Sustainable Water Management Solutions for Large Cities (Proceedings of symposium S2 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 293, 2005, 2-13

Abstract A metaphorical definition of resiliency is used in this paper: the capacity to weather and adapt to stress from hazards, and the ability to recover quickly from their impacts. Resiliency is often discussed in conjunction with vulnerability, a measure of the adverse effects of a hazardous event on a system, the magnitude of which is influenced by the system’s resiliency. Vulnerability is determined by risk-proximity or exposure to hazards, which affects the probability of adverse impact and is a robustness-measure of the system’s ability to adapt to a wide range of possible future conditions, at little additional cost. The greatest challenges for urban water infrastructure design, planning and management lie in our limited ability to quantify potential future conditions. This paper explores the utility of the fuzzy set theory in the field of water resource systems reliability analysis and proposes three new fuzzy reliability measures: (i) a combined reliability–vulnerability index, (ii) a robustness index, and (iii) a resiliency index.

Key words fuzzy reliability; fuzzy robustness; fuzzy vulnerability; large cities;