On exposed coasts, wave action in harbours can be surprisingly violent. Ken Endean examines mooring tactics
Seamanship in small harbours
‘Safe in harbour’ is a comforting phrase but can be dangerously misleading. In 50 years of mooring and anchoring yachts in all kinds of places, the only times when I have been seriously worried about risk of damage have been while tethered to harbour walls or well-secured pontoons.
Those objects are harder and stronger than a typical hull, so in any impact from a boat, the boat is likely to come off worse. Also, wave action within harbours is often quite violent. Despite the best efforts of engineers and builders throughout the ages, there are many small ports where a vigorous sea state outside means that a yacht will not be safe inside unless her crew adopt elaborate mooring precautions. Sometimes, staying at sea may be the only sensible option.
Yacht owners who do most of their sailing between sheltered estuaries, such as in SW or SE England, much of Brittany and even SW Ireland, may encounter nasty surprises if they venture into cruising grounds where protective headlands are few and moorings are only sheltered by man-made walls. I certainly adjust my own thinking when planning passages beyond the Lizard or up the East Coast.
Mullion (or Porth Mellin), in Mount’s Bay, is good example of a bad harbour: a tiny basin among steep-to cliffs, with no protection from the west and notorious for rapidly-deteriorating conditions. The chaos seen above between the quays was caused by a fairly modest swell – nothing exceptional for West Cornwall. As at many other small harbours, the main function of the short breakwaters is not to create a safe mooring area but to protect the landing beach, so that boats may be run in and hauled clear of the sea. Sometimes that protection is inadequate. A few days earlier a fishing launch had turned over on top of its owner, who was lucky to survive. It can be calmer for short spells but the risks are obvious, which is why visiting yachts are advised to anchor off.
By way of contrast, the above view of St Michael’s Mount looks like a blissfully peaceful scene, and yet it embodies a message about serious seamanship, because the boats demonstrate prudent mooring arrangements for an exposed coastline. The harbour faces inshore, away from Atlantic weather and waves, but swell hooks round into the basin. Apart from a ferry launch, which is collecting passengers from steps by the right hand pierhead, none of the boats in the harbour are moored against the rough granite walls: they are all secured fore-and-aft to ground chains so that they can move freely with any wave action. The two visiting yachts have anchored outside, well clear of the masonry.
How do waves and walls interact?
In general, the most vulnerable harbours are on coasts exposed to ocean swell. Swell waves have long wavelengths and ‘feel the bottom’ in great depths. This slows them progressively as the water shoals, so that they wrap around promontories and swing into places that look as though they should be sheltered.
At Newquay, the bay faces north and some pilot books warn of trouble in north winds, but conditions inside the basin can actually be worse when low swell is rolling in from the west and bending around the headland.
As these waves reach the harbour mouth they radiate into the basin. That is why the moorings look like the spokes of a wheel, aligned to and from the harbour mouth. The boats all surge fore-and-aft but keep clear of one another, and the ground tackle has heavy chains to damp the movement. No local craft would moor against the walls for any length of time because it could get tangled up with projecting ladders and other obstructions. On a first visit, I was given a quayside berth and it was such an alarming experience that next morning I begged the loan of a fore-and-aft mooring.
That fore-and-aft surging is known as the wave scend. In normal wave action, the surface of the sea moves both vertically and horizontally. Starting from the front face of a wave, the sequence is: up, forward, down and back… and repeat. Taken together, this constitutes a circular or orbital motion, which also affects the water below the surface, down to a depth of half the wavelength (typically 50-100 metres for swell around the UK).
When a wave is in shallower depths, vertical movement is restricted by the sea bed, so the circle is compressed to an ellipse and this becomes progressively flatter as depths decrease, until the motion is almost entirely horizontal. The surface looks placid, without prominent wave crests, but the scend may be enough to shift a boat by a couple of metres in each direction, which means trouble.
If a surge meets a vertical wall, the water piles up in a short-lived crest before reflecting back again.
Porthgain is an old quarry harbour in Pembrokeshire where coasters once loaded road stone while moored against the quay on the right. Most of the water surface appears harmless but a mound of foam in the far corner shows where a wave is rearing up against the end wall. With solid stonework all round that basin, the waves are bouncing back and forth, with vertical movement at the ends of the basin and a horizontal scend in the middle. Nobody would want to moor a yacht in the far corner, but would the middle of the quay be any more comfortable?
