We know that the condition of the banks, especially the dilapidated steel sheet piling is a major concern and addressing it in the CMP is a high priority of the community. The condition of the riverbanks along the Cooks River and its major tributaries were assessed, identifying areas at risk of erosion. Additionally, a Foreshore Public Safety Assessment Memo was completed, mapping public safety hazards related to sheet piling and recommending interim safety measures.

• As part of the study, approximately 29 kms of the foreshore was assessed to characterise and map erosion risks, allowing for priority locations to be systematically identified.
• Natural bank failures were mainly due to degraded riparian vegetation, while constructed asset failures stemmed from poorly designed, or end-of-design-life erosion protection works, such as the metal sheet piling.

         

 

• An erosion risk assessment throughout the whole study area was undertaken. This included an assessment of:
  • Consequence of ongoing erosion:
    • Environmental impact
    • Erosion severity
    • Safety/ amenity impact
    • Infrastructure impact
    • Cultural heritage impact
  • Likelihood of ongoing erosion:
    • Estimated future trajectory of erosion
    • Presence and condition of erosion protection
    • Condition of bank
    • Distance from the foreshore to landward assets

 

The risk assessment results are mapped below (note that low risk sections are not included):

 

Concept designs for stabilisation options were proposed based on site constraints. These consider the presence or absence of sheet piles and the space available behind the foreshore to use more natural and environmentally friendly techniques which include:

• establishment of an intertidal bench
• revegetation/ bank reprofiling
• eco-friendly toe protection
• fluvial energy reduction
• incorporation of inter-tidal habitat features

 

The following table shows concept designs for potential stabilisation works based on the amount of available space.

Space available	Stabilisation Option
10+ m of space Full bank reprofile. Extensive habitat features and native vegetation.
5–10 m of space Moderate bank reprofile, intertidal bench and other constructed habitat features.
Less than 5 m of space Minor bank reprofile. Use of natural materials to create an eco-friendly near vertical structure.

 

Other considerations that have been explored during the CMP process includes:

• Determining ownership of and responsibilities for the degraded assets
• Exploring potential funding arrangements for works
• Incorporating design features to provide a range of benefits (i.e., environmental, cultural, recreational)