Topic: Sand - Three Sisters Beach

Topic type:

THE THREE SISTERS BEACH

The Three Sisters Beach is situated on the southern side of the Tongaporutu River.  It, along with the Four Brothers Beach are my prime working areas.  This is primarily due to ease of access.  The Gibbs have kindly granted me access through their farm to a track down to the beach.  This saves me time and cuts out having to navigate around from the Tonga toilet to Mammoth Rock and then access the beach.  Sometimes the river is close up to the cliffs making access difficult, especially as I lug heavy camera gear and am not the world’s fittest person!

The Three Sisters Beach has three distinctive zones.  For ease of description, I will disseminate the beach information into these site specific zones.

ZONE ONE.  This extends from MAMMOTH ROCK to the FIRST ARCH.  This area includes a dune that, like the dune at Pilot Point, connects to the cliffs.  (A barn is visible at the top of the cliffs above the Three Sisters dune).  The dune also has a sand/land bridge that connects to Mammoth Rock.  This is built atop beached logs and it prevents the sea from encircling Mammoth Rock.  Marram grass, flax and pink flowering sand convolvulus are well established.  According to Victor Gibbs (discerned later in 2009), this sand bridge has been intact for at least 50 years.

On the seaward side of the dune the above plants are accompanied by lupins and coastal forest.  This forest consists mostly of pohutukawa, mahoe, coprosmas, karakas and pepper trees.  There was also a cabbage tree that was around 20 feet back from the seaward side of the dune.  Other plants, some of which are weeds, include hebes, pampas, Scotch thistle, blackberry and cape gooseberry (yum).  The dune for the most part, slopes gently down to the beach.  Access to the beach is easy.  Vegetation clothes the dune down to the beach level.  Marram grass and sand convolvulus being closest to the sea.

The beach proper is quite extensive and is mostly well-endowed with sand, particularly at the upper and lower sections of the beach.  The middle section often contains a distinctive V formation that variously contains stones and water.  There are some broken caterpillar-like rock formations that flow in an east/west direction.  Old fossilized tree parts are visible in one of these near the arch.  Further out, in the low tide zone, though covered in water, old tree snags sometimes become visible.  This is dependent upon the beach and sea state.

During periods of low high tides, good sand cover and calm weather, there is an upper high tide free beach area that leads up into the dune.  This in turn makes it a temporary collection point for driftwood and flotsam.  The prevailing current which runs north, from the south-west, delivers the driftwood up to the dune’s sand bridge, thus helping to reinforce it and build it up.  This allows more sand to take up residence, then plants in a continuing cycle.

When the sand/land bridge that connected the dune area to Mammoth Rock was intact, logs would regularly collect on either side of this bridge.  On the river side of the bridge the log field was more substantial.  As the beach on either side of this bridge was usually well built, the log fields tended to be semi-permanent, although they waxed and waned in extent.  However, when the sand bridge was destroyed in July 2008 after being intact for the past 50 years, all that changed.

I haven’t mentioned the beach area from the northern side of Mammoth Rock across to the Tongaporutu River.  This is because for the most part, I haven’t accessed it.  However, how far out and how extensive the sand bar is in this location is dependent upon which side of the estuary the river flows into the sea from.  The sand type here can vary between straight sand cover to squishy sand islands that are either surrounded by tidal created low channels of water, or low lying dry sand channels.

 

ZONE TWO.  Travelling south, this encompasses the area from the arch to just before Elephant Rock.  There is no upper high tide beach area here, therefore no driftwood nor flotsam can accumulate, unlike in Zone One.  THE THREE SISTERS ROCK STACKS, THE MAORI CARVINGS CAVE and the large, open domed three SISTERS CAVE ARE LOCATED HERE.  The southern boundary extends to the end of the cliff section that houses the Three Sisters cave.  (This turns around into a cove which, along with the nearby Elephant Rock, is incorporated in Zone Three).

Zone Two is what I term a turbulent zone.  The localised topography here renders it particularly susceptible to water turbulence and channelling.  Due to this, sand cover can be so completely stripped away that bedrock is frequently exposed, sometimes for quite extended periods of time.  A number of rock platforms and rock shelves that inhabit this zone are variously covered and uncovered with sand.  The tops of the highest of these platforms and shelves usually remain sand free, but on rare occasions of exceptionally high localised sand cover, they too can be buried.

Beach sand coverage or lack thereof is determined by the prevailing weather and sea state conditions at the time and over a period of time.  Life for mussels and other flora and fauna is perilous and for the most part, short-lived.  Sometimes, some do survive long enough to reproduce, but as a general rule, those that do, inhabit the low water mark and/or beyond to seaward.  Further, generally speaking, the higher the rock top is above base bedrock, the longer flora and fauna gets to live, grow and reproduce.

 

ZONE THREE.  This EXTENDS from the large cove immediately to the NORTH of ELEPHANT ROCK, SOUTH to the POINT.  Specifically, it starts where the cliff that houses the Three Sisters cave ends and turns around into a large open cove.  The Point on the southern boundary of Zone Three separates the Three Sisters Beach from the Four Brothers Beach.  The area at the Point is covered separately.

Zone Three contains several forming blind caves and mini coves.  There is also one through arch.  Elephant Rock, a large rock stack, also inhabits Zone Three.  The beach here generally has good sand cover, but between Elephant Rock and the Point, bedrock and rock shelves are sometimes exposed due to water turbulence and channelling.  The cliffs here are very wet due to the presence of tiny water courses or soaks.  This constant flow of water cascades down onto the beach.  This could be a minor causal channelling factor.  Some rock platforms reside on the immediate southern side of Elephant Rock.  I have never observed them to be completely covered in sand, (but that doesn’t mean that they can’t be).

As with the other beaches, sand cover over all three zones on the Three Sisters Beach can be well built up at the cliff faces and well built up as sand bars or sand banks at the low water mark, but be shallower in the middle in a V type formation.

 

2001

8 July 2001  

PHO2007-157, PHO2007-167

PHO2008-843, PHO2008-845

This was my first visit to the Three Sisters Beach.  It was before the Tongaporutu project started.  I didn’t keep any notes at the time, apart from just recording it in my photographic notepad.

The weather was exceptionally fine and calm.  At all three zones, the sand cover was good.

 

2002

12 May 2002  

PHO2008-872

Though this photo is taken from the Pilot Point cliff top, it looks across to the Three Sisters Beach.  The sand cover in Zones One and Two looked good.  I presumed that the sand cover in Zone Three was also good, but Elephant Rock blocked this section of the beach from view.

 

2003

8 June 2003  

PHO2007-319, PHO2007-321,  PHO2008-893

 

It was reasonably fine, but there was a strengthening north-westerly.

Zone One.  The beach was well built up.  I couldn’t access beyond this, but from what I could see, Zone Two was also well built up.

 

11 June 2003  

PHO2008-018, 021-022, 919-920

After yesterday’s freezing, (southerly gale) windblown conditions, today was fine and calm.

All three zones, including between Mammoth Rock and the Tonga River.  From various viewpoints, the beach cover was good.

30 June 2003  

PHO2008-032

Although the weather didn’t look promising, I decided to go up to Tonga.  This was because I wanted to photograph the Little Sister before she broke up even more in the current weather systems sweeping across.  On 12.6.03, she collapsed to roughly half her size.  The evolution of the Little Sister and other rock stacks is detailed in Section Six on Sea Stacks.

I only took one photo, a standard view of the Three Sisters located in Zone Two.  I don’t mention the beach state, but it appears to be reasonable, except that a number of rocks in the foreground are sitting quite high above the sand level.

 

13 July 2003  

PHO2008-050, PHO2008-051, PHO2008-053, PHO2008-934, PHO2008-939

A calm, sunny, clear winter’s day.  It follows a strong south-easterly yesterday.  At All three zones the beach level was good, except that the caves and cliff pillars were hollowed out at the bases and surrounded by water.  At the Sisters in Zone Two, the rocks in the foreground were now almost completely buried in sand.

 

27 July 2003  

PHO2008-068, PHO2008-970

 

A cold north-easterly was blowing.  There was high cloud with lighter patches.  They were the advanced tentacles of an approaching low in the Tasman Sea.  At Zones One and Two, the sand level was high.  Even the cave with the Maori carvings in Zone One was now covered in sand, whereas a fortnight ago, they were filled with water at the bases.  However, at the Three Sisters, the rocks that were almost buried a fortnight ago were revealed again.

 

30 July 2003  

PHO2008-083, PHO2008-988

A glorious day for the middle of winter.  PHO2008-083 shows part of Zone Three looking across to the Hole in the Rock and the Point.  PHO2008-988 shows the Middle Sister.  Though the beach state isn’t well highlighted in this evening photo, the sand level was good in all three zones.

Please note, PHO2008-083 has also been included under the Point.  As the Point is a boundary, there will be some overlap that includes part of either the Three Sisters Beach or the Four Brothers Beach.  This will also be true of other ‘boundary points, such as the Gibbs’ Fishing Point, etc.

