Topic: Pilot Point - 2003
18.5.2003 PHO2007-203-204, PHO2008-888-889
The Tonga River appears slightly biased towards the Pilot Point side of the estuary.
The Family of Rocks are partially enveloped with water. The sand level is reasonably high to landward. Mussel spat is present.
30.6.2003 PHO2008-037, 049, 928, 931, 933
The Tonga River is roughly in the middle of the estuary.
The Family of Rocks. All of the rocks up to the Point were covered in sand. And the Family of rocks, they appeared to have been shuffled around like a deck of cards. Like they had been in a giant washing machine. Around four feet of sand covered the outer rocks. Conversely, the gap between the Pilot Point arch and the cliff was scalloped out and filled with water. A lot of rocks here were uncovered.
I concluded that the northerly flow builds up the sand, apart from the Point and cliff pillars where it gouges it out. And that a south-westerly flow takes the sand away, but builds it up around the Point and cliff pillars. Upon examining the larger, but mostly buried rocks in the family of rocks, I noticed they were still covered in small mussels. I deduced from this that these rocks were not usually overturned, but turned around. And more importantly, that this process of covering and uncovering happens quite rapidly. If it didn’t, the young mussels would be smothered to death. (As I later learned, the covering and uncovering of sand doesn’t always happen rapidly and the mussels are smothered to death. They are constantly being replaced by fresh mussel spat. This is why they never grow to any great size, thus the attrition rate here is 100%).
13.7.2003 PHO2008-056-057, 059, 940, 944, 947-948, 953-954
The Tonga River appeared to be roughly in the middle of the estuary.
The Family of Rocks. Some of the rocks wallowed in sleepy pools. The sand level appeared to have reduced a little, but between the Pilot Point arch and the cliff it remained hollowed out. A small family of pristine rocks (no mussels or algae) were exposed atop a bedrock base. These were immediately north of the arch.
At the family of rocks, the mussel line was quite clearly delineated. Below this, everything had been smothered by sand. Above this, mussels survived.
20.7.2003 PHO2008-061, 955, 958, 960, 963-964
The images here show the Tonga River from a variety of different viewpoints, including from the Pilot Point dune.
27.7.2003 PHO2008-081, 975-978
The Tonga River is a little closer to Pilot Point. That is, it is just north of the middle.
The Family of Rocks. The gap between the arch and the cliff is now completely filled with sand. As the tide was coming in quite quickly with some largish washes, photography became even more urgent as I wanted to photograph the family of rocks to see if there was any difference in their location from last time (13.7.03). I wanted to see if what I suspected was really true. That the rocks get shuffled about slightly due to a process called liquefaction. As the sand gets washed away down to a depth close to their bases, I believe that in certain weather/water/tidal conditions, the swirling sand allows the rocks to ‘float’ on a horizontal escalator of sand. They don’t get turned upside down, at least I don’t think so. They just get turned a little and juggled about in relation to each other.
CLIFF SEQUENCING. Though this photo was taken on the Three Sisters Beach side of the Tonga estuary, it is valid here because it shows the Tonga River from a different perspective. The river is to the left of the image.
28.8.2003 PHO2008-186, 1007, 1009
The Tonga River was quite close to the Pilot Point side of the estuary. On the 27th, a stiff northerly and heavy rain pounded the province as a front went through. Today, a ferocious rip was tearing out to sea on the half tide. The surf was pounding away a fair way out, but due to storm surge conditions, the tide or at least the wave-line, was quite high. There were also some bore-like waves or surges coming in, opposite to the main outward flow of the river.
Keeping close to the cliffs, I made my way up to the Pilot Point arch. Enroute, I checked the high sand line for dryness, indicating where the tide had come up to. I then made my way along to the cave (north of the arch). I noticed a lot of flotsam; seaweed, branches, flax, etc. Upon seeing the flax, I suspected that a cliff face must have collapsed somewhere. At the cave the sand level was the highest I have seen so far. I quickly photographed it and walked towards the arch.
Just before reaching it, I noticed that some wave surges were coming a fair way up the beach, despite the surf line being a long way out, and the river going out at a rate of knots. I kept close to the cliff wall.
As I prepared to take a photo, a huge wave surge raced up the slightly inclining beach towards me. I calculated that I could reach the arch in around 6-7 seconds, but would have insufficient time to make it around to the first blind cave immediately around the corner. (The inside of the cave would have given me a greater separation distance from the incoming surge). I clung to the cliff wall which was about 3 seconds away. Not that there were any hand or foot holds, just a slippery bare wall.
As the wave, (its surge front, not breaking wave), slammed into the cliff, I hopped from one gum booted foot to the next, hoping only to have one gumboot dumped with water. And that’s what happened. Then, just as quickly, the surge front whooshed back out to sea down the slightly downward inclining beach.
After that, I rushed around to the cave to gather myself, but I still hadn’t gotten the shot I had been trying for. I waited for a while, a few minutes, and then foolishly decided to try again. I rounded the arch, but remained close to it, about 5 seconds away. I worked out that the so-called ‘dry sand’ of the upper beach was misleading as it dried out in a matter of minutes.
Then, a more powerful surge front swept up the beach. I calculated, again, that I could make it to the hole between the arch and the cliff, but that would be the worst place to be because the depth of water would increase due to the restricted space, and the surging water, coming from two different directions, would combine and thus be even more powerful.
