Applying shoreline morphology modelling supported by 40+ years of coastal monitoring to evaluate management options

Since the 1970s, the Government of South Australia’s Department for Environment and Water (DEW) has actively managed Adelaide’s shoreline through renourishment efforts. Despite recent large annual backpass campaigns, the shoreline between Adelaide Shores boat harbour and the West Beach Surf Life Saving Club (SLSC) continues to experience localised erosion. To address this issue, DEW has commissioned DHI to conduct a coastal processes modelling study. This study aims to enhance understanding of the coastal dynamics at West Beach and to explore alternative long-term management strategies.

Challenge

The Adelaide Metropolitan coastline comprises a discrete littoral sediment cell that extends along 30 km of the semi-protected eastern shoreline of Gulf St Vincent in South Australia. Sediment within the littoral cell is moved in a net northward direction with no significant supply of sediment provided from the south or offshore to replenish the beaches. The chronic sediment supply deficit combined with the impacts of historical coastal developments pose an ongoing challenge to the management of Adelaide’s Metropolitan coastline.

Solution

Providing models to assess management options

A comprehensive assessment of the coastal processes and observed erosion in the West Beach sediment cell was undertaken. This evaluation combines analysis of existing data with a state-of-the-art numerical modelling framework to predict long-term shoreline evolution.

Driven by MIKE Powered by DHI software, we developed hydrodynamic, wave and shoreline morphology models and calibrated them based on available measurements. In total, six management scenarios comprising of combinations of soft management options (nourishment, backpass systems) and hard structures have been simulated. For each scenario, the morphological evolution of the entire West Beach shoreline has been simulated for 7.5 years providing comparative assessments of the pros and cons of each scenario.

Results

The solution provided the Government of South Australia with:

• An updated description of coastal processes
  Utilising historic data and advanced modeling techniques, the solution provided a comprehensive understanding of coastal processes in the region, facilitating more accurate assessments of coastal behaviour over time.
• Comparison of management options and associated morphological impacts
  The solution offered valuable insights into how different management approaches might affect coastal morphology, enabling more informed decisions about which strategies are likely to be most effective in mitigating coastal erosion and other challenges.
• Data to support future decision-making for coastal management
  Reliable data is now available to support ongoing and future decision-making processes related to coastal management.