Northbank Foreshore Stabilisation Project

The City of Fremantle is working to assess the condition of a section of the Northbank Foreshore and develop options to address foreshore erosion.

The Northbank foreshore shoreline is subject to erosion. Historical foreshore reclamation (or riverbank realignment) has altered the shape of the shoreline and the river is trying to establish a new shoreline position between its natural and modified location. The erosion is caused by a combination of waves (from wind and boat wakes), tidal currents and storm surge.

We've engaged GHD to investigate the issues impacting the foreshore’s stability and recommend options to minimise future erosion and preserve the amenity of the public foreshore.

This area has environmental and recreational value, which are both important considerations. To inform any future action taken in this area we are carrying out a site analysis, reviewing existing studies and plans, engaging the community and stakeholders and undertaking a technical analysis.

Below: The current foreshore.


Based on the analysis, concept designs of five options to stabilise Northbank have been prepared.

Each option has advantages and disadvantages, you can explore them below and let us know your thoughts in the online survey below by 5pm Wednesday 6 June 2018.

This information and online survey is supported by a community information session. We recommend you consider attending before completing the survey. The session will be held Thursday 31 May 2018 between 5.30pm and 7.30pm, at North Fremantle Community Hall. There are two formal presentation sessions with question time being offered, one at 5.45pm and then repeating at 6.45pm.


Option 1A – Build a limestone wall along the river alignment

This option would have the least soil disturbed during construction as well as being a durable option with the smallest footprint and minimal impact on river processes. Using the river alignment would increase the useable land area above the riverwall and there is no need for ongoing beach replenishment.

The disadvantages of this option are that there is likely to be little or no sandy beach area and the wall would make access between land and water difficult.


Option 1B – Build a limestone retaining wall along the river alignment and place rocks along the water edge of shoreline (a ‘rock toe’)

This option is similar to option 1A but placing rocks and beach sand along the water edge of the shoreline would create some beach area.

The disadvantage of this option is an increase in beach replenishment requirements to maintain the beach area. The wall would make access between land and water difficult. It would require slightly more disturbance to the soil during construction and slightly increase the footprint.


Option 2A – Build a limestone wall along the land alignment

This is a durable option offering both land and some beach area, a footprint similar to 1A and minimal impact on river processes.

The disadvantages of this option are more soil disturbance during construction than option 1A or 1B and the wall making access between land and water more difficult. There would be ongoing sand replenishment costs to maintain a beach area as it likely to be subject to erosion.


Option 2B – Build a limestone wall along the land alignment and place rocks along the water edge of shoreline (a ‘rock toe’)

This option is similar to 2A (durable and minimal impact on river processes) however it would increase the stability of the beach area and slightly increase the footprint. The addition of a rock toe would reduce the sand replenishment costs of 2A because the beach is wider and further away from wave action. Because of the location of the wall this would require less sand replenishment than option 1B.

The disadvantages of this option are increased disturbance of soil during construction than for 1A or 1B and the wall making access between land and water more difficult. There would be ongoing beach replenishment costs to maintain a beach area as it is likely be subject to erosion but less so than 1B.


Option 3 – Build three rock groynes and use geotextile sand bags on the bank

This option also offers a land and beach area, with the stability of the beach comparable to 2B and allows easy access between land and water. It follows the land alignment above but offers less landscaped grassy area than any of the other options.

The disadvantages of this option are greatest soil disturbance during construction, the largest footprint, possible impact on natural river processes and the sand bags have a shorter design life than a wall. This option also has similar beach replenishment requirements to 2B, but adds complexity (and therefore cost) to the replenishment works by having to work around the groynes and sandbags.


Options at a glance


Option 1A

Wall along river alignment

Option 1B

Wall along river alignment with rock toe
Option 2A

Wall along land alignment

Option 2B

Wall along land alignment with rock toe
Option 3

Rock groynes and sand bags

Cost to build (indicative)
$550,000 to $750,000$850,000 to $1,400,000
$530,000 to $600,000
$850,000 to $1,200,000
$800,000 to $1,400,000

Cost to replenish beach (indicative)
$0
$200,000
$200,000
$100,000
$100,000
Size of land area provided
Greatest
Greatest
Moderate
Moderate
Least
Size of beach area provided
None
Least
Moderate
Greatest
Moderate
Access between land and water
Restricted by wall
Restricted by wall
Restricted by wall
Restricted by wall
Yes
Level of soil disturbance
Least
Lower
Moderate
Greater
Greatest
Footprint
Least
Lesser
Least
Lesser
Greatest
Natural river processes
Minimal interruption
Minimal interruption
Minimal interruption
Minimal interruption
May be impeded
Beach stability
N/A
Increased stability
Beach sand may erode
Increased stability
Increased stability
Design life (before replacement or upgrade)
50 years
50 years
50 years
50 years
25 years


Please tell us your thoughts in the survey below.

