LINZ’s hydrographic survey of Tūranganui-a-Kiwa/Poverty Bay
From Hydro by Adam Greenland, Brad Cooper, Jennifer Coppola, Annette Wilkinson
Like other hydrographic offices, Toitū Te Whenua Land Information New Zealand (LINZ) collects survey data for safety of navigation, producing and maintaining nautical charts and products in accordance with SOLAS Chapter V, Regulation 9.
Finding new and unusual features such as shipwrecks is the icing on the cake.
LINZ’s recent survey of Tūranganui-a-Kiwa/Poverty Bay uncovered two locally known but previously uncharted wrecks, mapping them both in 3D and igniting interest in their stories – their origins, their voyages and their eventual demise.
As the New Zealand Hydrographic Authority, LINZ provides navigational products and services that support safe shipping.
The information underpinning these products is captured through hydrographic surveys that map the seafloor.
This data gives a detailed view of the seafloor and can be used to obtain a better picture of how the marine environment has changed with time, weather and geological events.
New Zealand’s area of charting responsibility is vast for the size of the country, covering an area comparable to Europe and North Africa.
Not only does it cover New Zealand waters, but also parts of Antarctica and the South-West Pacific.
As an island nation, New Zealand relies on shipping for many of its imports and exports.
Seabed mapping provides the data needed to update nautical charts and to meet LINZ’s obligations to make navigating the waters around New Zealand, the South-West Pacific and the Ross Sea region of Antarctica safer.
Risk assessment and HYPLAN
New Zealand’s hydrographic survey plan, HYPLAN, was based on a novel risk assessment methodology completed in 2016.
The risk assessment considers AIS vessel traffic data, the locations of environmentally and culturally sensitive sites, hazards such as reefs and the age of the survey data currently on the chart.
The resulting heat maps of navigation risk help LINZ to determine priority areas for surveys, sometimes replacing data collected during Captain James Cook’s voyages more than 200 years ago!
Partnering to benefit tangata whenua and conservation
LINZ aims to ‘collect data once, use many times’, and proactively engages with local councils, other national agencies such as the Department of Conservation (DOC), and tangata whenua of Aotearoa (people of the land), who represent New Zealand’s Māori population.
Partnering with others allows New Zealand to optimize funding and collect datasets that can be used for many purposes.
In previous partnerships, LINZ extended the survey remit to cover areas for marine science research and collected additional data such as seabed samples and even seabird sightings.
Figure 1: New Zealand’s charting responsibilities are highlighted, and its exclusive economic zone (EEZ) outlined in black.
For the Tūranganui-a-Kiwa/Poverty Bay survey, local iwi (tribal groups) were interested in data from the coastal area to the south of Young Nicks Head/Te Kurī.
DOC also wanted Te Tapuwae o Rongokako Marine Reserve (ten nautical miles to the north) to be surveyed.
The reserve has never been mapped in such detail and the information discovered will help to care for this marine taonga (treasure).
Adding additional areas to be surveyed on top of the planned extent presents challenges; however, the benefits to iwi and for marine management and the protection of ocean biodiversity is of great importance to LINZ.
DOC also wanted Te Tapuwae o Rongokako Marine Reserve (ten nautical miles to the north) to be surveyed.
The reserve has never been mapped in such detail and the information discovered will help to care for this marine taonga (treasure).
Adding additional areas to be surveyed on top of the planned extent presents challenges; however, the benefits to iwi and for marine management and the protection of ocean biodiversity is of great importance to LINZ.
Approaches to Gisborne survey
Tūranganui-a-Kiwa/Poverty Bay is located in the Gisborne region, on the north-eastern coast of New Zealand’s North Island.
In New Zealand, many place and feature names are made up of an English name and an original te Reo Māori name.
Tūranganui-a-Kiwa is the Māori name for the bay, describing the long-standing or waiting place of Kiwa of the Horouta or Tākitimu waka (boat).
Poverty Bay was named by Captain Cook on his voyage around New Zealand because he was not enamoured with the district.
He wrote on 11 October 1769: “We weighed and stood out of the Bay, which I have named Poverty Bay, because it afforded us no one thing we wanted.” A large portion of the bay had not been mapped since the Royal NZ Navy’s singlebeam survey in the early 1950s.
Since then, technology has advanced hugely, revealing what lies beneath the surface in greater resolution than ever before.
Discovery Marine Limited (DML), based in Tauranga, New Zealand, was contracted by LINZ to complete the survey.
The survey covered two areas: the Tūranganui-a-Kiwa/Poverty Bay survey area was 88km2 and completed to LINZ-1 standard; the Te Tapuwae o Rongokako Marine Reserve was 21km2 and completed to LINZ-2 standard (see Figure 2).
Figure 2: Tūranganui-a-Kiwa/Poverty Bay survey area, including Te Tapuwae o Rongokako Marine Reserve.Two previously uncharted wrecks (Korua and Star of Canada) were mapped in detail during the survey.
