Mangawhai's nationally important sandspit is at risk of erosion from Pakiri seabed sand mining, according to Northland Regional Council (NRC).
Mangawhai sandspit's toe at the entrance to Mangawhai Harbour Photo: Tania Whyte / Northern Advocate via LDR
The NRC's comment comes in its submission to Auckland Council in the face of resource consent renewal applications to continue taking thousands of tonnes of sand from the sea floor off Pakiri Beach, just south of Mangawhai, each year.
Kaipara District Council (KDC) has also submitted, in opposition to the sand mining.
Pakiri sea floor sand has played a major role in Auckland's building scene. It is the concrete industry's sand source preference for major infrastructure projects, high-rise construction, and marine structures.
The NRC said the Mangawhai barrier spit was classed as outstanding in terms of landscape, natural character and natural features. These high-ranking values were a matter of national importance under the Resource Management Act.
It said Mangawhai Harbour and sandspit were already facing significant threats from the effects of climate change and associated increase in storm severity, frequency and sea level rise.
Seabed sand mining company, Auckland-based McCallum Brothers, is applying for two new resource consents to mine the sand off Pakiri Beach.
These consents would allow for the continuation of seabed sand mining off Pakiri/Te Arai Beach, immediately adjacent to the south side of the Northland-Auckland boundary.
The two applications seek to continue sand mining in the shallow five to 10-metre deep 'in-shore' area very close to the beach and in the 'mid-shore' area between 15 and 25 metres deep - for up to 35 years, contrasting with the 14-year duration of now-expired consents for doing so.
The 'in-shore' take would be up to 76,000 cubic metres annually, the 'mid-shore' 150,000 cubic metres.
The applications are for seabed sand mining across nine square kilometres of seabed along about 10km of Pakiri/Te Arai coastline.
The mining is allowed only as far north as the Northland-Auckland border. The boundary runs out from the land into the sea in a north-easterly direction from roughly the base of Mangawhai spit. Seabed sand dredging is allowed on the Auckland side of the border only.
NRC's submission said it was important any potential cross-boundary effects were addressed and Mangawhai spit was protected from adverse effects.
KDC's submission said Mangawhai Harbour, Mangawhai estuary, and Mangawhai Heads were at risk of exposure to the coastal elements should the spit's protection disappear or decrease.
"KDC opposes the two applications for sand extraction within the Mangawhai-Pakiri embayment ... Opposition is in full and pertains to actual or perceived adverse effects on the Mangawhai sandspit morphology, wildlife habitat of nationally critical or vulnerable bird species, as well as on the local Mangawhai community," the submission said.
NRC said the effects of climate change and the associated increase in storm severity, frequency and sea level rise meant Mangawhai Harbour and sandspit were already facing significant threats.
Sea level rise was likely to exacerbate the risk of erosion.
NRC said there were conflicting opinions on whether removal of sand from the extraction zones played a role in starving the spit of sand that would otherwise replenish it and potentially allow it to increase in size. A precautionary approach was therefore required.
It said work on the potential impact of changes to coastal processes resulting from the sand mining had not been done to the same standard for the area north of the Northland-Auckland regional boundary.
NRC said a 1km buffer zone should be established if sand dredging proceeded and further, that any resource consent granted for sand mining needed a consent duration "in line with" the 14 years granted in previous consenting - not the 35 years requested by the applicant.
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