At Newquay, there is less reflection because incoming waves that surge through the moorings then break on the shelving beach and disperse most of their energy. Well-designed harbours often incorporate artificial shallow slopes, known as spending beaches, positioned between the entrance and an inner basin, in order to damp down the waves. At Porthgain the slipway beach may perform this function to some extent, although it is rather too small because the builders had to cram the whole harbour into a very tight space.
A layout with multiple basins is another way to disrupt wave action and this features in many North Sea harbours, particularly on the Scottish Coast. In some places, a labyrinthine pattern of breakwaters developed when an original harbour was supplemented by new outer basins to accommodate more trade or a growing fishing fleet. The old, inner harbour then became the best-protected refuge during really foul weather.
However, at Hopeman on the Moray Firth the sequence of development was back-to-front. The present harbour has two basins but the original simple harbour, which had its entrance facing away from the North Sea, is now the outer basin; a new basin was grafted on to its western side and the old harbour forms part of a tortuous entrance or exit.
When Mary and I visited Hopeman our first-time entry was mildly traumatic, with wind and waves from the west shoving us in as we swept down the narrow slot between North and South Piers, before making a sharp, blind 180° turn to starboard. As the waves have to enter by the same route, most of them fail to make the turn and die on the beach in the outer basin.
Coming and going
If a walled harbour faces on to open water, arrival or departure is likely to be daunting in strong onshore winds. Waves reflecting from outer walls often create a messy sea for some distance offshore and crests rebound obliquely from pier heads, so that an incoming boat will meet the wildest water when nearing the entrance.
It makes sense to furl sails before closing the shore, while it can be done in a relaxed manner. On the other hand, some steadying canvas could be helpful; we often stow the mainsail with a mile or more to run but keep the jib set and drawing until almost into the harbour mouth, when it is rolled up quickly. Where a harbour operates a VHF radio service, contact the watchkeeper about 10 minutes beforehand to check that your entry will be unobstructed. When you are surfing in, pushed by the waves, you don’t want to debate Colregs with a big fishing boat.
‘Zig-zag to take the waves diagonally and soften the plunging motion’
Where a river discharges through the harbour, leaving under these conditions sometimes involves an extra complication. Waves normally become shorter and steeper as they reach shallow depths but any ebb stream flowing out will compound this effect, so that there is then a series of high, closely-spaced crests rolling into the entrance. A departing boat will not only be motoring into a stiff headwind but will also have to climb over these sharp ridges of water. Rearing up over one wave to bury her bow deep in the next could bring her more-or-less to a stop and this is frightening if the bow then starts to pay off towards one of the walls. Plenty of power is one answer but at places where the entrances are wide enough we have zig-zagged, so as to take the waves diagonally and soften the plunging motion. Again, this could be unpopular if you meet a large fishing boat, so check on the VHF before heading out.
The approach to Hopeman holds another hazard that is common along steep-to coasts: dozens of pot buoys. Where there are few headlands and the sea bed drops away into deep water, most shellfish pots are laid close in and some fishermen won’t bother to go far from their harbour. We were distracted by stowing sails and bouncing around in a mild tide race when we suddenly found ourselves surrounded by spherical confetti, some of it with floating lines. The harbour authority prohibits pots within about 200m of the harbour but they seemed to be clustered close outside that limit.
How can you make fast securely?
Once inside a harbour, if the quayside moorings are affected by wave action there are several useful precautions, starting with really big fenders if you have space to carry them.
A fender board is needed where ladders or other equipment project from a quay, and must be long enough to cope with the scend without hooking on the obstructions and lifting off its backing fenders.
I like to moor with only single warps fore and aft, so that there are no long springs to snag the quay, but I usually bend a short midships spring to the forward warp, creating a bridle that works in the same way as a spring and prevents the warp from snatching the bow in towards the wall.
This is also helpful in gusty winds, which cause a fore-and-aft movement similar to the wave scend, particularly at high tide when mooring lines are slack.
In marina-type berths, breast ropes and springs are short, with little scope for stretching, and the best way to damp movement is usually by rubber mooring snubbers. However, there may still be a jerking motion and squeaking fenders, particularly if some of the scend is athwartships. An alternative solution, for a boat between finger pontoons, is to rig a midships line between two yachts in the same bay, so that each is held away from its finger.
In our berth in the RNSYC basin at Lowestoft, we could not reasonably connect London Apprentice to the blue motor boat, because its owner was not on board, but we achieved the same result by a taut line from the starboard sheet winch to a pontoon cleat. The tension acted diagonally but held us away from the finger and preserved our beauty sleep.
Practical help in Portpatrick
Portpatrick has poor wave breaks, but is very popular with cruising yachts and there have been recent improvements in the moorings.
