Natural Disasters Analysis based on IDF Equations Ilza Machado KAISER a , Anna Silvia Palcheco PEIXOTO a,1 and Geórgia Jorge PELLEGRINA b a UNESP – Univ. Estadual Paulista. Depart. of Civil and Environmental Engineering, Bauru, SP, Brazil b UNESP – Univ. Estadual Paulista, Meteorological Research Institute, Bauru, SP, Brazil Abstract. Several climate models indicate an increase in the occurrence of severe thunderstorms in the Southeast region of Brazil, highlighting the importance of determining vulnerable areas to provide logistical support to agencies that work with victim assistance. A large number of natural disasters were recorded, in Sao Paulo state on the rainy season of 2009/2010 hydrological year. A search was carried out on the IPMET severe events database for significant occurrences triggered by precipitation. A synoptic description of the meteorological condition of the period is presented. The damage related to flooding and mass movements events were spatialized in São Paulo. Moreover, a systematic search for quantitative precipitation data was performed. The probability of occurrence of these events was determined using the usual hydrological resources, IDF equations. The difficulties to associate events with damage occurrence with precipitation threshold are discussed. Keywords. Hazard, Vulnerability, Mapping of risk areas, Natural disasters, SIG, Flood, Landslides 1. Introduction Climate is a description of average parameters of temperature, wind, rain with its periodic variations, intensifying or mitigating their values due the occurrence of global weather phenomena such as El Niño and La Niña. The rainy season of 2009/2010 was an example of this interference, with many flooding and landslides events reported by civil defense in Brazil, especially on the southeast region. The intense process of urbanization is a global phenomenon; the synergy of the climatic anomalies and intense urbanization process has generated numerous hazards in various locations around the globe. In recent years, there have been several significant events, such as floods and landslides all over the world [1], [2],[3] and [4]. Especially for developing countries, urbanization process occurs often in an unplanned manner. Due to real state pressure the poorest people live in areas at risk (rivers floodplains and vulnerable slopes). Moreover, a climate effect related to medium and large urban centers (heat islands) can intensify the precipitation process. From Fundamentals to Applications in Geotechnics D. Manzanal and A.O. Sfriso (Eds.) IOS Press, 2015 © 2015 The authors and IOS Press. All rights reserved. doi:10.3233/978-1-61499-603-3-3019 3019