Slips, coastal inundation pose threat to Ruby Bay scenic route
Sea level rise or a massive slip may force the permanent closure of the former coastal highway near the Ruby Bay bluffs.
Now part of the popular Ruby Coast Scenic Route, the section of Stafford Drive near McKee domain used to be part of State Highway 60 between Mapua and Motueka. However, the New Zealand Transport Agency transferred responsibility for the road to Tasman District Council in 2010 when the Ruby Bay bypass opened.
TDC transportation manager Jamie McPherson said NZTA spent "a considerable amount of money" constructing rock protection on the seaward side of the road prior to its handover but the route was still "quite vulnerable" to coastal inundation and storms.
"The road suffers closures a couple of times a year, due mainly to slips but also occasionally due to waves in some storms over topping the rock protection and depositing debris on the road," McPherson said. "As this section of road is not a strategic route ... the closures are generally just a nuisance and don't have a significant impact on road users."
Repair costs topped about $17,500 a year. The last major slip was in July, which involved about 400 cubic metres of material.
"The bluffs have a long history of slips," McPherson said. "That is just the nature of cliffs like these."
TDC data indicated the slips were not becoming more frequent.
"What we expect to see if sea levels continue to rise is more frequent inundation and damage to the road from waves," McPherson said.
At a recent council committee meeting, Cr David Ogilvie asked if there was "a long-term programme to close that road off".
McPherson responded: "It's something we probably want to talk about with the community because it is a reasonably popular tourist route or alternative route to the main Ruby Bay bypass ... but eventually, our hand may in fact be forced by the sea through that section."
When asked to clarify his comments after the meeting, McPherson said such a conversation with the community would probably follow a "very significant event, unlike what we have seen to date".
"For example, this might be a massive slip that exposes underlying geological risks or a storm that washes away significant portions of the road," he said. "There would be a point where most people would say the cost does not justify rebuilding and there would be better use for that money.
"However, it is not a conversation that is being planned at this stage."