Practical Study on the Fuzzy Risk of Flood Disasters
- PDF / 292,301 Bytes
- 12 Pages / 439.37 x 666.142 pts Page_size
- 21 Downloads / 268 Views
Practical Study on the Fuzzy Risk of Flood Disasters Lihua Feng · Gaoyuan Luo
Received: 15 May 2008 / Accepted: 21 August 2008 / Published online: 11 September 2008 © Springer Science+Business Media B.V. 2008
Abstract The simplest way to perform a fuzzy risk assessment is to calculate the fuzzy expected value and convert fuzzy risk into non-fuzzy risk, i.e., a crisp value. In doing so, there is a transition from the fuzzy set to the crisp set. Therefore, the first step is to define an α level value, and then select the elements x with a subordinate degree A(x) ≥ α. The higher the value of α, the lower the degree of uncertainty—the probability is closer to its true value. The lower the value of α, the higher the degree of uncertainty—this results in a lower probability serviceability. The possibility level α is dependant on technical conditions and knowledge. A fuzzy expected value of the possibility-probability distribution is a set with E α (x) and E α (x) as its boundaries. The fuzzy expected values E α (x) and E α (x) of a possibility-probability distribution represent the fuzzy risk values being calculated. Therefore, we can obtain a conservative risk value, a venture risk value and a maximum probability risk value. Under such an α level, three risk values can be calculated. As α adopts all values throughout the set [0, 1], it is possible to obtain a series of risk values. Therefore, the fuzzy risk may be a multi-valued risk or set-valued risk. Calculation of the fuzzy expected value of flood risk in the Jinhua River basin has been performed based on the interior-outer set model. Selection of an α value depends on the confidence in different groups of people, while selection of a conservative risk value or venture risk value depends on the risk preference of these people. Keywords Interior-outer set model · α level · Fuzzy risk · Fuzzy expected value · Flood
1 Introduction Among natural disasters, flood is one of the most common and destructive. In recent years, floods have become increasingly serious, as social and economic development has rapidly progressed [12]. It is estimated that losses caused by flood accounts for 40% of all total losses attributed to all disasters [22]. Floods occur with high frequency, affect vast areas, are L.H. Feng () · G.Y. Luo Department of Geography, Zhejiang Normal University, Jinhua 321004, China e-mail: [email protected]
422
L.H. Feng, G.Y. Luo
difficult to contain and cause the greatest destruction, representing a huge threat to lives and property, and are a constant risk facing mankind [15]. Risk is always accompanied by uncertainty [14]. If there were no uncertainty, there would be no risk. Due to many factors, human beings cannot accurately predict many incidents. Uncertainty always exists, and therefore, risk is inevitable [11]. Flood variations in the future are an issue of great uncertainty, and risk analysis of floods is absolutely necessary. Two main reasons for the inaccurate estimation of flood risk are: (1) People do not fully understand the distribution of the
Data Loading...
