Department of Land and Water Conservation
P.O. Box 3720, Parramatta NSW 2124
(02) 9895 7197, (02) 9895 7985
Soil Landscapes are areas of land with unique landform features and characteristic soil types. Because landscapes and their soils are formed by the same natural processes, Soil Landscapes are closely linked to other natural features such as vegetation, geology and hydrology.
The Department of Land & Water Conservation’s Soil Landscape program aims to progressively map and describe the Soil Landscapes across central and eastern NSW. 1:100 000 scale mapping is employed for intensively used areas (coastal populated areas and cropping) and broader-scale 1:250 000 mapping for broadacre agricultural areas (central NSW).
The program continues to generate a growing bank of information for public use. Soil Landscape reports include detailed descriptions of the landscape, typical soils and their properties, and landscape limitations and hazards. The more detailed 1:100 000 scale reports also contain chemical and physical laboratory test results for all dominant soil layers, and Soil Landscape capability ratings for urban and rural land uses.
This poster outlines the process of mapping Soil Landscapes, discusses the content of Soil Landscape Reports, and provides updates as to the current spatial and informational extent of the program.
What is a Soil Landscape?
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).
Soil Landscapes have a spatial extent that is delineated on a map by discreet polygons. Accompanying descriptions outline the soils and landforms of the map units. The scale at which the polygons exist depends on the scale of the mapping involved.
Because similar causal factors are involved in the formation of both soils and their landscapes, the Soil Landscape concept permits the integration of both soil and landscape characteristics into a single map unit (Chen & Mckane, 1996).
The process of mapping Soil Landscapes
All Soil Landscape mapping is carried out by Department of Land and Water Conservation (DLWC) Soil Surveyors. Mapping projects are carried out across a single Central Mapping Authority (CMA) map sheet. The surveyor begins the mapping project with an extensive literature review to collate background information relating to soils in the area.
Preparation. Mapping commences with examination and interpretation of remotely sensed imagery from different sources. Typically, these sources will include aerial photographs viewed with a stereoscope, geological and geomorphic linework, topographical data (Chen & McKane, 1996), Landsat Thematic Mapper satellite data, and radiometrics data. The surveyor identifies areas that could potentially be grouped to contain areas of unique soils and landforms. These are then delineated by hand-tracing the linework and may be digitised to produce an interim vector coverage of potential Soil Landscapes.
Recently, more intensive use of GIS is being incorporated into the initial mapping procedure. The various data sources and their derivatives are used as variables in spatial modelling. This is described more fully in Goldrick et. al., 2001. Spatial data and its derivatives (such as Compound Topographical Index or Solar Radiation derived from digital elevation models) which are deemed to be important factors in soil formation are combined in equations to create a surface which can be classified into ‘proto-’ Soil Landscapes. In this way spatial analysis does the work of the soil surveyor in identifying potential Soil Landscapes.
Initial survey. The Soil Surveyor uses this information to describe soil profiles at an observation level to evaluate the initial locations of map unit boundaries. Necessary adjustments may be made to boundaries, provisional Soil Landscapes divided or grouped together, and further sampling carried out.
Detailed survey. Sampling and soil and landscape descriptions are then carried out at a detailed level to fully characterise the variety and relationships of soils in each map unit. The aim is to achieve sufficient coverage of the map sheet (between 250 and 400 profiles may be necessary, depending on landscape variability), whilst obtaining a cross-section of the soils in each Soil Landscape. The Soil Surveyor visits areas of land within the map units and describes profiles exposed by road batters, gullies, trenches, soil cores or auger holes. Usually a minimum of six profiles are described for each Soil Landscape (Murphy, pers. comm.). Soil Landscape Variants, where different soil types are exhibited for particular landforms within a map unit, may be identified and additional soil profiles described. Photographs are also taken.
All soil profiles described are entered into DLWC’s database of soil information, the NSW Soil and Land Information System (SALIS) (McGaw et. al., 2001). Some profiles are selected to be Type Profiles, typical of their Soil Landscape, whose locations will be recorded in the Report.
