From aquaculture to vessel navigation and marine biodiversity, the health of the coastal ecosystem plays a central role to the quality of life in New Zealand. And it’s why Marlborough District Council, responsible for 1,800 km of coastline, is leading the charge nationally for seabed mapping - the mountains and valleys, canyons and plains, and ridges and reefs that make up the unique underwater landscape at the top of the South Island.
Following the successful mapping of Queen Charlotte Sound in 2016/17, Council and Land Information New Zealand (LINZ) have just completed Pelorus Sound/Te Hoiere, Admiralty Bay, and Te Aumiti/French Pass. With all of Queen Charlotte Sound/Tōtaranui and over half of Pelorus Sound/Te Hoiere now mapped, this provides valuable information for nautical charts, making it safer for the increasing number of vessels – from dinghies to cruise liners – using these waterways.
Mayor John Leggett, who chairs the Council’s Environment Committee, said the data will enable Council to make decisions for a wide range of stakeholders.
“This is incredibly powerful data that can help us to grow industry, while managing restorative projects in coastal areas. It has the potential to give us those insights that we need for our collective outcomes,” Mayor Leggett said.
Marlborough’s seabed mapping began in 2015 with D’Urville Island/Rangitoto Ki Te Tonga, and continued the following year with Queen Charlotte Sound/Tōtaranui and Tory Channel/Kura Te Au. The results from these initial projects exceeded Council expectations, said coastal scientist Oliver Wade.
“We were able to learn more about Queen Charlotte Sound/Tōtaranui than we anticipated in the initial round of mapping, and we’re hoping to learn even more about the Pelorus Sound/Te Hoiere. The data will enable us to effectively manage our coastal ecosystem and has led to unexpected research in Queen Charlotte Sound/Tōtaranui on topics ranging from high definition current flows to micro-plastic distribution in sediments,” Mr Wade said.
Other early learnings about Pelorus Sound have been related to marine farming and this will be an invaluable tool for both the marine farming industry and the Council in years to come. The seabed mapping, at over 110 metres deep in places, has been conducted using state-of-the-art multibeam echosounder technology.
Multibeam echosounders produce a fan of sound waves directly downwards from the bottom of a boat. These beams reflect off the seafloor, enabling the surveyors to calculate the depth, scan, and then map the habitat in detail.
The resulting three-dimensional habitat maps identify features such as reefs and canyons, which can then be targeted for sampling with underwater video and cameras to build a picture of the conditions and species present. With the latest round of mapping, hydrographic surveys of the areas have been completed to measure and describe the features that affect activities such as maritime navigation.
While multibeam technology is commonly used to map seabeds, the vast scale of the survey is unique and demonstrates Marlborough’s commitment to caring for the Sounds,” said Luke Grogan, Harbour Master.
“This dataset is the foundation to build the most comprehensive data-driven management practices for coastal areas in New Zealand,” said Mr Grogan.
Since the Queen Charlotte Sound data was made available, it has been used by the public and other science organisations. As data for Pelorus, French Pass and Admiralty Bay goes live on Council website, it’s the first time accurate tide and bathymetric data has been available to the public for these areas.
The Pelorus, French Pass and Admiralty Bay mapping project was funded by a $3 million investment from Council, with additional financial and operational support from LINZ.
“Our quality of life and well-being are dependent on how we use, develop and protect our natural and physical resources,” said Mayor Leggett.
“The health of our coastal environment is key to the prosperity of the region’s businesses and communities, and central to our social, cultural, ecological and recreational values,” said Mayor Leggett.
To access the new Pelorus data (from tomorrow 20 November) go to: https://maps.marlborough.govt.nz/seabedmaps