Once again, I was forced to hug the slippery cliff wall. There was slightly more water depth to this surge, just over gumboot height (below the knee). The strength of this surge pulled on me a lot more than the previous one. Then, just like the first, it was over very quickly. However, as I waited for the surge to hit, time seemed to slow as I had nowhere to go. I just had to wait and hope that I would survive it. While waiting, I thought about the two youngsters who had been lost at Twin Creeks under similar circumstances a while back.
I realized that if the surge front had been just a foot higher, I would have been a goner. That is, if there had been just two feet of water, I would have been unable to resist the terrific pulling power and been sucked out to sea.
The Family of Rocks. Due to high sand cover, the family of rocks were roughly 80% buried in sand. The sand level was just below the mussel spat present.
6.9.2003 PHO2008-204-205, 1019-1021,
The Tonga River was still quite close to the Pilot Point side of the estuary. There was a screaming south-westerly with five metre swells.
I studied the out flowing Tonga River. It was higher than normal. Due to its speed and increased volume, it was undercutting the incoming surf. In effect, holding it back, so that when the sea did come in, it tended to come in at times as tidal, bore-like surges. I thus concluded this was what happened the last time I was here on 28.8.03 when I was almost swept out to sea.
This was not so much ordinary surf being backed up by ordinary undertow, although that was happening, but by being undercut by the fast flowing, high volume of water. Under low river outflows and normal outflows, the undercutting, though there, is not compounded too much above normal tidal surges. Combine incoming storm surge with high river outflows and you end up with powerfully destructive bore-wave conditions.
The bores, when they occur, do so on a semi-regular basis. Not wave for individual wave, but on a time regulated basis. That is, the power of the river’s outflow is such that it prevents individual, lower strength waves from coming in, so the ocean generated waves ‘back up’. Then, when, say, four of them have effectively combined into one, they have accrued sufficient volume and power to temporarily overcome the outgoing flow. When this balance of power tips, the multiplied ‘wave’ surges in as a single bore.
It is important to note that this bore-wave does not increase as much in height, as it does in power and speed. In other words, bore-waves surge in with the power of a freight train, combined with the speed of an express train, but can look deceptively like an ordinary train. This is what makes them so lethal to the unwary, such as I was on 28.8.03.
The Family of Rocks. On the 5th, there had been a raging southerly storm. Because of this, I thought the family of large rocks may have moved. Down on the beach, from what I could tell, some of the rock family appeared to have been moved closer in to the Point and in a north-westerly direction. They were heading out to sea, so to speak. The sand was very high around them. Only the largest of the large rocks appeared not to have shifted, but of course I couldn’t be sure of this.
I also photographed the Family of Rocks from the cliff-top above for comparison purposes and to give a different perspective.
29.9.2003 PHO2008-216, 1034
An ALPHA STORM stomped through, destroying two rocks stacks, one on the Three Sisters Beach and one on the Four Brothers Beach in a frenzied attack.
The Tonga River. I arrived at the Tonga reserve at about 12.30 pm. The high king tide of 3.7 metres had occurred at 11.50 am. At the reserve, I watched in amazement at the powerful storm surges that frequently ‘tidal bored’ inward, up and over the outward flowing Tonga River that was in full flood. Some of these storm induced bores flowed over the boulder stop banks and up onto the parking area. Flotsam logs and debris deposited on the grass attested to the alpha storm’s ferocious power.
Such was the height of the river, being in full flood, combined with the king high tide and storm surge, that I couldn’t tell which side of the estuary the river was flowing closest to. As I last visited on the 6th September, I assumed it to be still close to Pilot Point.
I then accessed the top of Pilot Point. This gives the standard picture postcard view looking across the mouth of the estuary and across towards Mammoth Rock. Also, the Three Sisters, Whitecliffs, and on a fine day, Mt Egmont. At Pilot Point, roaring gale-force winds and a raging sea all but blew my senses such was the power of this mind-boggling storm.
6.10.2003 PHO2008-224, 1038, 1040-1041
The Tonga River. I haven’t stated which side of the estuary the river was closest to in my notes, but it appeared to still be reasonably close to Pilot Point. The tide was low.
The Family of Rocks. I photographed the family of rocks from the cliff-top, and then went down to the beach. Sand was quite high up to the cliffs, but scoured out from lower down. Rocks and bedrock were exposed.
As I reached the arch, the family of rocks had sand washed away right down to their bases. At the arch, the gap between it and the cliff was replete with sand. No bedrock or rocks were visible.
26.10.2003 PHO2008-353, 1082-1083
After I had completed CLIFF SEQUENCING at Rapanui South Beach and part of Pilot Point, I took several photos of the Tonga River.
The Tonga River. The river was right over on the Pilot Point side of the estuary.
The Family of Rocks. At the family of rocks, the sand had been excavated out around them, though the arch enjoyed high sand cover. Lots of cappuccino-like brown froth carpeted the pools enclosing my rock family. I photographed the family looking across the estuary. Though clear, Mt Egmont was all but lost in the salt spray haze.
This photo of the Tonga River was taken from the bridge that crosses the main highway. It looks across to the Tonga baches with the Tasman Sea on the horizon.