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Scenarios are a tool developed to undertake strategic planning in an environment facing multiple risks. They have been developed for situations where uncertainty is too large for conventional forecasting tools to be used. They are not a predictive tool that will inform what the future will be, but one that uses credible knowledge to show what the future might be. Use of scenarios by certain sectors, such as the military and business, is well-established. Scenarios are widely used to gain the understanding needed to develop strategies to manage risk and to assist planning and actions of possible future events.

Scenarios have two main uses:

1. To explore the effects of uncertain changes on a future situation using a sound evidence base for making projections. Several scenarios may be used to explore a plausible range of uncertainty covering key drivers of change. These are known as exploratory scenarios.

2. To explore what may happen if different sets of rules, values or goals are imposed on a situation. For example, to explore the effect of policies designed to increase sustainability, resilience or pathways for economic development. These are known as normative scenarios.

Scenarios exploring hazards or disaster/catastrophe scenarios are concerned with how one or more events may affect a system. To address risk ownership, a scenario needs to contain one or more events that cascade though the system of interest and have long-term consequences. In terms of severity, this places events at the high end of plausible risk, which aligns well with the need for disaster risk analysis to plan for events up to and including the worst case.

Constructing scenarios

Scenarios need to have a narrative or storyline. Situations and events represented within the scenario need to be plausible with a sound evidence base. Situations can be ‘stretched’ beyond conventional understanding if there is a sound case for doing so (e.g., proposing events more severe than the event of record based on a theoretical understanding of how climate may change). The elements of a hazard-based scenario require an event or events, a description of the key elements of exposure covering the major values put at risk, a social and physical description of the area of interest and, if needed, a backstory describing conditions preceding the event (e.g., a severe flood following a long drought) and any external factors needed to round out the scenario (e.g., social, economic or political factors coming in from outside). The scenario can be undated (e.g., an event happening any time) or dated, allowing projected changes in events and/or exposure to be quantified.

When workshop participants come from different locations and the workshop focus is not location-specific, the area being investigated should be fictitious but familiar. The scenario location is modelled on one or more familiar places but different enough to not be identifiable as any specific place. This allows the participants to leave their baggage at the door but bring their experience to the table. If the assessment is focused on a specific location (e.g., town, suburb, region or community), then the physical situation can be described faithfully, but the social settin needs to be noticeably different; e.g., by placing the event in the future and making the people involved different to incumbent community. This will also allow changes in exposure to be included in the narrative. Specific numbers attached to events or drivers of change may not be needed unless they will have a meaning for most of the participants. For example, providing depth of floodwaters, number of properties at risk, severity of bushfire may be very helpful if it provides focus without requiring technical skills to interpret. If the workshop group is technically adept, then the scenario can be more quantitative. This may also apply if there is an opportunity to do live simulations with computer models.

Scenarios prepared beforehand need to be put together by a skilled scenario writer who has some experience of scenario use within a workshop situation.

Applying scenarios

The scenarios used by the project to explore risk ownership were designed as part of a workshop program that is fully described in the workshop report (Young, C., et al. 2016). This was a guided exploration into values at risk and their ownership, impacts and consequences and risk actions. The template for the impacts and consequences exercise is shown below. The scenarios themselves described a region and its setting, a design event (flood, bushfire or heatwave) and key vulnerabilities.

As methods for strategic planning for natural hazards are still under development there is a great deal of potential for the development and use of scenarios throughout the planning process. The scenarios described here are hazard-based and exploratory but potential areas for expansion include:

n Experiential or role-play scenarios where participants ‘act out’ a particular storyline to gain greater understanding of how they would respond in certain situations. For example, appointing different people as risk owners in a scenario where ownership is shared, competing and ambiguous provides insights into the relationships between different types of ownership and how it is shared and transfer is negotiated.

n Scientific scenarios provide a greater level of quantification than most and are often used where some form of modelling or formal analytical assessment is likely to take place. These are prominent in climate change impacts and adaptation assessment and are being further developed to assessing changing climate-related hazards. These can be presented in many formats: such as visual, aural or written. Scenarios of changing exposure, through population growth and development pathways may also contribute.

n Gaming-based scenarios where issues are explored or examined through a structured game (e.g., war games, disaster simulations).

n Issues-based scenarios where a specific issue will be focused on and examined through a number of lenses. For example, a regional economy can be ‘shock-tested’ to see how resilient productivity across key sectors is to sequences or combination of events.

n Capacity-building scenarios where various actions and qualities such as resilience are explored for their ability to reach specific goals through the improved management of natural hazard risk (e.g., building ‘safe’ futures and resilient pathways).

Table E1Scenario exercise phases.

PRIOR TO SCENARIO EXERCISE (Divergence of ideas)

DURING THE SCENARIO EXERCISE (Exploration of ideas)

COMPLETING SCENARIO EXERCISE (Convergence of ideas) Unmanaged uncertainties Multiple perspectives Confusion Unrestrained ideas Investigation Analysis Visualisation Clarification Clarification New learnings New perspectives Insight

Example scenario: Forested upland region (risk of firestorm)

This is a hilly, mountainous and forested region of the central uplands. Sixty-five percent is forested. The region also contains horticulture requiring winter chill, numerous boutique wineries and is an area of winter sports-summer recreation with bike-riding becoming more popular. The regional population is 25,000, mainly in small towns and villages. The region also contains important water catchments feeding the capital city and rural towns, in addition to some irrigation supply. Hydro power generation is critically important within the region.

Most of the regional income is from agriculture, tourism including food tourism and forestry. Both local timber milling and high volume pulp export take place. However, the region is also a very important water source, although little of it is consumed in the region. Transport is mainly by road, but due to the mountainous terrain over half of the region is not highly networked, meaning that many areas are only fed by one or two routes.

Design event: the region is most vulnerable to firestorm conditions occurring during catastrophic fire danger conditions. Modelling has indicated which areas are most at risk of burning and where likely refugia occur, but also points to the potential that if a high proportion of vulnerable areas went up, available resources would be exceeded and a high degree of ‘triage’ required.

Worst case would see several communities devastated from an out of control fire, with major disruption to local infrastructure and commercial activities. Increased event frequencies and other hazards (e.g., flash flooding) could upset long-term recovery

Key vulnerabilities:

n A number of towns and villages are vulnerable.

n The dispersed population in the region means that in the worst case, many people who remain in high fire danger areas would be fending for themselves.

n Flash flooding following firestorm events, with debris flows, etc., has been recognised as a threat to water supply, especially of potable water.

n Quadruple whammy effect on food, forest, fun and water (smoke tainted wine, water quality loss, tourism interruptions and forestry resources).