How past sea-level changes can inform future planning: A case study from the Macleay River estuary, New South Wales, Australia

Climate change poses many challenges for the future management and development of the coastal zone. Uncertainties in the rate of future sea-level rise reduce our ability to project potential future impacts. This study seeks to further develop the past-present-future methodology proposed in Baker and McGowan and apply it to an additional case study, the Macleay River estuary, New South Wales (NSW), Australia. The past-present-future methodology uses evidence from the past, the Holocene and Pleistocene, to formulate a response function that can be used to project future sea-level heights. Three scenarios for 2100 were developed to emphasise the uncertainties surrounding future sea levels and the need to consider multiple sea-level rise scenarios when planning for the future: a best case (90cm rise), mid-case (2.6m rise) and worst case (5m rise). Light detection and ranging (LiDAR) data were used to project each of the three scenarios onto the case study area of South West Rocks. The methodology was tested by using shell samples extracted from cores which were AMS dated to determine whether or not Holocene estuarine conditions correlated with the proposed future sea-level rise inundation scenarios. We also conducted an audit of potentially affected infrastructure and land uses, and proposed possible future adaptation strategies for the case study area.