Where are acid sulfate soils located?
Acid sulfate soils are found in every coastal estuary and embayment in NSW. Over 260,000 hectares are considered high-risk areas, including about 150,000 ha under agricultural production.
Acid sulfate soils are common in areas of mangroves and salt marsh as well as underlying large areas of river deltas, levees, backswamps and other formerly brackish seasonal or permanent freshwater swamps.
The largest of these areas are on the coastal floodplains of northern NSW, particularly those of the Tweed, Richmond, Clarence, Macleay, Hastings, Manning and Hunter rivers.
The Shoalhaven floodplain is the largest such area on the state’s south coast.
Due to their estuarine origin, acid sulfate soils are found close to sea level, generally less than 1 metre Australian Height Datum (AHD). The upper surface of this material is commonly at about 0.2–0.4 m AHD, although several factors may complicate this generalisation. These include:
- variations in sea levels during estuarine depositional phases
- the fact that estuarine deposition is related to local tidal planes, rather than sea level itself
- scour of estuarine materials by higher energy current and wave flows
- slumping and peat loss
- vertical translocation and precipitation of oxidation-reduction products, sometimes causing acid sulfate soil scalds.
Aspects of Quaternary geology, geomorphic history, stratigraphy, soils and hydrogeology in the Edward–Wakool channel system, with particular reference to the distribution of sulfidic channel sediments is a new report describing the nature of acid sulfate soils on the Riverine Plain.
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Page last updated: 12 March 2014