D. I. Smith

Impediments to using GIS for real-time disaster decision support

This paper examines and evaluates the application of GIS for cyclone disaster risk management, focusing on observations from a real-time emergency management disaster scenario held in Mackay in far north Queensland, Australia. Results from scenario observations and post-scenario interviews with risk managers highlight the limitations of GIS for real-time disaster planning. Limitations include the scale of spatial data and its suitability for regional-scale decision making and the risk managers requirement for temporal detail rather than spatial detail. The paper also examines non-technical GIS impediments including custodianship and system implementation for disaster risk management. Findings have shown that the use of GIS for urban disaster risk management can readily fail due to implementation, user access and knowledge impediments, in addition to the availability of spatial data and models.

Actual and potential flood damage: a case study for urban Lismore, NSW, Australia

Abstract An urban land use survey of Lismore, New South Wales, was undertaken to assess the character of buildings affected by the major flood of March 1974. A questionnaire survey was then carried out on a sample of 140 residential houses, 212 commercial establishments and all 26 industrial concerns in the flood-prone area to assess actual flood damage. Potential flood damage was estimated by a professional valuer and by questionnaire information. Comparison of actual and potential damage showed that actual damage was only 52.4 per cent of potential damage in the residential sector, 23.5 per cent in the commercial sector and 6.1 per cent in the industrial sector. It is concluded that the relatively low levels of actual damage reflect the high degree of preparedness by the urban population, particularly in the commercial and urban sector. The results indicate the level of damage reduction feasible given adequate flood warning schemes and appropriate adjustments by the community.

Riding the storm: a comparison of uncertainty modelling techniques for storm surge risk management

Abstract In tropical Australia the risk from tropical cyclone disaster is significant and increasing, since much of the population inhabits low-lying coastal regions, which are experiencing further rapid urbanization. This paper examines GIS methodologies for predicting flood risk to urban communities that are at risk from cyclone-induced storm surge inundation, using as a case study the coastal community of Cairns. The methodologies attempt to account for the uncertainties inherent in risk predictions. Two uncertainty modelling techniques – the grid cell uncertainty model and the standard normal probability model – are implemented and evaluated in the context of improved risk management decision-making. Results show that, spatially, the results are almost identical, and for evacuation decision-making should be treated as such. The results of the methodologies confirm that the low-lying nature of Cairns contributes to the overall risk and that relatively high-frequency and small-magnitude surge events can cause major inundations. However, the techniques have very different computational overheads and implementation efficiencies and these are discussed in detail. The paper concludes by examining the implications of uncertainty modelling for risk management decision-making.

Flood history of the limestone ranges in the Kimberley region, Western Australia

Abstract Palaeoflood studies enable estimates to be made of the age and magnitude of past flood events. The key points are the location, stratigraphy and age of slackwater deposits. These are often best preserved in gorge sections and typically occur in association with side gorges, caves and on terraces. The slackwater deposits are allocated to specific flood events and the associated discharges are estimated from step-backwater modelling methods. Absolute dating techniques are used to assess the age of the individual slackwater deposit sequences. Studies of this kind were undertaken for Windjana Gorge in the Kimberley region of northern West Australia. The fieldwork was a contribution to the Kimberley Research Project 1988, jointly organized by the Royal Geographical and Linnean Societies. A sequence of five slackwater deposits was established and palaeodischarges calculated. Both radiocarbon and thermoluminescence dating were used to establish a chronology for the deposits, which varied in age from a few years to over 2000 years. The palaeodischarges were compared with estimates of extreme discharges obtained using other hydrological methods. For remote areas, river discharge records are of short duration and variable quality. Therefore, the use of statistical techniques based on the extrapolation of discharge and frequency are of doubtful value. The palaeodischarges for Windjana Gorge were also compared with estimates of the unit area runoff for extreme floods in Australia and worldwide. There are indications that palaeoflood studies offer a useful and independent approach to the estimation of past extreme flows. The method is especially valuable for regions that have only sparse hydrological records.

The worthwhileness of dam failure mitigation: an Australian example

Abstract In many parts of the world there are high-hazard dams that do not meet national and international safety standards. For many of these the potential risk to life will result in structural upgrading. It is, however, instructive to analyse the tangible damages that would be averted by mitigation against failure. The potential effects of a failure of the Googong Dam in New South Wales on the downstream cities of Queanbeyan and Canberra are used to illustrate the problems and methodology. The estimates of direct damage are based upon detailed building surveys and are presented for a range of floods, with and without dam failure. The problem of building collapse due to enhanced depth and velocity from dam-failure flooding is discussed, together with a qualitative assessment of indirect losses. The significance of well-designed flood warning systems in reducing potential loss of life is stressed. For Googong Dam the upgrading of the spillway to pass the probable maximum flood is considered to be worthwhile solely in terms of tangible damage averted.