It is envisaged that a Soil Landscape map will account for 90% of soil variation in a given area (Goldrick, pers. comm.).
Soil samples taken at Type Profile sites are prepared for laboratory analysis, which involves testing of physical and chemical properties.
Map and report production. The final map unit boundaries are then digitised and prepared for publication as a hard copy map, which is accompanied by a Report. The appearance of the published map and report is shown in Figure 1.
Figure 1. Appearance of the Soil Landscape map and Report.
Soil Landscape Reports
The Soil Landscape Report accompanies the Soil Landscape map and contains the information collected by the soil surveyor.
Each Soil Landscape is given a name based on the locality where it occurs, and a two-letter code abbreviating the name. For example, The Rock Soil Landscape near Wagga Wagga occurs on steep hills of The Rock Ranges (Chen & McKane, 1996). It is abbreviated to ro.
The soils in Soil Landscapes are described in terms of Soil Materials. These are soil layers identified as being typical to the Soil Landscape, and appear in given patterns often dictated by landform. Between 2 and 8 Soil Materials are described in detail for each Soil Landscape, and abbreviated by alphanumeric codes such as ro1.
Each Soil Landscape appearing on the map sheet covered by the Report is described in detail. The descriptions include a number of features.
Photographs. A photograph of countryside within the Soil Landscape is taken by the surveyor.
Location. A verbal description of the location of the map units and Type Profiles is given.
Descriptions of the landscape. The geology, topography, vegetation, climate and hydrology, land use and existing land degradation are summarised.
Qualities and limitations. Hazards and limitations of the soils and landscape, and capability for urban and rural land uses, are discussed.
Descriptions of characteristic soils. This may be either in terms of soil profile descriptions of Type Profiles with Soil Materials identified within them, or separate descriptions of individual Soil Materials. The features of all layers are detailed, including depth ranges, horizon codes, texture, structure, pedality, expected dry condition, coarse fragments, permeability, biotic activity, and layer boundary.
Occurrence and relationships diagram. A cross-sectional diagram summarising the occurrence of Soil Materials in the landscape, notes the soil types (Australian Soil Classification, Great Soil Group or Principal Profile Form) and, in some cases, Type Profile locations marked and Variants or surrounding Soil Landscapes included. This diagram is important in drawing together all the information for the Soil Landscape and placing it in context. An example of such a diagram appears in Figure 2.
Figure 2. Occurrence and Relationships diagram for The Rock Soil Landscape on the Wagga Wagga 1:100 000 Sheet, an important part of the Soil Landscape Report (Chen & McKane, 1996).
Soil Landscape Reports also contain a variety of tabular data. The results of all physical and chemical laboratory tests are given, together with derived attributes such as Plant Available Water Capacity or Universal Soil Loss Equation K factor (Chen & McKane, 1996). Tables of qualities and limitations may also be included, with landscape limitations such as flood hazard, and ratings of capability for urbanisation, grazing and cultivation for each landscape. Similar limitations information is included for individual Soil Materials, such as low fertility, sodicity/dispersion, or stoniness.
The Soil Landscapes program was initiated in the early 1980’s with the first map sheet, Sydney, published in 1989. Its aim has been “to provide soil and landscape resource information which can be easily understood” by readers with limited soils knowledge (Chapman & Murphy, 1989). The target areas are the more densely-populated areas of Eastern NSW and the agricultural regions to the North, South and centre of the state, with the scale of mapping determined by the intensity of land use. Central agricultural districts have been mapped at 1:250 000 scale, and most coastal areas at 1:100 000 scale. The maps are designed to be reliable only at the published scale (Chapman et. al., 1989).
Published soil landscapes currently cover some 135,456 square km, or 16.8% of the state of NSW. These areas are shown in Figure 3.
Figure 3. Current spatial extent of the NSW Soil Landscapes mapping program.
