Fiordland National Park – South Island, New Zealand
Land Information New Zealand
In early January 2019, iXblue and Discovery Marine Limited (DML) commenced a joint survey in the Fiordland National Park.
The Fiordland National Park is located on the south west corner of the South Island and is characterised by some of the most spectacular fiord systems in the southern hemisphere. The entire region is breathtakingly beautiful and accordingly is under increasing demand by local and international tourists visiting the region every year. The area is remote, and tourist access is provided by chartered aircraft and tour vessel operators.
Whilst a hydrographic survey was undertaken in this region a few years back, it was not completed with technology that imaged the entire seafloor. Accordingly, there remained the risk that uncharted rocks could cause a vessel grounding, and subsequent environmental disaster.
A major outcome of this project would be the creation of up to date, highly accurate charts to ensure mariners operating in the region stay well clear of any navigational dangers.
This project required a full seafloor survey, including detection and charting of any features that could cause a danger to surface navigation.
The survey was broken up into two main areas.
The first and largest of these, the Southern Fiords area of over 1,500 line miles (nm), needed to be completed within seven weeks. The Dusky Sound region features many miles of rugged and navigationally challenging coastline, and the entrance is particularly challenging, as it is exposed to south-westerly winds and the swell of the Tasman Sea.
The second area of just over 1,000 line miles included the Doubtful and Thompson, Bradshaw and Charles Sounds in the Central Fiords region, and was to be completed over a four week period.
The greatest challenge faced by the crews was surveying the entrances to the Fiords. There were very few days when wind and sea conditions permitted survey of these outer, offshore areas.
The Southern Fiords receive in excess of 8m of rainfall every year and is one of the wettest regions of New Zealand. Our survey team certainly received their fair share of rainfall, including a 500mm deluge in one day, mid-way through the project.
The third challenge was the notorious Fiordland sandflies. These tiny creatures love to feed on human flesh and blood and the crew needed to cover themselves vigilantly when working outside. Only hard rain or a howling wind gave the crew any respite from these nasty little biters.
DML and iXblue mobilised to the area in January with four survey vessels, each fitted with high resolution Multi-beam Echosounders. The wide variety of environmental conditions meant that each had unique vessel requirements for efficient and effective survey.
- The outer regions of the fiords were subject to challenging wind and sea conditions. These areas could only be safely surveyed by the 30m Survey Vessel – SILENT WINGS.
- The inner regions are characterised by shallow, rocky and navigationally constrained coastlines. For these regions we used the small and maneouverable vessel – the 16m KAREN D catamaran, and the iXblue DriX Unmanned Survey Vessel.
- For the very shallow areas, the DML owned 7m Stabicraft was relied upon.
Three Kongsberg Em2040C Multibeam systems and one Teledyne T20 Multibeam system were installed alongside iXblue PHINS Class Inertial Navigation Systems (INS). Despite operating extensively in steep sided fiords with significant satellite masking, the combination of high-grade INS and the Fugro MarineStar GNSS positioning service resulted in highly accurate and reliable positioning for the duration of the project.
The extraordinary rainfall meant there was a significant fresh water layer which wreaked havoc with the beam forming and data quality of the Multibeam echo sounders. Regular attention was focused on ensuring that sufficient Sound Velocity profiles were recorded both spatially and temporally. Valeport MiniSVS, RAPIDPro SVP and SWIFT SVP sensors were relied upon to obtain accurate and reliable Sound Velocity measurements.
After three crew rotations, the survey part of the project was completed in late April 2019.
Hundreds of kilometres of rugged coastline was laser scanned with the MERLIN mobile laser scanner, and over 2,880nm of MBES survey from all four vessels, before returning to their home port in Tauranga, New Zealand.
Post survey, the teams commenced the very different task of cleaning and checking the tidal and bathymetric survey data and compiling the Report of Survey. This will take hundreds of hours of expert attention and will be the final step of what has been a successful and very rewarding survey project.
It was rewarding to share the experience with the expert team from DML, and both a pleasure and a privilege to operate in this magnificent corner of the world.
We are confident that the exceptional efforts of project participants LINZ, DML, iXblue, Pacific7 and Environment Southland will result in enhanced navigational safety for the region, benefiting all mariners navigating the waters of the magnificent Fiordland for many decades, if not centuries, to come.