TECHNICAL REPORT WC/00/20 Overseas Geology Series DFID Project No. R5563 Volcanic hazard mapping for development planning P N Dunkley and S R Young BGS International® British Geological Survey Keyworth Nottingham NG12 5GG United Kingdom TECHNICAL REPORT WC/00/20 Overseas Geology Series DFID Project No. R5563 Volcanic hazard mapping for development planning P N Dunkley and S R Young With contributions by R A Nicholson A report prepared for the Department for International Development (DFID) under the Knowledge and Research Programme as part of the UK provision of technical assistance to developing countries. The views expressed are not necessarily those of DFID. DFID classification : Subsector: Geoscience Theme: G2 - Improve geological, geochemical and geotechnical hazard avoidance strategies in development planning Project title: Volcanic hazard mapping for development planning Project reference: R5563 Bibliographic reference: Dunkley, P N and Young, S R. 2000 Volcanic hazard mapping for development planning. BGS Technical Report WC/00/20 Keywords: volcanic hazards, risk mitigation, hazard mapping Front cover illustration: Perspective view of a digital terrain model of volcán Villarrica draped with volcanic hazard zones © NERC 2000 Keyworth, Nottingham, British Geological Survey, 2000 BGS Technical Report WC/00/20 Volcanic Hazard Mapping for Development Planning _________________________________________________________________________________________________________________ EXECUTIVE SUMMARY It is estimated that more than 500 million people are at risk from the hazards posed by volcanoes. The potential therefore exists for major loss of life and damage to property in a number of regions, especially where large urban areas occur in proximity to dangerous volcanoes. As population pressures intensify, hazardous areas are likely to become increasingly developed, so raising the level of risk. In the case of major eruptions, losses to property, infrastructure and economic activity can run into hundreds of millions or even billions of dollars and high casualty rates may be inflicted, although even relatively minor activity can have adverse impacts through the disruption of economic activity, lack of investor confidence and harm to health. Eruptions may therefore seriously disrupt development plans by causing burdensome economic setbacks that divert precious resources into relief and reconstruction, which would otherwise be destined for development. This can be severe in developing nations with small, poorly diversified economies. Because disasters are inextricably linked to human and economic development, the most efficient way to prevent them or reduce their impact is to take natural hazards into routine consideration when formulating development plans. An integrated approach to hazard management and development planning will also result in more realistic cost-benefit analyses of potential development projects, by taking into account the estimated costs and benefits of hazard reduction measures. Although numerous volcanoes pose a high level of risk in many developing countries, relatively few have been the subject of hazard assessments. The main objective of the project has therefore been the development and evaluation of rapid and cost-effective methods for volcanic hazard mapping in developing countries. Volcanic hazard mapping methods are described and the role that these have to play within the broader framework of risk reduction is discussed. With respect to this framework, the recurring problem of the failure of uptake and utilization of volcanic hazard information is examined within the context of the communications interface between civil authorities and volcanologists, and recommendations are made for improving the efficiency of the process through a number of measures. Two volcanic hazard assessment case studies were undertaken by the project on the Chilean volcanoes of Nevados de Chillán and Villarrica. A detailed assessment of Nevados de Chillán was carried out over several years by a team of specialists using a conventional approach, whilst a much more rapid and less expensive methodology was applied by a single geologist at Villarrica. These two studies, together with a pre-existing detailed assessment of Villarrica, allow the merits of rapid volcanic hazard assessment methods and conventional methods to be compared. Both case studies used reconnaissance survey techniques based upon the interpretation of aerial photographs and satellite images, and developed simple geographical information systems and digital cartographic methods for the production and presentation of hazard maps in forms which should be more easily visualised and understood by civil authorities and decision makers involved in the downstream processes of volcanic risk reduction. I BGS Technical Report WC/00/20 Volcanic Hazard Mapping for Development Planning _________________________________________________________________________________________________________________ The project has shown that it is possible to produce simple but effective hazard maps using techniques that are considerably more rapid and less expensive than conventional methods. The level of detail of hazard mapping is only slightly compromised using these methods compared with conventional assessments, and is certainly sufficiently accurate and informative to be fit for the purpose of development planning and disaster preparedness. The benefits of using hazard maps of this kind to reduce volcanic risk within the framework of development planning and civil protection are potentially very large, when compared with the disastrous impacts that volcanic activity can have on the vulnerable infrastructure of developing countries. A third case study was undertaken on volcán Irazú, situated close to the Costa Rican capital of San José. Various aspects of the 1963-65 eruption of Irazú were investigated, including the economic impact of the eruption and the vulnerability of the human population, buildings and infrastructure to the effects of volcanic ash and mudflows. Proposals were made by the sub- project for reducing the risks during future eruptions at Irazú through better community preparedness. The Montserrat eruption has provided a test bed for a number of aspects of volcano hazard and risk assessment addressed by the project. Experience gained through the project has been applied to the Montserrat crisis, leading to successful hazard and risk assessment and the provision of pertinent and timely advice to civil authorities. Whilst the project has demonstrated that the methods exist for producing effective and cost- beneficial hazard and risk assessments by rapid methods, the problem remains of convincing civil authorities that such assessments are necessary in the first place, bearing in mind the reluctance to implement risk-reduction policies under dormant volcanic conditions which normally prevail at most volcanoes. II BGS Technical Report WC/00/20 Volcanic Hazard Mapping for Development Planning _________________________________________________________________________________________________________________ LIST OF CONTENTS 1. INTRODUCTION ............................................................................................................. 1 1.1 Objectives of the project .......................................................................................................................... 1 1.2 Structure of the report .............................................................................................................................. 2 2. NATURAL HAZARD ASSESSMENT IN DEVELOPMENT PLANNING ................ 4 2.1 Natural hazards and disasters in developing countries ............................................................................ 4 2.2 Disaster reduction measures: prevention, preparedness and emergency response .................................. 5 2.3 Hazard, vulnerability and risk assessment ............................................................................................... 6 2.3.1 Hazard assessment .......................................................................................................................... 6 2.3.2 Vulnerability analysis ...................................................................................................................... 7 2.3.3 Risk assessment ............................................................................................................................... 8 2.4 Planners and the interface between hazard mapping and risk assessment ............................................... 9 2.5 Digital cartography and geographical information systems .................................................................. 10 2.5.1 Digital mapping techniques used in the case studies of this project .............................................. 11 3. GENERAL CONSIDERATIONS OF VOLCANIC HAZARDS AND HAZARD ASSESSMENTS .............................................................................................................. 13 3.1 Size and frequency of volcanic eruptions .............................................................................................. 13 3.2 The impact of volcanic disasters ............................................................................................................ 16 3.2.1 Casualties ...................................................................................................................................... 16 3.2.2 Economic impact ..........................................................................................................................