Land: Mass movement
- Authors
- Reviewer
- Key findings
- Indicators and summary of status
- Importance
- Pressure and condition
- Response
- References
Authors
Andrew Hammond and Nate Peterson, School of Natural Resource Sciences, Queensland University of Technology, Brisbane
Reviewer
Leonard Cranfield, Department of Mines and Energy
Key findings
- The overall incidence of mass movement (landslips) recorded in Queensland during the 2004-06 reporting period has been low as a result of lower than expected rainfall patterns in this period.
- Most of the 78 landslide events recorded on the Geoscience Australia Landslide Database (Figure 4.5) were triggered by high-intensity rainfall events such as tropical cyclones over short time periods on susceptible soils, rock types and geological structures (EPA 1999, 2003). These include landslides associated with tropical cyclone Grace, which led to the closure in March 2004 of the highway between Cairns and Port Douglas, and the widely publicised Currumbin Hill landslip on the Gold Coast in July 2005.
- Continued high levels of population growth in the coastal cities, particularly in south-east Queensland, have led to increasing pressure to develop steeper coastal upland areas for a range of residential and other uses. The potential for mass movement, accelerated erosion and sedimentation from these areas is likely to increase in the future, because they receive higher levels of rainfall than adjacent areas.
- Before site development, professional advice should be sought from the Department of Natural Resources and Water, the Department of Mines and Energy (Geological Survey of Queensland), Geoscience Australia, local shire councils and geotechnical consultants to identify pertinent geotechnical issues and provide the best approach for risk assessment and management.
- One of the major challenges for state and local government is to delineate all areas within the state that are at risk and record this information on a geographic information system (GIS) database. Managers can then use this information to implement appropriate operative strategies that will not place people, infrastructures or the environment at risk of loss, failure or degradation, respectively.
Indicators and summary of status
Indicator |
Status of indicator |
Areas affected by soil mass movement |
In the previous reporting period areas of potential mass movement were identified in the more densely populated areas of south-east Queensland and around Cairns under Geoscience Australia's Geohazard Program, the Cities Project. This formed Australia's contribution to the International Decade for Natural Disaster Reduction (IDNDR). Outcomes of this project have been incorporated into the Integrated Planning Act 1997 and its various amendments. Little extension of the Cities Project into other parts of the state has occurred during the current reporting period other than a limited coverage of some of the basalt plateaux in south-east Queensland. The results of work undertaken by private consultants are not readily available. [ |
Area of vegetation clearance on slopes |
No specific analyses of historical aerial photographic and satellite imagery have been undertaken for slopes other than the regulatory monitoring of vegetation clearance to comply with the Vegetation Management Act 1997 . [ |
Areas zoned as being potentially hazardous |
Limited coverage by state and local government. In the more densely populated areas such as Cairns and coastal cities in south-east Queensland, development is subject to Integrated Planning Act 1997 approval. [ |
]
Figure 4.5 Landslide locations and elevation, 2004-06
Source: Geoscience Australia 2007
Importance
Mass movement is triggered by natural causes such as geological predisposition to failure, meteorological phenomena and/or human activities. Almost half of the reported incidences result from infrastructure such as buildings, roads, railways and pipelines, vegetation clearance and agricultural pursuits. Deleterious effects include loss of productivity, property and infrastructure, injury to or death of people, and environmental (landscape) degradation. This issue is often a manageable hazard: the identification of susceptible areas, combined with adequate planning, public education and risk management, can mitigate the more deleterious consequences described.
In Queensland, the following forms of mass movement have been identified: rotational slides, debris and earth flows, and rock falls in a range of rock types (EPA 2003). Slope failure often results from a complex interplay of factors including:
- the amount and intensity of rainfall, particularly high-intensity rainfall over short periods that fills soil pores and increases pore water pressures;
- vegetation clearance and replacement of natural vegetation by shallow-rooted species more susceptible to erosion; and
- rock, soil and sediment types (geologies) susceptible to failure and flowage.
The impacts of mass movement cost the state many millions of dollars annually; the exact cost has not been adequately quantified. The effects over this reporting period have been less dramatic and costly than those resulting from other natural hazards, such as cyclones, because of the prolonged drought conditions and the implementation of controls on broad-scale vegetation clearance. This will change if or when the climate reverts to a wetter cycle.
