Abstract

The aim of this poster paper is to increase awareness of how DLWC’s soil landscape mapping program and associated derivative products, which can assist land managers in identifying constraints to land use and assist them in making informed land use planning decisions.

Soil Landscape Mapping Program - Background

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

Soils and the landscape have similar factors of formation and it is this close association that allows soil suites to be mapped relatively quickly over fairly broad areas. Unlike soils, landscapes can be identified by land surface expression using interpretation of aerial photographs, satellite images and more frequently, using Digital Elevation Models. It is the soil landscape mapping method that is used by the Department of Land and Water Conservation to provide soils information across the central and eastern areas of the State. The western area of the State has previously been mapped using Land Systems (Walker 1991).

The systematic mapping of soil landscapes officially started off as two specific programs in the mid-1980s conducted by the former Soil Conservation Service of NSW. The first, a 1:250 000 scale soil landscape mapping program, provides soil information for broad acre agriculture mainly in the wheat sheep belt of the State. The second, a 1:100 000 scale program, provides more detailed information for areas under intense land use pressure or land use change, such as cropping and coastal areas

Generally the more intensive 1:100 000 mapping program provides more detailed information than the broad scale 1:250 000 program. Both programs have evolved over time to accommodate the increasing need for soil and landscape information. Thus variation occurs between some map sheets within the same program.

The aim is to have complete soil landscape mapping coverage of the central and eastern areas of the State by 2010. Soil landscape mapping now covers 13.5 million ha which is approximately 30 percent of the target area. (Figure 1).

Figure 1: Current status of the NSW Soil Landscapes mapping program.

Information Collected and Laboratory Testing

Soil landscape mapping defines both soil and landscape attributes, which are collected from remote sensing information (including aerial interpretation of landscape features), field survey and laboratory testing of the dominant soil materials in the landscape.

Soil materials are “three dimensional soil entities that have a degree of homogeneity and lateral continuity” (Atkinson 1993).

The soil and landscape attributes are clearly defined in detailed reports that accompany each soil landscape map sheet. The report contains detailed descriptions on the lithology and geology, the dominant vegetation communities, land use, existing land degradation, dominant soil layers and their occurrence and relationship to the landscape.

Between 300 to 400 field locations are studied in detail (hundreds of observations are also made) for soil and landscape properties for each 1:100 000 sheet area and these are stored in the Soil and Landscape Information System (SALIS). Typical profiles of each main soil type (within each map unit) are sampled for laboratory testing, which involves a broad range of both chemical and physical tests (Table 1).

Table 1: Chemical and Physical Soil Analysis undertaken for dominant soil types in each soil landscape (1:100 000 mapping, recent 1:250 000 mapping)

Soil Chemical Tests	Soil Physical Tests
Phosphorus Sorption	Particle Size Analysis
Exchangeable. Potassium	Dispersion Percentage
Exchangeable. Calcium	Volume Expansion
Exchangeable. Magnesium	Linear Shrinkage
Exchangeable Aluminium/estimated Cation Exchange Capacity	Unified Soil Loss Equation (Erodibility Factor K)
Soil pH Buffering Capacity	Wind Erodibility
Soil Acidity	Field Capacity
Soil Alkalinity	Permanent Wilting Point
Salinity - Electrical Conductivity	Available Waterholding Capacity
Sodicity Exchangeable Sodium Percentage	Emerson Aggregate Stability
Plant Available Phosphorus	Estimated Bulk Density
Organic Matter

The land degradation survey of NSW (Graham 1988) was designed to provide an estimation of the State affected by various form of land degradation. The survey identified amongst other types of land degradation, 26% of the State was affected by moderate to severe wind erosion, 12 per cent suffered moderate to severe gully erosion, and 18 per cent suffered from moderate to severe soil structure decline. Soil analysis such as Particle Size Analysis, Emerson Aggregate Tests, Organic Matter Content, Soil Dispersibility, and Exchangeable Sodium are very useful to the soil practitioner in assessing the fragility of a soil, and what appropriate land use management is desirable to help mitigate the problem.

To help users understand the agricultural potential of the soil, tests such as Particle Size Analysis, Cation Exchange Capacity, Exchangeable Cations, Phosphorus levels, Soil pH, Electrical Conductivity, Organic Matter Content and Estimated Bulk density are undertaken.