 

13 August 2003  

PHO2008-116, PHO2008-117, 2008-118, PHO2008-120, PHO2008-121, PHO2008-123, PHO2008-133, PHO2008-135

 

CLIFF SEQUENCING.  The weather was fine with a light south-easterly. The past six weeks have been unusually calm, mild and fine.  At all three zones the sand cover was good.  At the Three Sisters in Zone Two, apart from some rock fall debris at the base of the Middle Sister, the rocks in the foreground were mostly buried in sand.

 

PHO2008-116-118 show Zone One.  PHO2008-120, PHO2008-121, PHO2008-123, PHO2008-133 show parts of Zone Two while PHO2008-135 shows part of Zone Three.

 

 

28 August 2003  

PHO2008-199, PHO2008-200, PHO2008-203, PHO2008-1018

 

A westerly breeze was accompanied by spectacular cloud build-ups.  Showers were forecast.  Yesterday, a stiff northerly and heavy rain pounded the province as a front went through.  On the previous Saturday, (23rd), a ferocious south-easterly roared all day.  The strongest wind in three years.  A big swell was running.

 

At all three zones the beach level was good.

 

 

29 September 2003  

PHO2008-218, PHO2008-210

 

An ALPHA STORM struck Taranaki yesterday with thunder, lightning and north-westerly winds.  At Tonga, the wind raged, the sea boiled and the sights, smells and deafening sound all blew the senses away.

 

Down at the beach in the afternoon, it was like a bomb had struck.  At Zone One, the sea had surged up the dune and into the bushes.  This was evidenced, (but not photographed unfortunately), by the salt foam and flotsam deposited there.  Vast amounts of sand had been scoured out, to the point where bedrock and lots of rocks I hadn’t seen before had been exposed.  This was true of both Zones One and Two.  I couldn’t access Zone Three.

 

The cliff faces looked really battered and I noticed lots of rock debris in the hollows and caves indented into the cliffs.  The Little Sister in Zone Two had been destroyed and the rocks in the foreground of the Sisters were uncovered.

 

 

6 October 2003  

PHO2008-249, PHO2008-250, PHO2008-1044, PHO2008-1045, PHO2008-1046

 

A cold, sunny day with a slight westerly breeze.  The sea was still running high after a recent double whammy of storms (the 6th and 28/29th September).  Down at the beach, All three zones were still severely scoured out.  They looked even more so than last Monday, 29th September.  At Zone Two, the rock platforms to the rear of the Sisters were very prominent.  Also, the interior of the Three Sisters cave was heavily scoured out and filled with rocks.  Though there was heavy scouring, there was still fair sand cover in places in all three zones.

 

 

8 October 2003  

PHO2008-1058

The weather was fine.  A light north-easterly breeze was blowing.  I had arranged to meet with Dr Peter King, D.Sc, a sedimentary rock geologist.  At Zone Two I photographed him measuring part of the cliff face to the rear of the Three Sisters.  The beach remained heavily scoured out with lots of rocks and pools of water present.

 

24 November 2003  

PHO2008-413, PHO2008-415, PHO2008-427, PHO2008-1113, PHO2008-1120,

 

There was a mix of high cloud and blue sky.  A stiff westerly was blowing.  There was a fair surf running, but it was jumbled up at the wave-line.

At  all three zones, the sand had been ‘barred up’, (sand bar), at the lower level.  Up at the cliffs in a zone of approximately 30-50 feet, lots of rocks were exposed as the sand had been excavated out.  A V formation was present.

At  Zone Two, the sand level was good but the rocks inhabiting this region were exposed.

At  Zone Three, at the low tide mark, numerous sand islands were present on the southern side of Elephant Rock.  There was lots of froth at the surf line and in the temporary pools enclosing the sand islands.

 

 

1 December 2003  

PHO2008-1124-1125

I had taken my 300 mm telephoto lens up to Tonga as well as my wide angle lens to photograph some of the flora, particularly on the Three Sisters Beach.  These two images were taken in Zone One.  Quite a few small pebbles were present on the beach.

 

26 December 2003

During the past week there had been a couple of heavy dumps of rain.  Today, there was a strong, cold south-westerly with frequent showers.  All three zones.  As on my previous visit, the beach was built up further out to seaward, but also it was built up close to the cliffs, but slightly hollowed out in the middle in a shallow V formation.

 

2004

5 January 2004  

PHO2008-501

Had a blinding, light induced headache from a bright, early morning photo shoot.  I was staying up at the Gibbs’ farmhouse.  Zone One.  The beach level was very high leading up to the dunes.  So much so that a huge pile of driftwood had taken up residence there.  The high tides were ‘low’ high tides, and combined with a high beach level, this was now a temporary dry upper tide area.  Despite being very tired and feeling sick with a thumping headache, I managed to document the scene.

23 Janaury 2004  

PHO2008-1204

Zone One.  There were still lots of logs jammed up on the beach as the sand cover remained good.  I also noticed some of the smallish, mostly grey, mudstone rocks had been splatter-gunned by the recent heavy rains.

 

 

4 February 2004  

PHO2008-651-652

After days of persistent rain, I decided to go up to Tongaporutu.  Everything was lush from all the wet weather.  Zone Two.  The sand level was good around the Three Sisters, but the resident rocks and rock shelves were visible.  Brown frothy sea foam inhabited the wet zones.

 

 

5 April 2004  

PHO2008-776-783

The day wasn’t promising with very strong south-westerlies.

Zone One.  A flotilla of logs had been chucked right up to the dune’s leading edge, courtesy of the 3.6 metre high tides.  The sea was roaring and if any birds were singing, they couldn’t be heard above the din.  The noise was much louder than usual.  The sand level was good.

Zone Two.  The sand level was reasonable, but some rocks and shelves were visible.  Also, at the Three Sisters the usual family of rocks and shelves were exposed.

Zone Three.  Here too, the sand level was reasonable, but like Zone Two, some rocks were visible, along with pooling water in the sand depressions.  These were more prevalent at the lowering water mark.

18 Septemeber 2004  

PHO2008-1305, PHO2008-1308, PHO2008-1311, PHO2008-1312, PHO2008-1314  PHO2010-0473

From June 2004 through to June 2005, in the change-over from computers, the diary notes from this period have been lost.  However, I didn’t visit much during this period.  (The photographic notes were and continue to be, recorded separately.  They remain extant).

Zone One.  The beach level was good.  Of crucial importance however, is a photo I took with my Spotmatic 35 mm film camera.  This was taken from the cliff top overlooking Mammoth Rock.  It clearly shows the sand/land bridge that connected the dune to Mammoth Rock.  It is the only photo I have of this.

 

2005

24 September 2005  

PHO2008-1383, PHO2008-1384, PHO2008-1385, PHO2008-1386

There was a westerly wind.  It was cloudy with some sun.  At all zones the sand was piled high up the beach and up to the cliffs, but had been gouged out further down.  Lots of rocks were uncovered.

 

20 August 2005  

PHO2008-1408

There was a slight north-easterly breeze.  It was mostly fine with some cloud around the mountain.  The beach level in all zones was good, but some rocks and shelf tops were visible.  In Zone Three, on the southern side of Elephant Rock, a large pool of water had some small fish trapped in it.

 

21 August 2005

There was no wind, the sea was almost flat and the sky was filled with high cloud.  The beach level in all zones was good, but some rocks and shelf tops were visible.  Even though sand levels can be high, some rocks and rock shelf or rock platform tops can still be above the sand height, but not usually by much.

19 September 2005  

PHO2008-810,  PHO2008-1454, PHO2008-1456, PHO2008-1457, PHO2008-1459, PHO2008-1461, PHO2008-1463,

 

An ALPHA STORM slammed into Taranaki.  A huge sea was running and the wind was hurtling in from the west, south-west.

 

Zone One.  At the dune face, most of the marram grass had been ripped out.  Also, great chunks of the banks had been washed away, along with resident flaxes and other shrubs such as coprosmas.  Storm debris, including bits of trees had been flung right over the top and onto the land.  This even exceeded what had similarly occurred during the Alpha Storm of 29.9.03.  Again, I didn’t photograph this!

There was roughly a two foot drop off to access the beach from the usual track.  At this high end of the beach, it is often a graveyard of dead logs.  All had vanished, apart from one or two transient newcomers.  It was as if someone had come down with a giant broom and swept everything away.

All zones.  Huge swathes of sea foam frothed up and around the cliffs, filling all of the nooks, crannies and caves.  The boiling surf was also replete with foam, much of which was being blasted up into the air.  The beach level was relatively good, but rocks and rock shelf tops were exposed.  At Zone Three in particular, between Elephant Rock and the Point, the beach was temporarily polished with wet.  So much so, that I alone was privileged to witness wind partnered frothy gobs of sea foam, deliver a mesmerizing performance across this most ethereal of dance floors.

