Sea rise and slips threaten Ruby Bay road

Nelson Mail - - NEWS - CHERIE SIVIGNON

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 (NZTA) 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.

How­ever, 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 con­ver- sa­tion 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.’’

MARTIN DE RUYTER/NEL­SON MAIL

Cars drive through floods in 2006 at Ruby Bay.

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