Surf, sand and rising tides: Our changing beaches

30 May 2018

Karin Bryan for web

Professor Karin Bryan's lecture will focus on New Zealand's changing coastline.

New Zealanders love their beaches; they argue over which beach is best, for swimming, surfing and sourcing kaimoana.

But our beaches are forever changing, and how and why they change is the focus of Professor Karin Bryan’s research.

At her inaugural professorial lecture this month, the University of Waikato professor of Earth and ocean sciences will be speaking on surf-breaks, beach morphology and the impacts of climate change on the coast. “The sea kills more people in New Zealand than any other natural hazard,” she says. “So a lot of my work seeks to understand the dynamics of sediments and water exchange in coastal environments, and how the dynamics contribute to coastal change.”

Despite the random and unpredictable nature of surf, Dr Bryan says some intriguingly simple patterns emerge. “Rip currents and sand bars often order themselves into neat arrangements which take substantial storm events to reconfigure. Headlands, which are common on our volcanically controlled land, play a special role, channelling currents seaward and trapping sand. Such variations make it difficult to assess coastal hazard zones, plan beach safety and prepare for sea level-rise.”

Professor Bryan is lead researcher on a near-completed study of New Zealand’s leading surf breaks and how they may be threatened by coastal activity, such as dredging and marina development. The MBIE-funded study wraps up in October this year and has involved collecting data about wind and wave conditions and underwater topography at seven of New Zealand’s popular surf beaches to assess changes in “surfability”.

She says the results of the million-dollar study will support the 2010 New Zealand Coastal Policy Statement that states surf breaks of national significance need to be protected. “If we understand how surf-breaks work it will help communities and decision-makers be better informed about sustaining and protecting these significant breaks and provide guidelines for other breaks in the future.”

Professor Bryan was on the four-person panel tasked over the 2017/18 summer with choosing New Zealand’s best beach. “That was a great experience, we got so much feedback and it just reinforced how emotional New Zealanders get over their beaches,” she says. (For the record, Whangamata was judged number one.)

Beaches close to home, such as Tairua and Pauanui, have also been studied by Professor Bryan and her students, including rips, hazards and the impacts of coastal erosion. Further afield, in the Mekong Delta, Professor Bryan has been a major investigator of the good and bad of effects of mangroves, part of a USA Office of Naval Research project. She and her colleagues from Waikato joined American researchers to study the currents around the roots of the trees to determine how obstacles affect waves and currents. The movement of sediment controls the expansion or shrinking of the delta.

Professor Bryan’s inaugural professorial lecture takes place on Tuesday 19 June at 5.15pm at the Gallagher Academy of Performing Arts.