 

30 November 2005  

PHO2008-1524

It was warm and sunny with a westerly breeze.  All zones.  The sand level was well built up, especially so at the cliff bases.  The sand level was about three feet higher than normal right up at the cliffs and around a foot to eighteen inches higher than average on the beach in general.  Most of the rocks were covered with quite a few small, round rocks on top of the sand around the high tide mark.

 

2006

 

 

1 January 2006

It was very windy with a stiff westerly.  Down on the beach it was extremely unpleasant with in-your-face wind, a surging sea combined with lots of salt spray.  All zones.  The beach was still well endowed with sand, especially up at the cliff bases.

 

15 January 2006  

PHO2008-812

There was high cloud and a westerly wind.  All zones.  The beach level was good.  I was particularly taken with the rainbow coloured sea foam bubbles that frothed on the beach.

 

 

30 January 2006  

PHO2008-1561

The weather was fine with no wind.  I was up at Tonga to participate in a film shoot by Sticky Pictures for the upcoming Blood, Earth, and Fire exhibition at Te Papa Museum in Wellington.  My Tonga project was to be one of six that would be shown.  All zones.  The sand was being built up further out on the seaward side of the beach as opposed to the cliff side.  The middle rock shelves had more rock exposed.  The beach as a whole was sand covered, with it being built up more at the wave line.

 

31 January 2006  

PHO2008-1570

I lucked in with a helicopter ride during the film shoot by Sticky Pictures.  Unfortunately, I lucked out with the dull weather.  Though the image isn’t tack sharp, it is important because it shows the sand/land bridge that connects the dune to Mammoth Rock in Zone One.  Also shown in Zone One is the beach on the seaward side of the dune.

 

1 March 2006  

PHO2008-1595

There was a low tide of 0.0 metres (due at 6.05 pm), accompanied by a high tide of 3.9 metres.  They were the lowest and highest tides for the past three years.  The weather was partly cloudy with a stiffening westerly.  In all zones, the sand had built up towards the cliffs and dune edges.  The sand was also built up in most places at the wave-line.  The photo here shows Zone Three between the Point and Elephant Rock, looking north.

 

At Zone Two, in the middle of the beach and extending to the Little Sister, rocks, rock shelves/platforms and mini-reefs were exposed.

 

At Zone Three, rocks were also visible in the middle section of the beach.

 

30 March 2006  

PHO2008-1610, PHO2008-1611, PHO2008-1612, PHO2008-1616

A very low tide of 0.1 metres was due at 4.40 pm.  There had been wind from the easterly quarter for quite some time.  Today however, the sea state was calm and the day fine with no clouds.  All zones.  Sand had been gradually building up at the wave-line, but was excavated out around the rock stacks.  Sand was partly built up at the cliffs.

In Zone Two, rock shelves/platforms that had been exposed on my last visit on 1.3.06 (at the Little Sister line), were now covered with sand.  The low mini-reefs immediately south of the Little Sister were in the process of being covered by sand.  Rock pools surrounded the Sisters.  There were nice wave and ripple patterns in the sand on the northern side of the Sisters.  They resembled water ripples and waves.

 

17 May 2006  

PHO2008-1624, PHO2008-1625, PHO2008-1626, PHO2008-1627

The weather was fine with a light westerly.  At all zones the beach was reasonably built up with sand, but it was plain sand, not patterned when I photographed my magical image of the Three Sisters on 30.3.06.  in Zone Two, various small rocks here had pools around them, while in Zone Three a small rock shelf was visible.

 

 

13 June 2006  

PHO2008-1629, PHO2008-1631, PHO2008-1632, PHO2008-1633

Yesterday, a weather bomb crossed the country.  Though bad here, it had affected the South Island worst of all.  We had fierce northerly winds and rain.  Today, the wind changed around to a strong south-easterly.  This offshore wind flattened the ferocious sea.

Down at the beach in Zone One, the vegetation bordering the beach had taken a beating.  Storm surge conditions meant that there would be no such thing as a low tide today.  In all zones, quite a few rocks were exposed from what I could see.

 

 

26 September 2006  

PHO2008-1952

The day was sunny.  The wind had finally died down after the past few days of rough weather.  Down at the beach, between Mammoth Rock and the Three Sisters (Zone One), the sand cover was quite well built up. Skeletal shrub and tree remains littered the beach close to the dune.  Small pebbles were scattered across the beach.

At the archway leading into Zone Two, the archway was scoured out with rocks exposed.  Rocks were also present a quarter of the way out from the cliffs.  Rocks and rock platforms were also exposed at the Sisters.  Sand was built up at Elephant Rock in Zone Three.

 

10 August 2006

It was calm early on, but the wind then got up from the south-west and it turned cloudy.  At all zones, the beach appeared to be more built up than on my last visit, particularly near the shore-line and cliffs.

September 2006  

PHO2008-1998

 

There was a slight north-easterly breeze and it was raining steadily when I arrived at Tonga.  A very low tide of 0.1metres was due at 4.51 pm.

 

In Zone One, on the upper beach, there were skeletonised small tree corpses.  These had been eroded out of the dune’s seaward face by the sea.  I didn’t photograph them but should have.  I also noticed that the beach was well built up on the landward part of the beach.  In the middle, rock shelves were prominent and further out, the beach built up again, except in the vicinity of the Sisters.  It roughly resembled a V with a flat line on either side, with the V being in the middle.  (This is where I got the idea of a V formation from).

 

The rock shelves and platforms were present in all zones, but particularly so in the vicinity of the Three Sisters, (Zone Two).  A reef was also visible at the shoreline.  In the V part of the beach, the rock platforms were very pronounced with the sand having being severely excavated from in and around them.  On the northern side of the Three Sisters, I was intrigued by three large, well exposed rock platforms at the wave-line.  I wanted to photograph the Sisters from an unusual and rare perspective.  That is, further out than usual due to the exceptionally low tide and highly exposed rock shelves.

 

The tide was so low, that I noticed three dark, shark-like dorsal fins protruding from the water just beyond the low water mark.  They stood out from the surrounding rocks.  From what I could see, they appeared to be the remains of ancient trees, all virtually identically pointed like black shark dorsal fins.

 

 

 

2007

 

 

15.7.2007   PHO2011-1021

 

The breeze, originally a gale, had been blowing from the south-east for some time.  The sky was clear as was Mt Egmont.  At Zone One, I noticed how much the shore-line (dune edge) had retreated.  Much of the marram grass had gone and tree skeletons tumbled down onto the beach.  Lots of small stones littered the beach.  The sand level was high hard up to the vegetation line, but hollowed out midway to the surf line where the beach appeared to build up again like a ‘sand reef’.

 

At Zone Two, hard up to the cliffs in the vicinity of the Three Sisters, it was all rocks, shelves and platforms.  At least two feet of sand had disappeared.

 

Zone Three.  On either side of Elephant rock there was plenty of sand, but some rock shelves were visible at the wave-line.

 

 

23.12.2007   PHO2011-1120-1123, 1147

 

The day was fine with a slight northerly.  At Zone One, the shoreline had extensively eroded since my last visit on 15.7.07.  Sand cliffs were forming at the dune area.  At the base of the largest sand cliff, was a cluster of semi- rounded stones.  They looked like scaled up versions of sand grains.  I believe they scale fractally.  The sand/land bridge remained connected to Mammoth Rock, but there were lots of logs on the upper beach area.  Sand was pushed high up to landward.  There was a highly visible V formation in the middle of the beach where it had been extensively scoured out.  Lots of rocks and bedrock were visible.  It was the lowest I can remember seeing it.  Past the middle, the sand built up again, rather like a sand reef or bar.

 

Zones Two and Three were well endowed with sand.  Some rocks and shelving were visible, but sand had been replenished around the Three Sisters, whereas in July virtually all the sand in this location had disappeared.

 

 

 

2008

 

 

10.2.2008   PHO2011-1166-1167

 

Today there was a light northerly, sea mist and light rain.  For the most part, the country had been experiencing drought conditions.  At Zone One, the beach level was even more built up than last time.  Even the central V which is normally a rock garden was covered with sand, although the sand was pot-holed with pools of water.

 

At zones Two and Three, the sand level was good, but some rocks were visible.

 

 

6.4.2008   PHO2011-1207

 

There was a 0.2 metre low tide, no wind, but a big swell was running.  Down at the beach, All three zones were very well endowed with sand to high levels, especially towards the cliffs.  Some rocks, rock shelves and platforms at Elephant Rock and other places that are never totally water free at the very low tide mark, very rarely get completely covered in sand.  Rocks, rock shelves and platforms that are free of water during low tides, can be completely covered with sand during high sand cycles.

 

 

6.5.2008   PHO2011-1227

 

There was a cold, light southerly blowing and it was sunny.  At Zone One, the beach was well built up, but the beginnings of a middle V formation were apparent.  Aside from this, at all zones the beach level was good.

