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Coastal and Estuarine Risk Mitigation Program (CERMP) – Protecting our Coastline

What is CERMP?

Council was successful in an application to the Australian Government’s Coastal and Estuarine Risk Mitigation Program to secure funding for the Hazard Risk Reduction in the Southern Beaches Region project. A total of $1.8 million was funded, which coupled with Council’s investment of $622,000, provides $2.4 million to promote disaster risk reduction in the coastal communities.

Project Objectives

The main objective is to deliver safe coastal living in the Southern Beaches region by providing safe stormwater services to assist with safeguarding our foreshore and remediating stormwater eroded dunes. The project will also assist in education and awareness about the importance of estuarine wetlands which harbours diverse flora and fauna and plays an important role of buffering floods in our coastal communities.

These projects will deliver a range of improvements and benefits for our local community and environment. All the outfalls to be upgraded will have a project design requirement for improved coastal erosion and outfall water quality.  Importantly, this project will not increase the outfall size or the number of outfalls, rather it will enhance the quality of outfall in the foreshore with improvement in the quality of water.

What’s included in the 3 year program?

  • Upgrade 25 outfalls in the stretch of 23 kilometres of Southern Beaches foreshore from Lewisham through to Dunalley
  • Reduction of hazard and erosion to dunes
  • Water sensitive urban designs
  • Improvement of the water holding capacity of wetlands
  • Improvement of the Blue Lagoon wetland
  • Education and awareness on Carlton Estuary which buffers flooding nearby coastal communities

ur first Community information Session was held on Tuesday 30 January 2024 at Carlton Park Surf Lifesaving Clubhouse. Thanks again to everyone who attended and participated in the discussions.

The aim of this session was to cover:

  • CERMP overview
  • Natural Values Assessment – Stormwater Outfalls Southern Beaches Report (North Barker Ecosystem Services)
  • Criteria and assessment process to identify 25 stormwater outfalls
  • Year 1 projects – Five priority outfalls (e.g. why they were selected, what benefits will be realised on completion of the works, sharing of concept project designs)
  • Questions from the community

Information presented and notes are available here:

Five priority outfalls were slected for stage one.

Concept Design plans for 5 Priority Outfalls

These five projects have all been completed.

A further fifteen outfalls will be upgraded in this stage.

OUTLET 01- SE112522-020-0 15 CARLTON RIVER ROAD

OUTLET 02- SC112325- 36 LEWISHAM SCENIC DRIVE

OUTLET 03- SE112555- 27 CARLTON BLUFF ROAD

OUTLET 4- SE112520- KUNEEAMEE STREET

OUTLET 05- SD106947- 93 CARLTON BEACH ROAD

OUTLET 06- SE115471- 753 PRIMROSE SANDS ROAD

OUTLET 07- SE115472- 69 SUSANS BAY ROAD

OUTLET 08- SE115533- 77 LEWISHAM SCENIC DRIVE

OUTLET 09- SE112569- 63 LINDEN ROAD

OUTLET 10- SE112526- 50 LEWISHAM SCENIC DRIVE

OUTLET 11- SE112579- 1 CASUARINA CLOSE

OUTLET 12- SE115468- 749 PRIMROSE SANDS ROAD

OUTLET 13- SE112525- 11 FULHAM ROAD, DUNALLEY

OUTLET 14- SE115411- KUNEEAMEE STREET

OUTLET 15- SE112530- 115 LEWISHAM SCENIC DRIVE

 

These fifteen outfalls are being improved using innovative water-sensitive urban design principles.

Key Design Features of CERMP Outfall Upgrades

  1. Floating Wetlands

Floating wetlands are innovative, man-made structures that float on the surface of stormwater channels. They are planted with a variety of native wetland vegetation whose roots extend into the water. As stormwater passes beneath the floating mats, the plants’ roots absorb excess nutrients such as nitrogen and phosphorus, which are common pollutants from urban runoff. These nutrients, if left untreated, can lead to algal blooms and poor water quality in coastal ecosystems.

