Many thanks for the replies so far, and in particular to Beanzy for your interesting list.
In the hope of getting the ball rolling, I offer the following definitions which have built up in my head over time and various geographical regions.
I am open to challenge and suggestion on any of them, and again I appreciate that many terms are interchangeable and have multiple meanings. I must also point out that although many of the terms and the characteristics of each feature set out below is based upon personal experience over the years, they also incorporate the observations of others, and I make particular reference to the "Reading Rivers, Tracing Trout" articles written by this Forum’s Terry Cousin, which can be found as a sticky marked "Reading Rivers" at the top of the “Trout and Grayling Fishing” forum. These excellent articles certainly raised my game and taught me to fish with a very different mindframe.
Stickle – a fast piece of water with its bed made up of stones of all sizes, with water so shallow that the stones stick up above the surface. Too shallow for fish of any reasonable size to be in. Broken surface with plenty of white, broken water. A very important habitat for all kinds of food items – can be seen as the river’s larder. High oxygen content at its tail and below.
Popple / popply run – fast flowing water of up to a foot or so in depth with rounded “popple” stones on the bed which results in a lumpy but not broken surface to the water.
Riffle – fast flowing water of up to a foot or so in depth but (unlike a “popply run”) with broken surface water – a “deep stickle”, in effect, but not as oxygenating and not as fertile food-wise, but not far off. Deep enough to hold fish, but energy-sapping for them to remain in. Riffled surface hides them and makes them feel more protected than glassy-surfaced flows.
Scour – same depth and speed as a riffle, but with a bottom made up of fine gravel, resulting in a smoother surface than either rifle or a popply run. Typically found in artificially “canalised” chalk streams where they run through picturesque towns.
Run – a deep riffle – more than a foot deep, but with a slightly ruffled surface, with a decent flow / push of water going through it.
Glide – a section of stream not covering the entire width of the river, quite deep (say 2-3 ft) with a glass-smooth surface, but with enough pace to carry wet flies and spiders. Relatively uniform flow. Due to the flat water, fish will tend to be absent or very spooky when the water is clear and the sun is out, particular where plenty of predators arep resent.
Flat – a section of stream covering the entire width of the river and of considerable length, over 2ft deep, with a glassy flat surface and insufficient flow to carry wet flies and not really enough for even a single spider either. Relatively uniform flow. Again, due to the flat water, fish will tend to be absent or very spooky when the water is clear and the sun is out, particular where plenty of predators are present.
Rapid –reasonably deep / deep flow with extreme turbulence and fast flow, with lots of white water and furious, boiling currents caused by a heavy push of water going over / around / against various rocks, boulders and other obstructions Difficult to fish, and difficult for fish (and fishermen) to remain in. Water below will be well oxygenated and cool, probably with significant amounts of drowned insects and other dislodged sub-surface food items.
Pool - a chunk of slow, deeper water covering the entire width of the river, set in between faster water upstream and downstream (usually stickles or riffles). The head / neck at the upstream end will be well oxygenated, with a well rippled surface and quick but slowing flow. The change of depth at this point can be dramatic, with the river bed falling away sharply from the stickle or riffle upstream. However, the transition from the faster water into the head of the pool can be extremely gradual, sometimes making it impossible to distinguish where the pool begins. The tail at the downstream end can have quite an abrupt break between the slow water of the pool and the faster water of the stickle or riffle below. Water here will have relatively lower concentrations of oxygenation, and most of not all “static / non-active” food items brought into the pool from upstream will either have fallen out of the flow by this point, or will have been intercepted by fish further up the pool. However, there might be significant concentrations of airborne insects which have fallen into the pool itself, or that have hatched within it. The body of the pool is usually too slow to carry wet flies, but unlike a cauldron (see below) there is still a significant push of water mostly going downstream.
Cauldron – I haven’t heard this one being used much, and is a fairly rare (but I think quite distinct) feature. It is a very deep round pool, often ten feet or more in depth, with relatively little water flowing in and out of it. Those flows whish do exist are extremely weak, complex and often varying / undulating and difficult to read. They are often deep and slow enough to have significant temperature layers. Also, the water is typically extremely clear. Most of the ones I have seen are below waterfalls, which are weak outside of spates. Surface is flat, making resident fish spooky and surprisingly difficult to spot, even in clear conditions. Difficult and often soul-destroying to fish!
