Locks, Lifting Bridges and Weirs

Prerequisites

You should already be able to handle a small cruiser at low speed, come alongside and leave a berth, and tie a round turn and two half hitches, a cleat hitch and a bowline. You should have studied the earlier ICC lessons on CEVNI signs and inland fairway marking. For inland cruising in most of Europe you will need an ICC with the CEVNI endorsement. This lesson covers the lock and bridge part of the CEVNI test and the practical locking skills tested on the ICC inland assessment.

Learning Objectives

By the end of this lesson you should be able to:

• Explain how a lock works, and the difference between going up (rising) and going down (falling).
• Read the standard CEVNI lock and movable-bridge signals.
• Prepare a boat and crew for a lock: fenders, lines, roles and communication.
• Enter, secure in, and leave a lock safely, both rising and falling.
• Describe the main dangers in locks (sills, turbulence, hanging up, crushing) and how to avoid them.
• Use waiting berths correctly, and pass lifting and swing bridges.
• Recognise weirs and their warning signs, and keep clear of them.

How a lock works

A lock is a chamber with gates at each end that lifts or lowers boats between two water levels. To go up, you enter the empty chamber from the low side, the lower gates close, and water is let in from the upper level through sluices (paddles) in the gates or in culverts in the walls. The boat rises with the water. When the levels match, the upper gates open and you leave. To go down, the process is reversed: you enter from the high side, the upper gates close, water drains out through the lower sluices, and the boat sinks with it.

Lock sizes range from small manual locks on French canals (about 38.5 m by 5.05 m, the Freycinet gauge) to huge Rhine and Moselle locks 190 m long with rises of 10 m or more, where you will share the chamber with commercial barges. Small locks may be worked by the crew, by a lock keeper (éclusier in France, sluismeester in the Netherlands, Schleusenwärter in Germany), or automatically. Automatic locks may be triggered by a pole hanging over the water that you twist, a sensor, a remote control handed out by the authority, or a phone call.

Rising versus falling

The sill is a ledge at the upper end of the chamber where the upper gates seal. When you are falling, it is underwater at the start and gradually appears as the level drops. If the stern or rudder is over it, the boat can land on it, tip bows-down and flood or sink. Most locks mark the limit of the sill with a white line or a painted sign on the wall. Stay forward of it.

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Lock signals

Most CEVNI countries use the same lights at locks. They show on each side of the entrance or above it.

Some locks add arrows, signboards or loudspeaker instructions, and locks with two chambers show separate lights for each. On big locks the keeper allocates places by loudspeaker or VHF, often calling commercial vessels first. Many countries list the lock VHF channel on a board at the waiting berth and in the waterway guide. If you are in doubt, wait, and listen.

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In CEVNI, one long blast means "attention". Some national rules let you sound a signal to ask for a lock; others forbid it. Follow the board at the waiting berth.

Waiting berths

Before most locks there is a waiting area, marked by signs (often a blue sign with a white boat or the word "attente", "wachtplaats" or "Wartestelle") and fitted with bollards or a pontoon. Use it:

• Moor up and wait; do not hover in the approach where barges are manoeuvring.
• Commercial vessels usually have priority. Some berths are reserved for them; read the signs.
• Keep your place in the queue. Boats lock in order of arrival unless the keeper says otherwise.
• Use the time to set up fenders and lines on both sides and brief the crew.

Never moor just below a lock against the lower gates or in the jet of water from the sluices. When the lock empties, a lot of water comes out very fast.

Preparing the boat and crew

Fenders

Put fenders on both sides unless you know which side you will lie on. Hang them low enough to protect the hull at the waterline but not so low they ride up. Rough or slimy lock walls quickly wreck soft fenders; many inland boats carry a fender board (a plank hung outside the fenders) for walls with recesses or vertical ladders. A bow fender protects against the gates.

Lines

• At least one bow line and one stern line, each about twice the depth of the lock plus the boat's length, and usually 15 m or more for big locks.
• Lines should be clear, coiled, and with no knots or loops at the ends that could jam.
• Never tie a fixed knot round a lock bollard. Lines should go round the bollard and back on board, so you can let them out or take them in from the boat and release them instantly.
• Keep a sharp knife at hand in the cockpit, in case a line jams and the boat starts to hang.

