Natural Resource Management

Soil Landscape Mapping Program - Terminology and Definitions

Terminology

Terminology used follows Abraham and Abraham (1996); and McDonald et al. (1990).

Definitions

Soil. For the purposes of the soil landscape mapping program, soil is defined as a natural body consisting of layers or horizons of mineral and/or organic constituents, of variable thickness, that differs from its parent material in morphological, physical, chemical and mineralogical properties and biological characteristics (Birkeland 1984).

Soil Landscapes. Soil landscapes are areas of land that have recognisable and specifiable topographies and soils, that are capable of presentation on maps, and can be described by concise statements (Northcote 1978).

Landscapes can be used to distinguish mappable areas of soils because similar causal factors are involved in the formation of both landscapes and soils. Similarly, constraints to rural and urban development of land are related to both landscape and soil qualities. The soil landscape concept permits the integration of both soil and landform constraints into a single mapping unit.

Each soil landscape is given a name based on the locality where a typical example occurs. On the map, this is represented by a two-letter alphabetic code.

Soil landscapes are described to be as representative as possible for the map sheets in the series. While most attributes of a soil landscape are constant over the entire extent of a soil landscape, there may be slight differences in some attributes on the same soil landscape across adjacent map sheets.

Associated Soil Landscapes. Associated soil landscapes are soil landscapes whose area on the map is of limited extent (usually <5 km²). In many instances, associated soil landscapes occur largely on adjacent map sheets. Associated soil landscapes are briefly described in the appropriate section (by soil landscape grouping) of the report. Laboratory tests are not usually carried out on soil materials within associated soil landscapes.

Included Soil Landscapes. Included soil landscapes are small areas of other soil landscapes that occur closely within any particular soil landscape but are too small to show at the scale of 1:100 000. They are listed in the soil landscape descriptions in the report.

Soil Landscape Variants. Soil landscape variants are very similar to their parent soil landscapes and usually vary in only a few physical features. They are either not sufficiently different or of sufficient areal extent to be soil landscapes in their own right.

Soil landscape variants are identified by a three-letter code. The first two letters stand for the parent soil landscape and the third letter identifies the variant. The parent soil landscape description should be referred to in the report for more detailed information. Variants are listed alphabetically in chronological order. In some cases, the first named variant for a particular soil landscape may not exist on adjacent map sheets.

Soil Landscapes on Adjacent Map Sheets. Soil landscapes are described to be as representative as possible for the map sheets in the series. While most attributes of a soil landscape are constant over the entire extent of a soil landscape, there may be slight differences in some attributes of the same soil landscape across different map sheets. The difference may be due to climatic gradients and/or parent materials changing over tens of kilometres beyond the map sheet where the soil landscape was originally described. The effect is usually small.

Landform Elements. Landform elements or groups of landform elements collectively form soil landscapes. They are the next level of detail below soil landscapes. Landform elements are usually too small to be depicted on maps of this scale but are shown on the soil distribution diagrams.

Type profiles. Type profiles are typical sequences of soil materials that occur over significant portions of a soil landscape. Type profiles are usually the most common arrangement of soil materials within any landform element.

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Soil Landscape Groupings. Colours on the map represent soil landscape groups and portray processes that link the landscape and soils together. Several soil landscapes may belong to each group.

Soil landscape groups are named after either recent and current land forming processes, or conditions that influence soil parent material or soil type, or, where simple process names do not exist, after environments where soil formation is influenced by current and recent processes.

Soil landscape groupings are determined by interpretation of landform/topographic, soil material and soil parent material features.

All soil landscapes and their associated soils are, or may have been, subject to a variety of contemporary or previous land forming processes/environments. Where more than one landscape grouping is significant, compound landscape groupings are used. The first group indicates that process is considered most influential in affecting prevailing soil and landscape qualities and limitations. Map colour is based on the first grouping.

Soil landscape groups that occur on soil landscape maps are described below.

Residual Soil Landscapes are dominated by sites where deep soils have formed from in situ weathering of parent materials. Residual soil landscapes typically have level to undulating elevated landforms. Landform elements include some summit surfaces, plateaux, terrace plains, peneplains and old ground surfaces. Stream channels are usually poorly defined.

Vestigial Soil Landscapes are dominated by sites where shallow soils have formed from in situ weathering of typically resistant parent materials. Landform elements can include summit surfaces, plateaux and old ground surfaces. Rock outcrop may be common.

Karst Soil Landscapes are dominated by solutional processes, particularly on limestone and related rock types. Soil parent materials include accumulations of less soluble minerals. Drainage patterns are deranged and solution hollows are common. Landform patterns may include tors, hillslopes and dolines.

Colluvial Soil Landscapes are affected by mass movement. Soil parent material consists mostly of colluvial mass movement debris including scree and talus along with other landslide, mudflow and creep deposits. Colluvial soil landscapes usually include alcoves, cliffs, cliff-footslopes, scarps, landslides, talus, some moderately inclined to precipitous hillslopes and areas with commonplace evidence of mass movement. Slope wash processes are considered less dominant.

