Prior to the 1994 eruption, Rabaul had the most extensive infrastructure compared to any other town in Papua New Guinea. Combined with its natural beauty and warm, friendly people, Rabaul was an ideal place to live, work and visit. The eruption of September 1994 and the ensuing aftermath damaged or destroyed most of the town. A similar eruption in 1937 also damaged a large section of the town, therefore the effects of an eruption are clear but the means of dealing with these massive forces of nature are not so obvious.

SMEC International as prime consultant working in association with Beca Gure (PNG) Pty Ltd, Asia Pacific Surveys Pty Ltd and M+E Partnership was commissioned to assess the damage to the infrastructure, identify hazards and risks, assist in re-planning the town and ascertain the best means of restoration. This was achieved during a fourteen-month project with a multi-disciplined team of foreign and local experts involving engineering feasibility, physical planning, and detailed engineering design and documentation.

The aim of this submission is to portray the engineering excellence involved and the appreciation applied to the restoration of a town extensively damaged twice by volcanic eruptions within 55 years. All evidence predicts there will be another eruption of equal magnitude within 40 years. The plan prepared and now implemented takes this fact into account and aims to mitigate the loss of life and infrastructure should such an event occur.

The members of the team found themselves grappling with concepts of 'risk', 'compromise', and 'mitigation'. The goal was to plan and design a town to meet the needs and aspirations of the community and government, but also ensure life and property is less susceptible to the various current and future hazards. SMEC and its associates were able to achieve this goal and in the process demonstrate the definable features of engineering excellence required to fulfill the real demands of such a challenging project.

Features of excellence can be summarized as:

SMEC International achieved these features of excellence was duly recognized by the client as described in a letter (Annex 1) from the Project Manager of the Gazelle Restoration Authority.

Prior to the eruption Rabaul town had an excellent port, a developed industrial and commercial sector, comprehensive infrastructure, offices of National and Provincial Departments, and community facilities such as a public library, swimming pool and orchid gardens. In general, this was a modern town that was able to provide all of the services expected of a larger city.

The eruption of 1994 demonstrated in catastrophic terms the physical damage and destruction of public and private property. The volcanic hazards, identified in the course of the project that produced most of the damage in Rabaul during and after the eruption were:

• ashfalls
• mudflows and flash floods
• mudfills
• earthquakes
• tsunamis
• corrosion.
  
  

Apart from volcanic eruptions, planning the restoration of Rabaul had to take into account all present and future hazards. Rabaul has also been exposed to earthquakes, tsunamis and landslides that may not be directly connected to a volcanic eruption.

During the last eighty years there have been 12 seismic events of intensity 7 to 8 on the Modified Mercalli scale. Earthquakes of this magnitude have generally produced only minor structural damage.

Seven tsunamis have occurred in Rabaul over the last 110 years; two caused by volcanic eruptions in 1937 and 1994, four caused by tectonic earthquakes and one caused by a large avalanche from Ritter Volcano in West New Britain. All of these tsunamis ranged between 2-3m high within Simpson Harbour. These tsunamis have caused only minor damage but the recent disaster in Sandaun Province is a stark reminder of the danger of these natural events.

All infrastructure within Rabaul was affected by one or more volcanic hazards resulting from the eruption. It was important to understand these hazards, as it would set the parameters for mitigating their effects in the Engineering Plan. A summary of the findings is detailed below:

Mudflows and flashfloods quickly destroyed buildings within the flow paths. The momentum and destructive power of the ash-laden water was intensive even at shallow depths of less than 0.5m. In February 1994, during a 70mm rainfall, standing waves up to 1m high were recorded indicating velocities of several metres per second.

Some 24 hours after the initial eruption a sequence of small, localized earthquakes were experienced in Rabaul. At this time a significant amount of the ashfall had already been deposited across the town. Therefore, the combination of the ash loadings and horizontal seismic loadings, even though of small magnitude, accelerated the rate of structural failures within Rabaul.

The tsunami caused only minor damage in Rabaul, however 30 houses at Matupit Island were destroyed and timber wharves in the port area were damaged.

Once the condition of the town was established and the hazards and risks realised, the development of a clear picture for the future town was the next step in Rabaul's restoration. SMEC played a pivotal, independent role in the Town Plan development. SMEC was able to act as facilitator in the process of developing a plan, evaluating dissenting opinions and reconciling solutions. The Town Plan was therefore a compromise. Rather than having negative connotations, it expressed a positive meaning towards establishing an intermediate position between conflicting opinions and issues reached by mutual concession. The Town Plan was to become the key instrument for the use of government, the community at large, and the funding agencies.