Earthmovers and engineers on the other hand, are interested in the soil's stability for building structures such dams, houses and roads, which all require a stable foundation. Physical tests and interpretations such as the Unified Soil Classification, Volume Expansion, Linear Shrinkage, Emerson Aggregate Test, Particle Size Analysis, Organic Matter Content, Dispersibility and Electrical Conductivity provide a guide to the stability of soil materials.

Interpretation of Soil and Landscape Information for the Users

Soil and landscape information gathered from the interpretation of remotely sensed information, detailed soil and landscape information collected in the field, and laboratory testing of dominant soil types, provides a plethora of information that can be interpreted for many land uses.

Soil laboratory testing, collection and collation of soil properties in the field allow the identification and assessment of a variety of limitations for the use of those soils in the landscape (Table 2). Shrink Swell Potential, Soil Acidity, Soil Salinity, Soil Erodibility (wind and water), Soil Permeability and Soil Fertility are a few of the limitations that will assist the user to identify which areas have soil types that are best suitable for a particular use.

Table 2: Soil Limitations assessed for dominant soil materials of type profiles within each soil landscape unit (1:100 000 mapping recent 1:250 000smapping)

Non-cohesive Soils	High Permeability
Organic Soils	Low Permeability
Periodically Frozen Soils	Water Repellence
Plasticity	Acidification Hazard
Shrink-Swell Potential	Acidity
Soil Fire Hazard	Alkalinity
Soil Structural Decline Hazard	Aluminium Toxicity Potential
Stoniness	Potential Acid Sulfate Soils
Wet Bearing Strength	Salinity Hazard
Erodibility	Plant Available Waterholding Capacity
Hardsetting Surface	Poor Seedbed Conditions
Sodicity/ Dispersion

Soil qualities and limitations combined with landscape characteristics allow the interpretation of a number of broader landscape qualities and limitations for general land use to be assessed (Table 3). Productive Arable Land, Steep Slopes, Mass Movement Risk, Soil Erosion Hazard, Poor Soil Fertility, Foundation Risk, Salinity Risk and Flooding Hazard are a few of the landscape limitations assessed that provide the user with a guide as to the limitations they may encounter.

Table 3: Landscape Qualities and limitations identified for each soil landscape unit (1:100 000 mapping, recent 1:250 000 mapping)

Complex Terrain	Gully Erosion Risk
Mass Movement Hazard	Inherent Sheet Erosion Risk
Rockfall Hazard	Wave Erosion Risk
Rock outcrop	Wind Erosion Hazard
Steep Slopes	Complex Soils
Drainage	Engineering Hazard
Flood Hazard	Dryland/Irrigated Salinity
Permanently High Watertables	Seepage Scalds
Run-on	Dieback
Seasonal Waterlogging	Poor Moisture Availability
Groundwater Pollution Hazard	Woody Weeds
Potential/Known Recharge Area

This assessment of soil material and landscape properties allows the Department of Land and Water Conservation to assess the capability of the land for general urban and rural (cropping and grazing) capability and to provide appropriate recommendations to guide land management.

Users of Soil Landscape Information

It is the comprehensive combination of soil and landscape properties assessed together with the broad range of laboratory tests undertaken that provides the Department of Land and Water Conservation with the ability to provide information to a wide range of users and has been responsible for the success of the soil landscape mapping program. A cost benefit analysis commissioned by the Australian Collaborative Land Evaluation Program (ACIL 1996) identified the Gosford-Lake Macquarie 1:100 000 Soil Landscape Map and Report as having a cost:benefit ratio of 44:1. This is a return of $44 of value to the public for every dollar spent on the project.

Soil landscape information is used by a large number and extremely varied category of client. Department staff use them as a benchmark to ensure environmental impact statements address all the major land resource issues. Environmental consultants use them to provide baseline information for environmental studies. Arborists have used them to identify difficult soils in which to remove trees.

The maps and reports aid the Sydney and Hunter Water authorities to identify where pipes across Sydney may be prone to structural decline due to problematic soil types. Councils have used them to guide tree-planting programs in cleared areas (where there is little information on original vegetation) or to limit development due to the severe limitations present. The maps are used to identify areas in Sydney that require special building foundations to cope with the high shrink-swell soils. They are used by land purchases to identify the location of the best property to buy that is well drained and suited for citrus and cut flower production, or land that is very flat and poorly drained for intensive aquaculture farms.

The above list provides examples of how a few of our customers have used soil landscape information to make more informed land management decisions.

Soil Landscape Derivative Products

Soil Landscape mapping provide ready access to land resource information and general capability for urban and rural uses. But soil landscape maps and reports are limited for clients who are interested in a specific land use. Prior to the advent of GIS, clients had to interpret the information which was often “buried” in the reports and then constantly refer to the soil landscape map to make an assessment of the land they were interested in.