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Crew roles

Give every person a clear job before the lock:

1. Helm: controls the boat, decides when to enter, watches the bow and stern, and keeps the engine running throughout.
2. Bow crew: handles the bow line, fends off the gates and wall, and calls the distance to the wall.
3. Stern crew: handles the stern line, watches the sill marker when falling.
4. Shore crew (in small locks, if needed): steps off at the waiting berth or the lock side to take lines and help work the lock.

Everybody should wear a lifejacket or buoyancy aid in a lock, and in Germany wearing one is often required by local rules or hire conditions. Keep children and pets clear of lines. No one should stand between the boat and the wall, or put a hand or foot between them to fend off: use a fender or a boathook.

Entering, securing and leaving

Going up

1. Wait for the green light (or the keeper's signal).
2. Enter slowly, at minimum steerage speed. Take care at the entrance: water can still be moving and side winds funnel through.
3. Head for the place the keeper gives you, or, in small locks, towards the rear of the chamber, well back from the upper gates and sluices.
4. Stop the boat using a short burst astern. Do not rely on lines to stop the boat.
5. Pass the lines up. In deep locks a crew member may climb a ladder (only if safe and allowed) or the keeper takes them; otherwise throw them, or use a boathook to drop a loop over a bollard.
6. Take each line round the bollard and back to a cleat on board. Hold it with a single turn on the cleat so it can be adjusted.
7. As the water rises, take in the slack steadily, keeping the boat against the wall. The turbulence can be strong at the start: hold the bow in to stop it swinging out.
8. Some big locks have floating bollards set in recesses in the wall. Tie to these with a single line and they rise with you, no adjustment needed.

Going down

1. Enter on the green light, and position the boat well forward of the sill marker.
2. Put lines round the bollards and back on board, as above.
3. As the water drops, pay the lines out steadily. Never leave a line made fast: the boat will hang on it and tilt, possibly flooding or capsizing.
4. Watch the stern and the sill, especially at the start.
5. As the lower gates open, wait for the signal before moving.

Leaving

• Wait until the gates are fully open and you are told to go (green light, keeper's signal, or the barge ahead moving).
• Recover the lines from the bollards cleanly, from on board.
• Leave slowly in the order you entered. Barges ahead will produce strong prop wash as they start; hold back until it settles.
• Keep a lookout for boats waiting to enter.

Sharing with commercial craft

When you share a lock with a barge:

• Let the barge go in first and come out first, unless the keeper says otherwise.
• Stay well astern of it, never alongside its stern, where its prop wash is strongest.
• Expect a lot of turbulence when it starts its engine. Keep your lines snug.
• Never moor to a barge without permission.

Dangers in locks

If something goes wrong (a line jams, a boat is hanging, someone falls in), shout to the lock keeper at once to stop the sluices. Most locks have an emergency stop button on the wall. Know where it is.

Lifting and swing bridges

Movable bridges are common on Dutch, Belgian and French canals. The signals are similar to locks:

Before a bridge:

• Check your air draught against the closed clearance. If you fit underneath, you do not need it opened (but watch the yellow light rules).
• If not, slow down early and hold station, or use the waiting berth. In the Netherlands, many bridges open only at set times or in convoy ("blokken"): check the opening times in the Almanak voor Watertoerisme or the ANWB guides.
• Some bridges need you to call on VHF or press a button; some charge a small fee, collected by a clog on a fishing rod.
• When the light turns green, go through promptly, one at a time, and keep station behind the boat ahead.

Never try to pass a bridge as it begins to close, or while the barrier or warning bells are going.

Weirs

A weir is a dam across the river that controls the water level. Locks are usually built beside weirs, with the weir stream in a separate channel. Weirs are among the most dangerous features on any river:

• Water going over a weir creates a stopper: a recirculating current at the foot that holds a boat or person and can drown them.
• Above a weir, the current accelerates towards the crest, and in strong flow a boat with a weak engine can be drawn over.
• Weirs are often low and very hard to see from upstream until you are close.

Weirs are marked by warning signs (danger sign, or a sign showing a weir), booms, buoys or cables across the approach, and they appear in the waterway guide and on charts. CEVNI sign D2 (recommended area) and the A10 boards often guide you away from the weir channel towards the lock cut. At a bifurcation just upstream of a lock, check the guide to make sure you take the lock branch, not the weir branch.

