ASR - A Global Partner for the Sustainable Management of Coastal and Marine Resources


Location: Gisborne, New Zealand

Type of Project: Numerical Modeling, Metocean Assessment

Client: Port Gisborne Ltd, New Zealand

ASR Projects- Gisborne

(Left) Summary of the Waitangi Day wave event showing the rapid increase in swell height and period and the strong southwesterly aspect to the swell direction. (Centre) The Jody F Millennium grounded at the entrance to Port Gisborne at 2245 (NZDT) on the 6th of February 2002. (Right) Numerical model output for a south swell direction (190ยบ).

Project Overview:

ASR Ltd worked on a series of reports which investigated the complex circumstances surrounding grounding of the Jody F Millennium logging ship on Waitangi Day (February 6th), 2002.

Project Outcomes:

For the first study, ASR Ltd presented a detailed investigation in to the metocean (swell, wind and tide) conditions which occurred on the day of the grounding. The key finding of this study was that the wave and wind conditions on that day were of an extreme nature with large significant wave heights and very long period swells. This report was followed by a second study which statistically analysed the wave conditions. This study showed that a rare combination of rapidly changing wave conditions contributed to the grounding. Furthermore, this study showed that this combination of factors created a situation which could not have been predicted and was much more severe than expected based on past experiences in the Port.

A third study used numerical modelling to simulate the wave penetration into the port. This study confirmed the assertion of the previous reports that it was a unique set of circumstances which contributed to the grounding of the Jodi F. Millennium. While the waves on this day were not the largest recorded in recent years, the onset of the large waves and long period swell occurred very rapidly relative to other events while the direction of wave approach was also optimal for maximum wave penetration into the port. Finally a fourth study showed that dredging operations at the Port did not contribute to the wave conditions experienced as the ship was leaving port and were therefore not directly related to the vessel grounding.

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