Coastal compartments for Australia or Improving coastal erosion assessments

Contents 

Coastal erosion and shoreline recession from sea-level rise is a significant risk to coastal Australia. Individuals, businesses and local governments undertake coastal risk assessments to understand how they might be affected now and in the future.

Coastal erosion

Coastal erosion in Scotts Head, New South Wales

The Coastal Compartments Project aims to help users undertake or commission best-practice risk and erosion assessments using a consistent approach based on the physical characteristics of the coastal environment. Such an approach will ensure that assessments can be easily compared with adjoining areas, or upscaled to fit within larger regional assessments.

As part of this project, Australia’s coastline has been mapped as compartments based on landforms and patterns of sediment (sand and other beach material) movement. There are three main levels of compartments, each suitable for different types of decision making:

  • primary level based on the influence of large landforms and offshore processes, suitable for regional planning or large-scale engineering such as ports
  • secondary level on medium landforms and regional sediment processes, useful for smaller engineering or local planning decisions
  • tertiary level based on individual beaches, suitable for very small projects unlikely to restrict sediment movement, such as deciding the exact location of a groyne or sea wall within a broader management plan.

For more detail on this project, read the Summary for Policy Makers prepared at the request of the Department by Professor Bruce Thom.

Maps

Primary and secondary compartments have been mapped for Australia and are available on the Geoscience Australia website.

Case studies

Map showing case study locations

Case study locations where coastal compartments
approach was tested

To demonstrate the use of the coastal compartments as an assessment framework, the Department also commissioned two case studies in WA and NSW, designed to show the framework’s application to a variety of coastal environments.

WA Case study

The project in WA (conducted by Damara) examined how a coastal compartment framework can guide impact assessments at primary, secondary and tertiary scales and provide a more detailed assessment of coastal sensitivity to dynamic coastal processes, such as sea level rise.

NSW Case study

The Water Research Laboratory of the University of NSW studied two tertiary-level compartments, Avoca Beach and Cabarita Beach, to test the applicability of deterministic and probabilistic approaches to coastal impact assessments. The two areas are both open sandy coasts, but represent ‘closed’ and ‘leaky’ sediment compartments which respond differently to coastal hazards.