 

 

20.7.2008   PHO2011-1247-1248, 1250,

 

SUPER-STORM EVENT.  Super-Storm One.  We have had a low pressure system from the north, with north-westerly winds and a ton of rain.  Upon my arrival at Tonga, the angry sea said “Hi.”  Bad tempered, it was frothing brown with runoff from the swollen Tongaporutu River.

 

Down on the beach at Zone One, the vigorous depression had monstered the beach and the coastline from what I could see of it.  It is the worst destruction I have seen and quite surprising as I have documented more potent, individual storms.  A low tide of 0.6 metres was due at 5.15 pm.  It was combined with storm surge conditions.  In short, there was no such thing as a low tide.

 

Having said that, the tide, though only 0.6 metres had retreated far enough out for me to venture onto the seaward side of Mammoth Rock.  This was due to sand being shovelled off the beach and being built up on a seaward side sand bar.  The Tonga River was running fairly close to the Pilot Point side of the estuary.  There were lots of sand islands surrounded by foamy water channels over on this side.  At the beach proper in Zone One, the sand cover was good and even, particularly at the upper beach zone.  There was no V formation or bedrock, none that were visible anyway.  There were logs and lots of debris, including live vegetation that had been ripped from the shoreline.  Huge chunks of dune had been gouged out and there was a roughly three foot drop to access the beach from the Gibbs’ track via the dune.  The sand cliffs I observed in the dune face on 23.12.07 were continuing to grow and expand.  (PHO2011-1247 looks across towards Pilot Point.)

 

In Zone Two, the beach had been scoured right down to its bare bones of bedrock, rocks, rock shelves and platforms.

 

 

24.7.2008   PHO2011-1267-1271

 

SUPER-STORM EVENT.  Super-Storm Two.  A severe storm with north-westerly winds had pounded the North Island yesterday with heavy rain, high winds and massive swells.  The weather today was calm with a light southerly.  Upon arrival at Tonga however, I was greeted by a huge swell with mountainous waves breaking well offshore.  A high tide of 3.1 metres was due at 1.41 pm.

 

Down at the beach at Zone One, I could see that the storm surge had come right over the bank.  Also, you could no longer access the beach from the usual spot (Gibbs’ track leading down from the barn).  This had been further gouged out and there was now about a five foot drop to the beach proper.  I thus followed a track that ended opposite Mammoth Rock.  The SAND/LAND BRIDGE THAT HAD CONNECTED THE DUNE TO MAMMOTH ROCK HAD BEEN DESTROYED!  I later learned from the Gibbs that it had been in place for at least the past 50 years.

 

Part of the low lying dune here, (the river side) had an overgrown log field.  That is, logs and sand, long since buried, were anchored in place with grass and flaxes, etc.  A small creek marked the dune’s boundary with the landward cliff.  The seas and presumably high river runoff had ripped out vegetation, thus exposing a sand wall of around five feet in height.  This lead around to the seaward side of the dune where the sand wall grew into expanding sand cliffs.  These were subject to slumping and had plants such as flaxes, slipping down towards the beach.

 

Between Mammoth Rock and the cliff, there were a lot of live plants, including mature flaxes, tossed up at the cliff line.  I clambered up onto an outcrop on Mammoth Rock that overlooked the Tonga River.  (The river was now running closer to this side of the estuary).  Just after I’d climbed up onto the outcrop, a huge surge swept past.  It came in like an express train packed with tremendous energy.

 

On the beach proper in Zone One, the sea, though going out, seemed ‘high’.  This to mean that due to storm surge it was more bulked up than usual.  The beach itself though for the most part clothed with sand had been swept clean.  All the logs and other debris had vanished.  Such was the power of the waves that I could hear the stones clinking together as they were rolled up and down the beach.

 

At the base of the dune on the seaward side, a number of rounded stones were accumulating.  I slowly walked along the beach, with one eye on the ten foot sand cliffs that have been carved out and the other on the surging waves.  Boulders were cluttered close to the first arch.  I couldn’t access the beach beyond Zone One.

 

NOTE:  Re the sand/land bridge that connected the dune to Mammoth Rock, it could have been ripped out around the 20th July.  If so, it’s strange that I made no mention of it until the 24th, the date of this diary entry.  Whichever date is correct, I didn’t photograph it until the 24th.  Because I could still access the beach at Zone One via the track that leads down from Gibbs barn, I had no reason to go around the corner to Mammoth Rock (where the sand bridge was out of my line of sight). This was because south, not north of where I accessed the beach was where all the action had occurred (Three Sisters, etc), or so I thought.  So, the sand/land bridge could have been destroyed on or around the 20th July.

 

It was only when I was forced to use for the first time, the second access track to the beach, which is directly opposite Mammoth Rock, did I discover that the sand bridge had been breached.  From the 24th July 08 onwards I have been accessing the Three Sisters Beach via the Gibbs’ ‘Dunny Track’.  This second track is located on the Tonga River end of the cliff (north of the barn), whereas the original track down to the beach is immediately south of the barn.  This track provides horse and vehicle access to the bottom.

Specifically, the ‘Barn Track’ gives, or gave, direct access to the beach proper, whereas the ‘Dunny Track’ gives access to the beach at the rear of Mammoth Rock.  The Gibbs kindly let me access the beach via their farm.  This saves me time.  Also, sometimes the Tonga River is hard over to the cliff, making beach access from the Tonga Reserve dangerous and time-consuming.  Visitors can pick and choose when they come; I have to come in all conditions for observational purposes.

 

I have just had lunch after typing this up this morning (1 pm, 4.1.2010), when I thought about the photos I took on the 20th.  From where I had visited on the beach, I couldn’t have helped but notice that the sand bridge had gone.  Upon checking my notes, I make no mention of it until the 24th.  Either it had been swept away on the 20th and I didn’t notice that it had, or, that it really was destroyed on the day of my visit, the 24th July.  (I now actually believe it was swept away during the 12.59 am, 3.2 metre high tide that occurred on Wednesday 23rd July).  What makes me think that this is correct is that I mention how ‘bulked up’ the sea looked on the 24th.

 

 

3.8.2008   PHO2011-1273-1276

 

SUPER-STORM EVENT.  Super-Storm Three.  A 0.3 metre low tide was due at 5.14 pm.  This was later than I would have liked, but with storm conditions over the past two weeks, I didn’t have much choice.  This was the third storm in a trilogy and it had been very wet before they occurred.  It was cold, showery and very windy with north-westerlies.  Being ill with the flu added to the uncomfortable mix.

 

Down at the beach at Zone One, I was amazed at how much additional destruction had occurred.  Where there had been a roughly three foot drop, then a five foot drop, there was now a ten foot drop to the beach.  And this part of the flat area was being eaten back towards the track.  A frightened cabbage tree perched precariously close to the new dune boundary.

 

At the beach access site opposite Mammoth Rock, lots of flotsam was strewn about.  On the beach proper, lots of stones were present.  Though the sand cover was reasonable, the pile of rounded stones that I had observed at the dune’s base on the 24th July had grown considerably.  There were also frothy, watery shallow channels present on the beach.  Also, more rocks were becoming exposed.

 

The damage to the dune was tremendous.  Huge, ten foot sand walls or cliffs led to huge gouges far up the cliff near the first arch.  The beach was still scoured out at Zone Two and there was no access beyond the first arch.

 

 

18.8.2008   PHO2011-1288-1289, 1294-1295, 1297-1299

 

I’m still recovering from the flu.  This is the fourth week and I am still lumbered with chest congestion.  Today is a sort of break in the terrible weather we have been experiencing these past few weeks.  A low tide of 0.4 metres was due at 4.48 pm.

 

Down at the bottom at Zone One, I continued to be amazed at how much more of the dune area had been lost.  The dune bank on the seaward side had been scoured back almost to the track.  The poor cabbage tree had gone and the white fence that I haven’t mentioned before was at the bottom of the sand bank.  (The fence was to the rear of the cabbage tree).  If this scale of destruction continues, I fear for the entire dune area down here.

 

Entering the beach opposite Mammoth Rock, I noticed that there was a lot more flotsam and stones compared to my last visit.  And I thought it had been bad last time!  As the tide was a fair way out, I could see more of the beach.  The beach state was terrible.  Tons of seaweed – never seen this much before.  Caterpillar rock formations were exposed as was bedrock, rock shelves and other rocks and stones.  I also saw lots of mature green lipped mussels and loads of empty red and white gastropod shells.  The underwater damage must be truly staggering.

 

At Zone Two the beach, (PHO2011-1289), apart from a small patch of rare sand, had all been stripped right back to bedrock.  In all of my trips up to Tongaporutu, I have never seen anything that comes close to this orgy of destruction.  It really, really is mind-blowing.  I trudged on rock platforms, bedrock and small stones towards Elephant Rock.  Zone Three resembled Zone Two.  Any thoughts of accessing the Four Brothers beach remained just that.

