Risk Assessment - Marine Oil Spill

This case study sets out to provide a risk assessment in Maritime New Zealand given the occurrence of an oil spill. The study was carried out by Navigatus Consulting using the most recent Marine Oil Spill Risk Assessment (MOSRA15).

The study was carried out with the goal of guiding the management of oil spill response planning in New Zealand. MOSRA15 represented the latest model developed in the effort to understand the maritime oil spill risk profile which has spanned from 1992 to present day. MOSRA15 marked a significant advance on the previous risk assessment study (MOSRA10) with ability to, for the first time, provide an oil spill risk profile for off shore and vessel activity in the open water around New Zealand.

MOSRA15 is able to provide visualisations and listings of the overall national shoreline risk profile and environmental sensitivity, graphical displays of oil spill probability around “high risk” coastal areas and ports. Notably, MOSRA15 was also able to provide information as listed above for a range of future scenarios associated with vessel trading and offshore exploration.

The MOSRA model used in this risk assessment has been progressively developed and implemented for two and a half decades with improvements occurring at each step in development. Each model was built on the previous model to ensure the utilisation of earlier developments while also building into future developments.



Summary of national marine oil spill assessments


The main stages undertaken to develop MOSRA15 as outlined in the Navigatus report are outlined below:

   - Develop / build base model - Stage 1 (design);
   - Developed offshore environmental model;
   - Developed navigational safety risk functionality;
   - Developed and built the base model - Stage 2 (build / test);
   - Detailed review and update of environmental shoreline information and ratings;
   - Stakeholder engagement;
   - Developed scenario model capability;
   - Prepared MOSRA15 report.

MOSRA is a web based tool - with reports and supporting information at the Maritime New Zealand Webpage and modelling is available through the Navigatus Consulting Website.



 Example of oil distribution from offshore installations and exploration rigs


Risk profiles are the dominant output from this modelling tool, these profiles give a visual representation of shoreline and open water risks regarding a marine oil spill. The risk profiles are based on several controlling factors including identification of possible sources (e.g. vessels, bunkering, wells) and types of events that could lead to marine spills (e.g. vessel collisions) and environmental consequence; basically the risk rating, from very low to very high was determined using Probability of Oil x Environmental Rating = Risk.



Shoreline and open water risk profile for all of New Zealand


In comparison to earlier models, MOSRA15 is more capable in modelling of sea currents, modelling of sea temperatures and modelling the effects of wind. This is in addition to a more advanced consideration of the factors that cause navigational risk, something that was covered in less detail by previous models but has a heavy weighting on the probability of the occurrence of marine oil spills.

The MOSRA15 report  has highlighted the improvements present in the MOSRA modelling framework which now provides a more accurate and comprehensive view into modelling marine oil spills than earlier version.


 RISK ASSESMENT data flow2

Model summary showing main analytical components and data flow.


These improvements in modelling highlighted that cook straight is at a significantly higher risk to marine oil spills than first modelled when more advanced modelling of wind and current are considered. This was just one example where MOSRA15, which is based on continually improving science and up to date shipping information, could be used to inform policy or decision making. With a model that provided a more comprehensive and accurate assessment of the factors governing the risk of marine oil spills its outputs can more confidently be used to identify areas of high risk to better improve planning and response strategies.

Associated Models

Risk Assessments

Risk assessment is a step in a risk management procedure.