Additionally, the microbial communities that grow around the plant roots further assist in breaking down pollutants, enhancing water purification. Beyond nutrient treatment, floating wetlands provide habitat for aquatic wildlife and can also improve the visual appeal of stormwater management areas. By intercepting pollutants before they reach the ocean, these wetlands contribute significantly to maintaining healthy marine environments.

  1. Bio-Retention Ponds

Bio-retention ponds, also known as rain gardens, are designed to capture and filter stormwater before it reaches sensitive coastal areas. These ponds consist of layered soils, mulch, and carefully selected vegetation, which together help:

  • Filter out sediments and debris, reducing the risk of clogged waterways.
  • Absorb nutrients like nitrogen and phosphorus that contribute to water pollution.
  • Slow down the flow of stormwater, preventing erosion and reducing the impact of sudden water surges during heavy rainfall events.

The plants in bio-retention ponds not only absorb pollutants but also stabilize the soil, reducing erosion risks. This natural filtration system is crucial for improving the overall quality of outfall water entering the ocean and protecting coastal biodiversity.

  1. Reduction of Outfalls on Pristine Beaches

A key goal of the project is to minimize the number of stormwater outfalls that discharge directly onto pristine beaches. Excessive and uncontrolled outfalls can lead to:

  • Increased erosion of sensitive coastal dunes.
  • Pollution of beach areas, affecting both marine life and recreational spaces.

To address this, the project incorporates water-sensitive urban design solutions, such as:

  • Grass swales: Shallow, vegetated channels that slow down and filter stormwater. As water flows through these swales, sediments and pollutants are naturally filtered, and some water infiltrates the ground, reducing runoff volumes.
  • Safer outfall redirections: Where possible, outfalls are redirected to less sensitive areas, allowing for natural water treatment processes.

These approaches not only reduce the burden on sensitive dunes but also enhance the opportunity for natural filtration, ensuring cleaner water reaches the ocean.

  1. Erosion Control and Dune Reinforcement

Coastal dunes play a critical role in protecting inland areas from storm surges and flooding. However, dunes are highly susceptible to erosion, especially when impacted by uncontrolled stormwater flows. The CERMP project focuses on:

  • Stabilizing dune structures by managing stormwater flows that would otherwise erode these areas.
  • Reinforcing dunes with native vegetation whose root systems bind the sand, making the dunes more resilient against wind and water erosion.
  • Installing erosion control measures, such as geo-fabrics or flow velocity control, to provide immediate dune stabilization while vegetation establishes.

These interventions will not only preserve the natural landscape but also ensure that the dunes continue to act as natural barriers against the impacts of climate change, including sea-level rise and increased storm intensity.

  1. Weed Removal and Native Revegetation

Invasive weeds threaten coastal ecosystems by:

  • Displacing native species that provide essential ecosystem services.
  • Destabilizing dune systems, as many weeds lack the deep root systems required to hold sand in place.

The project includes a targeted weed removal strategy, followed by revegetation with native plants, which:

  • Stabilize dunes and coastal areas, preventing erosion.
  • Support local biodiversity, offering habitat and food for native wildlife.
  • Improve ecosystem resilience by restoring natural ecological functions that help the environment adapt to climate stressors.

Revegetation also enhances the aesthetic appeal of the coast and promotes a healthier, more diverse coastal ecosystem, capable of absorbing and adapting to future environmental changes.

Why These Features Matter

By combining nature-based solutions like floating wetlands, bio-retention ponds, and revegetation with engineering interventions for erosion control, the CERMP project ensures a holistic approach to stormwater management, coastal protection, and ecosystem restoration. These measures:

  • Treat stormwater naturally, reducing pollutants entering the ocean.
  • Protect and stabilize dunes, safeguarding communities from coastal hazards.
  • Enhance biodiversity through restoration of native vegetation.
  • Promote sustainable urban water management, aligning with best practices in water-sensitive urban design.

Together, these efforts contribute to a more resilient coastline, capable of adapting to climate change while maintaining the pristine nature of Southern Beaches for future generations.

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