Geographic Information Systems allow interpreted, regional scale, specific purpose maps to be produced quickly and at a reasonable cost in both hardcopy and digital formats. Although not site-specific, being done at a broad scale, these maps can provide the user with a good guide to identify specific land resource issues.

Case studies

Following are three regional examples of soil landscape derivative maps that have been produced by DLWC to provide specific interpreted information to answer key questions on specific land uses.

Case study 1

In 1996, the former Hawkesbury Nepean Catchment Management Trust (HNCMT) approached DLWC to provide information on the capability of the area for Septic Trench on-site effluent disposal (DLWC 1996a). This arose after concerns that many trench disposal systems were failing and adding pollutants to the Hawkesbury Nepean River System. The Department produced a series of 1:100 000 Degree of Limitations for Septic Tank Trench Disposal maps using available soil landscape information. This included maps for Sydney (Chapman & Murphy 1989), Penrith (Bannerman & Hazelton 1992), Gosford Lake-Macquarie (Murphy 1993), Katoomba (King 1994), and Wollongong-Port Hacking (Hazelton & Tille 1990) 1:100 000 map sheets. The maps showed that most of the lower catchment had moderate to severe constraints present. This allowed the HNCMT to target likely areas where such systems are likely to be failing and to develop appropriate solutions.

Case Study 2

In 1997, the Roads and Traffic Authority requested information from DLWC to assist with the planning of the Pacific Highway upgrade between Hexam (just north of Newcastle) and Corindi near the Queensland Border. Soil Landscape mapping along a 10 km wide strip of the highway was put together from published and draft soil landscape mapping. Interpretations of the likely physical limitations for major road construction and farming (Table 4) was provided.

Table 4: Physical Limitations Assessed for Roads and Traffic Authority Corridor (Atkinson et al. 1997)

Physical Limitations for Major Road Construction	Physical Limitations for Farming
Rugged Terrain	Rugged Terrain
Flooding Hazard	Flooding Hazard
Water Erosion Hazard	Water Erosion Hazard
Wind Erosion Hazard	Wind Erosion Hazard
Waterlogging	Waterlogging
Mass Movement Hazard	Mass Movement Hazard
Acid Sulfate Soils	Acid Sulfate Soils
Low Strength Soils	Physical Plant Growth Hazard
Shrink-Swell Soils	Chemical Plant Growth Hazard
Plastic Soils	Soil Workability Hazard
Excavation Difficulty	Soil Salinity

The maps have provided RTA with appropriate land resource information on which to make informed planning decisions. They identify potential hazards for road construction that may be able to be avoided or appropriately managed, while also identifying areas of high capability for farming that should not be disturbed if possible.

Case study 3

Lake Macquarie City Council Area on the Central Coast of NSW sought assistance from DLWC in providing soil erosion information to assist in the review of its Local Environmental Plan. 1:100 000 scale soil landscape mapping from the Gosford Lake-Macquarie (Murphy 1993) and Newcastle (Mattei 1995) mapping as well as slope terrain mapping (Thomas unpubl.) was used as a basis for the assessment of project. The SOILOSS program (Rosewell 1993) was used to derive soil loss estimates for sheet erosion whilst soil landscape laboratory data on Dispersibility and Emerson Aggregate Test were used to identify concentrated flow erosion hazard. The soil erosion hazard and potential source pollution hazard map (DLWC 1997, Figure 2) shows maximum soil loss, erosion hazard, and the months of the year suitable for development based on rainfall distribution modified from Morse and Rosewell (1996). The map is being used to strategically plan for appropriate development in the future and to revise erosion control practices and policies to protect the fragile soils in the shire.

Figure 2. Urban Soil Erosion Hazard and Source Pollution Hazard (extract DLWC 1997)

Providing Soil and Landscape Information in the Future

The Department is working on placing all the soil profile and landscape information (which is currently stored in soil landscape reports) and spatial coverages into SALIS (Milford et al. 2001).

In the past only soil profiles were able to be stored in SALIS. Soil Landscapes were laboriously written by the author in MS Word format and produced in hardcopy. Although this format has proved an efficient way of presenting information in the past, DLWC recognises the growing need to have soil landscape information available in a digital format which can be readily accessed, queried, and linked to map coverages. The Department will soon be undertaking a massive data enhancement project to manually enter published soil landscape attributes into SALIS.