 

 

28.9.2008   PHO2011-1321, 1323, 1325, 1335-1336

 

A low tide of 0.4m was due at 4.07 pm.  Today was a short weather window.  It was fine and sunny with a south-easterly breeze.  Storm conditions had prevailed for some time.  The sea, though relatively calm, had a large storm swell running.

 

Down on the beach at Zone One, the sand was building back up, but some of the caterpillar rock formations were still visible.  Near to the arch, the sand was squishier, being composed of sand islands and water channels.

 

At Zone Two, bedrock, rock shelves and platforms remained the dominant feature of this area of the beach.  Some sand was present, but not much.  Zone Three was similar, but more sand was present, particularly at the Point where the beach had built back quite a bit.

 

When the beach level drops;  that is when it is mostly stripped of sand, the sea can come in much further during low tides, especially if combined with storm surge conditions.  Under such conditions, there is almost no such thing as a low tide.  This would give the appearance that the sea level had risen by a foot a more. 

Conversely, when the beach is well endowed with sand, it is higher, so that the tide can appear to go out further than what the actual low tide mark of, say, 0.6m would indicate.  This would give the impression that the sea level has dropped by a foot or more.

 

Unless a beach is paved with unchanging concrete, beach height information can be manipulated for Climate Change purposes by choosing which beach state one wished to measure.  In other words, dependent upon which side of the climate change fence one sits on – a believer or non-believer, one can give a believable, but one-sided and false result.

15.10.2008   PHO2011-1356

 

The weather was fine with a slight northerly breeze.  At Zone One, on the beach there was the usual debris field of logs and other vegetation scattered about.  The sand cliffs at the dune, the lower dune bank and the beach proper, appeared to be relatively stable.

 

At Zone Two, the area was completely devoid of sand.  What little bit had built up on my last visit had now vanished.  Roughly a metre of ‘beach’ (sand), had been lost in this area.  In fact, some of the fragile rock slabs (part of the bedrock), have started to be smashed up.  This is something I haven’t observed before; such is the length of time these bedrock slabs have been exposed to the sea’s corrosive power.  Usually, particularly in the past, they have been covered with a protective blanket of sand.

 

Of the beach as a whole, it was irregular in height.  In places the sand was being built up at the wave-line.  Rock platforms and tables were being exposed in the middle, with sand building up again on the landward side.  The obvious exception being Zone Two between the Three Sisters and Elephant Rock.  This was virtually all bedrock and rock shelves/platforms right up to the cliff.  This extended from the Little Sister to the seaward end of Elephant Rock.

 

 

12.11.2008   PHO2011-1398, 1401

 

It was fine with a light westerly.  A low tide of 0.4m was due at 3.47 pm.  Down at the beach at Zone One, I was confronted by a mass of plant material.  They had emanated from a massive cliff section collapse that I had first observed from the Pilot Point side of the Tonga River while enroute to do cliff sequencing at Rapanui beach and Pilot Point.  Towards the main arch, I noticed that islands of plant material were increasingly being isolated by cascading ‘rivers’ of sand/rocks in the cliff to the left.  The next heavy rainfall should see them crash down onto the beach.

 

At Zone Two, due to the tide coming in, I could only partially observe the beach state.  Sand was building back, particularly close to the cliffs, but a lot of bedrock, rock platforms and rocks were still present.  Some of the rocks and boulders were obviously from the cliff section collapse.

 

 

23.11.2008   PHO2011-1407, 1415, 1419-1421

 

A high low tide of 0.9m was due at 1.40 pm.  Normally I wouldn’t go up under such tide conditions, but I wanted to document the evolution of the cliff section collapse that I observed on 12.11.08.  The weather was very hot with high cloud and a stiff northerly.

 

Down at the beach at Zone One, the sand appeared to be building up again on the landward side of the beach.  Specifically, up to the seaward facing sand banks of the dune.  Quite a few stones festooned the upper beach.  At the gap between the dune and Mammoth Rock, the dune bank was still in retreat.

 

At Zone Two which I couldn’t properly access, though sand was present, bedrock, rocks and rock platforms were the main items on the menu.

 

 

14.12.2008   PHO2011-1424-1426, 1429-1430, 1434, 1436, 1438, 1467, 1469

 

CLIFF SEQUENCING.  A low tide of 0.2m was due at 6.04 pm.  The weather was hot and cloudy with a north to north-west breeze.  At Zone One, the beach was building up nicely, particularly at the landward end.  There was a slight dip or V in the middle of the beach, and then it built up again leading out to the wave-line.  There was more damage to the sand cliffs and cliffs along the dune’s leading edge.  This appeared to be more due to instability than anything else.  Things just sliding down and dropping off.  Plants, rocks, etc.  Rock platforms and rocks were still visible around the first arch, but sand cover was returning, particularly to seaward.

 

At zones Two and Three, the sand was also building back with rocks shelves and platforms to seaward being mostly buried with just their tops visible.  Rock platforms and bedrock, where visible, were more prominently exposed in the middle and closer to landward.

 

 

 

2009

 

 

11.1.2009   PHO2011-1488, 1490, 1493, 1503, 1509-1510

 

Upon arrival at Tonga there was no wind but the sky was promising to deliver rain.  At all zones, the beach was building back nicely, the main exception being in the vicinity of the Sisters.  Some rock shelves were just visible, while some rock platforms; particularly in Zone Two were more prominent, being higher than shelves.

 

 

8.2.2009   PHO2011-1573-1574

 

A low tide of 0.5m was due at 4.00 pm.  The weather was hot with little wind.  At Zone One the beach was well built up at the landward end and across to Mammoth Rock.  I don’t think the high tides now come right up as the driftwood and truly dead flax bushes were still there.  Even though it was only a 0.5m low tide, the tide was well out, more like a 0.3m low tide.  The sea state was calm.

 

At zones Two and Three, the beach was also built up, but in Zone Two, rock platforms and shelves, particularly in the central V area of the beach were quite prominent.  At Zone Three, some shelves in the middle section were visible.  The sand on the seaward side of this V area had numerous sand islands and pools of water, combined with squishy sand islands and dry channels.

 

 

11.3.2009   PHO2011-1579, 1582-1583, 1585, 1587-1588

 

A low tide of 0.2m was due at 5.13 pm.  The weather consisted of south-westerly gales and showers.  Down on the beach at Zone One, at the gap between Mammoth Rock and the dune, there was an accumulating log pile.  Water from a nearby stream flowed across the gap that separated Mammoth Rock from the dune.  The wind was horrendous.  It was the worst I have experienced on the beach.  Normally I wouldn’t go onto the beach under such conditions, but I had to come up to Tonga to deliver photos to the three farming families, the O’Sullivans, the Gibbs and the Mackenzies.

 

The beaches at zones One and Three were well built up.  However, in Zone Two, bedrock, rock shelves and platforms, particularly in the middle section were visible, having been stripped of sand.  Surging pools of water made for an interesting composition.  The sand cover was reasonable at the landward end of the beach.

 

In Zone Two, I set up the camera on a sand bar close to the Little Sister.  This part of the beach, looking back towards Elephant Rock, had, as I have already mentioned, been scoured out down to bedrock.  This created a large sea-water ‘lake’ here.

 

 

12.4.2009   PHO2011-1592-1593

 

The weather was fine, but there was a lot of grey cloud about.  Down at the beach, there was the usual log fest at the top of the beach in Zone One.  In all zones, the beach was well built up at the landward end with rock platforms, shelves and rocks being hollowed out in the middle V section, particularly in Zone Two.  At the seaward end of the beach, the sand built up again.  It’s like a beach is loosely divided into thirds.  The top third is usually well endowed with sand.  The middle third is like a V or a dividing line where the beach has a tendency to hollow out in a depression, and then the bottom third can be well built up with sand again in a fluid sand bar.  This is obviously a rough generalization, but on balance it holds true.

 

 

25.5.2009   PHO2011-1595

 

There was a very strong south-easterly, coupled with overcast conditions.  At Zone One, down at the gap between Mammoth Rock and the dune, I was surprised to see that the dune sand bank (where a small stream exited onto the beach), had been eaten back.  The building sand bar between the mainland and Mammoth Rock had gone and the big seas which we recently experienced have once again begun to eat into this corner.

 

People were present on the beach.  I found out later on from Adam Buckle that from the public access (The Tonga Reserve), the sand bar between the river and the cliff leading towards Mammoth Rock, was built up to the point where you could push a stroller along it without sinking knee deep into the mud, or, falling into the river if it was hard up to the cliff.  This probably explained the upsurge in people during the past few months.  Easier access from the Tonga Reserve to Mammoth Rock, plus Tongaporutu is perhaps getting better known.