It was originally a cove from which small sailing boats provided a ferry service from Scotland to Ireland. In the 19th Century an inner basin was excavated to take steamer traffic and long breakwaters extended to seaward. The sea soon demolished the breakwaters and, although the square basin remains intact, waves can now enter and slosh around inside. For many years the lifeboat was kept on a fore-and-aft mooring, off the walls, because the RNLI’s engineers judged that, in bad weather, sea state within the basin could be too severe for a pontoon.
In 2015, after being owned by a series of private individuals, the harbour was acquired by the Portpatrick Harbour Community Benefit Society, finally giving locals a real say in its operation.
When we visited in 2016, the lifeboat had a new berth outside the basin where wave action is reckoned to be less dramatic. Of more immediate interest to us, the harbourmaster had provided practical, seamanlike hospitality.
At each visitor berth, four large fenders are threaded on to vertical lines, secured to the quay and tensioned by heavy weights, so that the fenders rise and fall with the tide. These arrangements were very effective, at least in reasonably benign conditions. We played safe by also stringing a horizontal row of fenders below our gunwale – an alternative to a fender board – but this extra precaution proved unnecessary.
What if the inner basin is closed?
At a few harbours, entry might be barred if there are storm-proof gates or barriers to isolate the inner basins. This is most likely in winter months, as at Porthleven where timber beams are lowered into slots in the stonework. However, last summer when Mary and I put in to Gourdon harbour, on the East Coast of Scotland, we found that its inner gates were closed for the night. They operate by hydraulics but nobody was around and the harbourmaster was based at Stonehaven, further up the coast. Luckily, we could raise him by mobile phone and he kindly asked his son to call in and check that we would be OK in the outer basin overnight.
Next day, in a strong northerly wind, we tried for Stonehaven and hoped to make a sheltered passage in the lee of the land but squalls off the cliffs were hitting the sea like bombs and we backtracked to Gourdon – with our tail between our keels, so to speak. On the quay was a fisherman who had evidently watched our exciting return through the outer reefs and immediately offered us his inner berth until the following noon, when he would need it to load his gear.
We have found this is typical of small fishing ports: the old animosity between some fishermen and yacht crews is a thing of the past. I have a theory that, with current fishing restrictions and catch limits, it is the most efficient fishing skippers who are still in business and they are not going to waste their time on clashing with yachties. Nowadays, one of the pleasures of visiting these small working harbours is that a yacht will normally be treated, and respected, like any other craft.
Of course, low tide at a drying harbour will have the same effect as a gate. When we finally made our passage to Stonehaven, there was the usual residual swell from the north, but quite slight and apparently nothing to worry about.
Arriving near low water, we could not enter the drying inner basins and prepared to moor at the outermost quay. It was Sunday and no-one was answering phones. The water looked innocent and when we went alongside I looped a short line through a ladder, to hold us still while Mary carried our warps along the wall and I prepared to take up the slack. Abruptly, a vicious surge started to ram us against the concrete and then pull us back sharply, threatening to dismantle the ladder.
We quickly changed our plans and moored the boat diagonally across the outer basin, well clear of the walls, until equally violent longitudinal movements flung us to the limits of both warps and I really thought they might snap. Finally, we abandoned the quays and anchored fore-and-aft, laying the bower anchor just clear of the entry-exit channel and the kedge well back in a corner, with a chum weight on the kedge warp to give it gentle tension and prevent us wandering around. That worked. The surface still looked innocent and there was very little indication of wave action, either vertical or horizontal.
Where a harbour wall only serves to protect a landing place and is unsuitable for mooring boats afloat, as at Sennen Cove, it might be OK to anchor off and go ashore by tender. However, it’s worth taking time to study the wave action, which will often increase and decrease as ‘sets’ of larger waves arrive at regular intervals. On a sloping beach or slip, if the waves vary the depth between ankle-deep and thigh-deep the crew will be pretty soggy before they reach the pub. Where there is vertical water motion at a ladder, stepping out of the dinghy mainly requires good timing, but horizontal scend may cause more difficulty if crew members have to hold the dinghy still by resisting the surges.
When alighting on masonry, such as at the side of a slipway, look for good hand holds and try to avoid slippery weed. If larger waves roll in, don’t hang on to a ladder or stonework but keep away from the walls until completely sure that disembarking is realistic.
On any partly-enclosed area of water, whether a bay or a harbour, a boat will usually be quite safe while bobbing about in the middle: it’s the hard edges that are hazardous.