Guideline for landslide susceptibility, hazard and risk zoning for land use management

There are a number of natural hazards which are relevant to urban, residential, rural and undeveloped property throughout Australia. These include flooding, bush fire, coastal processes and landslides. This guideline addresses landslide susceptibility, hazard and risk zoning for land use planning.

In 1998, following the Thredbo landslide in which 18 persons were killed, the Institution of Engineers Australia and the Australian Geomechanics Society (AGS) formed a Taskforce on the Review of Landslides and Hillside Construction Standards. The Taskforce after reviewing the Australian Standards and relevant codes on landslides and hillside construction concluded that they were inadequate and recommended the production of four guidelines:

• Landslide hazard zoning for urban areas, roads and railways
• Slope management
• Site investigations, design, construction and maintenance
• Landslide risk assessment

The Australian Geomechanics Society “Landslide Risk Management Concepts and Guidelines”, already under preparation at the time of the Thredbo landslide, was published in 2000 (AGS 2000, 2002). This document touched on all four areas but mainly addressed the fourth. It is used extensively throughout Australia.

In 2005 the Australian Geomechanics Society in collaboration with the Sydney Coastal Councils Group, was successful in obtaining funding under the Australian governments’ National Disaster Mitigation Program (NDMP) to further the development of the guidelines which had been recommended by the Taskforce. Work to prepare these guidelines has progressed in 2005 and 2006 and has involved extensive consultation with those involved in landslide mapping for land
use planning and the application of such mapping for planning in local government.

This Guideline for Landslide Susceptibility, Hazard and Risk Zoning for Land Use Planning provides:

• Definitions and terminology.
• Description of the types and levels of landslide zoning.
• Guidance on where landslide zoning and land use planning is necessary to account for landslides.
• Definitions of levels of zoning and suggested scales for zoning maps taking into account the needs and objectives of land-use planners and regulators and the purpose of the zoning.
• Guidance on the information required for different levels of zoning taking account the types of landslides.
• Guidance on the reliability, validity and limitations of the investigation methods.
• Advice on the required qualifications of the persons carrying out landslide zoning and advice on the preparation of a brief for consultants to conduct landslide zoning for land use planning.

The guideline considers landslides occurring in natural slopes and from failure of constructed slopes including cuts, fills and retaining walls and the impact of the landslides on the area to be zoned. It is intended for use by local, state and national government officials, geotechnical professionals, land use planners and project managers.

This guideline has been developed at the same time as similar guidelines prepared by the JTC-1 The Joint International Committee on Landslides and Engineered Slopes and there has been an interchange of concepts and detailed inputs between the two guidelines.

Through the NDMP, Australian governments (at Commonwealth, State and Local Government levels) are also funding the development of a Practice Note Guideline (AGS 2007c) to supersede the Landslide Risk Management Guideline (AGS 2000, AGS 2002), and a series of GeoGuides on Slope Management and Maintenance (AGS 2007e).