The moaning of the bar
Unpredictable and treacherous, New Zealand’s harbour bars are the mariner’s dread.
At 9.00 A.M. on a calm winter’s day the two-masted schooner Esther Ann lies off the entrance to the Hollyford River, in Fiordland. For days she has been cowering from gales in Milford Sound, some 30 km to the south. Now, on July 10, 1870, a break in the weather has allowed her to sail back up the coast. On board are settlers from Dunedin, eager to start a new life in the month-old settlement of Jamestown.
While the captain, Thomas Brenchley, waits for the tidal stream to ease, ominous clouds build up over the mountains and the barometer falls. Suddenly, a gale springs up from the west-south-west. Trapped on a lee coast, Brenchley finds he is unable to work his vessel back out to sea. He makes a decision. Rather than be blown ashore, he will seek the safety of the river.
I can picture the scene. Brenchley approaches the entrance on a tight angle. To the south of the river mouth is a long sand spit; to the north, a rocky headland. Beneath the keel lurks an ever-shifting sand bar. He has little room to manoeuvre, and his ship is being buffeted by a heavy westerly swell.
He steers a fraction too close to the shore and is momentarily stranded on the spit. Breaking seas pick up the schooner and it slews around, broadside to the river. Everyone on board is terrified, and Captain Brenchley is frantically thinking how he might save his passengers and their property.
But Esther Ann is no longer his to command. The river takes control of what the sea has passed it, carrying the vessel onto the rocks. Possibly the sound Captain Brenchley hears loudest as his ship breaks up—above the cries of women and children, the shouts of men and the rending of timbers—is the moaning of the bar.
No one died in the wreck of the Esther Ann, but the settlers lost most of their belongings and, crucially, a sawmill they needed to build their homes. Nonetheless, they battled on and helped establish Jamestown.Their work was in vain. Within three years Jamestown was a ghost town. Isolation and the difficulty of resupply from the sea sealed its fate.The Hollyford bar was too unpredictable for captains to risk crossing from the Tasman Sea into the sheltered harbour of Lake McKerrrow.
The Hollyford wasn’t the only treacherous port entrance European settlers wrestled with in the latter half of the 19th century. At that time more than 40 ports around New Zealand had an overseas trade, while many more catered for local trade. In a mountainous country without roads, sea travel was the primary means of communication and commerce. Competition within the shipping industry was fierce, and vessels—most of them privately owned—were prepared to go anywhere for a cargo, however small.
Two especially difficult ports lay within harbours on the North Island’s west coast: Manukau and Kaipara. In 1863, the Manukau bar was the site of the country’s worst shipwreck, that of HMS Orpheus. That year, the Waikato land wars were looming, and Orpheus was sailing to Auckland with soldiers and stores to assist Governor George Grey’s military effort. To make up time after delays in Sydney, the ship’s commodore, William Burnett, headed for the port of Onehunga rather than wasting extra days rounding the North Island to berth in Auckland.
The key to crossing the Manukau bar, then as now, was to follow one of three deep channels that cut through the great curving sand banks reaching out from Manukau Heads. To assist ships as they crossed the bar, a semaphore station had been installed on the northern headland.
On this day, February 7, Edward Wing, the harbourmaster’s son, was manning the station. Out at sea he could see the square-rigged Orpheus approaching under full sail. Conditions were good, so Wing raised the signal take the bar. However, he was concerned to see the ship approaching to the south of the safe channels. He hurriedly hoisted a second semaphore arm to advise street north, but the ship sailed on, so he lowered the first arm, indicating do not take the bar.
Aboard Orpheus, the signals were ignored. Only one man expressed concern: a quartermaster from HMS Harrier, who was being transported back to his ship and who had crossed the Manukau bar on a previous occasion. He spoke to his petty officer, then to his divisional officer, and fi nally to the commodore directly, pointing out that the ship was off course and that safe passage lay to port.
Too late, Burnett realised his error. Orpheus surged onto the first sand bar, jamming her propeller—she was powered by both steam and sail—and possibly damaging her rudder. Still under sail, she struck the next sand bar and stuck fast. A wave smashed over her stern, sending a cascade of water down the length of the upper deck and washing men off their feet.