 

At Zone Two (and Zone One), the beach was well endowed with sand up to the cliffs, but bedrock was exposed midway out and beyond to the surf-line.  The rock platform to the rear of the Inner Sister has been consistently exposed for an extended period of time.  At Zone Three there was good sand cover, but there had been a fresh cliff collapse to the rear of Elephant Rock which had impacted the area with boulders and rocks.

 

 

22.7.2009   PHO2011-1619, 1622, 1627

 

Today was a weather window between active weather fronts.  A very low tide of 0.2m was due at 3.55 pm, but due to storm surge conditions I wasn’t expecting the tide to retreat much.  At Tonga, the weather was fine.  The seas were big and noisy, but there was little wind.  The westerlies had been howling in New Plymouth.  At Tonga, the wind appeared to be deflected by the angle of the hills.

 

At Zone One, the sand cover up to the Sisters was good, especially up at the landward end of the beach.  The dune area appeared little changed despite high seas and big tides.  The dune was still eroding back, but gradually, not being torn out in huge chunks like during July 08.

 

At Zone Two, the beach was scoured right down to bedrock.  This seems to be a more common occurrence at this site of late.  Shelves and platforms were also visible, as they were in Zone Three, although sand cover was better in Zone Three.

 

It is interesting to note that rock platforms occur to the rear of the Inner Sister and to the rear and slightly south of Elephant Rock.  The top of the rock platform to the rear of Elephant Rock is always free of sand, but sand does on occasion bury its lower half.  The rock platform to the rear of the Inner Sister mostly has its top free of sand, but it can on occasion be completely buried with sand.

 

 

2.8.2009   PHO2011-1628-1629

 

We were between weather fronts, but a stiff westerly was still blowing.  Down on the beach at Zone One, the gap between Mammoth Rock and the mainland dune was widening.  There was a big drop down to the beach as more of the sand/land bank boundary had been eroded away by big seas.  The quite high sand bank here was being carved from right to left.  That is, the prevailing wave direction is from the seaward (southern) side of Mammoth Rock.  The waves flow through the gap towards the Tonga River, carving out the dune bank in the process.

 

 

22.8.2009   PHO2011-1630, 1632, 1634-1636, 1639, 1641, 1655

 

The weather had been calm for a while with breezes coming from the south-east.  North-easterly breezes developed today.

 

Down at the beach at Zone One, the Tonga River was well over to this side mid-way between the Tonga Reserve and Mammoth Rock.  At one point it was running only about ten feet from the cliff.  Getting onto the beach proper was difficult because the seaward side of the dune bank had been heavily scoured out by the king tides.  The bank was about 10 feet high with an angled drop.  Though the swell was about 2 metres, that wasn’t out of the ordinary, nor was it pumped up by storm surge conditions.

 

I then went around to the small stream that empties onto the beach at the gap opposite Mammoth Rock.  This too had around a 4 foot dead drop to the beach.  The ‘sand wall’ that had been building up near the cliff had now gone.  The gap continues to widen here.  Basically, the sand/soil bank here is being undercut.  That is, the base is being eaten out by water.  This causes the sandy material above to collapse.  Due to the openness of the sand/soil fill, only a few centimetres of water is all that it takes to cause a huge amount of damage.  Though the water may have little depth, it often packs an enormous amount of energy.

 

On the beach proper, there was a line of roundish stones that were roughly one foot in diameter.  Of the beach itself, the sand level was good but there were a lot of smaller pebbles littering it.  There was also a large wet area in the middle section.  On the northern side of Mammoth Rock, the sand level was also good and extended a fair way out to sea as did the rest of the beach at Zone One.

 

At Zone Two, the beach remained in a mostly bedrock, rock platform state with little sand.  What sand was present was mostly in the form of small sand islands, particularly at the low water mark.

 

 

26.8.2009   PHO2011-1658-1662, 1883-1887

 

A high tide of 3.1m was due at 1.48 pm.  This was accompanied by big seas that had been churned up by a series of potent fronts.  I wanted to document the gap separating the dune from Mammoth Rock at high tide to document how the sea impacts on the dune and to record what actually happens.  (General wave dynamics are detailed in Section Two on Weather).

 

Up at Tonga, it was sunny but very hazy due to a dense ‘fog’ of salt spray.  This extended several kilometres inland.  I planned to utilize both my digital and film cameras.

 

At Zone One, or more precisely, from above it, I took several images showing waves surging around Mammoth Rock and through the gap.  I also photographed the seaward portion of the beach.

 

Down at the gap, there was roughly a 5 foot clean drop from the highest point of the exposed dune bank down to the beach.  And, once down on the beach, you couldn’t clamber back up onto it again due to its height.  The only reasonable access point was where the stream entered the beach.  This was due to slumping sand hillocks.

 

This small stream was a natural separation point.  On the Tongaporutu River side of the stream, the cliff proper began.  On the seaward side of the stream, the dune proper began.  The leading edge of the dune travelled west towards the sea, then turned sharply left (south) to face the beach proper.  On the seaward side of the dune, the sand banks/cliffs were higher than on the gap side looking across to Mammoth Rock.

 

Adding to the mix was the Tonga River.  It was running close to this side of the estuary and had been for some time.  Combined with storm surge conditions, it was running high with periodic storm bore waves that surged landward over the top of the fast, seaward flowing river.  At the gap there were three separate wave actions that impacted on the dune.

 

The water depth surging through the gap averaged around 6 cm, with occasional wave tongue depths reaching around 20 cm.  Though the water depth was relatively shallow, it packed a huge amount of energy, as attested by stones and driftwood being tossed around.  I found it hard to believe that such a shallow sliver of water could topple a five foot sand wall, but it can and did.  And this is why.  The dune strata here had pure compressed sand for the lower half, while the top half consisted of soil.  With sand being a highly ‘fluid’ medium so to speak, when dissolved away by water, it causes the top soil strata to overhang.  When this overhang reaches a critical point, gravity causes it to collapse, thus the bank preferentially erodes back, usually in discrete chunks.

 

Thus, due to the sand base being a highly unstable medium, it is easily preferentially carved out by water, irrespective of the depth of the water acting upon it.  Obviously, the greater the depth of water, usually a highly energetic wave tongue, then the greater the carving action.  The primary wave carving direction is from right to left.  The secondary wave carving direction is from the opposite direction.

 

The topsoil depth indicated that the dune had been intact for some considerable amount of time (at least 50 years according to the Gibbs).  This is because it takes time for decaying plant material to rot down sufficiently and also to allow time for the depth of soil that was present, roughly two and a half feet.

 

There were fairly lengthy periods between beach topping surging waves.  This is because the beach is building back at the seaward end of the dune.  (The corner where it turns to face the beach proper).  Thus the beach at the seaward end of the gap is slightly elevated.  It then falls off gradually as the beach grades downwards towards the Tonga River.  Closer to the river, the beach height falls off quite markedly.

 

There are two types of dune bank failure, if we ignore the added impact of rain.  The first is, if the wave tongues are shallow, say having a depth of just a few centimetres, then the bank foundation is carved inward, both backwards and forward, while the top remains insitu.  This small scale carving to include both small chunks of sand dune at the base and longer, ‘low hedge’ cutting at the base.  When a certain angle of recession has been reached, then the top part becomes unstable to the point where even the binding ‘glue’ of vegetation roots cannot stop the top of the bank from toppling down onto the beach.  This is gravity in action.  This kind of failure tends to occur over time, say from one big high tide to the next high tide or even longer if the energy state of the wave tongues are relatively benign as in settled weather conditions.

 

If the wave tongues have greater depth, then the whole bottom half – the sand base will be carved out, causing the top half of the bank to sink.  As the dune bank doesn’t run in a straight line, but follows fractal scaling, it won’t all collapse evenly.  The jutting out parts of the bank will be more directly affected.  Direct wave action however, as found on the Three Sisters Beach proper, is more destructive because while there may be no overtopping, the dune is subject to both carving and smashing actions simultaneously.  Also, the vibration/shockwaves generated by both actions will be multiplied.  Thus the destruction tends to be more catastrophic and affect a greater area.

 

The dune bank/sand wall facing directly onto the Three Sisters Beach is higher than the dune bank/sand wall at the gap that separates Mammoth Rock from the dune.  On the Three Sisters Beach side, the dune sand wall gains in height until it joins up with the cliff proper near the first arch.  Towards this end of the beach (south), the sand bank is better described as a sand cliff.

 

On the Three Sisters Beach, the dune bank is only subject to the action of single waves striking it.  The angle of hit can vary, but the single wave action remains consistent.  At the gap however, the dune bank is subject to the actions of three separate waves coming from three different directions.  Two directions are directly opposed, (they emanate from opposite sides of Mammoth Rock), while the third is obliquely opposed.  The obliquely opposed wave action is caused by a bore wave travelling over the top of the Tonga River, particularly when in flood and over on the Mammoth Rock side of the estuary as it currently is, and hitting the mainland cliff.  This funnels the wave action westward close to and past the dune bank.

