Rivers After the First Floods: Reading Water That Has Changed

Every autumn the first serious rain comes through and the river you knew all summer stops existing. Gravel moves, holes fill in, new ones scour out, snags arrive and others disappear. Anglers who fish the same three swims out of habit have a poor autumn. Anglers who go and look have a very good one.

What a flood actually does

Moving water carries energy, and when a river comes up that energy rearranges the bed. Shallow gravel runs get scoured deeper. Deep holes fill with silt and sand. Fallen trees shift downstream and lodge somewhere new.

The result is that the depth map in your head is out of date. That swim that was five feet deep in August might be three now, and the featureless glide next to it might have a four foot trench in it that was not there before.

None of this is a problem. It is an opportunity, because most people will not bother to find out.

Go and look when the water is down

The most useful thing you can do all autumn is walk your stretch when the level drops back after the first flood, ideally on a bright day with clear water.

Take an hour and no rod. Look at where the gravel is now, where the new scours are, where debris has piled up. Photograph anything useful on your phone. That hour will earn you fish all winter, because when the river comes up again you will know where the new features are without being able to see them.

New snags mean new swims

A tree that has come down and lodged against the bank is the single best thing that can happen to a stretch of river. It creates slack water, cover, and a food trap, and chub and barbel will find it within days.

Look for fresh debris. A pile of branches and reed stems caught on something is telling you there is an obstruction there, and there will be fish behind it.

Fish these carefully because they are also where you will lose tackle. Strong line, and approach from downstream so you can steer a fish away rather than through.

Silt and where it settles

Flood water carries a huge amount of fine material and it drops out wherever the flow slows. That means slacks, inside bends and the tails of pools fill with soft silt.

This matters for two reasons. First, it changes what lives there, because a clean gravel bed and a silt bed hold entirely different food. Second, it changes your presentation, because a lead and a bait can sink into soft silt and disappear.

Where I suspect fresh silt I fish a bigger, more buoyant bait or a longer hooklength so the bait sits on top rather than in it.

The fish reposition too

After a flood the fish redistribute. Some of that is them moving to new features. Some of it is simply that a flood pushes fish downstream and they work their way back up over the following weeks.

The practical consequence is that a swim that was reliable in September might be empty in October and full again in November. Do not write a swim off after one blank session in autumn.

Reading the surface for what is underneath

With the water still carrying colour you cannot see the bed, so you read the surface instead.

A smooth, slightly raised patch usually means an obstruction underneath pushing water up. A line of broken water in an otherwise even flow means a gravel bar or a change in depth. A slick with no ripple means deeper, slower water.

Boils on the surface indicate something significant on the bottom. Fish just downstream of them.

Do not fight the river

The last point is about expectations. In high flows the fish are in a small proportion of the river and the rest is effectively dead water. Do not try to fish the middle of a raging river because it looks like the main event. It is not.

Fish the edges, the slacks and the soft water. Two rod lengths out is often too far. That is where the fish are and that is where the fishing is.