Another wave smashed the windows of the great cabin in the stern, and water rushed below decks. Soon the breakers forced the ship around until she was broadside to their relentless pounding. Her cannons tore loose and careered along the deck, crushing many.
Burnett ordered the boats away. First to go was the ship’s launch, with 40 men aboard. As Orpheus rolled, her anchor snagged the launch and lifted it from the water,throwing its occupants overboard.None survived.
Two other boats were lowered successfully and headed for Onehunga to raise the alarm. But before rescuers could reach the stricken vessel, the mizzen mast fell. The remainder of the ship’s company had been ordered into the rigging to escape the waves. Now the men tumbled out of the shrouds like so many birds’ eggs from a falling tree. Of the ship’s complement of 259, 189 died.
Further north, Kaipara Harbour was for a quarter of a century one of New Zealand’s busiest ports. On a single day in the 1880s, 14 oceangoing vessels left the harbour on the high tide, and for many years the port held the record for both the value of its exports and the dues paid. But over the years the bar at the harbour entrance took its toll. Between 1840 and 1933 it accounted for a total of 43 ships lost, and countless other vessels suffered minor groundings and damage. The bar also claimed dozens of lives and millions of metres of timber intended for export.
Sand bars form wherever sediment-carrying currents are forced to slow down and drop their load. Just as clouds release rain when their passage is blocked by mountain ranges or atmospheric barriers, so river and tidal flows shed silt when they meet stronger flows, or when they simply run out of energy.
Sand bars that form at the mouths of rivers are called river deltas, while those that form in estuaries and harbour entrances are called tidal deltas, a name that reflects the role of tidal currents in their formation. A sand bar may also form a short distance beyond an estuary. Such a bar is known as an ebb-tidal delta, being the result of a combination of river flow and receding tidal currents carrying vast amounts of sediment out to sea. The speed of this disgorgement tends to maintain a clear channel, or “throat,” into the estuary, the sand settling on the seabed where the current is no longer strong enough to carry it.
Ebb-tidal deltas are never permanent features—they regularly shift under the influence of changing wave and wind patterns. Such movement is sometimes associated with erosion of adjacent shores, or the opposite process of shoreline advance. For example, since the mid-19th century the northern shoreline at the entrance to both Kaipara and Manukau Harbour has been built out almost a kilometre.
In the future, it is possible that this process will reverse and the sea reclaim the new coastal land in an equally short time.
To understand how a bar can affect the lives of local residents, I visit the West Coast town of Okarito. The settlement lies on the shores of Okarito Lagoon, New Zealand’s largest unmodified wetland, which covers a tidal area of 2500 ha.
Gold lured settlers to Okarito in 1865, although the prospect of the voyage from Hokitika can’t have filled travellers with confidence, for the coast was littered with wrecks. In 1866, the Hokitika bar claimed an average of one vessel every 10 weeks, and to reach Okarito ships had to cross a second bar, at the entrance to the lagoon.
Despite the risks of sea travel, by December 1865 Okarito boasted 33 stores serving a population of nearly 800. In March 1866, the rush was still on and the population had swollen to 1500, with another 2500 at Three Mile and Five Mile Beaches. Yet only 18 months later, when the easy gold had run out, Okarito, Three Mile and Five Mile were practically deserted, and they have largely remained that way.
Today Okarito has about 40 residents. As a road now offers a more reliable route into the area than the sea does, coastal ships no longer have to contend with crossing the bar—and just as well, as the channel regularly silts up, sealing the lagoon from the sea.
When I arrive, the surf is pounding and the sky is grey. Down the coast, angry black welts indicate heavy rain on the way. I hurry inside to talk to Ian James, who has been closely involved with Okarito Lagoon and its bar for 25 years. For the past decade he has offered guided kayak trips though the wetland, and this summer has taken to running a tour boat.
When the lagoon entrance becomes blocked, which it does every two or three years, it is the responsibility of the regional council to open it, Ian explains. He is the person the council employs to monitor the condition of the bar and advise when intervention is needed.
“During the 2001 winter the bar was blocked for about three weeks, and the lagoon flooded,” he continues. “The rise in water level killed all the gorse, which wasn’t a bad thing, and the tutu died as well.” Other effects were less beneficial, however: the inundation caused septic tanks to overflow.