 

On the beach proper, the sand was being pushed up to the dune bank.  Also, such was the power of the waves that stones, roughly a foot in diameter, were being rolled up the beach.  Many of these roundish stones were forced together in a distinctive pile that was hard up against the dune at the cliff end of the beach (south).  As to the dune wall, chunks of it were slumping down onto the beach and clumps of grass and flax were being dumped into the sea.

 

 

6.9.2009   PHO2011-1888-1891, 1893, 1896-1897

 

The weather was fine with a slight south-easterly breeze.  A low tide of 0.5m was due at 4.49 pm.  Down on the beach, I used the digital camera only.  At Zone One, at the gap, it appeared to have lost more material.  On the beach proper, there were lots of small pebbles and the beach had been scoured out from midway down to the wave-line.  There were also sand islands separated by channels of water.  Orange soil was present here and at the wave-line.  This was due to a massive cliff collapse at the cliff section collapse site.  (Observed on 12.11.08).

 

At the top end of the beach next to the bashed up dunes, the sand level appeared to be pushed up.  I presumed the beach was in this state due to the ferocious conditions I had encountered on 26.8.08 when the beach was being thrashed by massive surf.

 

At Zone Two, the beach was still in a high rock state and now with this latest cliff collapse, more debris had been added to the growing rock field.  Soil and soil balls were also prolific.  There were some interesting rock formations near the cliff collapse site.  One was a bedrock bridge that spanned a small pool.  Another consisted of two rock pillars that resembled smaller versions of the Sisters rock stacks.

 

At Zone Three from what I could see, the sand cover was better, particularly at the wave-line.

 

Lastly, I took a couple of panoramic images with my panoramic film camera from the Pilot Point overlook.  This showed the standard postcard view of the Tonga River, the Sisters, White Cliffs and Mt Egmont.  It also showed the beach state.

 

 

19.9.2009   PHO2011-1667, 1674, 1680, 1682, 1904, 1912

 

It was fine with a south-easterly wind.  A very low tide of 0.1m was due at 4.03 pm.  Before venturing down onto the beach, I spoke with Victor Gibbs who was doing some fencing above the cliff section collapse site.  We discussed the dune area.  He said that the sand/land bridge had been breached on several occasions in the past, but it had never gone back as far as it had this time.

 

Down on the beach at Zone One, more of the dune area at the gap had been washed out, particularly at the corner where it turned south to face the beach proper.  Lots of plant material and some stones were present.  The beach area opposite the seaward facing side of the dune had lots of small pebbles.  It was also scraped back to smooth, flat bedrock at the midway point (V section), between the dune and the wave-line.  Closer to the first arch, several broken caterpillar-like rock formations marched down to the low water mark.  They appeared to be composed of two distinct rock strata, one grey and the other orange.  Ancient tree remains were also present in some of them.

 

About half way down the beach travelling towards the arch, a lot of medium sized, roundish rocks were piled high up into the dune’s sand cliff face.  The pure sand cliffs at this end of the beach were around twenty to thirty feet in height.

 

At Zone Two, some sand was building back near the cliff face.  However, from the Sisters to just before Elephant Rock, there was an extensive rock garden, inhabited by undulating bedrock, rock shelves, rock platform islands or ‘tables’, and rocks and pools.  Just before Elephant Rock, the beach assumed a sand mantle which extended through to Zone Three.

 

 

18.10.2009   PHO2011-1683, 1925-1926, 1929, 1933-1934

 

The weather was cloudy with some showers and there was a light to moderate southerly breeze.  A low 0.3m tide was due at 4.41 pm.  Most of the photography was done with the digital camera.

 

At Zone One, the gap appeared to have widened a bit more.  There was more vegetation down on the beach.  Most of the carving action appeared to be at the corner of the dune where it turned around onto the beach proper.  I estimated that the dune on the seaward side had retreated between twenty and thirty feet.  At the gap, I estimated that the gap separating Mammoth Rock to the dune to be around eighty feet.  In other words, the dune’s sand/land bridge and dune proper had roughly retreated by about eighty feet.  I took a photo of Mark Robbins in front of the sand cliffs to give scale.

 

The main beach area had been heavily scoured out with lots of bedrock and rock platforms being exposed.  The main exception was the top third of the beach leading up to the sand cliffs.  Here, it was built up, but mostly it consisted of medium sized roundish rocks that had been carried there by wave action observed on 26.8.08.  There was also a beautiful pale blue rock seam at the base of the cliff.  It was soft to the touch and showed up nicely in the wet light.

 

A continuation of bad weather was continuing to cause a high level of erosion damage.  The cliff face that leads around to the arch – the northern side, was now mostly devoid of vegetation.  I took a series of images of the beach from the gap to the arch and Sisters.  These are to be stitched together for a panorama.  The broken caterpillar rock formation near the arch was still present.

 

At Zone Two, apart from the cliff section collapse site and the Sisters, the beach is now well endowed with sand.  ZONE THREE was also well endowed with sand.

 

 

15.11.2009   PHO2011-1938-1939, 1943, 1945-1946

 

The weather was crap.  It was raining with a stiff north-westerly wind.  The only reason I was up at Tonga was because I had arranged to take a tour group from the Taranaki Geological Society.  In the event, only three people turned up.  A low tide of 0.5m was due at 3.38 pm.  I only used my digital camera for the photography.

 

Down at the beach at Zone One, all the vegetation I had observed earlier on the beach at the gap was now dead.  The beach level had built up just sufficient at the gap so as to have halted the carving process.  At the corner and around to the seaward side of the dune, it was still in the process of being carved out, but the carving action appeared to have slowed.  Over the summer, this beach area should continue to build back, providing there are no big tide timed storms.  Also, the Tonga River had moved away to the northern side of the estuary, so this further reduced the erosion process.

 

The beach was building up nicely, particularly at the top third of the beach.  There was a relatively small lake of smallish roundish stones immediately south of the seaward end of Mammoth Rock.

 

At Zone Two, near the Inner Sister, a smallish rock platform was almost smothered by the rising sand level.  For the most part, the entire length of the beach here was now mostly filled with sand.  The exceptions being the encircling water channels surrounding the rock stacks and some of the protruding cliff bases.  The rock shelves and platforms that had been starkly exposed on 19.9.08 were now mostly buried in sand.

 

At Zone Three, the beach cover was good.

 

 

2.12.2009   PHO2011-1699-1700

 

A low tide of 0.5m was due at 4.40 pm.  Currently, we are experiencing swamp-like conditions.  Today there was a north-westerly breeze, low cloud and sea fog.

 

At Zone One, the beach was quite well built up, especially at the landward (dune) end.  A low V was forming in the middle, roughly between Mammoth Rock and the first arch, then the sand level rose again.  This consisted of squishy sand, water and a large tree trunk that was being uncovered.  Sand islands separated by water channels were on the seaward side of Mammoth Rock.  The powder blue rock seam near the arch was still visible but it was largely covered with sand now.

 

At the dune on the beach proper, the sand wall appeared to have stabilized somewhat.  It was still losing ground to the sea, but the pace had slowed.  The large collection of roundish stones that had accumulated at the base of the dune at the southern end of the beach were still there, but were now mostly covered with sand.  At the gap this part of the dune also appeared to have stabilized to a large degree.  The beach here was building up quite nicely.

 

Having said that the dune area as a whole had stabilized, I take this to really mean that its destruction had slowed or stalled temporarily.  Material was still being dislodged but at a much slower rate.  I will get a better handle on what is really happening next winter.  I think the dunes will continue to lose ground long-term and that they will only enjoy temporary reprieves during summer periods.  Specifically, I believe too much has been lost (roughly a third), for them to fully recover.  Combined with sea-level rise, I believe the dunes to be unrecoverable.

 

At zones Two and Three, the beach had good sand cover, but some rock platforms and shelves had their tops exposed.  A channel of frothy, brown coloured water separated two of the rock platforms.  Also, there was the usual rock garden around the Sisters and in the vicinity of the cliff section collapse and the cliff collapse site to the rear of Elephant Rock.

 

 

 

2010

 

 

16.1.2010   PHO2011-1711-1713, 1715-1716, 1718-1719, 1721

 

Zone One.  A 0.6m low tide was due at 5.50 pm.  The weather was fine, but with a stiff south-easterly wind.  Previous to this it had been an El Nino summer with cold, south-westerly winds and frequent rain.  Down at the gap, the sea state was energetic with a 2 metre swell.  At the gap, the dune was showing no signs of building back.  Conversely, it appeared to have stabilized, albeit temporarily.  A small section of sand area in the vicinity of the corner appeared to be high enough to prevent high tide encroachment.  However, the sea still flowed around Mammoth Rock as the sand level here was lower.

