The Trieux is the river I send nervous first-timers up. After the rock-dodging round the Ile de Brehat it feels almost civilised: a buoyed, beaconed channel between wooded banks that carries water at every state of the tide, leading to a marina where you do not have to wait for a lock to open. It is the gentlest introduction to North Brittany river work I know, which is exactly why so many British boats make Lezardrieux their first French landfall after the hop down from Guernsey.
Gentle is relative, though. This corner of the coast runs some of the biggest tides in France, and the streams across the river mouth deserve respect. Here is how I plan the approach.
Finding the river mouth
The Trieux opens to the north, guarded on its western side by the white La Croix lighthouse standing on the rocks off the south-east corner of Brehat. La Croix is your gatepost. Coming in from seaward you leave it to port and pick up the line of beacons that lead you in: the Vieille de Bodic tower lower down, then a string of marks up to the Les Perdrix beacon that sits just below the marina. The Trieux is navigable for about 17 kilometres between the entrance off La Croix and the inland port of Pontrieux, though most visitors stop at Lezardrieux a couple of miles up.
This is transit pilotage rather than buoy-hopping for the first stretch. The old leading lines still work, and on a clear day they are easier to trust than the plotter, because the tide here can set you sideways faster than you expect. Keep your marks in line, watch your cross-track, and do not let the stream walk you off the channel onto the drying rocks that flank both sides of the entrance.
Why the tide rules the timing
The Brehat archipelago carries one of the largest tidal ranges on the French coast, second only to the Mont Saint-Michel and Saint-Malo corner. On a big coefficient the water can fall as much as fourteen metres on the seaward side in a single six-hour ebb. All that volume sluices around the island and into the rivers, and the streams across the channel entrances run hard as a result.
For a first visit the local rule is simple: aim to be at the entrance buoys an hour or so before high water, working in on the last of the flood when the rocks are well covered and the stream is easing. You get maximum water under the keel, the marks are clear, and the tide is no longer at full bore. Coming out, I like the early ebb for the same reasons. If your timing has gone wrong, there is no shame in anchoring off Brehat and waiting for the next slot. The understanding of how a French tidal coefficient maps to stream strength is the single most useful thing to bring with you here.
Speed limits up the river
Once inside, the Trieux is a managed waterway and the speed limits are policed. You may make five knots from the Vieille de Bodic starboard tower up to the Les Perdrix beacon, then it drops to three knots above Les Perdrix as you come into the marina reach. They matter for more than the rules: the river is narrow, there are moorings, oyster boats and the passenger launch working the banks, and a wash thrown against a moored fleet wins you no friends. Throttle back, enjoy the wooded banks, and let the current do the work if it is fair.
The river squeezes past the Les Perdrix beacon, a red-and-white tower that marks the rocks below the marina and is the landmark you steer for on the final approach. Leave it to port coming up, swing in towards the pontoons, and you are there.
Lying at Lezardrieux
The marina is one of the easiest in the region to use because most of it floats through the tide. There are tidal pontoons strung out in the river that you can reach at any state of water, plus a basin behind a sill that retains around two metres at low water for boats that want a guaranteed depth. Because the river pontoons stay afloat, you are not chained to a lock window the way you are at Saint-Malo or Granville.
The one piece of seamanship the river pontoons demand is this: come alongside near high or low water, not at mid-tide. The stream runs hardest through the pontoons at half ebb and half flood, and berthing across three knots of current with a crosswind is a job you would rather not attempt twice. Plan your arrival for slack, brief the crew on lines and fenders before you turn in, and approach into the stream so you keep steerage at low boat-speed.
Ashore, Lezardrieux is a tidy Breton village with the usual marina facilities, a couple of restaurants, a small supermarket for provisions and good walking. It makes a sensible base for a few days while you explore by dinghy.
Carrying on up to Pontrieux
If you have the time and the right tide, the run further up to Pontrieux is one of the prettiest river passages in Brittany. The Trieux narrows and the woods close in, and at Pontrieux there is a small lock and a quiet basin in the heart of an old town. Time it for high water, go up on the flood and come back on the ebb, and treat the upper river as a high-water-only excursion since the mudbanks dry out hard. The Pont de Lezardrieux suspension bridge, a listed national monument, crosses the river just above the marina and makes a fine sight as you pass beneath it.
How it fits a cruise of the north coast
Lezardrieux is the secure heart of a wider exploration of this coast. The island that guards its mouth deserves a day or two in its own right, and the piece on the Ile de Brehat and the Trieux river covers the visitor buoys at La Corderie and the anchorages off the island where you wait out the tide before coming in.
If you are working the whole granite coast, the North Brittany cruising guide lays out the harbours and the tidal gates from the western abers across to Saint-Malo, and explains how the rivers like the Trieux fit into a coast-hopping plan. Arriving from the Channel Islands, many crews treat Lezardrieux as the staging post before pushing on through the Raz de Sein passage towards the south coast, so it pays to know the tidal logic of both ends.
Arriving from Guernsey
For a great many British and Channel Island boats, Lezardrieux is the first French port they ever see, and the reason is geography. The run across from Guernsey is an easy day sail of around 35 nautical miles, short enough to do in daylight on a fair tide and into a marina you do not have to lock into. That combination, a manageable crossing and an all-tide berth, is why the Trieux gets so much British traffic and why the customs and formalities here are a well-worn routine.
If you are making that hop, the same tidal thinking applies at both ends. You want to leave Guernsey to carry a fair tide across the bay and arrive off La Croix with enough water and a slackening stream. Plan the crossing backwards from the entrance window, not forwards from your breakfast, and the whole passage falls into place. Coming the other way, west and south towards Biscay, the river is a comfortable last secure night before you take on the bigger tidal gates of the western corner.
What to watch out for
A few practical hazards are worth flagging for a first visit. The river is busy with oyster cultivation, and there are stakes and trestles on the banks that dry out, so keep to the marked water and do not be tempted to cut inside a beacon at high tide when the dangers are covered. The passenger launch, the Passeur du Trieux, crosses the river and works up and down it, and like the Brehat ferries it has priority and a schedule of its own. Give it room.
The other thing is depth in the upper reaches. Below Lezardrieux the channel carries water at all states, but above Les Perdrix the river shoals and dries in patches, so any exploration towards Pontrieux is a high-water exercise. Plan to go up on the flood with the rising tide under you and come back before the ebb leaves you sitting on the mud, and you will enjoy the prettiest part of the river without the embarrassment of an unplanned dry-out.
The short version
La Croix to port, in on the last of the flood, five knots to Les Perdrix and three above it, berth at slack. Do that and the Trieux delivers you to a comfortable pontoon under a handsome bridge with the rocks of Brehat astern of you. It is one of the friendliest rivers in a coast that does not give much away for free, and it earns its reputation as the British sailor's gateway to the Pink Granite Coast.