The survey was done in two phases to take advantage of weather windows and optimize vessel use.
The offshore phase was completed in November 2022 with a 23m (length), 6.4 m (beam) aluminium monohull vessel.
The inshore phase was conducted between October and December 2023 using the 7.7m (length), 2.49m (beam) Senator 770.
The multibeam (MBES) used for both phases of the survey was the single-head Teledyne Reson SeaBat T50-R.
Other key equipment included the Applanix POS MV WaveMaster II, AML Oceanographic Micro X sound velocity sensor and AML-3 LGR sound velocity and temperature profiler.
Positioning was done using Trimble’s Fugro Marinestar.
The MBES was operated at a frequency of 300kHz for the duration of the survey.
Besides the bathymetry required for updating nautical charts, other datasets such as acoustic backscatter and water column data were simultaneously acquired from the MBES system.
To help reduce the large data volumes associated with water column data, two operating modes were adopted: ‘normal operation’ mode offered higher compression, and ‘area of interest’ mode offered lower compression with higher resolution over suspected freshwater springs and reef areas.
In all, 8.1TB of raw data was collected, which besides updating charts can be used for habitat and sediment deposition mapping, flood planning and 3D visualization of shipwrecks.
Shipwrecks rediscovered during survey
Star of Canada
The Tūranganui-a-Kiwa/Poverty Bay survey mapped two previously uncharted shipwrecks: the Star of Canada and the Korua.
While the local community was aware of these wrecks, they have never been mapped to such fine detail (Figure 3).
The 7,280-ton steamer Star of Canada first voyaged to New Zealand in 1910.
For the next two years, it regularly travelled from Australia and New Zealand to England, carrying chilled and frozen meat and other produce.
On 23 June 1912, a southerly squall blew the vessel onto Kaiti Beach, where it struck rocks and began taking on water.
The next couple of days was spent salvaging as much of the cargo as possible, including mutton, oats, wool and antimony.
Fortunately, no souls were lost.
A heavy swell finally broke her hull, and she was abandoned to the underwriters.
The two-storied wheelhouse and captain’s cabin, plus part of the deck superstructure, was purchased by a local engineer and brought ashore.
In 1983, the Star of Canada was bequeathed to the citizens of Gisborne and, in 1985, the wheelhouse was moved with great pomp (in a festival that coincided with high tide) to its current location.
The superstructure now sits along the Tūranganui River in Gisborne and houses the Tairāwhiti Museum.
The captain’s cabin largely contains the original fixtures and fittings and many artefacts that were salvaged from the ship.
The offshore phase was completed in November 2022 with a 23m (length), 6.4 m (beam) aluminium monohull vessel.
The inshore phase was conducted between October and December 2023 using the 7.7m (length), 2.49m (beam) Senator 770.
The multibeam (MBES) used for both phases of the survey was the single-head Teledyne Reson SeaBat T50-R.
Other key equipment included the Applanix POS MV WaveMaster II, AML Oceanographic Micro X sound velocity sensor and AML-3 LGR sound velocity and temperature profiler.
Positioning was done using Trimble’s Fugro Marinestar.
The MBES was operated at a frequency of 300kHz for the duration of the survey.
Besides the bathymetry required for updating nautical charts, other datasets such as acoustic backscatter and water column data were simultaneously acquired from the MBES system.
To help reduce the large data volumes associated with water column data, two operating modes were adopted: ‘normal operation’ mode offered higher compression, and ‘area of interest’ mode offered lower compression with higher resolution over suspected freshwater springs and reef areas.
In all, 8.1TB of raw data was collected, which besides updating charts can be used for habitat and sediment deposition mapping, flood planning and 3D visualization of shipwrecks.
Shipwrecks rediscovered during survey
Star of Canada
The Tūranganui-a-Kiwa/Poverty Bay survey mapped two previously uncharted shipwrecks: the Star of Canada and the Korua.
While the local community was aware of these wrecks, they have never been mapped to such fine detail (Figure 3).
The 7,280-ton steamer Star of Canada first voyaged to New Zealand in 1910.
For the next two years, it regularly travelled from Australia and New Zealand to England, carrying chilled and frozen meat and other produce.
On 23 June 1912, a southerly squall blew the vessel onto Kaiti Beach, where it struck rocks and began taking on water.
The next couple of days was spent salvaging as much of the cargo as possible, including mutton, oats, wool and antimony.
Fortunately, no souls were lost.
A heavy swell finally broke her hull, and she was abandoned to the underwriters.
The two-storied wheelhouse and captain’s cabin, plus part of the deck superstructure, was purchased by a local engineer and brought ashore.
In 1983, the Star of Canada was bequeathed to the citizens of Gisborne and, in 1985, the wheelhouse was moved with great pomp (in a festival that coincided with high tide) to its current location.
The superstructure now sits along the Tūranganui River in Gisborne and houses the Tairāwhiti Museum.
The captain’s cabin largely contains the original fixtures and fittings and many artefacts that were salvaged from the ship.
