, whereas with a wave it doesn't matter as much where you go and you will always be swept out the other side.

I think that it can be difficult to tell them apart because most natural holes and waves have a bit of both. The edge of the hole will be acting like a wave whereas the centre is a big meaty hole. The picture od Steve Fisher shows this well wherein the top 1/4 of the picture you can see an area of frothy white extending downstream of the pile which is the recirculating water.
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wezzzy
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Re: Wave vs Hole ?

Post by wezzzy » Wed Feb 04, 2009 10:42 pm

Neilo, I can see why you are confused.
I like the picture explanation and I will stick to that one if asked but as in grades different people will ave different ideas.

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Edwindle
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Re: Wave vs Hole ?

Post by Edwindle » Wed Feb 04, 2009 10:43 pm

Now we've cleared up that one, whats a "sump"?
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Re: Wave vs Hole ?

Post by Adrian Cooper » Thu Feb 05, 2009 8:05 am

I think the real problem is that 'hole' is too general a term. River features are many and varied and a change in river bed level (or the effect of the water travelling over an obstruction) can cause a wide range of consquent features, usually dependant on the volume of flow or difference in water level up and down stream.

As a progression, you could start with the 'simple' wave; all green water flat above, dropping down behind the obstruction and climbing back with a lift above general water level below. As the feature becomes steeper, you get a break in the surface at the crest of the downstream wave, crashing back towards the valley. This is usually called a breaking wave. Steeper further, this breaking element increases until it meets the bottom of the valley and might then be referred to as a 'surface stopper', the green water is still approximately as the first example. Maybe this is the point at which people start calling it a 'hole'. So we have considerered what is happening downstream of the obstruction but what about the water going over the obstruction? If the obstruction is steep enough for water to 'pour' over the top of it rather than 'flow' and this is the classic 'stopper' or 'pourover' scenario, a deep water stopper does not normally create a 'wave' as such.

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Neilo
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Re: Wave vs Hole ?

Post by Neilo » Thu Feb 05, 2009 10:41 am

Many thanks to you all for your efforts and desciptions. I think I have a clearer understanding now. The main point, for me, is knowing the difference between a 'breaking wave' and a 'hole' and at which point the former becomes the latter. I guess it's when my smile disappears.

I relate it to man made weirs mainly, as that is where I usually get to paddle, thanks to RichA for using Shepperton as an example, as I know it well, so that is helpful. I know to my cost the dangers of the side spills and the strong towback there ! !

Regards, Neil.

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RichA
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Re: Wave vs Hole ?

Post by RichA » Thu Feb 05, 2009 11:44 am

Glad the Shepperton examples helped. I guess in terms of the main wave, the more white it is then the more of a hole it is. The more green the more a wave it is. If no one is paddling it there's probably a good reason!

The side stoppers are evil. For artificial drops like those, I tend to use the idea that the more benign looking they are, the more dangerous they are! Really quiet stoppers can have massive towbacks and look like nothing.

http://www.fremontrescue.org/low-head_dams.htm

At the end of the day, if you're paddling down a river and you see a stopper, you decide if you can paddle through it or not, and if you'd want to paddle through it at all! It's a yes/no answer. The learning process to be able to make that decision can be dangerous, but I'd recommend paddling with people that already know and can pass that knowledge on to you, without the danger!

I sometimes explain the differences to people in terms of ocean waves. They start small and green, get steeper but still green (green wave), start to break (breaking wave), then crash over and become a hole of sorts.

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StoneWeasel
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Re: Wave vs Hole ?

Post by StoneWeasel » Thu Feb 05, 2009 12:20 pm

I realised I was sat with a graphics tablet in front of me (todays work is photoshopping images of ladies in bikinis) so quickly doodled a diagram I hope might help clear things up a little, it's not very good though.

Image

A. Hole.
B. Breaking Wave (note there is still a surfable face before the foam pile).
C. Unbroken Wave.
D. Evil Nasty Stopper of Death.

I'm afraid I am no William Nealy when it comes to the drawings but hope that helps a little.

Denzil

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