Activities that damage acid sulfate soils

The most common activities that trigger oxidation and the production of acid from acid sulfate soils are:

  • drainage for agriculture – industries commonly in acid sulfate soil areas include sugar cane and tea tree cultivation, dairying and other grazing and cropping, and aquaculture
  • infrastructure works, especially flood management drainage works (levees, floodgates), maintenance dredging, laying of utilities (water, sewerage, communications), roads and railways
  • urban and tourism development
  • extractive industries, such as sand and gravel extraction from rivers or floodplains.

Note that most of these works require some form of consent or approval. If proposing to carry out such works, contact your local council first.

Although the activities that cause the oxidation of acid sulfate soils are important, it is the agricultural management practices of the past, such as drainage and tidal and flood mitigation works, that have contributed most to the current environmental problem in NSW.

Drainage of coastal lowlands

Drainage works for agriculture commenced in the late 19th century, with the construction of private works and the formation of the first drainage unions. The NSW Public Works Department constructed major drainage works on floodplains from the Tweed to the Shoalhaven from the early 1900s.

Following major flooding in 1949 and the early 1950s, several large flood mitigation and drainage schemes were commenced, often extending and augmenting the early drainage networks.

The 1960s appear to have been the most energetic period for the construction of drainage and flood mitigation works generally, with works continuing into the mid-1970s.

Drainage networks

The coastal floodplains of NSW have now been extensively drained, with large networks of floodgated drainage channels. At last count in 2000, there were over 5000 kilometres of major drains (> 0.5 m deep) on the North Coast (Tweed to Manning). These works are now owned and operated by councils, drainage unions and private landholders.

Details of floodgates, weirs, culverts and other structures that significantly inhibit tidal flow or fish passage have also been recorded. This data includes their location, number, size, condition and ownership, allowing the association of drainage networks with known acid discharges to be determined. The data is used together with hydrological modelling to develop strategies for managing acid sulfate soils.

Although the main construction period of major drainage works has now passed, their impact has been ongoing through important changes in the pattern of land ownership on floodplains. Landowners have subdivided properties into smaller holdings, often consisting of lower floodplain land only, which depend heavily on effective drainage and flood mitigation for their economic viability.

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Page last updated: 11 October 2013