Figure 3: 3D image of the Star of Canada wreck.Korua
The second wreck found during the survey was the remains of the dredge Korua (Figure 4), off Young Nicks Head/Te Kurī.
This vessel was used to dredge nearby Napier and Gisborne harbours in the 1930s.
She played a significant role in the establishment of the Port of Gisborne.
At the time, several harbour schemes had been proposed for Gisborne.
A breakwater groyne was constructed in the early 1900s and the river diversion wall was built in the 1920s to reroute the Tūranganui River.
Between 1925 and 1931, Korua’s role was to excavate 1,920,000 tons of spoil.
Today, the Port of Gisborne is critical for primary industry exports such as logs, kiwifruit and squash.
Korua was scuttled in 1940 when it was no longer of use.
Interestingly, the 1953 navy survey did detect a shoal sounding (three fathoms, two feet, roughly equal to 6.1m) in the location of the Korua wreck (Figure 5).
With today’s technology, the wreck can be mapped in much higher resolution.
The least depth over the wreck is now 11m, which suggests the wreck may have toppled over in the 70 years since it was last detected by an echosounder.
Figure 4: The remains of the Korua shipwreck scattered on the seafloor.LINZ open data services
Data captured in the Gisborne hydrographic survey, including details of the two wrecks, will be used to update nautical charts of the area and help to make navigation safer.
The upcoming LINZ 3D Coastal Mapping programme will map up to 40% of New Zealand’s coastline and could also reveal previously unknown features such as shipwrecks.
In keeping with LINZ’s goal to ‘collect once, use many times’, LINZ’s open data policy means that all data it collects is available for anyone to use under Creative Commons Attribution 4.0 International licence (CC-BY 4.0).
Bathymetric surfaces in the form of two-metre depth grid models can be downloaded from the LINZ Data Service (https://data.linz.govt.nz/).
Other data is available upon request by emailing hydro@linz.govt.nz.
The upcoming LINZ 3D Coastal Mapping programme will map up to 40% of New Zealand’s coastline and could also reveal previously unknown features such as shipwrecks.
In keeping with LINZ’s goal to ‘collect once, use many times’, LINZ’s open data policy means that all data it collects is available for anyone to use under Creative Commons Attribution 4.0 International licence (CC-BY 4.0).
Bathymetric surfaces in the form of two-metre depth grid models can be downloaded from the LINZ Data Service (https://data.linz.govt.nz/).
Other data is available upon request by emailing hydro@linz.govt.nz.
Figure 5: A 1953 survey detected a shoal sounding (three fathoms, two feet) in the location of the Korua shipwreck.The figure shows the historic sounding sheet superimposed on the high-resolution multibeam depth surface.
Conclusion
LINZ surveys the waters of its charting area as part of its international obligations and determines survey extents based on hydrographic risk assessments.
The data needs of local stakeholders and other government agencies are considered in LINZ’s hydrographic survey plans, which acknowledges the wide use of hydrographic data.
Among the rich dataset of the Gisborne survey, two known wrecks were mapped and charted for the first time, improving navigational safety in the area.
Each wreck has its own story, but one shows the value of increased coverage with MBES compared to an old SBES survey that detected an anomaly but did not identify the wreck.
It is also noted that features such as wrecks make for a very engaging way to get the public interested in hydrographic surveying.
LINZ is currently updating its risk assessment, which will help inform the future HYPLAN.
Who knows what wrecks will be uncovered next…
For more information, see here.
LINZ surveys the waters of its charting area as part of its international obligations and determines survey extents based on hydrographic risk assessments.
The data needs of local stakeholders and other government agencies are considered in LINZ’s hydrographic survey plans, which acknowledges the wide use of hydrographic data.
Among the rich dataset of the Gisborne survey, two known wrecks were mapped and charted for the first time, improving navigational safety in the area.
Each wreck has its own story, but one shows the value of increased coverage with MBES compared to an old SBES survey that detected an anomaly but did not identify the wreck.
It is also noted that features such as wrecks make for a very engaging way to get the public interested in hydrographic surveying.
LINZ is currently updating its risk assessment, which will help inform the future HYPLAN.
Who knows what wrecks will be uncovered next…
For more information, see here.
Figure 6: Black and white image of the dredge, Korua.(Image courtesy: Stan Vincent, Tairāwhiti Museum)
Links :
- GeoGarage blog :New map reveals New Zealand's seafloor in stunning detail / Mapping Aotearoa New Zealand's seafloor for safer ... / Scientists to survey uncharted seafloor area / Kiwi scientists uncover stunning underwater insights / Origin of seabed more complex than scientists first imagined / NIWA survey reveals deep water canyons off Otago coast ... / "Striking" new images show impact of Kaikoura earthquake ... / The mighty quest to unveil our blue planet / A name directory for the ocean floor / Uncharted NZ shipwrecks mapped for first time / We thought New Zealand was an island nation. Scientists ... / Scientists detect huge fault rupture offshore from Kaikoura / The missing continent it took 375 years to find
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