Study of the shape of sands to come

University of Otago students Teresa Konlechner (left), a botany and geography PhD candidate, and Charlotte Kidd, a third-year professional surveying student, prepare to collect data in the sandhills at St Kilda yesterday. Photo by Gerard O'Brien.

The pair, Teresa Konlechner and Charlotte Kidd, are engaged in a GPS survey of St Clair, St Kilda and Middle beaches, which aims to build a three-dimensional digital model showing the shape of sand deposits on the beaches.

The work is the latest in a series of monthly surveys undertaken by students, contracted to the Dunedin City Council, since last year's severe storms caused more erosion problems, stripping sand from the area.

And it's surprisingly tough work - the students cover up to 22km each day while taking up to 4000 measurements in the hot sun, and have survived close encounters with curious locals including, earlier this week, an angry sea lion and her young pup.

But the work was important, as it would show how sand accumulated, moved around the beaches or vanished completely over time, supervisor and Department of Geography senior lecturer Dr Mike Hilton told the Otago Daily Times yesterday.

Together with cameras capturing weather information from St Clair, the data could help predict the erosion likely to result from certain storm patterns, and how best to respond, he said.

The work was part of "about a dozen" DCC-led projects aimed at understanding and combating erosion along the strip of beaches between St Clair's Hot Salt Water Pool and Lawyers Head.

This followed dramatic erosion in 2007 and again last year.

"This is probably the first major commitment the council has made to understanding the coast, as opposed to building things on it. It's pretty significant," Dr Hilton said.

The beaches were "pretty well formed" with plenty of sand at present, as sand generally accumulated during more settled summer months, he said.

However, the risk to the area would be at its greatest during winter, when violent storms could cause further erosion.

Should that happen, the survey data gathered could, for example, be used to calculate how much dredged sand was needed to restock the beaches, a process known as beach renourishment, Dr Hilton said.

And there was no doubt the work was vital.

"They [the council] have been quite shocked by the degree of erosion in the last few years, and the last 12 months in particular," he said.

Dr Hilton, who specialised in coastal management, said the under-seige coastline had changed a lot from the days 100 years ago when there was a wide buffer between the sea and valuable coastal infrastructure, allowing room for the energy from storm waves to dissipate.

"Now, it's subjected to attack by the sea. It's not a problem that's going to go away . . .I think some adjustments will need to be made," he said.