The reason the lagoon was left to flood for such a long time was as much tradition as anything else, says Ian. “For years the guideline for opening the bar has been that when the water level reaches the doorstep of a certain house in town, then it’s time. But by then a large portion of the village is flooded, and there is a real stench from overflowing septic tanks—not to mention the health risk. Our drinking water is taken from artesian wells in the lagoon.
“Once that guideline made sense. When the bar had to be unblocked by hand, you needed a large height differential between the lagoon and the sea. Then the force of the water would punch a deep trench, opening the bar like a burst dam. Now, with modern machinery, it doesn’t matter how great the height difference is. Nonetheless, I’ve had the devil’s own job to try and change the level at which the bar is opened.”
Ian is also concerned about the ecological effects of flooding on the lagoon. During those three weeks in 2001 the lagoon changed from being an estuary to an inland lake. The salt content fell so low that great beds of shellfish died. “That was an ecological disaster. I just hope some of them in the bottom of the channel survived. Flooding also affects the white herons in a major way. The lagoon is a feeding ground, and it is difficult for them to wade around the edges when it gets too full. They generally move away, which can reduce the number of chicks reared.”
Okarito lagoon owes its existence to the bar that forms its seaward flank, and the bar is formed and replenished by material eroded from the Southern Alps. Measurements taken at the mouth of the Grey River indicate that 300 million cubic metres of sand flows up the western coastline of the South Island each year, most of it derived from the mountains.
If the Southern Alps weren’t being worn down at such a rate they would be Himalayan in stature. Geologists estimate that in the past three million years the uplift on the eastern side of the Alpine Fault—the tectonic boundary which has created the Southern Alps—has been 18,000 m. Without erosion, Mt Tasman, New Zealand’s second-highest peak, would be five times as high as it is.
A graphic illustration of the amount of sediment transported out of the mountains can be seen in the Waiho Gorge. The gorge used to be a 30 m-deep trench through which the Waiho River drained the Franz Josef Glacier. During World War II, pilots in training would fly under the road bridge. Now the gorge has become filled with sand and gravel, and downstream the riverbed is several metres higher than an adjacent campground, which is protected only by flood banks.
Spoil from the Waiho and other rivers is carried northward along the coast by longshore drift—a current which results from the refraction of waves hitting the shore at an angle.
Sand bars on the West Coast and elsewhere around New Zealand are formed when material transported by longshore drift accumulates. This happens in places where the current is impeded or slowed, typically by the cross-flow of a river. The larger the river, the greater the deposition.
West Coast rivers don’t come any bigger than the mighty Grey and Buller, which have large sandbars across their mouths.
I have a favourite song by Gordon Lightfoot, “The Wreck of the Edmund Fitzgerald,” which includes the poignant lines, “Does anyone know where the love of God goes when the waves turn the minutes to hours?” I’m sure many people in Greymouth and Westport have asked that question. One who has seen the fury of the sea more times than he cares to remember is David Mather. He was a commercial fisherman for 30 years, but quit because “I got sick of taking the risks.”
Mather lives in a weathered cottage with a view of the Grey River mouth—a spot which still gives him the shivers. Reluctantly, he tells me of an incident. “I was on standby to relieve a crew member who was out at sea fishing. The guy’s wife was due to have a baby, so they were going to come in and I would take over. But they never made it across the bar, and both crew were killed.
“You don’t usually drown when you get wrecked on the bar. It’s violent—the boat gets physically picked up and thrown down. You’re in the wheelhouse, arms braced across the walls. You’re effectively trapped. You usually get killed by objects flying around the boat. As a final indignation, the sea tears your clothes off.”
In 2001, the Maritime Safety Authority, concerned about the number of vessels capsizing when attempting to cross bars at harbour and river mouths, produced the National Code of Practice for Bar Crossings. The document warns:
Extreme caution must be exercised when crossing bars. Conditions prevailing on a bar or in river approaches may cause unusually sudden steep and often breaking seas. Conditions change quickly and unpredictably. The skipper’s experience and the vessel type should be taken into account when a bar crossing is considered. However, no amount of experience or boat type makes crossing a bar safe when the conditions are marginal or adverse. No situation warrants taking the risk, so if in doubt “Stay out.”
Mather considers the code of practice a good idea, but thinks it will take more than a document to get fishermen to change their attitude to bars. He says the quota management system increases the pressure on skippers to take risks. For instance, if time is running out to fill the quota on a particular species, a fisherman may try to cross when conditions are marginal.
