Risk analysis: a focus on Urban Exposure estimation

In risk analysis, extremes natural phenomena become hazardous when they strike human beings, tangible and intangible assets. In urban areas, the exponential growth of population and its density makes cities more exposed to the effects of natural impacts that could become catastrophic and generate high-risk situations. As a result, the current situation makes the population and its economic and social activities highly exposed to the different natural risks. In the last 40 years, the Exposure of built-up area and population to natural hazards doubled: now seismic hazard could affect 2.7 billion, volcanoes eruptions 414 million people and tropical cyclones over 1.6 billion. Authors consider Exposure as the quantity and quality of the different anthropic elements (population, settlement system, infrastructure network, elements of the environment) of a given territorial area and whose conditions and operation can be damaged, altered or destroyed by natural hazards. Therefore, the exposure assessment of the different urban functions becomes the basis for implementing risk reduction interventions. The presented research defines a methodology to study the location and distribution of population (spatial and temporal dynamic entity), the different urban functions, human assets and their activities. In particular, authors analyze the statistical possibility that human beings are in an area at risk in a well-defined period of time (24 h a day, 7 days a week and 365 a year). It depends on city structure, functions distribution, its widespread elements and through these elements authors estimate Urban Exposure.