Two Northland environmental agencies are investigating concreting on a waterfall's edge that the local hapū believes is impacting on safe passage for fish and their migration cycle.
The Whatitiri Resource Management Unit (WRMU) has filed a written complaint to the Northland Regional Council (NRC) and the Department of Conservation (DoC), together with photos of the alleged illegal works at the Karukaru/Riro Falls on Carruth Rd, Poroti.
WRMU believes the concrete placement was done without a consent early in the Covid-19 lockdown, either in March or April, and is concerned about the impacts on elvers or longfin eel.
WRMU spokesman Millan Ruka said it appeared the work was done to attempt to divert the course of some of the water from the falls, without seeking professional advice or cultural impact advice from the hapu.
NRC has registered the complaint as an environment incident and is investigating it, and so is DoC.
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Ruka said his hapū is concerned lime may have leached into the waterway when the concrete was poured, which was highly toxic to tuna (eels).
He said the permanent alteration was illegal and required whoever was responsible to have gone through the Resource Management Act process and that his hapū should have been notified.
"Elvers or longfin eel migrate up these falls each year around September through to January. The natural ladder passages have largely been closed off by some 75 per cent as a result of this concrete placement."
Ruka said the concreting-off caused severe confusion to juvenile elvers that naturally followed the paths of those that climbed the falls the year before and for thousands of years prior.
It seemed apparent, he said, a ready-mix load of concrete was delivered to the site and discharged by chute direct to the stream.
Ruka said whaka tuna heke/migrators were the adult tuna that migrated once annually out of the upper catchments and out to sea and hikoi to the Tongan Trench, more than 2000km away to mate and fertilise their eggs.
"Reinstatement of the falls back to its natural state is achievable and appropriate and should be carried out by professional contractors and supervised by engineers who are qualified in environmental sensitive works,'' he said.
"We request to NRC that our hapū be present and appropriately remunerated to oversee the reinstatement of the falls to best it can be back to the original condition."
NRC group manager regulatory services, Colin Dall, confirmed the concreting was not authorised by a resource consent and that there was a range of enforcement actions the council could take, such as issuing abatement and/or infringement notices, enforcement orders and prosecution.
The maximum penalty for successful prosecutions under the RMA was two years in prison or a fine not exceeding $300,000 for a person or a maximum fine of $600,000 for a company.