The Department has recently developed and is now trialing an Access database which can be used to enter soil landscape information in the field via a rugged laptop computer. Modifications to SALIS will allow the information to be directly downloaded from the Access database. It is envisaged that soil landscape reports will be built from SALIS or the Access database and published as hardcopy.

Direct access through the Internet will allow users to identify spatially the soil landscapes and soil profile information available and allow users to "drill down" for more detailed information on a specific landscape or soil profile. The Department is also hoping to provide access to coverages of Derivative maps based on landscape limitations and general urban and rural capability through SALIS.

References

ACIL Economics & Policy Pty. Ltd. 1996, The Development of an Economic Framework and Instruments for Assessing the Benefits and Costs of Land Resource Assessment in Australia, Report to the Australian Collaborative Land Evaluation Program (ACLEP), Canberra.

Atkinson, G. 1993, ‘Soil Materials – a Layer Based Approach to Soil Description and Classification’, Catena 20:pp411-418.

Atkinson, G., Eddie, M.W., Matthei L.E., Milford H.B. & Murphy, C.L. 1997, Soil Landscapes of the Pacific Highway Corridor Hexam to Corindi, Department of Land and Water Conservation, Grafton.

Bannerman, S.M & Hazelton, P.A 1990, Soil Landscapes of the Penrith 1:100 000 Sheet (Map and Report), Soil Conservation Service of NSW, Sydney.

Chapman, G.A & Murphy, C.L. 1989, Soil Landscapes of the Sydney 1:100 000 Sheet (Map and Report), Soil Conservation Service of NSW, Sydney.

Department of Land & Water Conservation (DLWC) 1996, Degree of Limitations for Septic Tank Trench Disposal, Series of 1:100 000 scale Soil Landscape Derivative Maps prepared for the Hawkesbury Nepean Catchment Management Trust for the lower Hawkesbury-Nepean Catchment, DLWC, Sydney.

Department of Land and Water Conservation (DLWC) 1997, City of Coffs Harbour Urban Capability Dorrigo/Coffs Harbour Soil Landscape Derivative Map, prepared for Coffs Harbour City Council, DLWC, Sydney.

Department of Land and Water Conservation (DLWC) 1997, Soil Erosion Hazard Map Lake Macquarie Council Area, Prepared for Lake Macquarie Council, DLWC, Maitland.

Graham, O.P. 1988, Land Degradation Survey of New South Wales, Soil Conservation Service of NSW, Sydney.

Hazelton, P.A. & Tille, P.J. 1993, Soil Landscapes of the Wollongong-Port Hacking 1:100 000 Sheets (Map and Report), Soil Conservation Service of NSW, Sydney.

King, D.P. 1993, Soil Landscapes of the Katoomba 1:100 000 Sheet (Map and Report), Department of Conservation and Land Management, Sydney.

Mattei, L.E. 1995, Soil Landscapes of the Newcastle 1:100 000 sheet (Map and Report), Department of Land and Water Conservation, Sydney.

Milford, H.B., Simons, N.A., Chapman, G.A., Murphy, C.L., McGaw, A.J.E., Edye, J.A. & Macleod, A.P. 2001, 'The Soil Profile Attribute Data Environment (SPADE): NSW Soil Information On-line', in Proceedings of New South Wales Government’s Spatial Soil and Landscape Products, DLWC, paper presented to the Geospatial Information and Agriculture 5^th Annual Symposium, Sydney.

Morse, R.J and Rosewell, C.J. 1996, 'Use of the Universal Soil Loss Equation as a tool in the Management of Urban Lands', in Proceedings of the Annual International Erosion Association (Australasia) and Stormwater Industry Association Conference on Soil and Water Management for Urban Development, 9 - 13th September 1996, Sydney.

Murphy, C.L. 1993, Soil Landscapes of the Gosford Lake Macquarie 1:100 000 Sheet (Map and Report), DLWC, Sydney.

Northcote, K.H. 1978, 'Soils and Landuse', in Atlas of Australian Resources, Division of National Mapping, Canberra.

Rosewell, C.J. 1993, SOILOSS: A Program to assist in the Selection of Management Practices to Reduce Erosion, Technical Handbook No. 11 (2nd edn), DLWC, Sydney.

Thomas, D. (unpubl.), Slope Terrain Mapping of the Lake Macquarie City Council Area, 1:25 000 scale map, DLWC, Newcastle.

Walker, P.J. 1991, Land Systems of Western NSW, Technical Report No. 25, Soil Conservation Service, Sydney.