Before you slip the lines: check the numbers

Rivers are not canals. A canal is a puddle with a timetable; a river is a living thing that changes temper in a night. After heavy rain, the water in your reach can still be rising long after your own sky has cleared, because the rain fell in the hills hours ago and is only now arriving. Look at the trend, not just the figure: a gauge that has dropped a few centimetres from a very high peak is still a fast river. Check whether flood warnings or strong-stream advice are in force. If the advice is to stay put, that is not a challenge to be overcome. It is a free evening in a decent mooring, and the river will still be there tomorrow.

Reading the water

Water tells you what it is doing, if you look at the surface rather than the map.

• Debris lines and brown water. Floating twigs and a soup of rubbish mean volume and push. A line of debris along the bank is a good mark of where the fast water sits.
• Narrows and bridge piers. Anywhere the channel tightens, the flow speeds up. Keep the bow straight and aim for a span you are confident about.
• Eddies. Slack water hides behind bridge piers, on the inside of bends, and below islands and moored boats. These are your resting places and turning points.
• Boils and upwellings. Flat swirling patches that rise and fall mean turbulence, often over a submerged obstruction. They will shove your bow sideways, so give them room.
• Strainers. Fallen trees and overhanging branches, with current pushing through and under them. Never let the boat get sideways onto one; that is how a hull is pinned and rolled.

Throttle and steering: keep the boat working

Steering comes from water flowing past the rudder, not from the rudder alone. Running downstream in a strong current, the boat travels with the water and the rudder has little to bite on, so you need more throttle than you would expect – just enough to keep positive, responsive steerage. Going upstream you already have flow over the rudder, so you can often use less. Make small, early corrections and think well ahead. Hard astern is rarely useful: reverse gives poor steerage and can swing the stern out. If you need to slow down, ease the throttle early and let the current do the work.

Whenever possible, do your slow manoeuvring with the bow upstream. It is the single most useful habit in a rising river. With the bow into the flow, the current helps you stop, the rudder answers, and you can hold station on a whisper of throttle. Aim well upstream of any point you want to reach and let the current carry you down to it. Cross the river with a ferry glide: angle the bow upstream, hold that angle, and use power to slide sideways across the channel rather than driving straight across.

Turning, mooring and passing

Never let the boat sit broadside in a strong flow; a hull sideways to the current takes on enormous force and can be pushed onto anything downstream. Turn deliberately, swinging the bow upstream through the whole arc, and use an eddy if there is one. When mooring, come in at a shallow angle from upstream, so the flow helps pin the bow in rather than flushing you past. Get a line ashore early and use spring lines to stop the boat surging along the bank. Passing moored boats, slow down but not so much that you lose steerage; a boat with no way on has no rudder. Heading downstream, it is often easier to turn, come back up and moor facing the flow.

Anchoring when things go wrong

Anchoring in a fast river is a serious business, but it beats being swept into a weir. Anchor from the bow, never the stern. Use a proper anchor with chain, and let out a great deal of warp: in strong current think seven or eight times the depth rather than the usual three or four. Let it out slowly, walking the boat back, so the anchor sets gently rather than snatching. Choose slack water if you possibly can.

If it drags and you need to recover it, do not haul against the current: take the load off with the engine, motor gently upstream of the anchor, then break it out. If you are already in trouble, aiming for a soft bank and beaching the bow is a legitimate last resort, and a line ashore to a sturdy tree can save the day.

Knowing when to stop

The best technique of all is judgement. Strong-stream advice, red boards, flood warnings and closed reaches are not suggestions. Plan your day so you could be off the river at short notice, and check the next gauge up- and downstream before committing to a long reach. Turning back early is easy; turning back after two hours of pushing upstream in a rising river is not. Keep lifejackets on, keep the cabin closed, and if the flow looks faster than you would happily swim in, tie up and wait. It will fall. It always does.