Some background info of the shire

The Sutherland Shire is situated on the south-eastern rim of the Sydney basin. Its natural attributes of beaches, waterways, bushland and proximity to the Sydney CBD and sub-regional centres is a major contributing factor to the Shire’s character and attractiveness.
With 370km2 in area, its size and location provides a diversity of landforms that include rugged sea cliffs, sandy beaches, dunes and estuarine and riparian systems. It is in the Shire that Gunnamatta Bay lies and is a very popular destination for families.

Topography and soils
The geology of the Shire is predominantly sedimentary in origin. The Woronora Plateau, which covers most of the Shire, is a dissected sandstone plateau with shale lenses interspersed.
Major soil types of the Shire are within the Hawkesbury Sandstone and Wianamatta Shale groups. Other soil types include a mosaic of sands from the Wollongong, Kurnell and muddy sediments of the Mangrove Creek soil landscapes, the Hawkesbury, Lucas Heights and Faulconbridge soils, with isolated pockets of Blacktown and Gymea. Within the Royal National Park, there are Bundeena, Yarrawarrah, Hawkesbury
and Watagan soil landscapes.
Of the various soil types in the Sutherland shire acid sulfate soils have the greatest influence on land use activity along the coastal fringes. The major concern about acid sulfate soils is their potential to produce sulfuric acid that can:
• corrode and weaken concrete, iron, steel and certain aluminium alloys
• affect biodiversity and ecological integrity by degrading habitat, soil and water quality, killing or
disease of fish and other aquatic organisms
• dissolve certain essential elements from the soil–turning it toxic so plants will die
• kill fish and aquatic life, including plants with long term effect of reduced hatching and growth rates

http://www.sutherland.nsw.gov.au/ssc/rwpattach.nsf/viewasattachmentPersonal/20062007_SOE_Report_web.pdf/$file/20062007_SOE_Report_web.pdf