Effective urban landslide hazard assessment

Landslide hazard assessment is a vitally important component of any strategy for the management of risk of instability in hilly areas. Within many urban areas, reactivation of landslides is an important component of risk. Yet, most qualitative approaches do not differentiate between the hazard of individual landslides. Two quantitative approaches are introduced in this paper both of which utilise GISbased accurate maps of geology and landslip as well as a landslide database. The first method is based on historical recurrence of individual landslides. The second method is based on monitoring of subsurface shear movements, and their relationships to rainfall. Both methods can provide reliable information on hazard. Hazard ranking based on the first method has been validated in the Greater Wollongong area of the State of New South Wales in Australia. This paper does not address the potential hazard associated with sites which are recognised to be stable with no known history of instability

Sydney Basin Landslide Susceptibility, NSW, Australia

University of Wollongong GIS-based Landslide Inventory has been expanded to facilitate reliable modeling of landslide susceptibility and hazard zonation over the wider Sydney Basin area. Landslide inventory development is underway after designing a state of the art inventory structure following a comprehensive international literature review. The alphanumerical as well as spatial data bases of landslides have been updated after field verification of landslides in Sydney and Newcastle as the stepping stone for the wider Sydney Basin area landslide susceptibility model development. In the lead up to this, landslide susceptibility modeling in two smaller sub-regions of Sydney (Wollongong Local Government Area and the Picton area) has been undertaken by the Landslide Research Team at the University of Wollongong. In tandem with the development of the landslide inventory, new tools and methods have been developed to aid application of Data Mining techniques within a GIS framework to obtain more reliable modeling, analysis and synthesis. The main aim of this paper is to report the latest advances in landslide inventory development, preparation and compilation of data for the modeling work

ArcGIS V.10 landslide susceptibility data mining add-in tool integrating data mining and GIS techniques to model landslide susceptibility

Landslide susceptibility modeling is an essential early step towards managing landslide risk. A minimum of $4.8 million is lost due to landslide related damages every year in Illawara region of Australia. At present, Data mining and knowledge discovery techniques are becoming popular in building landslide susceptibility models due to their enhanced predictive performances. Until now, the lack of tools to undertake data extraction and making the predictions have limited the applicability of this novel technique in landslide model building. This paper discusses the development of the LSDM (Landslide Susceptibility Data Mining) toolbar which was designed to utilize machine learning techniques within a GIS environment by coupling GIS and data mining software (See5) capabilities. The software development kit available with ArcGIS v.10 has been utilized in developing the toolbar add-in. The fundamental tasks; data preparation, model optimizing, derivation of decision trees, predictions and validation are all performed using the individual controls available in the toolbar. This tool automates the entire model building process and in preparation of training data and producing outcomes that are compliant with both national and international Landslide Risk management guidelines

Monitoring and management of a landslide on the main motorway between Sydney and Wollongong, NSW Australia

The Mount Ousley Road section of the M1 Princes Motorway is one of the main transportation links between the cities of Sydney and Wollongong, New South Wales (NSW), on the east coast of Australia. The road was originally constructed during World War II as an alternative defense route and now supports approximately 50,000 vehicle movements per day. The road negotiates 4.4km of the Illawarra escarpment at grades up to 1:8. A section of the road traverses the largest landslide in the Wollongong Landslide Inventory, Site 141. The surface area of the landslide is 67,000m2, which includes a 350m section of Mount Ousley Road affecting all six lanes. The landslide is a deep seated, episodically active translational debris slide with a maximum depth of sliding of 20.5m. The landslide is managed by a continuous real-time monitoring system and is dewatered by nine 30m deep pumping wells to maintain lower ground water levels. The dewatering system was installed in 1988, but has been upgraded three times to enhance serviceability and most recently to provide a further 10 years of landslide management. This paper presents some analysis of data collected from the continuous real-time monitoring system established by the University of Wollongong Landslide Research Team, in partnership with NSW Government organizations including Roads and Maritime Services (RMS) and NSW Public Works and highlights the troubleshooting work associated. Periodic and continuous monitoring has been successful in identifying needs for the dewatering system upgrades, assessing thresholds for slope movement and evaluating the overall effectiveness of the remedial measures installed

Slope instability, hazard and risk associated with a rainstorm event - a case study

Over the last few decades there has been an increasing awareness of landslide hazard and risk in many coastal regions of Australia. Urban communities in hilly areas are, from time to time, adversely affected by rainfall-induced landsliding. However, acute awareness of hazard may be absent during periods between significant rainstorm events. In general, the serious consequences of landslides to property and life have been underestimated in Australia. It is now known that at least 80 deaths can be attributed to a number of landslides (Leiba, 1998). Some of these events have focussed the attention of the public, the most important being the Thredbo tragedy associated with the loss of 18 lives at the Thredbo in the Snowy Mountains region of New South Wales on July 30, 1997. That landslide was, however, not the consequence of a rainstorm event unlike most of the slope instability that occurs in Australia. This paper is concerned primarily with landsliding associated with the August, 1998 rainstorm event which affected the hilly suburbs of Wollongong along the Illawarra escarpment south of Sydney (Fig.1). The importance of protecting the escarpment is highlighted by the report of a recent commission of enquiry ordered by the State Government of New South Wales in recognition of widespread and sustained public concern (Commission of Inquiry, 1999)