Pressure and condition
Pressures influencing mass movement
Queensland 's coastal cities have experienced some of the highest population growth rates in Australia. This growth is strongest in south-east Queensland, which absorbs 80% of the state's new residents. The state has experienced increased developmental pressure to provide housing, infrastructure and other essential services along the coastal fringe. Much of this development has proceeded inland towards the hillslopes, escarpments and eastern flanks of the Great Dividing Range. No data relating to the total area of land that may be susceptible to mass movement are currently available.
The incidence of broadscale vegetation clearance on sloping and higher ground, a matter of concern in previous reporting periods, is now of less concern following the implementation of the Vegetation Management Act 1997 . Of concern, however, are those areas that have already been cleared and developed. Binding root material is either absent or is in the process of degrading, which may impinge upon slope stability.
Response
Response to growth
The unprecedented population growth along the coastal fringe of south-east Queensland and in other coastal cities has led to continued expansion of suburban and infrastructural developments. In response to these pressures the Office of Urban Management in the Department of Local Government, Planning, Sport and Recreation has implemented the South East Queensland Regional Plan 2005-2026 whereby growth will be monitored and managed in compliance with the Integrated Planning Act 1997 and its latest amendments. A critical issue is the way management plans and legislation will deal with vegetation clearance on sloping ground.
Since the previous reporting period landholders and the community, with funds from the Natural Heritage Trust, have continued the revegetation of slopes susceptible to soil erosion, which includes mass movement. Specific data pertaining to the mass movement issue-for example, locations, areas revegetated and costs incurred-have not been formally recorded. Currently, no government agency has prime responsibility for collecting such data.
Legislative responses
Geoscience Australia, in collaboration with state government agencies, has initiated a number of scientific and community-based programs since 2003 to make communities safer and better informed about risk-reduction strategies. Examples include the Cities and Critical Infrastructure Project, the National Risk Assessment Project, the Risk Assessment Methods Project and the Natural Disaster Mitigation Program (Granger and Hayne 2001; Granger et al. 1999; Granger and Michael-Leiba 2001).
The Department of Emergency Services and other stakeholders undertook a review of the Disaster Organisation Act 1975 , resulting in its replacement by the Disaster Management Act 2003 (DM Act) (DES 2003) in March 2004. The DM Act includes a focus on disaster management. These legislative responses were tested after the Currumbin Hill landslip on the Gold Coast in July 2005. The Department of Emergency Services, as custodian of the Queensland Disaster Management System (QDMS), declared a Disaster Situation under the DM Act. All three levels of this multi-tiered system-state and local government as well as the Gold Coast Disaster District community-were activated to ensure a coordinated and effective capability to prevent, prepare for, respond to and recover from this disaster. The local District Disaster Management Group (DDMG) met regularly to discuss issues facing residents and was responsible for initiating reports and recommendations from geotechnical and structural engineers concerning the safety of affected land and buildings (Serodio 2005).
References
Cranfield, L.C., Grayson, R.G. and Tuttle, J.S. (compilers) 2006, Slope stability on basalt plateaux in southeast Queensland (a series of reports on constraints to closer development and an ARCGIS and MAPINFO GIS version), Department of Natural Resources, Mines and Water, Brisbane.
DES 2003, Disaster Management Act 2003 , Department of Emergency Services, Queensland, viewed 18 December 2006, www.disaster.qld.gov.au.
EPA 1999, State of the Environment Queensland 1999 , Environmental Protection Agency, Brisbane.
EPA 2003, State of the Environment Queensland 2003 , Environmental Protection Agency, Brisbane.
Geoscience Australia 2007, National Landslide Database , viewed 12 December 2006, www.ga.gov.au/oracle/landslid/landsl_online.jsp.
Granger, K. and Hayne, M. 2001, Natural Hazards and the Risks They Pose to South-East Queensland , Department of Industry, Science and Resources, Canberra.
Granger, K., Jones, T., Michael-Leiba, M. and Scott, G. 1999, Community Risk Assessment in Cairns: A Multi-hazard Risk Assessment , Department of Industry, Science and Resources, Canberra.
Granger, K. and Michael-Leiba, M. 2001, Community Risk Assessment in Gladstone: A Multi-hazard Risk Assessment , Department of Industry, Science and Resources, Canberra.
Serodio, Y. 2005, 'Currumbin landslip, emergency test for disaster system', Emergency Magazine August 2005, pp. 14-17.
Return to State of the Environment Queensland 2007 content page
Last reviewed 16 May 2011
Last updated 4 September 2007