 

At the point where the stream exits onto the gap, the bank appeared to have been eaten back further, but not by much.  The blue board that had been visible nearby had now gone.  The access down to the beach was still via a dead pepper tree that remained anchored to the lower part of the bank by its roots.  Between the stream and the Tonga River, specifically at the base of the cliff, there was a debris field of logs and flotsam.  These all sat atop a low sand shelf that was currently above the high tide mark.

 

On the beach proper, the beach was well built up with sand, particularly at the dune wall.  There was still a slight V formation roughly in the middle of the beach which channelled water.  Also, the resident log that was lazing there on 2.12.09 was still there.  On the seaward side of the V formation, the beach level rose again.

 

The high tide water mark stopped at the base of the sand dunes.  The beach was relatively free of driftwood, apart from a few recent new arrivals.  The dune sand walls and sand cliffs appeared to have stabilized.  No more plants were flopping into the sea and the cliffs and walls didn’t have a fresh look to them, more a ‘been there a while’ look.  Loose sand was still coming down, but more in dribs and drabs, assisted by the wind.  This was now swinging around to the south which blew directly onto the beach.

 

Towards the latter end of the sand cliffs where they were almost at their highest, there were some unusual shelving or cross slab sand formations present.  These were quite distinct from the surrounding ‘sand avalanche’ or free flowing sand that generally prevailed.  I presumed that these sand slabs had formed a considerable amount of time ago and had long since been buried beneath a covering layer of sand and vegetation.

 

For want of a better description, there appeared to be two distinct types of sand.  The darker coloured slab sand was what I would call ‘bottom sand’, while the loose top sand that was continuous with no shelving or slabbing, was what I called ‘top sand’.  To give a better analogy, the top sand would be found at the top, dry end of the beach and the bottom sand would be found just above the water-line where it would be subject to wicking.  Here, it would be dense, heavy and sticky by comparison to the smooth, free-flowing dry top sand.  I photographed Jessie Gibbs who was down at the beach surfing with others, to give scale.

 

The clump of roundish rocks that had been deposited at the base of the sand cliff on

26.8.09 by immensely powerful seas was still there, but due to high sand cover, only the top portion was visible.

 

At Zone Two the sand cover was very good.  At the Sisters only the rock platform to the rear of the Inner Sister was visible, and towards Elephant Rock only two rock platform tops were visible.  The sand was especially well built up at the cliff bases and out just beyond the wave-line.  At the cliff section collapse site, mostly only the large boulders, now much rounded and smoother were visible.

 

At Zone Three, the sand cover was equally very good.

 

 

30.1.2010   PHO2011-1738-1739, 1741-1742

 

Zone One.  A 0.2m low tide was due at 5.05 pm.  The weather was fine with a moderate sea being chopped up by an onshore westerly.  The sand level on the beach was good.  It was building up in a bar between the gap and the seaward corner of the dune.  Overall, the dune appeared to be in stasis, but due to the king tides, the wave tongues were able to come right up to the base of the dune and importantly, through the gap.  Some grassy type plants were growing in the sand at the base of the dune bank opposite Mammoth Rock.  I also noticed clumps of grass and grass like plants right down the Four Brothers Beach.  As I didn’t observe any relevant cliff collapses that had these types of plants, I assumed that the dune bank opposite Mammoth Rock was still being undercut.  The undercutting is small scale and is only currently occurring during the highest tides.  It was unusual for the plants to travel south down the coast.  Normally, flotsam travels northwards up the coast

 

The rest of the beach in Zone One right down to and including the Sisters was well endowed with sand.  There was the usual V formation in the middle of the beach from Mammoth Rock to the first arch.  There was a substantial sand bar between Mammoth Rock and the Tonga River.  Also, due to the extremely low tide, mini reefs as well as the more usual rock platforms were visible.  The rock platform to the rear of the Inner Sister only had its tops uncovered.

 

When I returned from the Four Brothers Beach, the tide was right out beyond the Little Sister.  Quite a few people, some with dogs, were on the beach due to it being a beautiful day.  Some were also gathering mussels that had been uncovered

 

Zones Two and Three.  Once again, overall the beach was well endowed with sand, particularly up at the cliff bases.  Mini reefs and some rocks and rock platforms were exposed due to the very low tide.  This was particularly true of the mini reefs which are normally covered with water at the low water mark.  Some rock platforms mostly have their tops visible irrespective of the sand cover.  This is because of their overall height.

 

I found it interesting to note that the mini reefs immediately south of the Little Sister, were well endowed with good sized mussels.  Due to the high sand cover, only the highest, landward sides of these reefs were uncovered.  A photo taken on 30.3.06 shows these same reefs, but they were completely devoid of mussels.  This is detailed in Section Nine on Flora and Fauna.

 

 

28.3.2010   PHO2011-1955

 

The digital camera was used.  A 0.3m low tide was due at 3.20 pm.  The weather was fine but cloud persisted over the Tonga hills.  There had been some rain but nothing to shout about.  It had been calm for some time.  The breeze, what little there was, was from the south-east.  The sea state was playful with small waves that played tiddlywinks on the beach.

 

Today was a planned field trip for any members of the Taranaki Geological Society who wished to come up.  The first trip in November 2009 was accompanied by hideous weather and only three people came up.  Eight people, including George Mason, came today.

 

Down at Zone One the sand cover was exceptionally high.  So high in fact that there was no V formation in the centre of the beach whatsoever.  At the dune area, particularly at the corner that leads around to the rear of Mammoth Rock, despite the very high (and low) tides, there was a dry upper high tide area.  The dune as a whole appeared to have stabilised and sand was building up between Mammoth Rock and the dune.  It dropped down to a lower level close to Mammoth Rock;  the width of this being approximately 10-15 feet.  Sea water still encircled Mammoth Rock at high tide.  A log field appeared to be well established on the eastern side of the tiny stream that flows across from the dune towards Mammoth Rock before exiting into the Tonga River.  Though the log field was established, it didn’t appear to have had any new members added to it.  This wasn’t surprising as the weather hasn’t been stormy of late.

 

Zones Two and Three.  As with Zone One, the sand cover was very good, especially up towards the cliffs.  However, the rock platforms located lower down the beach, especially in Zone Two, were heavily scoured out.  This particular ‘platform field’ which also includes reefs that extend beyond the low water mark, is quite intensive.  It extends from the vicinity of the Little Sister until just before you reach Elephant Rock.  Presumably some of the good sand cover high up the beach originated from this platform field.  Just north of Elephant Rock, then continuing south, a well built up sand bar was present at the low water mark.  PHO2011-1955, though taken at the Point and included in the Point, is also repeated here because it looks towards Zone Three on the Three Sisters Beach.

 

 

27.6.2010

 

Zone One.  Though I didn’t visit the Three Sisters Beach, I could see most of Zone One from Pilot Point.  From what I could see, the beach appeared to be well endowed with sand.  I couldn’t really assess the state of the dune, except that the gap separating the dune from Mammoth Rock was still present.  No build back appeared to have occurred.

 

 

11.7.2010   PHO2011-1812, 1818, 1820

 

Zone One.  The sand cover at the gap and on the main beach up to the first arch was very good.  It was higher up to the cliff and the dune wall and a bit lower in the middle.  However, there was no V type formation.  The sand was also well built up in a substantial bar at the wave-line.

 

The gap separating the dune from Mammoth Rock remained and was largely unchanged.  The dune continue to erode back, but erosion wasn’t significant and was patchy.  That is, some places had seen little change while at others, flaxes continued to tip down the unstable sand walls to the beach.  Overall, the dune remained in a state of retreat, but currently the rate of recession had slowed.

 

Zones Two and Three.  As with Zone One, the sand cover was very good, particularly up near the cliff and down at the waveline.  Rock platforms were visible, but they were roughly three-quarters bedded down with sand.

 

Compared to July 2008 during the super-storm event, the current beach state couldn’t be more different.

 

 

18.9.2010   PHO2011-1854, 1857, 1860-1861, 1863, 1867, 1869-1870, 1872

 

MEGA-STORM.

 

Zone One.  This truly mind boggling event generated so much sea foam that the beach on the seaward side of the dune couldn’t be seen.  It was buried beneath several feet of foamdrift.  This was being driven hard up to the dune bank and in places up into the flax plants.

 

Around at the gap, though huge swathes of sea foam were present, it being deposited by waves enciricling Mammoth Rock, the sand was mostly visible.  The beach here was well built up on either side of the stream that exits onto the beach.  It being higher close in to the dune bank, and lower next to Mammoth Rock.  This was due to scouring caused by through-going wave action.  On the landward side of the stream, a ribbed sand platform had built up.  Driftwood and fresh flax plants littered both sides of the stream.

 

From what I could see, the dune was still receding, particularly at the corner and on the seaward side.  The dune bank opposite Mammoth Rock however, appeared to be fairly stable.  This could be due to a buildup of sand.  This buildup allowed for easy access to the beach.  In the past, the dropoff down to the beach was quite high, whereas now it is much lower.

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