A landslide database for landslide hazard assessment

Assessing the hazard and risk of slope instability and landsliding requires a consideration of basic geological and geotechnical factors which control stability as well as external agents or events which decrease stability and which may trigger landsliding. Prediction of slope performance is difficult and it is, therefore, considered appropriate to develop approaches for hazard and risk assessment. This paper is concerned primarily with one important aspect or element of such an approach. The essential and desirable features of a landslide database are outlined with particular reference to an urban area in New South Wales, Australia. The procedures and processes for developing such a database are introduced and attention is given to uncertainties which are associated with the processes of identification, mapping and describing landslide sites. Several features of a database which was recently developed are described and discussed

Resilience and sustainability in the management of landslides

There are many regions worldwide which are susceptible to landslides, which cause loss of life and adverse impacts to infrastructure, environment and communities. Landslides are often triggered by exceptional rainfall and large-magnitude earthquakes. A range of strategies and methods have been developed to mitigate the occurrence of landslides and to reduce their impact, including risk to human safety. The adopted approaches and systems must be sustainable and resilient in relation to the communities that are at risk. This paper refers to an Australian regional case study of urban landslide management in the Wollongong region, New South Wales. The research carried out by the authors over two decades at the University of Wollongong has enhanced the resilience and sustainability of landslide management in the region. Reference is also made to Hong Kong as a case study of urban regional landslide practice, with particular reference to the upgrading of man-made slopes

Quantitative landslide hazard assessment in an urban area

Before decisions can be made concerning the management of sloping areas subject to landsliding, systematic approaches for hazard and risk assessment must be developed. This paper is limited to a discussion of hazard assessment and describes quantitative approaches which have been developed for existing landslides. Consideration of areas of potential landsliding is outside the scope of the paper. The approach described here is based on (a) monitoring of subsurface shear movement at instrumented sites and (b) the percentage exceedance time of cumulative rainfalls considering different selected periods of antecedent rainfall. This approach is used in conjunction with a simpler approach, described in a previous paper, which is based on the historical frequency of landsliding. Numerical values of hazard thus calculated enable a ranking of all landslides to be made in descending order of hazard levels. The approach has been validated in the particular study area considered in this paper, ie, the northern suburbs of the City of Wollongong

An Inventory of Landslides within the Sydney Basin to aid the development of a refined Susceptibility Zoning

The University of Wollongong GIS-based Landslide Inventory is currently being expanded from its Illawarra centric coverage (664 landslides) to include the 31,000km2 geological extent of the Sydney Basin and ultimately all of New South Wales (hereafter this inventory will be referred to as the NSW LI). In 1998, this inventory stood at 319 sites of instability and in 2010 it had grown to 616 landslides. The population of the Sydney Basin in 2006 was approximately 4.9 million people, representing approximately one quarter of the population of Australia. When this current phase of expansion is completed, the NSW LI will include up to 1600 landslide sites, and it will continue to expand over the next few years. The NSW LI is being redesigned following an international literature review and is being re-compiled into an ESRI ArcGIS v10 Geodatabase. This work is being undertaken in the Faculty of Engineering at the University of Wollongong with a joint Faculty of Engineering and SMART doctoral research scholarship that commenced in late 2011. In tandem with this development, additional GIS-based datasets are being compiled to facilitate the refined modelling of Landslide Susceptibility across the Sydney Basin Region

Landslide risk assessment - development of a hazard consequence approach

Several Landslide Hazard and Risk Assessment methods have been developed and used in the State of New South Wales (NSW), Australia. The Rail Services Australia Geotechnical Services and the Roads and Traffic Authority of NSW have each developed Risk Assessment procedures suitable to their own specific needs. A generic risk management methodology is presented in the Australian Standard/New Zealand Standard (AS/NZS) 4360:1995. An approach similar to the (AS/NZS) 4360:1995 Risk Management Standard has been applied by a NSW State Emergency Services geotechnical team (which included one of the writers) to 191 problem sites in the Wollongong Area, following a major rainstorm event in August 1998, (GTR, 1998). The writers at the University of Wollongong (UOW) are developing a more comprehensive hazardconsequence approach. This has required careful and precise definitions of the terms and parameters being used. It is the writers\u27 intention that this will lead to effective, efficient and consistent assessments of hazard and risk. Field Data Sheets based on the stated concepts are being developed and tested at several field sites. The formalisation of field data collection will provide a good mechanism for consistent data capture. Data collected in this manner is most suited for management in a database environment