Thursday, 20 December 2018

WHITIANGA WEATHER

Residents carefully watching results of groyne at Flaxmill Bay

A group of Mercury Bay residents are carefully watching the results of an unconsented groyne at Flaxmill Bay.

The groyne, really just a row of sandbags on the beach, was the initiative of a Flaxmill Bay local concerned about the beach erosion at the eastern end of a rock wall that was constructed as an emergency measure to protect Purangi Road from suffering erosion damage.

According to the local, the groyne was a few weeks ago put in to harness the movement of sand along the beach. The effect of the groyne, according to the local, is getting better every day.

Thames-Coromandel District Council coastal engineer, Jan van der Vliet, says they aren’t considering a groyne as an immediate option to curb the erosion occurring at Flaxmill Bay. “I’ll admit that the sandbag groyne that’s at the moment on the beach at Flaxmill Bay seems to be delivering positive results building up the high tide beach, but the effectiveness of groynes can only be measured over time,” he says.

“What we’re finding around Mercury Bay is that beach erosion is at its worst where hard and soft options - in essence rock walls and sand dunes - meet. We’ve recently lodged a resource consent application with Waikato Regional Council for the construction of a design which will hopefully address this problem at Flaxmill Bay. The consent application makes provision for a transitional design from a rock wall to a backstop wall that will enable sand build-up in front of the backstop wall and then onto natural dunes.

“To make this design work, the backstop wall will have to be constructed as far landward as possible to best protect Purangi Road, while minimising damage to the beach. Unfortunately this could mean that two of the pohutukawas at the beach might be lost, however replacement tree planting will be incorporated into the new design.”

TCDC is busy preparing another resource consent application for the construction of a similar transitional design at the eastern end of Cooks Beach, where the Captain Cook memorial toppled into the ocean during a severe storm in July.

Jan says TCDC isn’t discounting the potential value of groynes in the battle against beach erosion and will consider their value in the Shoreline Management Plan they’ve recently started working on. “The Shoreline Management Plan will take a holistic view of areas as a whole and what can be done to better control beach erosion,” he says. “We’ll specifically look at Mercury Bay, Thames and the Thames Coast, which are the beach erosion hotspots on the Coromandel Peninsula at the moment. Work on the plan is progressing well. We’ve identified several work streams and are finalising tenders for consultants to work with us in the development of the plan.”

TCDC announced on 11 November 2015 that the Mercury Bay Community Board agreed to trial a wooden groyne at Buffalo Beach in Whitianga. It was, at the time, expected that the groyne, which was to be approximately 25m in length, would cause sufficient sand build up to avoid extending the Buffalo Beach rock wall, which was at the time, and still is, stretching from just north of the Buffalo Beach Road/ Albert Street intersection to a short distance past the Buffalo Memorial.

Allan Tiplady, TCDC District Manager North, says TCDC didn’t progress with the construction of the groyne as there was strong lobbying from within the Mercury Bay community, and they have received advice, to rather focus on soft (dune restoration and planting) options as a means to rebuild the dunes and beaches and curb the erosion.

“The Mercury Bay Community Board decided in early 2016 to shelve the construction of the groyne and rather adopt a programme in terms of which dunes around the Mercury Bay area would be restored through planting with native dune plants,” he says. “Since then extensive dune plantings have taken place along Buffalo Beach in Whitianga, at Flaxmill Bay and also along Cooks Beach.”

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The Mercury Bay Informer is a highly popular community newspaper, based in Whitianga. The paper is distributed throughout the Coromandel Peninsula, coast to coast from Thames to north of Colville.