Advisory Note: How to consider a sea level rise along the Victorian Coast

Purpose

The Victorian Coastal Strategy (VCS) is a policy document that provides a comprehensive integrated management framework for the Victorian coast. The Coastal Management Act 1995 requires the VCS to be reviewed every five years. One element of the strategy is the consideration of sea level rise. This note aims to provide guidance for decision makers in using the sea level rise predictions in the VCS.

What is sea level rise and what does it mean for the coast?

The VCS identifies that during this century it is likely the Victorian coastline will be impacted by sea level rise and increased frequency and severity of storm events which are likely to lead to greater coastal inundation and erosion. This may cause damage and loss to property and assets.

Figure 1: Contributions to coastal sea level from tides, storm surge and wave processes. Sourced from CSIRO website.

Further information on sea level rise can be found at the CSIRO website.

Who defines the sea level rise benchmark ?

The Intergovernmental Panel on Climate Change (IPCC) is the most authoritative international scientific advisory body on human induced climate change science.

In its fourth Assessment Report, (November 2007), the IPCC projects the upper limit of sea level rise as being 0.8m by 2100. This includes a provision of 0.2 meters to take into account the projected extent of ice sheet melt to that time. On the basis of this IPCC information and until nationally consistent benchmarks for coastal vulnerability are established, the Victorian Coastal Council has recommended in the VCS 2008 that a minimum sea-level rise estimate of 0.8 metres by 2100 be applied for planning purposes.

It should be noted that as new information emerges from the IPCC on climate change, sea level rise projections will be refined and the interim benchmarks will be superseded by national benchmarks.

Why should it be considered in long term planning?

Sea level rise should be taken into consideration in long term planning as part of national, state and local responses to adapting to climate change.

Principles that underpin the importance of sea level rise information for long term coastal planning include:

1. The precautionary principle - where there is the potential for serious or irreversible threat to the environment, climate systems or ecological systems, the lack of absolute certainty about the precise quantum of sea level rise and other aspects of climate change science should not be used as a reason for postponing adaptation measures.

2. Informed decision making - in all decision making regarding coastal planning and in particular in making decisions concerning land use and development there is a need to consider all relevant information available at the time. The impacts and risks of climate change including sea level rise need to be taken into account to make informed decisions.

3. Reduction of uncertainty - there is a level of uncertainty in every decision making process. However, the consideration of all relevant information available to the decision maker at the time the decision is made allows for informed decision making.

How should a benchmark be used?

Relevant decision makers, (eg planning authorities, catchment management authorities and public land managers amongst others), may require erosion or vulnerability investigations to assist in making informed decisions about development, planning and management along the coast.

If coastal erosion or vulnerability assessments are required, data inputs should include factors such as sea level rise, storm surge information, coastal processes, flooding and inundation, local geology, etc. A prudent measure for sea level rise based on best available science at the time will inform high quality coastal vulnerability assessments.

Currently the data input for sea level rise as part of any erosion or vulnerability assessments is to use the IPCC upper projections of 0.8 metres by 2100 as a prudent measure. This figure will be refined as new scientific data becomes available. As the figure is refined the new figure should be be used by relevant decision makers.

Further Information on sea level rise consideration

A range of products are being developed to support relevant decision makers when they are considering climate change impacts for future planning.

The development of these products will be led by the Department of Sustainability and Environment. Key government departments such as the Department of Planning and Community Development will be closely consulted.

The proposed products include:

A guideline for coastal erosion and inundation assessments and set backs
Mapping of areas physically vulnerable to climate change impacts along the coasts (delivered as part of the Future Coastal Program)
Decision making support tools (delivered as part of the Future Coastal Program)

For more information on products generated through the Future Coasts Program, visit www.climatechange.vic.gov.au/futurecoasts.