Dune experiment results positive

A drone image of the dunes shortly after the gaps were carved. Photos supplied.
A drone image of the dunes shortly after the gaps were carved. Photos supplied.
Sand build-up behind the face of the dunes.
Sand build-up behind the face of the dunes.

A University of Otago research project appears to have strengthened at-risk sand dunes below John Wilson Ocean Dr.

In April, University of Otago second-year master of science student Tom Simons-Smith had three gaps carved in the dunes below the drive to encourage wind to funnel sand closer to the road and move a greater portion of the dune away from storm surge.

Mr Simons-Smith said the trial was half completed and before-and-after drone images of the dunes showed a positive amount of increased sand cover.

"At the end of the day, it is experimental. The scale at which we have done it now isn't going to save South Dunedin.

"But on a larger scale, I think it could buy the coastline a year or two.''

Research organiser Associate Prof Michael Hilton said early results from the study were positive.

"The purpose of this exercise is to assess notching as an approach to foredune management.

"We hypothesise that a more dynamic dune, one which involves more landward movement of sand, will be less vulnerable to erosion during storm events ...

"So far the results are encouraging.''

University of Otago second-year master of science student Julia Moloney used a drone to record changes in the distribution of sand on the dunes.

Miss Moloney said the dune with the largest gap had increased sand cover by 119sqm, while two other dunes with smaller gaps had 49sqm increased cover.

Mr Simons-Smith said it was important to have different size gaps in the dunes to gather data on the effectiveness of gap location and size.

The students were also analysing the frequency of storms to hit the beach, to understand the degree to which large amounts of sand could be moved by sporadic weather events.

Mr Simons-Smith said public feedback from people using John Wilson Ocean Dr had been "very positive''.

"People are supportive of it.

"They want to see something done to strengthen the area.''

margot.taylor@odt.co.nz

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