River flow

[Mr Raffles]

I know this seems a silly question, but if say i am fishing mid stream in a fast flow, is the water on the bottom flowing as fast as the water on the top.

Cause if it is any freebie bollies or pelets wont hang around the hook bait for long.

Cheers lads & lassies

Mr R

[Grumpy Git @]

Not being a very clever chap like some of the meastro's on here, I will put some brain power into the question!

I would say that the flow at the top of the water is faster flowing than the bottom because of the drag factor. The river bed, rocks, weed etc will slow down the flow somewhat in normal conditions. In flood flows this drag would not be quite so effective so the speeds would be very much the same.

I look forward to being shot down any moment now [img]/forum/smilies/big_smile_smiley.gif[/img]

[Wobbly Face (As Per Ed)]

That's my view as well Grumpy. Plus fishing the near or far bank creates drag on the water. There are some exceptions though, depends on twists and turns and even or rough river beds.

[Alan Tyler]

Absolutely right; if you fire a line of mixers across a river, the ones in the middle will be well on their way to sea while those near the edges are still pootling round the eddies, and the same order of difference exists between the surface and the bottom.

I stumbled across a rule of thumb that said that at 20% depth, the flow is 80% of that at the surface; 80% of the way down, the flow is 20% of the surface speed.Although that was on the internet and so must be taken with a pinch of salt, I'd be surprised if it's far out.

Right at the bottom, there are static pools, vertical eddies, scours, and Lord knows what else. I remember watching pebbles dancing on the bottom of a gravel run for ages before I realised I must be looking at an underwater spring! Sometimes it makes you wonder how we ever catch anything ... not that I do.

[Peter Jacobs]

The flow on the bottom of a river can be considerably slower than at the surface.

This is precisely why, when trotting a stick float, we are constantly holding the float back in an effort to keep the down the line shot and the hookbait ahead of the float for better, more natural, presentation.

In stronger flows you often have to hold the float back constantly and just inch the float through the swim, which is a lot easier, and steadier, on a centrepin reel than on a fixed spool reel.

Hope this helps.

[keora]

At most flow rates the rate of flow at the bottom of the river will be slower than the surface flow in the middle of the river. Similarly the flow rate nearest the bank will be slower than the flow in the centre of the river. It's caused by friction between the water molecules rubbing against the river bed or river bank. In contrast, there's less friction between thewater molecules at the surface of the river so they can travel more quickly.

At extremely high flow rates, when the flow is turbulent -imagine a steep mountain river in full flood - then there may not be much difference in flow between the water on the surface of the river and the bottom of the river and the margins. But there will still be pockets of slower moving water behind rocks and boulders where fish can avoid the full force of the current.

[Graham Whatmore]

I am not an expert by any stretch of the imagination but from what I have read the flow on, or very near, the bed of the river is considerably slower, even static in depressions and behind obstructions. Bear in mind we are not talking feet here, we are talking less than an inch and in the case of feed less than half that. Even a small stone on the riverbed will have a small area of static water behind it where the water is deflected over and around it and given the amount of small and large stones on the riverbed plus the depressions it is not hard to imagine that some feed will lie in these obstructions, even in the middle of such rivers.

Having said that most float anglers would choose to fish and feed the crease rather than the centre of a fast flowing river and the reasons for this are patently obvious of course. Maybe fishing shallows in warm weather because of the increased oxygen levels is the exception to this but shallows are usually very stony and this would hold quite a considerable amount of the feed you throw in.

All of this sounds like a good argument for fishing the lead rather than the float to me... If you use one just light enough to hold bottom, you can ease it downstream a little at a time by lifting the rod just enough to dislodge it (and giving a small amount of line to avoid the bait swinging across the flow). Works well.

[Mr Raffles]

Thanx for all the replies. So it looks like best way to leave freebies near the hook when fishing fast flowing rivers for Barbel is a PVA bag.

Also like Laurie`s idea of lifting rod so lead moves down the swim.

Cheers lads

Mr R

[Avon Aquatics - Ryan]

The bottom of most rivers, will be moving more slowly, than at the top.

Science Bit.

The bottom of the rivers, will appear to move in layers (Laminar Flow) with the bottom, affected by friction, and the next layer, by the slower moving water below. In some cases, the water nearest the bottom, could almost be classified as not moving. This occurs, on a relatively smooth river bed, with the river moving at a slow steady pace.

During Flood, Uneven river beds, Faster rivers, the flow is Turbulent, i.e. It has underwater whirlpools, eddies etc. Because of this the water under the surface could be moving at any direction at any speed.

Ryan