Overview

Over the past ten years, Mount Martha North beach has experienced severe coastal erosion. The Department of Environment, Land, Water and Planning (DELWP) has taken a number of short-term actions to limit the impacts of erosion, including beach renourishment and construction of revetments.

Sand loss at Mount Martha North beach is part of ongoing natural processes. Winter weather conditions generally move sand offshore and to the south, and summer weather moves some sand back along the beach to the north. Overall, there is a net loss of sand from Mount Martha North beach towards the Mount Martha South beach.

DELWP’s objectives for managing the beach are to ensure public safety and to protect natural and public assets.

To help determine the best possible engineering solutions to stabilise sand loss from the beach area, a technical study was commissioned in 2018. To ensure that community values regarding Mount Martha North beach are considered in the study, beach users were invited to complete a brief survey in early 2019. The survey results were used to influence criteria weightings in the technical study.

The study has now been completed and the report is available for download on this webpage, with the key findings summarised below.

Key findings & next steps

The options analysis report produced by Water Technology, released in August 2019, showed that none of the engineering options assessed would restore sand - either short or long-term - along the entirety of Mount Martha North beach; or prevent beach erosion from happening.

Any localised improvements would be limited and offset by adverse effects elsewhere.

The two highest-scoring options as identified in the multi-criteria analysis were the current option (the revetment), and a small rock groyne. The next highest scoring option was a small offshore reef (breakwater).

Detailed modelling was undertaken for the small rock groyne and two locations for a small offshore reef (breakwater).

The report found that the most technically feasible option at Mount Martha North is to monitor, and if necessary, formalise the current temporary rock revetment; and allow natural processes to take place without further intervention.

This option aligns with the Victorian Coastal Strategy’s directive to allow natural coastal processes as the preferred approach to coastal erosion management.

Based on the study’s findings, and the ongoing need to ensure public safety on Mount Martha North, DELWP will continue to monitor the cliff and rock revetment quarterly over the next 12 months. DELWP will not progress with any other engineering options at this time.

Community open house

An open house session will be held for interested community to ask any questions about the options analysis. People can drop in at any time, registering their attendance on arrival. Images of modelling done as part of the analysis will be available to view; and coastal engineers from Water Technology and geotechnical engineers from Senversa will be there to answer technical questions.

Details:

Saturday 24 August, 1-3PM
Mount Martha Lifesaving Club
The Esplanade, Mount Martha

Project context

Moutn Martha North beach looking south on a calm day. Includes view of beachboxes backing onto cliffs, with water at base. Some sand reamins on the beach.

Mount Martha North beach

Mount Martha North beach is located on the eastern side of Port Phillip Bay and runs approximately 600 metres from the mouth of Balcombe Creek at the southern end, to a headland separating it from Hawker Beach, to the north.

Please refer to the map in the Document Library section on the right hand side of the screen for more details.

Sand loss at Mount Martha North beach is part of an ongoing natural process. Winter weather conditions generally move sand offshore and to the south, and summer weather moves some sand back along the beach to the north. Overall, there is a net loss of sand from Mount Martha North beach towards Mount Martha South beach.

Recognising that the coastal process of sand movement will always occur, the primary objectives for DELWP are to maintain public safety for the Mount Martha North beach and protect public infrastructure and natural assets.

Multi-criteria analysis

DELWP engaged Water Technology, a specialist water, coastal and environmental consultancy, to carry out a multi-criteria analysis of four engineering options that were recommended in a 2017 coastal processes study, aimed at slowing sand loss from the beach.

The full coastal processes study may be viewed in the Document Library section on the right hand side of the screen.

The following criteria were applied in assessing each engineering option:

  • environmental (impacts and benefits)
  • financial (life-cycle cost)
  • social
  • technical
  • upfront (construction) cost.

The multi-criteria analysis scored and ranked each option and selected two of the highest ranked options to model in detail. The modelling developed and tested options to determine what scale, design and positioning would be required for preferred engineering works to stabilise Mount Martha North beach.