Every hillwalker in Britain and Scandinavia eventually meets a river that has to be crossed. Usually it is a small burn tumbling off a hillside, crossed in one stride without a second thought. Occasionally it is something much bigger — a spate river in spate after a night of rain, brown and loud, pushing hard against a bank that you really do need to reach. Knowing the difference, and knowing what to do about it, is one of the most useful skills you can carry into the hills.

Start by asking whether you need to cross at all

The best river crossing is the one you avoid. Before you start scanning for a shallow spot, look at the map and ask the honest question: does the route actually require this? On a circular walk you can often simply reverse the direction of travel, walking the loop the other way so the awkward crossing becomes a footbridge or a road bridge later in the day. In Scandinavia, where trails frequently cross the same glacial stream three or four times, following the bank upstream for a few hundred metres often reveals a snow bridge or a fallen log that the path itself ignores.

If you are on a linear route with no alternative, at least check whether the river narrows and splits further up. Braided channels are usually shallower and slower than a single deep thread, and a wide, shallow crossing is almost always safer than a narrow, deep one, even if it means wet feet.

Scout properly before you step in

Never wade in at the first point where the path meets the water. Walk the bank, upstream if possible, and read the river the way you would read a slope.

• Look for the widest section. Where a river spreads out, it loses energy and depth.
• Avoid bends, especially outside bends. The water is deepest and fastest on the outer edge of a curve.
• Watch the surface. Smooth, glassy water on a green or dark background usually means depth. A riffled, choppy surface over gravel tells you it is shallow.
• Check the exit. The far bank matters as much as the entry. A muddy, undercut or boulder-strewn bank is a fall waiting to happen when you are cold and off balance.
• Time it. Rivers fed by snowmelt in Norway and Sweden often run lower in the early morning and rise through the afternoon.

Give yourself a full minute of standing and watching. Look for a diagonal route — crossing at roughly forty-five degrees downstream — so you are working with the current rather than purely against it.

Technique: feet, poles and body position

Undo your rucksack sternum strap and, if you have a waist belt with a proper buckle, loosen it. If you go down, you want to be able to shed the pack rather than be dragged by it. Keep your boots on — bare feet and riverbeds do not mix, and trainers offer no ankle support on slippery rock.

Move sideways, facing upstream or slightly downstream depending on the current, and shuffle rather than step. Keep your feet apart for a wide base, and plant each foot only once you have felt the bed beneath it. In Scandinavia, the classic hazard is slick, algae-covered rock; in the UK, it is often greasy boulders and unexpected drop-offs into pools. Test each foothold with a little weight before committing.

Walking poles are genuinely transformative. Two poles give you a third and fourth point of contact with the bed, and they let you probe ahead for depth and holes. Plant them upstream of you and lean gently into them. If you have only one pole, use it on your upstream side and side-step.

Cross in a group with the strongest person slightly downstream of the weakest, forming an eddy of bodies. Link arms at the elbow rather than holding hands, which is stronger and quicker to release.

Know when to turn back

This is the part that matters most, and it is the part we are worst at. Set your limits before you leave the car park or the hut.

• If the water is above your knees on a fast-flowing river, think very hard about it.
• If you cannot see the bed through the water, you cannot judge it.
• If the current pushes you off your line, it is too strong.
• If you are cold, tired, or the light is going, do not cross.

Being able to say "we are turning round" is a skill, not a failure. A river that looks marginal now will look genuinely dangerous in an hour if rain continues upstream, and many hill rivers rise fast and without warning. In practice, the most common mistake is not ignorance of technique but a reluctance to abandon a planned route after a long walk in.

A few final habits worth building

Keep your phone or map in a dry bag, and carry a small towel for drying feet before you put boots back on — cold, wet feet for five hours are a genuine route to hypothermia. Learn the crossings on your local hills and check them in different conditions, so you know what "normal" looks like. And treat every river with the respect you would give a snowy ridge: they are beautiful, they are part of the reason we go out, and they will not negotiate.