Flash flooding is one of the most severe hazards that damage infrastructure, threaten life and property, and can lead to catastrophic outcomes in arid mountainous regions. Like other natural
hazards, mitigation strategies aim to reduce frequency and alleviate impacts (Comfort, 1999) with respect to susceptibility, probability, and risk (Varnes, 1984). There are different terms, but similar ideas, used to characterize susceptibility, probability, and risk, such as vulnerability, hazard, and exposure (Crichton, 1999). For a hazard of interest, susceptibility is measured by the environmental factors that in combination make places vulnerable to the hazard, probability represents the likelihood of hazardous event to occur in a
place, and risk reflects the expected cost resulting from the exposure of infrastructure, life and property to a hazardous event. In short, the three elements evaluate where (i.e. environmental susceptibility/vulnerability), when (i.e. likelihood of hazardous
events), and how much cost (i.e. risk/exposure) for a given hazard