The City of Fremantle is working to assess the condition of a section of the Northbank Foreshore and develop options to address foreshore erosion.

The Northbank foreshore shoreline is subject to erosion. Historical foreshore reclamation (or riverbank realignment) has altered the shape of the shoreline and the river is trying to establish a new shoreline position between its natural and modified location. The erosion is caused by a combination of waves (from wind and boat wakes), tidal currents and storm surge.

We've engaged GHD to investigate the issues impacting the foreshore’s stability and recommend options to minimise future erosion and preserve the amenity of the public foreshore.

This area has environmental and recreational value, which are both important considerations. To inform any future action taken in this area we are carrying out a site analysis, reviewing existing studies and plans, engaging the community and stakeholders and undertaking a technical analysis.

Below: The current foreshore.


Based on the analysis, concept designs of five options to stabilise Northbank have been prepared.

Each option has advantages and disadvantages, you can explore them below and let us know your thoughts in the online survey below by 5pm Wednesday 6 June 2018.

This information and online survey is supported by a community information session. We recommend you consider attending before completing the survey. The session will be held Thursday 31 May 2018 between 5.30pm and 7.30pm, at North Fremantle Community Hall. There are two formal presentation sessions with question time being offered, one at 5.45pm and then repeating at 6.45pm.


Option 1A – Build a limestone wall along the river alignment

This option would have the least soil disturbed during construction as well as being a durable option with the smallest footprint and minimal impact on river processes. Using the river alignment would increase the useable land area above the riverwall and there is no need for ongoing beach replenishment.

The disadvantages of this option are that there is likely to be little or no sandy beach area and the wall would make access between land and water difficult.


Option 1B – Build a limestone retaining wall along the river alignment and place rocks along the water edge of shoreline (a ‘rock toe’)

This option is similar to option 1A but placing rocks and beach sand along the water edge of the shoreline would create some beach area.

The disadvantage of this option is an increase in beach replenishment requirements to maintain the beach area. The wall would make access between land and water difficult. It would require slightly more disturbance to the soil during construction and slightly increase the footprint.


Option 2A – Build a limestone wall along the land alignment

This is a durable option offering both land and some beach area, a footprint similar to 1A and minimal impact on river processes.

The disadvantages of this option are more soil disturbance during construction than option 1A or 1B and the wall making access between land and water more difficult. There would be ongoing sand replenishment costs to maintain a beach area as it likely to be subject to erosion.


Option 2B – Build a limestone wall along the land alignment and place rocks along the water edge of shoreline (a ‘rock toe’)

This option is similar to 2A (durable and minimal impact on river processes) however it would increase the stability of the beach area and slightly increase the footprint. The addition of a rock toe would reduce the sand replenishment costs of 2A because the beach is wider and further away from wave action. Because of the location of the wall this would require less sand replenishment than option 1B.

The disadvantages of this option are increased disturbance of soil during construction than for 1A or 1B and the wall making access between land and water more difficult. There would be ongoing beach replenishment costs to maintain a beach area as it is likely be subject to erosion but less so than 1B.


Option 3 – Build three rock groynes and use geotextile sand bags on the bank

This option also offers a land and beach area, with the stability of the beach comparable to 2B and allows easy access between land and water. It follows the land alignment above but offers less landscaped grassy area than any of the other options.

The disadvantages of this option are greatest soil disturbance during construction, the largest footprint, possible impact on natural river processes and the sand bags have a shorter design life than a wall. This option also has similar beach replenishment requirements to 2B, but adds complexity (and therefore cost) to the replenishment works by having to work around the groynes and sandbags.


