Atlas of Australian Acid Sulfate Soils

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Atlas of Australian Acid Sulfate Soils

The National Committee for ASS (NatCASS) commenced a national project to identify the extent and severity of the problem in both coastal (Stages 1 and 2 for completion in June 2008) and inland (Stage 3: estimated completion in 2009) acid sulfate soil environments.  Whilst some parts of Australia had been previously mapped, no consistent method or format was used.  Mapping is an important tool in managing ASS.  Land managers need to be able to identify areas where development is best avoided or areas that will need special management if disturbed.  Mapping also guards against the unintentional disturbance of ASS, which can damage both infrastructure and the surrounding environment.

The methodology for Stage 1 involved the collation and assembling of all published ASS, land systems, marine habitat, elevation (DEM), tidal, estuarine, bathymetry, vegetation and remotely sensed data through using GIS to develop a unified Australian coastal atlas of ASS with:

• Consistent national classification and terminology; common legend.
• Identification of probabilities of occurrence:
  • high (Class A; >70% of mapping unit)
  • low (Class B; 6 - 70% of mapping unit)
  • extremely low (Class C; 1 – 5 % of mapping unit)
  • no probability of occurrence (Class D; <1% of mapping unit; e.g. thick outcrops of hard rock, ferricrete, calcrete, silcretes).
• Various types of ASS such as:
  • Profoundly disturbed areas
  • Sulfuric and sulfidic materials in profoundly disturbed terrain (x)
  • Subaqueous sulfidic materials submerged in subtidal wetland (a)
  • Sulfidic material in tidal zones (e.g. mangroves) (b to d)
  • Sulfidic material in non-tidal zones or floodplains (e to g)
  • Sulfidic material often under non-tidal zones with sandplains and dunes (e.g. > 10m elevation above sea level) (h to j)

The “Atlas of Australian Coastal ASS (Stage 1) was uploaded as a web served GIS at the Australian Soil Resource Information System (ASRIS) site (www.asris.csiro.au) in 2006. The coastal ASS atlas estimates that Australia contains:

• 95,000km2 of coastal ASS, which equates to two billion tonnes of sulfidic material (Potentially 3 billion tonnes sulfuric acid) Of which:
  • 74,000 km2 is on coastal land
  • 21,000 km2 is below the low tide mark as submerged or bottom sediments
  • 1,000 km2 is disturbed and acidified.

From 2006 to 2007 the coastal ASS Atlas component was further developed by incorporating major refinements to the ASS legend. Map boundaries were refined and a database added (Stage 2). The revised legend consisted of:

• 4 classes of “probability of occurrence” (A, B, C and D).
• 4 “levels of confidence” (1, 2, 3 and 4)
• 10 optional descriptors or modifiers (e.g. f = Fill materials, which overlay ASS materials)

The third and final stage of the Atlas of Australian ASS (Stage 3) incorporated information about “inland acid sulfate soils”.   The Inland ASS classifications are derived from National and (in the case of Tasmania) state soil classification coverages combined with 1:250K series 3 Hydrography and Multiresolution Valley Bottom Floor Index (MrVBF). A matrix was devised by several members of the Atlas of Australian ASS working group and used to translate combinations of Soil Order and landscape “wetness” to inland ASS Legend codes.

The inland ASS map was overlaid with the existing Coastal ASS map on ASRIS to create a complete Australia-wide coverage of ASS, which displays all forms of ASS.  This overall coverage exists as two separate data sets and is currently being merged into one seamless data layer.  The national ASS map will be uploaded to ASRIS by 31th July 2008 together with metadata - information describing the lineage, positional accuracy and attribute accuracy of the data.

In summary, this final dataset depicts a national map of available Acid Sulfate Soil (ASS) mapping and ASS qualification inferred from surrogate datasets. ASS mapping is classified with a nationally consistent legend that includes risk assessment criteria and correlations between Australian and International Soil Classification Systems. Existing digital datasets of ASS mapping have been sourced from each coastal state and territory and combined into a single national dataset. Original state classifications have been translated to a common national classification system by the respective creators of the original data and other experts. This component of the Atlas is referred to as the “Coastal” ASS mapping. The remainder of Australia beyond the extent of state ASS mapping has been “backfilled” with a provisional ASS classification inferred from national and state soils, hydrography and landscape coverages. This component is referred to as the “Inland” ASS mapping.

For the state Coastal ASS mapping, the mapping scale of source data ranges from 1:10K aerial photography in SA to 1:250K vegetation mapping in WA and NT, with most East coast mapping being at the 1:100K scale. For the backfilled inferred Inland ASS mapping the base scale is 1:2.5 million (except Tasmania) overlaid with 1:250k hydography. As at June 2008 the Tasmanian inland mapping has been re-modelled using superior soil classification map derived from 1:100k landscape unit mapping.

It should be noted that this is a composite data layer sourced from best available data with polygons depicted at varying scales and classified with varying levels of confidence. Great care must be taken when interpreting this map and particular attention paid to the “map scale” and confidence rating of a given polygon.  It is stressed that polygons rated with Confidence = 4 are provisional classifications inferred from surrogate data with no on ground verification.

Development of priority (hotspot) regions/areas and sites across Australia

A uniform national database for storage and display of ASS data was established for several key priority regions across Australia.