Boil –a deep / relatively deep piece of river where upwelling flows push up to the surface, due to a large underwater obstruction or a deep severe “scoop” put of the river bed. Can also occur on the outsides of sharp bends in the river or under waterfalls.
Deadwater – a piece of slack along a bank where the flow from the river has no influence – the water within this feature is completely still, and sufficiently isolated during normal flows so that the water does not change / get refreshed by fresh water from the river. In long-term low water conditions, water can even begin to stagnate. Often has a scummy film and litter / flotsam floating over it. Usually entirely fish-free, especially in the height of summer.
Seam – the line between two channels of flows of significantly different speeds.
Channel – a strip of water within a river running downstream which is distinguishable by its different pace and / or depth.
Slack – slower water usually situated along a bank which I is slower than the flow alongside it, but is still predominantly pushing in a downstream direction.
Pocket – a relatively round chunk of slower water in amongst faster water on all sides, which tends to cancel out / prevent any circular currents. Water currents in pockets are often very weak indeed, often too weak to carry even a single spider, and those currents that are there are often very complex and constantly changing, particularly of there is any swirling weed nearby. The seams between the slack water in a pocket and the faster water alongside can be extremely distinct, causing passing food items to suddenly appear and fall into the pocket. The surface of a pocket can be very flat, making them difficult to approach.
Eddy – slack alongside faster water which peels off and comes around enough to travel upstream, and even around again to go downstream to create a mild whirlpool. By definition, tends to be quite round in proportions – may be found at the head of (and feeds into) a slack channel downstream of it. Due to their nature, eddies are usually found next to steep banks, and so have faster flows only along one side, which creates the upstream swirls / whirlpool flows.
Whirlpool – like an eddy, but where the turning flow is strong enough to rotate 360 degrees and beyond, which can concentrate light food items into a tight pillar / column in the centre of the whirlpool.
Buffer - Big mid-stream boulders and similar obstacles usually have pockets and / or slack seams downstream of them, but in addition they have a very strange area of slack situated against the upstream side which is created by the buffer of water flow being stopped in its tracks. Fish often sit in these buffers to watch for food being washed downstream to them. They are difficult to fish, as the water immediately upstream of them is often much faster, and if the boulder does not break the surface, then the surface flow above the buffer can be very quick. The flows leading out of the buffer and around the sides of the boulder will also usually be very fast.
Weir – anything from the obvious man-made weir structure to a more natural ridge of obstacles across the flow which the water has to push over, to a dramatic change in the level of the river bed across most / all of the width of the river. Fish on my river have a strange habit of rising immediately upstream of small natural weirs, which is a shame as I find these spots very difficult to fish!
Stop - a bar of water immediately below a weir or sloping waterfall, etc. where the water flow rolls back on itself, which (depending on is strength) can hold down onto the river bed and retain food items, fished flies and even fishermen!
Weed beds - usually very rich in terms of food items, and can provide very reassuring cover for fish. Their swirling, swaying nature can make fish spotting very difficult. Substantial, thick patches can create significant flow patterns, and the swaying tails of large weed beds can create complex and constantly changing flow patterns. These can be real fish magnets, particularly those situated in riffles in the height of summer – the fish can benefit from the rich food sources and high oxygen content of riffles whist having protection from the sun, predators and fast water flows. They can be tricky to fish, but they can often be approached quite easily as the fish will often be hunkered into narrow channels.
Hope that this might help someone – comments / contradictions warmly welcomed!
__________________
strikealight
Dynamite fishing is always effective.
Last edited by strikealight; 09-03-2010 at 11:56 AM.
Reason: typo
|
but there you go, I had to type it anyway for a guide for when we're studying, recording and 'zoning' the river catchment over the next few years so this post just gave me a reason to type it up. ta for the push. 
Linear Mode
