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$5 million plan to stop sediment flow into Mahurangi River

Posted at 8:00am Monday 10 May, 2021

Examining the Mahurangi River catchment map, from left, Shelley Hackett, Adam Schelhammer, Colin Harvey (MERRA) and Leo Van de Wijdeven (landowner).
Examining the Mahurangi River catchment map, from left, Shelley Hackett, Adam Schelhammer, Colin Harvey (MERRA) and Leo Van de Wijdeven (landowner).

Managers of a project designed to stop thousands of tonnes of sediment flowing into the Mahurangi River each year outlined how they planned to achieve that goal at a public launch event at the Mahurangi West Hall last month.

Late last year, the Ministry of the Environment contributed $5 million to the Mahurangi East Land Restoration project (MELR) to stop the flow of sediment. MELR is managed by Auckland Council and the Ngāti Manuhiri Settlement Trust.

The project is designed to complement dredging of the Mahurangi River, ensuring that the river does not simply  refill with silt once it has been dredged.

Project managers Adam Schelhammer and Shelley Hackett told the gathering of around 100 landholders and environmentalists that the MELR would build on the work of the Rodney Local Board and previous efforts by Auckland Regional Council and Rodney District Council to contain sediment.

The managers said to do this, MELR would focus on four problem areas – rural land use, forestry, small construction sites and unsealed roads.

Mr Schelhammer said the MELR would provide funding to landowners to stop sediment running off their properties.

“Do you have a piece of land with a stream that needs to be fenced or re-planted?

Do you maybe need to do wetland reconstruction? Do you have a stretch of unsealed road that you are aware is dumping sediment into a waterway? We can help with that,” he said.

On forestry, the project managers said they would  provide landowners with information on low-impact harvesting techniques and regulatory requirements. They would also seek to protect landowners from “cowboy contractors”, who offer cash for trees but then quickly depart after removing them, leaving an environmental mess behind.

On unsealed roads, MELR would pilot maintenance techniques to reduce sediment loss from dirt and gravel roads.

Mr Schelhammer said sealing was not always the answer. Often it was more important to address underlying drainage issues.

On construction sites, managers said MELR would engage with construction crews and developers to advise on regulatory requirements and the best way to contain sediment.

Mr Schelhammer said MELR would aim for voluntary compliance, but could levy penalties on developers who broke the rules.

Shelley Hackett said the Mahurangi River catchment covered about 13,500ha and included 206km of rivers and streams.  

An estimated 21,000 tonnes of sediment was being washed into the river each year. Around 55 per cent came from bank erosion, 17 per cent from pasture land and 22 per cent from native open space and forestry.

She said about 70 per cent of the catchment was farmland, hence MELR was making a big effort to engage with farmers and support their efforts to contain sediment.

She said currently valuable topsoil was being lost from farms and its presence in waterways was creating a hostile environment for marine life.      

Info: Shelley.Hackett@aucklandcouncil.govt.nz

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