Westport, so the saying goes, was founded on gold, built on coal and is now nourished by cement. Westport is a busier port than Greymouth because of the transportation of cement, manufactured from local limestone. Holcim, which owns the cement works and the ships used to carry the cement away, controls the port and regularly dredges the bar.
On a day cut from a gem I sit in the sun with David Barnes at his home near Westport. Barnes skippered oil tankers for 35 years and is now the Westport harbourmaster. He was involved in formulating the Maritime Safety Authority’s code of practice and is committed to educating fishermen about it.
He mentions Leighton Forrester, a fisherman of 30-odd years who died a few years ago while crossing the bar. “It really shook the local fishermen,” Barnes says. “At ten to eight in the morning I got a fishing boat in across the bar from Australia. It was flat calm. You’d have a job to see an ‘eyebrow’ on the water. And then at ten to eleven Leighton was dead.
“The wind had got up to 40 knots within an hour, smashing down from the north-east, completely against the sea. The bar was very shallow and we’d dredged a channel which faced the north-east, and rough seas were being stuffed down this channel. Leighton should never have tackled the bar in those conditions. Fishermen tend to think ‘If it’s rough out here at sea I must get into shelter,’ but if it’s rough at sea imagine what the bar is going to be like.”
The better strategy at such times, says Barnes, is to seek sea room—to batten down and heave to. Besides, if it’s that rough, the harbourmaster will have closed the bar.
““Does anyone know where the love of God goes when the waves turn the minutes to hours?” I’m sure many people in Greymouth and Westport have asked that question.”
Of course, a bar can’t be closed physically with a gate the way a road can, but if a vessel crosses when it is officially closed, and is considered to have taken an unnecessary risk, a report is filed with the Maritime Safety Authority. Should a boat capsize and someone die, a manslaughter charge can be laid.
Barnes concludes: “The statistics show that boats that stay out come home, while those that try and cross the bar may never come home. It’s as simple as that.”
Barnes uses the dredge Kawatiri to keep the bar as safe as possible. Soundings are taken over the bar area from the pilot boat Bob Gower, and these are entered into a computer on the dredge. The dredge then shaves strategic amounts of sand off the bar.
In 1998, 39,000 cubic metres of sand was removed from the bar just to maintain the channel. Over the following years 63,000 cubic metres, 89,000 cubic metres and, in 2001, 133,000 cubic metres was removed.
Barnes reckons that dry weather on the Coast pushed the figure up. In a good flood, the river itself “blows a hole through the bar,” he says. For instance, in the summer of 2000, 400,000 cubic metres of material was pushed out of the river mouth after a big flood.
“That’s the idea of the tip heads,” he says, referring to long groynes that have been built out into the sea. “They focus the flood into a narrower,more powerful flow—like holding your finger over the end of a hose.”
On a day when the sea has changed from a maelstrom to a flattish expanse of whitecaps, I walk down to the tip heads. The Buller River flows past me, fast, thick and brown. A white line of foam marks where the treacle-coloured river water meets the green sea. A barge and tug from Australia are bringing in a load of gypsum for the cement works, and will depart laden with coal.
Up the coast, empty cement boats are waiting their turn. They’ve been waiting a week to cross the bar. Barnes has finished his latest soundings and decided it is safe. There has never been a major accident involving the cement boats, which load for an under-keel clearance of between 0.8 and 1.0 m. Every now and then they brush the bottom as they cross the bar, losing a little antifouling paint.
I have mixed emotions watching these large vessels slide effortlessly in from sea. Part of me wants to see one of them ride a breaking wave, thundering down its face with the foam flying. Some locals come to the tip heads when it’s rough to watch the fishing boats do this. From the security of the tip head buttresses, with the sea roaring below, you’re close enough to cheer them on or yell advice. But having talked to people who have known fishermen killed crossing the bar, I have no desire to join them. I don’t wish to be a witness to someone in mortal danger and be powerless to help.
Even so, standing here I can understand the excitement of a bar crossing—of being hammered out at sea and surfing the waves into the sanctuary of a calm port.
I may never experience that thrill myself. But I will continue to go down to a river mouth with a swell pushing in from the Roaring Forties and listen for the moaning of the bar.