Developing conceptual designs

Many of the seawalls in Marks Point and Belmont Souths are showing signs of walls, scouring behind walls, degraded structures, and exposed materials are commonly Vertical seawalls further provide no escape for wrack to wash out of the water, in anaerobic conditions which has led to a significant community issue in the area.

Some areas may be restricted to the use of seawalls due to limited land available, foreshore slopes and exposure to weather processes. Where seawalls may be approved, the treatment need to consider the alignment of the foreshore, how to minimise potential impacts on neighbouring foreshores, and how to include environmentally beneficial features. The ‘Environmentally Friendly Seawalls’ guide is available publicly online to provide ideas on how to improve the environmental value of seawalls (pictured right). [9]

Not a concrete solution… While seawalls were once a common practice to stabilise the foreshore, these ‘hard’ structures are no longer a preferred treatment. Over time seawalls have been increasingly While seawalls were once a common practice to stabilise the foreshore, these ‘hard’ understood to be associated with a range of negative impacts. Vertical designs are unable to structures are no longer a preferred treatment. Over time seawalls have been increasingly absorb wave energy leading to the transference of erosion onto neighbouring properties. understood to be associated with a range of negative impacts. Vertical designs are unable to absorb wave energy leading to the transference of erosion onto neighbouring properties. During the construction of seawalls, the removal of vegetation, modifications made to During the construction of seawalls, the removal of vegetation, modifications made to shoreline profiles, and poor structural design permanently change the natural landscape of shoreline profiles, and poor structural design permanently change the natural landscape of the shoreline and remove the natural buffering systems that absorb wave energy. the shoreline and remove the natural buffering systems that absorb wave energy.

Working Group members engaged Council's City Projects department to develop preliminary foreshore treatment design concepts.

KEY CONSIDERATIONS INCLUDED:

An independent Coastal Engineer was involved in the process of preparing the conceptual designs for the FMP. The Peer Review report assessed the treatment options and where different types of designs would be appropriate depending on environmental constraints.

Many of the seawalls in Marks Point and Belmont Souths are showing signs of failure. Slumping walls, scouring behind walls, degraded structures, and exposed materials are commonly seen. Vertical seawalls further provide no escape for wrack to wash out of the water, leaving it trapped in anaerobic conditions which has led to a significant community issue in the area.

Some areas may be restricted to the use of seawalls due to limited land available, foreshore slopes and exposure to weather processes. Where seawalls may be approved, the treatment need to consider the alignment of the foreshore, how to minimise potential impacts on neighbouring foreshores, and how to include environmentally beneficial features. The ‘Environmentally Friendly Seawalls’ guide is available publicly online to provide ideas on how to improve the environmental value of seawalls (pictured right). [9]

• Treatment options need to comply with legislative requirements designed to protect health, safety and the environment. • ‘Soft’ treatments such as sloping beaches and revetments are favourable. ‘Hard’, permanent treatments such as habitat-friendly seawalls may be considered in limited areas. • Consider local drainage structures and seagrass wrack build-up areas. • Prevent active erosion, dissipate wave energy, and limit wave overtopping landward of the structure. • Increase biodiversity and environmental values. • Allow water access and recreational use of the foreshore. • Consider coastal design principles including fetch, wave height, and how to minimise impacts on adjoining properties. • Consistent with requirements in the Marks Point

Belmont South LAP. • Foreshore works should be triggered by environmental change or events rather than specific timelines. • Maintain the natural alignment of the foreshore. • Consider the asset life and maintenance of treatments. • Consider potential land reclamation in areas of limited land widths or evidence of erosion scarps.

Not a concrete solution…

NOT A CONCRETE SOLUTION Many of the seawalls in Marks Point and Belmont Souths are showing While seawalls were once a common practice to stabilise the foreshore, these ‘hard’ structures are no longer a preferred treatment. Over time seawalls have been increasingly understood to be associated with a range of negative impacts. Vertical designs are unable to signs While seawalls were once a common practice to stabilise the foreshore, these ‘hard’ structures are no longer a preferred treatment. walls, scouring behind walls, degraded structures, and exposed materials Vertical seawalls further provide no escape for wrack to wash out of the water, in anaerobic conditions which has led to a significant community issue in absorb wave energy leading to the transference of erosion onto neighbouring properties. During the construction of seawalls, the removal of vegetation, modifications made to shoreline profiles, and poor structural design permanently change the natural landscape of the shoreline and remove the natural buffering systems that absorb wave energy. Vertical seawalls are unable to absorb wave Some areas may be restricted to the use of seawalls energy and can permanently change the due to limited land available, foreshore slopes and natural shoreline. They provide no escape exposure to weather processes. Where seawalls may for seagrass wrack to wash out of the water, be approved, the treatment need to consider the leaving it trapped and rotting which has led alignment of the foreshore, how to minimise to a significant community issue in the area potential impacts on neighbouring foreshores, and how to include environmentally beneficial features. Many of the ad-hoc seawalls in Marks Point and The ‘Environmentally Friendly Seawalls’ guide is Belmont South are showing signs of failure, available publicly online to provide ideas on how to with slumping walls and scouring behind walls commonly seen. In constrained areas where improve the environmental value of seawalls (pictured right). [9] seawalls may be the only viable option, the design needs to consider the alignment of the foreshore, how to minimise impacts on neighbouring foreshores, and include environmentally beneficial features. The ‘Environmentally Friendly Seawalls’ guide is available publicly online to provide ideas on how to improve the environmental value of seawalls (see references section).