In 2020, the services of a specialist coastal engineering consultant was engaged to determine the appropriate long term (end state) and interim (transitional) coastal protection options to reduce the exposure risks.
The investigation identified a strong need to mitigate immediate coastal hazard risk at the Sewerage Pump Station (SPS) opposite number 57 Mitchell Parade. One factor contributing to the erosion vulnerability at this location was the presence of a stormwater outlet which discharges onto the beach adjacent to the SPS. The process of sand scouring from the outlet discharge has formed a “disconnect” in the sand dune system. This resulted in a localised loss of natural dune protection in front of Mitchell Road and the SPS.
The investigation identified an appropriate ‘transitional’ coastal management option for protection of the SPS, stormwater outlet and adjacent Council road. This option comprises of the design and construction of a stormwater entrainment structure, to mitigate erosion hazards associated with the stormwater discharge on Mollymook beach. It will prevent meandering stormwater flows from the outlet adjacent to the SPS, which currently generates a wide zone of dune and beach erosion.
This work is intended to provide enhanced resilience of the local dune system to high-frequency storm events in the short-medium term and alleviate the erosion at what is currently a pinch point brought about by the stormwater outlet and the proximity to Mitchell Parade. The Detailed Design for the works are complete. Council aim to start the construction works in early 2023 (outside of peak public use periods).
These works are being implemented as a transitional measure, providing required upgrades to existing stormwater infrastructure assets and to enable a level of protection against immediate risk of erosion hazards while longer term management actions for the broader localised area and nearby assets are being assessed. It is intended to provide a moderate level of protection for less severe storm events and increase potential for dune resilience and recovery after storm events.