Posted on March 8, 2022
Mangawhai locals say sand mining is harming an ecologically sensitive spit which shelters their harbour and was home to the critically endangered fairy tern. Environmentalists are questioning why New Zealand still permits the extraction. Andrea Vance reports.
At first they came with shovels, planks and wheelbarrows.
Throughout the 1940s and 50s, glistening white sand was extracted from Mangawhai Harbour, an indispensable resource used for glass and concrete in the post-war building boom. It was trucked to Auckland for construction.
A new wave of beach lovers was slowly discovering the Pacific coastline and rolling farmland was being transformed into two settlements, Mangawhai Heads and Mangawhai township.
It became a popular seaside destination. Holiday-goers were drawn by the surf beach, and the tranquil warm waters of the harbour. It was sheltered by a long sand spit, dominated by the ‘Mangawhai pyramid,’ an enormous hill.
As the population grew, the mining continued. Over half a century, 750,000 cubic metres (enough to fill 300 Olympic swimming pools) was removed. As technology became more sophisticated, more sand was vacuumed up from the sea floor into huge barges.
By the 1990s, up to 15,000 cubic metres (six swimming pools) was mined from the inlet each year. Commercial operators also began suction dredging from the sandbars off Pākiri Beach, to the south.
At first the changes weren’t obvious. Major storms in the 1970s and 1980s – including 1987’s Cyclone Bola – saw the ocean break through the spit. The harbour entrance silted up and its clear, blue waters became stagnant and polluted. Navigating the new entrance was perilous for boaties, even at high tide.
Natural forces had spoiled treasured holiday spots. But locals also began to question if the industrial sand mining was also reshaping their coastline.
For now, they had to breathe life back into the dying harbour. In the face of passivity from Kaipara District Council, Northland Regional Council and the Department of Conservation, locals decided to try and close the breaches and force the tidal water flow back to the original entrance. The February 1991 rebellion became known as ‘The Big Dig.’
It didn’t work. The sea broke through again. But over the next five years, working with ocean engineers André and Robin LaBonté, the Mangawhai Harbour Restoration Society returned the waterway to a pristine state. It cost $1.8m dollars.
Dunes are natural habitats for native species. The sand spit is also a wildlife refuge, a breeding ground for the rare fairy tern/tara iti, the dotterel/tūturiwhatu and home to colonies of threatened red-billed gulls.
But they also protect land and property from erosion, storms, cyclones and tsunamis.
Locals liken the effect of dredging to taking a spoonful from a sugar bowl: crystals fall to fill in the hole. André LaBonté says the sand spit was deflating. “It wasn’t recovering as well as we had hoped.”
With their harbour restored, locals began a new fight – opposing the sand dredging. In 2004, Sea Tow and Norsand applied to Northland Regional Council to take 1.08 million cubic metres of sand from the harbour over 20 years.
The US-born LaBontés enlisted the help of their friend Professor Bob Dean of the University of Florida’s civil and coastal engineering department. He told the council New Zealand was the only developed country that allowed sand mining close to the shore for anything other than beach replenishment. Another engineer reported signs of erosion that mirrored that which had destabilised Omaha’s dunes.
The council’s own coastal consents manager and NIWA suggested mining be phased out to prevent long term damage. The council recommended to Minister of Conservation Chris Carter that he decline the applications. Both companies agreed not to appeal.
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