• The idea of a risk-free living environment was unrealistic, and personal perception of risk varied widely. The importance of any risk to the Rabaul community cannot be scientifically evaluated,
• Rabaul Town is not the sole product of a stable physical environment, but rather social and economic factors are more important,
• Risk is a comparative concept. People made judgments by making comparisons elsewhere. Members of the community compared some major cities in the world (and the western world at that) located in areas of high risk, and
• The biggest risks on earth statistically are hunger and war, both of which are absent in Rabaul. Community conception of well being focused more importantly on social and economic factors, rather than whether or not there may be another eruption in 30 or 40 years.

While the above were powerful arguments, this holistic view crystallised a common understanding that the real-world issue was really the financial risk of investing in renewed infrastructure.

The Provincial Capital functions had been relocated to Kokopo as part of an associated thrust to develop economically in other urban areas of the province outside Rabaul. The importance of Rabaul to the provincial economy as port was reinforced due to its magnificent natural harbour. Other acknowledged roles for Rabaul were as a commercial centre and tourist destination.

SMEC provided the impetus through the services of Ms Sandra Finster (Urban Planner) for the government and community to realize a common goal. Having officially accepted a future role for the town, and with it a community willing to return, government of every level had to be prepared to drop the barrier of 'volcanic risk' issue and deal with planning issues in a positive way. While any form of hazard cannot be prevented, the focus of government control was shifted to minimizing its effects.

It was apparent that if the new Town Plan was to be sensitive to need, and considered successful in its implementation, the planning process had to focus on the positive attributes and strengths driving the desire to re-build. It was clear to identify that Rabaul had unique qualities to do with its setting and historical past. The legacy of an enviable economic structure and social harmony have been difficult for other towns to emulate.

The complexity and detail lifted this study out of the ordinary. The difficult part of the process was the dilemma in evaluating the criteria, weighting them, and applying value judgements. This was under intense scrutiny, and must be answerable to any of the numerous stakeholders. SMEC understood there was no perfect answer. The aim was to maximise benefits across the board and the challenge was to unite the interests in the concept of a community-owned town image that everyone related to.

A Steering Committee was established to oversee the planning process, and must take credit for the success attributed to the final Town Plan. The committee performed numerous functions providing guidance, organising access to information and people, participating in assigning values, and decision-making in general. Its highest role was in acknowledging ownership of the outcome on behalf of government and the community. The committee had a broad representation, was knowledgeable, reliable, and above all committed. It had power and clout. Such a structure forming the backbone of the planning process was an ideal model for any study to follow.

A conscious effort was made by SMEC to keep design issues in the plan simple, flexible, and easily understood. In particular the oft-made mistake of introducing design prescriptions was avoided, but rather an encouragement was given to the implementation agencies to focus on town "character" and locally relevant impacts.

DEVELOPMENT OF THE ENGINEERING PLAN

Subsequent to the Town Plan, an Engineering Plan was formulated. In general, the Town Plan focused and prioritised the restoration needs of the civil infrastructure. This set the framework for the roads and drainage restoration and other works such as stabilization of the vast ash beds and siltation control. SMEC also coordinated a plan for the reconnection of utilities through the service departments such as Elcom, Telikom and the Waterford. The service departments were genuinely interested in restoring utilities to clients but would only reconnect services in the damaged and unoccupied areas when there was some government-endorsed reconstruction plan.

The Engineering Plan was then determined through a conventional design process from conceptual design to preliminary design through to final engineering design and documentation. The whole design process was monitored by the same committee that supervised the production of the Town Plan to ensure consistency with their restoration approach, and in particular, the staging of works.

• erosion control,
• restoration of roads and stormwater drains,
• reoccupation of individual stages, and
• reconnection of services.

Drainage, erosion and siltation controls were identified as critical aspects for restoration.

CONCLUSION

The results of the 1994 eruption in Rabaul were catastrophic yet the response by SMEC and its associates, in co-operation with the clients, government departments, and community resulted in a number of plans showing initiative and engineering excellence

SMEC and its associates grasped the complex issues involved in this project, such as the concepts of risk, compromise and mitigation. The features of excellence that SMEC's team displayed were;

To the credit of the community and the government who are prepared to support it, Rabaul will continue to live.

In years to come, when the events of September 1994 are fading in people's minds, it is hoped that Rabaul will again enjoy the status as the pre-eminent town in Papua New Guinea in which to live, work and visit. However, it is important to remember that there will be another eruption and opportunity now exists to rebuild a town that will be less susceptible to these forces of nature.