Rules for weirs:

1. Know where they are before you set off. Mark them on your guide.
2. Keep well clear of the weir stream. Stay in the lock cut.
3. Never moor or anchor close upstream of a weir.
4. In flood conditions, when river levels are high, do not navigate. Many authorities close rivers to pleasure craft in high water.
5. If your engine fails above a weir, anchor at once.

Worked Example: a falling lock on the Canal du Midi

You are on a 10 m hire boat with three crew, heading down through a manned lock on the Canal du Midi.

1. Approach. 300 m before the lock you slow to 3 km/h. The light shows red. You moor at the waiting berth on the right bank, put fenders on both sides, and lead a bow line and a stern line to the bow and stern cleats, coiled ready.
2. Brief. The helm stays at the wheel. Crew A takes the bow line; crew B the stern line and watches the sill marker. Everyone puts lifejackets on.
3. Signal. The gates open and the light goes green. A hire boat comes out first. You wait until it is clear, then enter slowly.
4. Positioning. The chamber is 30 m long; the sill marker is a white line 3 m from the upper gates. You stop the boat with a burst astern, with your stern 6 m clear of the line.
5. Lines. The keeper takes your bow line and drops it round a bollard. Crew B lassoes the stern bollard. Both lines come back to cleats on a single turn.
6. Falling. The keeper opens the paddles in the lower gates. The water drops about 2.5 m over five minutes. Crews A and B pay out steadily, keeping the boat close to the wall. B calls "clear of the sill" as the line appears on the wall.
7. Leaving. The lower gates open and the keeper waves you out. Crews flick the lines off the bollards from on board and coil them. You leave at slow speed, thank the keeper, and check for boats waiting below.

Common Mistakes

• Tying a fixed knot round a bollard. The boat hangs as the water drops, or snatches as it rises. Lines go round and back on board.
• Forgetting the sill. Every falling lock: know where the marker is and keep the stern forward of it.
• Using lines to stop the boat. Lines break or cleats tear out. Stop with the engine.
• Switching off the engine. You lose control if the turbulence or a barge's wash moves you.
• Fending off with a hand or foot. Crushing injuries are common. Use fenders and a boathook.
• Ignoring commercial priority. Barges have tight schedules and limited manoeuvrability; let them go first.
• Waiting in the approach. Use the waiting berth instead of hovering.
• Mistaking a weir channel for the lock cut. Read the guide and the signs at every bifurcation.

Summary

• Rising: water comes in with turbulence; stay back, take in lines. Falling: water goes out quietly; stay forward of the sill, pay out lines.
• Lock lights: two reds = out of service; red = wait; red and green = get ready; green = enter.
• Use waiting berths, put fenders on both sides, and brief the crew on roles.
• Lines go round bollards and back on board. Never fixed knots. Keep a knife handy.
• Keep the engine running; stop the boat with the engine; never fend off with hands or feet.
• Lifting bridges use the same red and green lights; a yellow light lets small craft that fit pass.
• Weirs kill: know where they are, keep in the lock cut, and do not navigate in flood conditions.
• Rules and opening hours vary between countries and waterways: check the national regulations and the local guide.

Check Your Understanding

1. What does one red and one green light at a lock mean?

Answer: Entry is not yet permitted, but the lock is being prepared; get ready to enter.

1. Why must you never tie a fixed knot round a lock bollard?

Answer: When the water level changes, the boat will either hang on the line (falling) or pull against it (rising), which can tip or flood the boat. Lines should go round the bollard and back on board so they can be adjusted and released.

1. Where should you position your boat in a small lock when going down, and why?

Answer: Forward of the sill marker, clear of the upper gates, so the stern or rudder cannot catch on the sill as the water drops.

1. Which is usually rougher, rising or falling, and why?

Answer: Rising, because water is let in from the upper level and creates turbulence in the chamber.

1. What does two red lights at a movable bridge mean?

Answer: The bridge is out of service. Passage is prohibited.

1. You share a lock with a barge. Name two precautions.

Answer: Any two of: let it enter and leave first; stay well astern of it, not alongside its stern; expect turbulence when its engine starts; keep lines snug; never moor to it without permission.

1. What is a stopper and why is it dangerous?

Answer: A recirculating current at the foot of a weir. It can trap a boat or person and hold them under.

1. Your engine fails 200 m upstream of a weir. What do you do first?

Answer: Anchor immediately, then call for help.