Climate change scenarios are scientifically developed ways of understanding how the climate may change in the future. They are tools used to consider a range of possible conditions, such as changes in rainfall and flood behaviour. In the land use planning, climate scenarios help ensure flood information and planning decisions reflect future risks and support resilient development.
Melbourne Water has updated the climate change scenarios used to inform flood information for land use planning decisions by transitioning from Representative Concentration Pathways (RCPs) to Shared Socioeconomic Pathways (SSPs).
This change is consistent with the latest Intergovernmental Panel on Climate Change (IPCC) assessment and updated Victorian Climate Science Report. For planning decisions, Melbourne Water is adopting a “not less than the high pathway” approach using SSP37.0.
The change maintains use of a high emissions scenario that is consistent with the latest science and advice from State and Federal Governments for land use planning decisions.
The Planning and Environment Act 1987 requires Victoria’s planning system to explicitly consider climate change by promoting sustainable development and for land use and development decisions to increase climate resilience.
The Victoria Planning Provisions (VPP) also includes objectives and decision guidelines on natural hazards and climate change that require planning decisions to address current and future climate risks.
SSPs are the latest scenarios used in climate science to understand future climate impacts.
For land use planning flood information, Melbourne Water is adopting SSP3-7.0.
The change will be applied progressively through Melbourne Water’s rolling flood modelling and flood information programs.
Supporting documents
Two documents have been prepared to assist with the decision making process for developers and planners.
This guideline explains how Melbourne Water and the Victorian planning system integrate climate change and flood risk into land use planning, using updated climate science, flood modelling, and statutory planning controls to ensure future development and infrastructure are safe and resilient to increasing flood hazards.
This document supports the above guideline and acts as a practical checklist that explains how climate change, particularly flooding and sea level rise, must be considered in land use planning and development decisions in Victoria. It sets out the statutory requirements, planning policies, climate informed flood standards, and key actions developers and planners should take to ensure proposals are resilient, compliant and aligned with state planning objectives.
Frequently asked questions
- Why the change from RCP to SSP?
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Shared Socio‑economic Pathways (SSPs) are the latest scenarios used in climate science.
- What are RCPs and SSPs?
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RCPs describe possible futures based on greenhouse gas concentrations. SSPs go further by combining emissions with different social and economic futures (for example, changes in population, energy systems and land use). Using SSPs helps decision makers, such as planners and developers, consider a broader range of factors that influence future flood risk.
- Why is Melbourne Water using the High Pathway SSP3‑7.0?
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Using SSP3‑7.0 aligns with updated climate science and rainfall guidance used for flood studies, and helps avoid underestimating future flood impacts. It also supports decisions with long lifetimes, such as new urban development and critical infrastructure.
Other scenarios (such as SSP2‑4.5 and SSP5‑8.5) may be used for sensitivity testing and to inform longer-term policy and infrastructure planning where appropriate.
Separate to this update, Melbourne Water continually reviews and investigates its own infrastructure and services. Melbourne Water assets have varying maintenance and renewal cycles. This change from RCPs to SSPs only relates to land use planning decisions.
- Will flood maps and planning advice change straight away?
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Not necessarily. The updated SSP settings will be incorporated progressively as flood models are developed and updated. This means some areas may transition earlier than others as studies are completed.
- What does this mean for property owners, developers and councils?
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The scenario update supports more consistent, evidence‑based flood information for planning decisions, such as development referrals, drainage planning and local planning scheme considerations. If you are preparing a planning application or strategic planning work, check the flood information applies to your site and seek advice early in the project.