Much of the state is covered by other DLWC soil mapping programs such as the Land Systems of Western NSW project (Walker, 1991) and the Northern and Southern Comprehensive Regional Assessment projects (DLWC et. al., 1999). DLWC soil mapping programs provide information at a finer scale and greater detail than federal projects such as the Murray-Darling Basin Soil Information Strategy (Bui, 1999) and the Atlas of Australian Soils (Northcote, 1960-68), which are the other sources of soil information encompassing significant areas of the state.
Further potential for the Soil Landscapes mapping program
A possible limitation of the Soil Landscape program is that the scale of mapping restricts the reliability of the information at finer scales. The concept of facets or sub-landscapes, which are further divisions of each Soil Landscape according to geology, landform, vegetation patterns, or exposure (known as Factors for Organisational Grouping or FOGs), has been introduced in response. In the Report for each Soil Landscape, patterns are generally identified which dictate soil types. For example, different soil groups may be identified for sideslopes and crests in a hillside Soil Landscape, or for plains and stream channels of an alluvial Soil Landscape.
Due to the variety of FOGs which dictate the divisions between facets, they are not mappable at present. However, since Soil Landscape Reports generally contain sufficient information to identify facets, the potential exists for representation on existing maps and inclusion in future mapping.
In the quest for accessibility of natural resource information, part of the Soil Landscape Program involves collating all the Soil Landscape data into a central spatial database. The NSW Soil and Land Information System (SALIS), which currently contains profile information for all profiles described by Soil Surveyors (McGaw et. al., 2001), has the potential to store a framework of Soil Landscape polygons with a suite of database fields for their accompanying descriptive data. As the project continues, it is envisaged that all soil landscape data will be entered into this system at a detailed level.
Chapman, G.A. and Murphy, C.L. (1989) Soil Landscapes of the Sydney 1:100 000 Sheet Report, Soil Conservation Service, Sydney.
Chapman, G.A., Murphy, C.L., Tille, P.J., Atkinson, G. and Morse, R.J. (1989) Soil Landscapes of the Sydney 1:100 000 Sheet, Soil Conservation Service, Sydney.
Chen, X.Y. and McKane, D.J. (1996) Soil Landscapes of the Wagga Wagga 1:100 000 Sheet Report, Department of Land and Water Conservation, Sydney.
Bui, E. (Ed) (1999) A Soil Information Strategy for the Murray-Darling Basin. CSIRO Land and Water project Report No. D5038.
Goldrick, G., Chapman, G.A., Simons, N.A., Milford, H.B., Murphy, C.L., McGaw, A.J.E., Edye, J.A., and Macleod, A.P. (2001) New technology and soil landscape mapping in N.S.W. In Proceedings of the Geospatial Information and Agriculture Symposium, Sydney 2001.
NSW Department of Land and Water Conservation, NSW State Forests, NSW National Parks and Wildlife Service, Earth Sciences Foundation and NSW Department of Mineral Resources and Energy (1999) Soil and Regolith Attributes for CRA/RFA Model Resolution. A project undertaken as part of the NSW Comprehensive Regional Assessments.
McGaw, A.J.E., Milford, H.B, Chapman, G.A., Murphy, C.L., Edye, J.A., Macleod, A.P. and Simons, N.A. (2001) SALIS: Accessible Soil Information for better natural resource management. In Proceedings of the Geospatial Information and Agriculture Symposium, Sydney 2001.
Murphy, C.L., Macleod, A.P., Chapman, G.A., Milford, H.B., Edye, J.A., McGaw, A.J.E., Simons, N.A. (2001) Department of Land and Water Conservation’s State Soil Landscape Mapping Program and Derivative Products. In Proceedings of the Geospatial Information and Agriculture Symposium, Sydney 2001.
Northcote, K.H. (Ed) (1960-68) Atlas of Australian Soils, Sheets 1 to 10, with explanatory data, CSIRO and Melbourne University Press, Melbourne.
Northcote, K.H (1978) Soils and Land Use. In Atlas of Australian Resources, Division of National Mapping, Canberra.
Walker, P.J. (1991) Land Systems of Western NSW, Technical Report No. 25, Soil Conservation Service, Sydney.