Mosman Municipal Council

Environment

• Environmental management
• CEC
  • Integrated Projects
  • Bushland
  • Stormwater
  • Seawalls
• Trees
• Bushland and Biodiversity
• Pests and Weeds
• Gardening
• Coastal and Marine
• Water Management
• Ecologically Sustainable Living
• Atmospheric Environment
• Food Safety
• Public Health
• Noise

Many of Mosman’s seawalls are nearly a century old and many are heritage listed. Some, including the walls at Mosman Bay, Quakers Hat Bay and the Spit are showing the effects of exposure to the elements, with collapsed and damaged sections, fallen sandstone blocks and subsidence behind the wall.

CEC Seawall projects at Quakers Hat Bay and Ellery Park (the Spit West) have employed innovative methods to restore damaged sections of seawall while enhancing areas of marine habitat. Work at Pearl Bay Seawall and the Spit is in the final stages of design and incorporates many of the successful innovations from Mosman’s seawall program while integrating some exciting new elements.

Quakers Hat Bay Seawall

The Quakers Hat Bay seawall project restored an old, collapsing dry laid sandstone seawall, while also improving habitat for aquatic organisms that live in the intertidal zone.

Natural rocky shores created a range of habitat for intertidal animals, including flat horizontal surfaces, overhangs, rock-pools and crevices. As more of the harbour foreshore has been modified for human use, these types of rocky habitats have been increasingly replaced by seawalls built with a vertical face to deflect wave energy.

Mosman Council conducted the Quakers Hat Bay seawall project in partnership with the University of Sydney’s Centre for Research on the Ecological Impacts of Coastal Cities.

Council redesigned and rebuilt the seawall using a boulder field design, creating more crevices and horizontal surfaces for aquatic organisms to inhabit. The Centre has continued to monitor the seawall after its completion.

This project also involved the construction of steps to provide access into the water for boat users, and the reconstruction of a dilapidated stormwater channel. Thanks to a separate grant, dinghy racks were built so that boat users are able to store their dinghys without harming vegetation in the foreshore bushland.

Pedestrian access to the Bay has been increased by the construction of a crushed sandstone walking track, meandering through the bushland and providing access to the bay and the dinghy rack.

Pearl Bay / The Spit

Council is in the final stages of redesigning the seawall at Pearl Bay to enhance pedestrian access, improve the amenity of the area, and to restore the seawall to increase the habitat for aquatic organisms.

The design incorporates a boulder field in front of the seawall, similar to that at Quakers Hat Bay with the addition of aquatic plant species in one section.

• Concept Diagram for The Spit Seawall Project (PDF 506KB)

The works will also improve access along and to the foreshore. Parallel pedestrian and bicycle paths have been designed along the seawall crest with access to the foreshore at five locations via new safer steps. One of the access points includes the provison of a kayak launch and the extension of the existing beach area.

The scheme will be complemented by terrestrial planting along the wall, new seating and the construction of a viewing platform.

The works are due to be undertaken during 2009.

Works are also planned at this time for Spit East Beach, Parrwi Point Seawall and Musgrave Street Seawall.