Climate change implications on the coast are mostly in relation to rising water-levels. This is a complex process that is thought to be the result of naturally fluctuating global temperature variations, exacerbated by anthropogenically induced global warming. Increases in greenhouse gases result in increases in global temperatures (the greenhouse effect), and the heat causes water to expand. The increase in temperatures also results in the melting of ice caps. The overall effect is an increase in static water-levels in most coastal areas of the world.

Although varying degrees of confidence relating to climate change projections exist, long-term tide gauge records around the world have shown steady increases in static water-levels over the last 50 to 100 years which should be considered and planned for regardless of the climate change debate. In Victoria, recent measured net rates of sea-level rise have ranged between approximately 1.3 and 2.8 mm/yr (http://www.bom.gov.au/oceanography/projects/abslmp/reports_yearly.shtml). However, as the effects of global warming become more apparent, the rates are expected to increase, especially toward the end of this century. Thus, the IPCC sea-level rise estimates vary depending on differing emissions and temperature scenarios, which in turn results in a very wide range of sea-level rise estimates that need to be considered in hazard assessments. For the purpose of this study, six sea-level rise benchmarks have been considered to ensure the wide range of sea-level rise scenarios are considered, these are 0.0 m, 0.2 m, 0.5 m, 0.8 m, 1.1 m and 1.4 m relative to 1990 levels. The amount of sea-level rise that has occurred since 1990 has not been removed from the benchmarks for this study.

A key difference between this study and others carried out in Australia is that the year that the sea-level rise benchmark is likely to occur has not been stated. The aim of this is to avoid tying the scenarios to a given time in the future, but rather to say that if a given amount of sea-level rise occurs, this will be the consequence. This allows some flexibility with future assessments, but also removes some of the uncertainty associated with having a line on a map that states the shoreline may be in a certain place at a certain time. For locations where more comprehensive background data sets exist, this may be appropriate; however, given the levels of certainty within this study, it is not considered the best approach.