Options at a glance


Option 1A

Wall along river alignment

Option 1B

Wall along river alignment with rock toe
Option 2A

Wall along land alignment

Option 2B

Wall along land alignment with rock toe
Option 3

Rock groynes and sand bags

Cost to build (indicative)
$550,000 to $750,000$850,000 to $1,400,000
$530,000 to $600,000
$850,000 to $1,200,000
$800,000 to $1,400,000

Cost to replenish beach (indicative)
$0
$200,000
$200,000
$100,000
$100,000
Size of land area provided
Greatest
Greatest
Moderate
Moderate
Least
Size of beach area provided
None
Least
Moderate
Greatest
Moderate
Access between land and water
Restricted by wall
Restricted by wall
Restricted by wall
Restricted by wall
Yes
Level of soil disturbance
Least
Lower
Moderate
Greater
Greatest
Footprint
Least
Lesser
Least
Lesser
Greatest
Natural river processes
Minimal interruption
Minimal interruption
Minimal interruption
Minimal interruption
May be impeded
Beach stability
N/A
Increased stability
Beach sand may erode
Increased stability
Increased stability
Design life (before replacement or upgrade)
50 years
50 years
50 years
50 years
25 years


Please tell us your thoughts in the survey below.

  • Northbank concepts available

    11 months ago
    Option 1a and 1b combined 23052018

    Five concepts for potential stabilisation of a section of Northbank are now available to view. This information and online survey is supported by a community information session. We recommend you consider attending before completing the survey.

    The session will be held Thursday 31 May 2018 between 5.30pm and 7.30pm, at North Fremantle Community Hall. There are two formal presentation sessions with question time being offered, one at 5.45pm and then repeating at 6.45pm.

    Community feedback will inform the analysis and selection of a preferred option.


    Five concepts for potential stabilisation of a section of Northbank are now available to view. This information and online survey is supported by a community information session. We recommend you consider attending before completing the survey.

    The session will be held Thursday 31 May 2018 between 5.30pm and 7.30pm, at North Fremantle Community Hall. There are two formal presentation sessions with question time being offered, one at 5.45pm and then repeating at 6.45pm.

    Community feedback will inform the analysis and selection of a preferred option.


  • Project Background

    11 months ago

    In July 2017 we began looking at options to address erosion at the Northbank foreshore. We asked for feedback from local residents on how they use this section of the Swan River and what they considered important for us to include when designing options to stabilise the foreshore.

    In the first step of community engagement we heard:

    • This is a popular area for swimming, kayaking and fishing.

    • There are different community preferences to minimise erosion.

    • The community wants to know more about the causes of erosion and stabilisation options.

    In the second step of community engagement we’ll present foreshore stabilisation options along with the pros and cons of each option and the estimated costs. Initially we expected this to commence by the end of September 2017. However, the complex nature of the project has caused some delay. Designing possible options requires balancing amenity, aesthetics, access, design life, construction costs, ongoing maintenance costs, environmental considerations and impact of the stabilisation option on other areas.

    To estimate a more accurate cost for each option we will also need to identify any remediation required to ensure contaminants below the surface soil are not released into the environment. Prior to housing development near the site, the land was used by industry. We need to better understand the impact of any required remediation when disturbing the soil on the overall cost of the concept options.

    These site investigations were initially planned for the design stage of the project. While bringing them forward has delayed drafting the concept options, the concepts will be better informed and potential cost variations at the detailed design stage will be reduced. Overall, it will reduce the time required to complete the final stage of the project. Funding will need to be secured to complete the works.


    In July 2017 we began looking at options to address erosion at the Northbank foreshore. We asked for feedback from local residents on how they use this section of the Swan River and what they considered important for us to include when designing options to stabilise the foreshore.

    In the first step of community engagement we heard:

    • This is a popular area for swimming, kayaking and fishing.

    • There are different community preferences to minimise erosion.

    • The community wants to know more about the causes of erosion and stabilisation options.

    In the second step of community engagement we’ll present foreshore stabilisation options along with the pros and cons of each option and the estimated costs. Initially we expected this to commence by the end of September 2017. However, the complex nature of the project has caused some delay. Designing possible options requires balancing amenity, aesthetics, access, design life, construction costs, ongoing maintenance costs, environmental considerations and impact of the stabilisation option on other areas.

    To estimate a more accurate cost for each option we will also need to identify any remediation required to ensure contaminants below the surface soil are not released into the environment. Prior to housing development near the site, the land was used by industry. We need to better understand the impact of any required remediation when disturbing the soil on the overall cost of the concept options.

    These site investigations were initially planned for the design stage of the project. While bringing them forward has delayed drafting the concept options, the concepts will be better informed and potential cost variations at the detailed design stage will be reduced. Overall, it will reduce the time required to complete the final stage of the project. Funding will need to be secured to complete the works.