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A geotechnical inspection report following the recent death of a woman from the cliffs at Rothesay Bay says measures required to secure the public from injury from rockfall right up to the foot of the cliff would be extensive, expensive and difficult to construct.
It says that a risk to public safety exists there but has not increased as a result of the recent rockfall.
The report by Tonkin & Taylor for Auckland Council says the risk of danger to the public is considered to have always existed.
“The nature of the cliff face erosion is one of attrition with progressive generally minor rockfalls,rather than large scale instability.”
It also concludes there is no evidence that the discharge of stormwater played a role in the incident.
Acknowledging the accident was tragic and thought to be the first known fatality of its type in Auckland, the report says that the measures required to secure the public from injury from rockfall right up to the foot of the cliff would be extensive, expensive and difficult to construct. “These measures would be significant and could include measures such as large scale rock nets or drapes (or possibly shotcrete) with significant and frequent anchors, and would require significant ongoing maintenance with associated high risk to construction personnel.
Similarly, prevention/control of access into the boulder fall zone would involve fencing and/or barriers within the harsh coastal environment of the tidal zone. This would restrict foreshore access to low tide.
The report by Tonkin & Taylor for Auckland Council says the risk of danger to the public is considered to have always existed.
“The nature of the cliff face erosion is one of attrition with progressive generally minor rockfalls,rather than large scale instability.”
It also concludes there is no evidence that the discharge of stormwater played a role in the incident.
Acknowledging the accident was tragic and thought to be the first known fatality of its type in Auckland, the report says that the measures required to secure the public from injury from rockfall right up to the foot of the cliff would be extensive, expensive and difficult to construct. “These measures would be significant and could include measures such as large scale rock nets or drapes (or possibly shotcrete) with significant and frequent anchors, and would require significant ongoing maintenance with associated high risk to construction personnel.
Similarly, prevention/control of access into the boulder fall zone would involve fencing and/or barriers within the harsh coastal environment of the tidal zone. This would restrict foreshore access to low tide.
“Restriction of public access to the area below the cliff is very difficult to control and is likely to be ineffective.”
“The risk of public danger due to rockfall has always existed at the site and the likelihood is considered to be very low.”
“The risk of public danger due to rockfall has always existed at the site and the likelihood is considered to be very low.”
The report says the expected rockfall volumes are likely to be relatively small as a result of the attrition of the cliff face. The boulder risk is primarily expected to occur within 10-15m of the foot of the cliff.
“This is consistent with published rockfall protection design charts used in the design of rock cuttings.”
The Council says there is some existing warning signage along the coast. The Council has added new international standard signs since last Saturday and more will be installed in the near future.
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1 Comments
It’s daft to think you can make cliffs like this perfectly safe. Can you imagine what they would look like with shotcrete blasted all over them. It would look like a theme park and the cost??? There are kilometres of cliff in Auckland
I learnt as a teenager 50 years ago when we arrived in NZ to be careful and on the lookout for falling rocks on the shoreline. These cliffs are naturally unstable and some cliff top houses in Seacliffe Ave Belmont are underpinned I understand right back under the street!
At school in geography we learned about the cliffs and how if the strata sloped down towards the sea they were even more unstable than when the strata sloped back from the cliff face…NEVER BUILD THERE SAID THE TEACHER!! wise words.
In the paper there was a photo of a swimming pool hanging half over the cliff where some daft owner has built it too close to the edge!! Some years ago a resident in Bayswater built a swimming pool like this and filled it with water, the weight was too much for the cliff and the whole lot ended up on the mud below!
Common sense seems to have gone out the window and we need continual regulated guidance to do anything now.