The key points covered in the presentation include:

Causes of Siltation

• Catchment Development: Uncontrolled post-war development in areas like Elanora Heights, Belrose, and Frenchs Forest eroded the local sandstone, leading to massive sand runoff into local creeks [cite:
• Volume: an estimated 3 million cubic metres of sand have washed into Middle Creek since the post-war period.
• Inadequate Controls: standard sediment controls (like sand fences) only handle minor rain events; major storm flows easily flush them out and move heavy sand loads down the catchment.

Impacts on the Environment and Lagoon

• Loss of Aquatic Habitat: Heavy siltation has clogged creeks (such as Middle Creek and South Creek), destroying natural habitats and eliminating species like platypus that once lived there
• Increased Flooding: As creek beds infill with sand, their capacity decreases, worsening local flooding problems.
• Delta Formation & Lagoon Turbidity: Sand eventually reaches Narrabeen Lagoon (forming deltas in the Western Basin), while finer organic runoff and shallow waters cause wind-driven turbidity and water quality changes.

Proposed Solutions & Remediation

• Targeted “Soft” Dredging: Instead of large-scale dredging that disrupts wildlife (such as bird life on deltas),  dredging specific spots would be preferable allowing natural water flows to gradually move remaining sand down, letting the creek re-adjust over time.
• Stricter Future Controls: Any future development (e.g., Lizard Rock) requires significantly better, well-funded sediment management rather than tokenistic controls.

Wakehurst Parkway Issues

•  building the Wakehurst Parkway altered and cut off natural creek loops, compounding the flooding issues by restricting flow paths