Enn Jamez takes a closer look at some of the recent slips that have occured in Waiotahe Beach.  

When reading the Ōpōtiki News last week about the slip at Waiotahe Beach, I realised that I had driven along that stretch of road but a few hours before it occurred. Others may well reflect on their good fortune at not having been buried alive without a bell.

The article also reminded me of big slips that occurred along that bluff when I was a boy in the 1940s.

Later, when playing at the beach as a teenager, I’d look west along the coast and imagine the original line of the ridge arching from the top of the bluff all the way out to sea (Fig 1).

I’d learn much later that over eons of time, the toe of that slope had been cut back by slowly rising seas thousands of years ago leaving exposed the brown-faced cliffs we see today (Fig 1).

The exposed snouts of these ridges are composed of layers of relatively soft alluvial and volcanic soils and therefore readily erodible, as recent past history shows.

The straight stretch of road from the corner near the Waiotahe River (Fig 1) to the corner to the east is about 800 metres (Fig 2). It is clear that the height of the slides from west to east become lower. The latter were likely caused by creating the road rather than by sea encroachment (Fig 2).

Over six decades ago, the Opotiki News reported in March 1941 of traffic being “diverted over the Paerata Ridge Road on account of a large slip at the Waiotahi bluff and portion of the road being washed away by the sea”.

It went on to say: “The Waiotahi river has changed its mouth considerably during the past few weeks, running for some distance parallel with the road and beach, and it was anticipated that trouble would result.”

Then in May 1949, the newspaper reported that, “The bulldozer which was buried under the slip …at the beginning of the week was successfully pulled out yesterday. Another bulldozer and a band of willing helpers had a strenuous few hours as it could only be worked at low water.

“The machine is extensively damaged and the huge blade which was wrenched off is still missing. Its…incredible that such a solid machine weighing several tons could have been pushed 100 yards into the sea by the force of the slip.”

Exactly a year later, the paper reported: “A large slip of about 50,000 c. yds (38,228 cubic metres) blocked the Ōhiwa road at the bluff. The road had to be reformed and metalled for a distance of 8 chains (161 metres) across the slip.” Over the next 50 years further slips occurred.

With these historic events in mind, I walked on Friday from near Island View Holiday Park westward nearly 3kms along the beach to the site of the new slip, which itself was about 80m across.

The workers were on their last day of cleanup, having been hard at work since early Tuesday morning (Fig. 3). I was told that around 3000 cubic metres of spoil was being taken each day and deposited onto the properties of owners who wanted it.

I watched the digger driver deftly plying his skills on a precarious cutting on the slope and was informed “He was perched higher-up earlier – one of the best in the business and still going strong after 44 years”.

Just to the east of the new slip is the face of an older scar (Fig. 4). I could see an old farm fence dangling most of the way down the slope, and wondered why the grass-covered ridge that leads to the lip of the bluff was not long ago planted in trees.

This, I imagined, would reduce the run-off in extreme rainfalls; perhaps reducing proneness to slumping. It is therefore interesting that last week’s Ōpōtiki News article reported that some pohutakawa trees that were left dangling over the cliff edge had to be taken away lest they fall downslope and onto the road.

It is also interesting to see the face of this older slip to the left in Fig 4 wearing a number of side-by-side vertically aligned cuts right across the lower layer of material. No doubt, these cuts are the result of the eroding effects of beating rains. They may well be signalling bigger things to come.

Walking further west of the new slip to where the road is close to the Waiotahe River (Fig. 1), it is apparent when looking back east about 600 metres there could be seen four major slip faces each separated by patches of shrubby growth of varying widths. But within that growth could be seen small recent slips too (Figs 3 and 4).

I walked back to my informant on the beach. He pointed out to me that seaward of the road out from the new slip, lengths of large pohutukawa logs had just been buried in the sand where they will root and grow into new trees (Fig 4).

The proof of this I was told was the grove of 20-year-old pohutukawa trees below the older slip face some 100 metres to the east. The bonus was him pointing out to me a young seal resting in a little cove under the young trees. Its big black eyes peered benignly out at me.

Walking further east, I realised that there are several clusters of young pohutukawa trees seaward of the road. Some were very small and likely recently planted. The larger trees were, however, likely grown from buried logs, planned or otherwise.  

It was also apparent, that the lower ridge ends at this end of the road gave rise to much smaller slips soon after the road was cut through many decades ago.

Given this recent and past history of slips along Waiotahe Beach Road, it is clear that the NZ Transport Agency will continue having much work to do maintaining and funding this 800-metre stretch of SH2 for years to come.  

Also, in last week’s Ōpōtiki News was an article highlighting Brett Wotton’s call for improved road safety in the Appleton Road to Paerata Ridge Road section of SH2 at the east end of Waiotahe Beach.

It is hoped that NZTA will act positively and quickly to this timely call for action.