Major study to assess erosion and sediment control

In Issue53 by FIEA

Safeguarding New Zealand’s waterways is the key driver behind a seven-year study into the performance of control practices for reducing erosion and sediment delivered to rivers from forest harvesting.

The Ministry for Primary Industries (MPI) has partnered with forestry company OneFortyOne New Zealand, providing NZ$1.37 million through its Sustainable Food and Fibre Futures fund to the NZ$3.6 million project.

The project is in its second year, with a long-term monitoring programme now established within control and treatment catchments at OneFortyOne’s Donald Creek Forest, near Tadmor in the Tasman district.

“We want to find out what erosion and sediment control measures work best, and we can only know this through robust real-world studies,” says Steve Penno, MPI’s Director of Investment Programmes. This project is exploring the effectiveness of current best practice in sediment control as well as some new innovations”.

“Later in the project, the researchers will construct a large sediment retention pond to see how that measures up compared to traditional methods. As well as the benefits of erosion and sediment control, the programme will also compare the costs of different practices.”

Brent Guild, OneFortyOne’s Executive General Manager New Zealand says as a long-term business, it makes sense to invest in long-term studies like this one. The data will help us understand the impacts of our business. It will help us learn what works well and where we might do better”.

“We’re not doing this alone. We have the best people helping us with this research, including Cawthron Institute, Envirolink, Manaaki Whenua – Landcare Research and the Ministry for Primary Industries,” says Mr Guild.

“Two similar plantation catchments have been set up, including a ‘control’ catchment that is exposed to the same weather events but will not be harvested. This is a valuable opportunity to test the performance of traditional and new in-forest sediment management techniques – and we are grateful for MPI’s support to help us do this important work, which we’ll be able to share widely with the forestry sector.

“We’ll also have a deeper understanding of which strategies are best value for money. For instance, if the results show that sediment traps are an effective treatment, we’ll have the confidence to persist with this practice without calling on additional resources. However, if we find that the environmental impacts are too disruptive, this would provide the rationale for investing more money in sediment control at source to achieve environmental benefits,” says Mr Guild.

Steve Penno says “the data collected from this project will inform how the forestry industry meets new government freshwater management standards for suspended and deposited sediment. It will also provide scientific backing for the most effective practices in forestry that have the best possible outcomes for our environment.”

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