Flood Defence`2002, Wu et al.(eds) 2002 Science Press, New York Ltd., ISBN 7-03-008310-5 Risk Assessment and Zoning of Flood Damage Caused by Heavy Rainfall in Yamaguchi Prefecture, Japan Jiquan Zhang a , Norio Okada b , Hirokazu Tatano b and Seiji Hayakawa c a Post Doctoral Fellow of JSPS, Foreign Collaborative Researcher of Disaster Prevention Research Institute, Kyoto University, Uji 611-0011, Japan, Northeast Normal University, China E-mail: zhang@imdr.dpri.kyoto-u.ac.jp b Disaster Prevention Research Institute, Kyoto University, Uji 611-0011, Japan c Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan Abstract: This paper presents the methodology and procedure for risk assessment and zoning of flood damage caused by heavy rainfall based on the “macro-zonation concept” in which regional macro-information such as meteorological triggering factor, natural and socioeconomic factors contributing to flood damage generating, and historical flood damages etc. is considered. In this study, Yamaguchi Prefecture in Japan is selected and its flood damage risk caused by heavy rainfall is assessed and zoned based on statistical data related to maro information. Keywords: flood damage, heavy rainfall, weighted comprehensive analysis, gray correlation analysis, AHP, risk assessment 1. INTRODUCTION The flood damage caused by heavy rainfall is one of the most important natural disasters in Japan, and affects human life and social development. Moreover, the frequency of its occurrence and disaster risk are considered to increase recently with global warming. Therefore, the study on risk assessment and zoning of flood damage caused by heavy rainfall is very important to make strategies for preventing and mitigating flood damage caused by heavy rainfall. Risk assessment of natural disasters is defined as the assessment on both the probability of natural disaster occurrence and the degree of danger caused by natural disasters (Zhang and Hayakawa, 1999). In Japan, previous studies on risk assessment of flood damage caused by heavy rainfall include those by Okimura and Sugimoto (1995), Suzuki et al. (1994) and Mizutani (1993) etc. They are based on limited factors contributing to flood damage. We assume that natural disasters result from the interaction of both physical impact (hazard) and human and environmental vulnerability (Mizutani, 1993; Carrara and Guzzetti, 1993). The factors which contribute to flood damage triggered by heavy rainfall include broad aspects related to meteorological triggering factor, natural factors in connection with the earth surface conditions and socioeconomic factors in connection with conditions of human being and society etc. However, these factors and their interrelation have not been fully considered in the previous studies. From this point of view, the methodology and procedure for risk assessment and zoning of flood damage caused by heavy rainfall were developed, whereby flood damage caused by heavy rainfall is regarded as the result of interactions among natural conditions, social and economical conditions and some complex chronological changes on the macro-zonation basis, from the viewpoints of climatology, geography, disaster science and environmental science and so on. The main objectives of this paper are (1) to identify and quantify key factors related to flood damage, (2) to evaluate their contribution to damage, and (3) to develop a methodology to assess and zone flood damage risk caused by heavy rainfall. 162