Erosional Soil Landscapes have been sculpted primarily by erosive action of running water. Streams are well-defined and competent to transport their sediment load. Soil depth is usually shallow (with occasional deep patches) and mode of origin is variable and complex. Soils may be either absent, derived from water-washed parent materials or derived from in situ weathered bedrock. In many instances, subsoils have formed in situ while topsoils have formed from materials washed from further up-slope. Erosional soil landscapes usually consist of steep to undulating hillslopes and may include tors, benches and areas of rock outcrop. Evidence of mass movement is rare.

Transferral Soil Landscapes are deep deposits of mostly eroded parent materials washed from areas up-slope. Stream channels are often discontinuous and slopes are generally concave. Transferral landscapes include footslopes, valley flats, fans, bajadas and piedmonts.

Alluvial Soil Landscapes are formed by deposition along rivers and streams. Soil parent material is usually deep, sorted and often stratified or previously stratified alluvium. Alluvial soil landscapes include current floodplains and alluvial deposits. Typical landform elements include those found on meander plains including bars, backplains, scrolls, scroll plains, flood-outs, oxbows, levees, lower terraces, prior and current stream channels.

Stagnant Alluvial Soil Landscapes occur as alluvial plains where erosion and aggregation by channel and overbank flow is barely active because of reduced water flow and stream migration. Typical landform elements are usually subdued and often inactive. They include plains, some higher terraces, prior streams, backplains and swamps.

Deltaic/Estuarine Soil Landscapes occur where rivers and streams enter large bodies of water such as the sea or inland lakes. Channel flow is dissipated and is also modified by wave and/or (in the case of estuarine soil landscapes) tidal action. Soil materials may also be influenced by saline conditions in both cases. Typical landform elements within estuarine soil landscapes include estuaries, deltas, tidal creeks and flats, and parts of coastal lagoons. Typical landform elements within deltaic soil landscapes include stream channels, levees, backplains and some swamps and lagoons.

Lacustrine Soil Landscapes result from infilling of lakes with sediments deposited in still water. Soil parent materials are usually fine-grained, well sorted and often varved. Ground surfaces are level to gently inclined and slightly concave. Landform elements include lakes, playas and some oxbows and lagoons.

Beach/Barrier Soil Landscapes have ground surfaces and soil parent materials that have been deposited by wave action, including accumulation of sand-sized coastal sediments during sea level changes. They typically occur near sandy coastlines or close to lake edges. Typical landform elements include bars, beaches, berms, beach ridges, dunes, swales, foredunes and some sandplains.

Aeolian Soil Landscapes have accumulated by deposition of sand-sized particles by wind action. Aeolian soil landscapes include dunefields, dunes, blowouts, sand sheets, lunettes and barrier ridges.

Swamp Soil Landscapes are dominated by ground surfaces and soils that are at least seasonally wet. Soil parent material includes large amounts of accumulated decayed organic matter. Watertables are frequently close to the surface. Landform elements may include swamps and some relic oxbows, abandoned channels, lagoons and swales.

Gilgai Soil Landscapes are those where seasonal shrink-swell is the dominant soil process. They are characterised by undulating microrelief, with small depressions, holes, shelves and mounds. Drainage is typically disintegrated. Gilgai types include crabhole, normal, linear, lattice, melonhole and contour.

Disturbed Soil Landscapes are dominated by ground surfaces arising from human activity. Soil parent materials have been moved, accumulated, removed or replaced (with soil or other items). Landform elements include fill-tops, embankments, cut faces, cut-over surfaces, dams, mounds and pits.

 

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Soil Materials. A feature of the methodology is the use of the soil materials concept to describe the soil. Soil materials are three dimensional soil entities that have a degree of homogeneity and lateral continuity (Atkinson 1993). Each soil material is defined and described in terms of its readily recognised and characteristic morphological properties and geographic abundance. The definitive attributes may vary from one soil material to another, depending on what is recognisably characteristic of the materials. In most cases, each soil material has a consistent set of properties and qualities. This is because soil materials are not necessarily defined by soil formation processes or position within a soil profile. Introduced fill, regolith or unconsolidated alluvium may be included; however, soil materials usually correspond with soil horizons. The vertical association of soil materials in a soil profile can be classified using traditional soil taxonomic systems such as the Australian Soil Classification (Isbell 1996) or Great Soil Groups (Stace et al. 1968). It is understood that soil materials often cross these traditional taxonomic boundaries.

Each soil material has a unique code consisting of two letters and one number. The letters are taken from the soil landscape in which the material is found and the number distinguishes it from other soil materials in the same soil landscape.

Soil material numbers may be missing where soil materials have been previously described for the same soil landscape on an adjacent map but are not sufficiently common on the current map sheet to be described in full.

Associated Soil Materials. Associated soil materials that are ephemeral or have limited extent are briefly described. Soil tests are not usually undertaken on these materials.

Australian Soil Classification (ASC). Soils are classified according to the Australian Soil Classification (Isbell 1996). The ASC has been endorsed and recommended by the Australian Soil Conservation Council, the Australian Collaborative Land Evaluation Program and the National Landcare Program as the official Australian soil classification. This soil classification is considered to be technically superior to Great Soil Groups (Stace et al. 1968) and Principle Profile Forms (Northcote 1979). A table listing comparable Great Soil Groups for major ASC classifications is included in soil landscape reports published after 1998.