Theory of hazard-affected bodies

With the growth of regional population and economy, the magnitude of disaster risk becomes more and more closely related to the characteristics of the hazard-affected bodies. People who are for the theory of hazard-affected bodies think that the risk carriers' vulnerability level has an important influence on the magnitude of disaster risk. And, under some sort of the effects of hazard-causing factors, the lower the vulnerability of hazard-affected bodies is, the smaller the possibility of loss the hazard-affected bodies will suffer. Accordingly, the less possible the disaster risk of hazard-causing factors it will take.

At present, a mature system has been formed internationally in vulnerability assessment of the natural disaster hazard-affected bodies. The main evaluation models have the following five types: Pressure and Release Model (PRM) put forward by Cannonl; Vulnerability Place Model (VPM) proposed by Cutter; the Hazards Dimensions of Vulnerability Model(HDVM) proposed by Tobin. Human Ecology Endangered Model, HEEM) put forward by Hewitt; the Circle of Vulnerability model (CVM) proposed by Alexander.

Vulnerability assessment, used to evaluate the degree of losses suffered by hazard-affected bodies, is an essential part of disaster risk assessment. The research on vulnerability assessment in existing literature mainly adopts the following two methods:

Regional vulnerability assessment based on historical data. This is a vulnerability assessment based on specific disasters and theirs consequences, with Disaster Risk Index (DRI) and Hotspots (Pelling, 2004).Dilley et al., 2005) as the most representative ones. Both of them are carried out in the global scope, using the historical data in EM-DAT and the ratio of the death toll to the number of people exposed in natural disaster to measure national vulnerability. Though this method is beneficial to compare the relative levels of vulnerability and risk of specific disasters among different countries around the world, it’s improper to use death toll as the measurement to evaluate the effects of disasters causing severe economical losses. Hot spot plan uses regional death rate caused by disasters and economic losses rate to give a comprehensive representation of regional vulnerability. By drawing the different levels’ regional vulnerability coefficient of seven regions obtained by solid evidence, the differences of disaster vulnerability in different social economic conditions are given.

The method of damage curve is also commonly used in the evaluation of disaster vulnerability based on historical data. Damage curve measures the relationship between disasters of different levels and economic losses caused by disasters in the form of curve. Compared with the DRI and hot spot plan, damage curve is relatively objective. This method measures the loss value accounts for the proportion of the total value, and quantitatively evaluate the relationship of different types of hazard-affected bodies and the loss degree of specific disasters.