A national protocol for showcasing priority/hotspot areas via the ASS atlas on the ASRIS website was developed.  This involved the development of a standard presentation format document for each region, area or site across Australia, which has been hotlinked to a national map of Priority areas in ASRIS.  More specifically, the database of representative priority case studies around Australia (with images appropriate to each case) has detailed information on the following:

• Soil data (e.g. morphological, chemical, physical, soil classification).
• Coastal (estuary) hydrology, geology and geomorphology.
• Climate, land use, vegetation, etc;
• Environmental hazard assessment such as pollution hazard rating, infrastructure impact rating (e.g. subsidence, corrosion), environmental sensitivity rating (e.g. proximity to RAMSAR wetlands).
• Major cause of oxidation or increased anaerobic conditions of ASS.
• Off-site impacts.
• Available options for amelioration and management and
• Estimates of the increase (or decrease) in area of acidified ASS or increased anaerobic condition of ASS.

Web browsers will be able to view a map of Priority regions/areas/sites on the web and access information about them via a hyperlink by clicking on the map.  South Australian examples of priority (hotspot) regions/areas and sites have been developed and published as a series of CSIRO Land and Water Science Reports (in PDF format with ASS data that reside on the CSIRO Land and Water ASS website and are hotlinked from ASRIS).  Several similar examples have been developed for all the other States as PDF documents, which reside on the respective State-based websites.

For example, the Gulf St Vincent (GSV) and Barker Inlet “Priority Region” (i.e. priority or hotspot region linked to the “Atlas of Australian Acid Sulfate Soils” website via the Australian Soil Resources Information System - ASRIS) report (CSIRO Land and Water Science Report # 35/08) summarise factors associated with formation of pyrite and sulfuric acid in the wide range of ASS types and the key impacts this has on coastal, estuarine and mangrove swamp environments that fringe the shoreline of GSV.  This report also provides the following critical database information on coastal ASS:

• Properties (descriptions of 6 major types of ASS materials that commonly occur as layers in soil profiles).
• Conceptual process models (schematic soil-landscape cross sections).
• Australian and international soil classification systems (Types of ASS based on the legend used in the Atlas of Australian Acid Sulfate Soils, Australian Soil Classification, Soil Taxonomy and World Reference Base).
• Distribution (ASS map and aerial extent in hectares for GSV and Barker Inlet).
• Impacts (Land and water degradation; noxious odours; climate change and greenhouse gas emissions).
• Management and remediation options (brief overview of general principles).

More information can be obtained from the following report:

• Fitzpatrick R.W, B.P. Thomas R.H. Merry and S. Marvanek  (2008) Acid Sulfate Soils in Barker Inlet and Gulf St Vincent Priority Region  CSIRO Land and Water Science Report 35/08. CSIRO, Adelaide, 22. pp. 
   www.clw.csiro.au/publications/science/2008/sr35-08.pdf

Similar priority or hotspot regions across Australia have been developed and are either published or in the process of being published for:

• South Australia – Inland ASS for the Lower lakes (Lakes Albert and Alexandrina) and lower River Murray regions.
  Fitzpatrick R.W, S.P. Marvanek, P. Shand, R.H. Merry, M. Thomas and Raven MD (2008)  Acid Sulfate Soil Maps of the River Murray below Blanchetown (Lock 1) and Lakes Alexandrina and Albert when water levels were at pre- drought and current drought conditions.  CSIRO Land and Water Science Report 12/08.  CSIRO, Adelaide, 10 p There are 2 versions of the report – one without maps as appendix and one with maps:
  www.clw.csiro.au/publications/science/2008/sr12-08_withmaps.pdf
  www.clw.csiro.au/publications/science/2008/sr12-08_nomaps.pdf

• Victoria (Corangamite CMA region, which includes detailed maps of 2 case study areas incorporating both inland and coastal and inland ASS)
  Fitzpatrick R.W, WS Hicks, SP Marvanek, MD Raven, PG Dahlhaus and JW Cox (2007) Scoping study of coastal and inland acid sulfate soils in the Corangamite CMA.  Report to Department of Primary Industries and Corangamite Catchment Authority.  CSIRO Land and Water Science Report 28/07.  CSIRO, Adelaide, 113p http://www.clw.csiro.au/publications/science/2007/sr28-07.pdf

• Queensland (East Trinity region; Gold coast plus North coast; areas and several other profile sites); Tasmania: (North east and North west regions); Western Australia (WA wheat belt region and Perth coastal area); Northern Territory (Adelaide River region and other key ASS profiles from Darwin area)

• NSW: two key regions on the east coast; New South Wales - Coastal ASS investigation in the Lower Hunter Estuary Wetlands. Recent project for the NSW Department of Primary Industries (2008) Acid Sulfate Soils Priority Investigations for the Lower Hunter River Estuary. Report to the Department of Environment, Water, Heritage and the Arts. NSW Department of Primary Industries (Aquatic Habitat Rehabilitation), Port Stephens. 161p [external site]

Contact Dr Rob Fitzpatrick

More information

• To view the mapping and web based tools go to: www.asris.csiro.au.
• To read more background about the Atlas

Contact Dr Rob Fitzpatrick