Definition of synthetic rainfall events for urban f looding estimation: the integration of multivariate statist ics and cluster analysis

The analysis of urban flooding and of the related d amage has a central role in urban areas. Climate change and the modification of urban enviro nment increase the frequency and the impact of flooding rising the interest of researche rs and practitioners on this topic. Zenithal flooding is mainly originated by rainfall that prod uces local or general failures of the underground drainage system. The highly non-linear processes taking part in the system during runoff propagation and flooding generation d o not allow to assume that flooding frequency is linearly dependent on rainfall intensi ty frequency. For this reason flooding frequency has to be estimated by the statistical an alysis of direct observations or by means of computational demanding long term numerical simulations. Using of synthetic rainfall events, with a specific return period, and of a limited num ber of simulations generally concur to affect the estimation of flooding frequency by larg e errors. The present paper investigates the use of multivariate statistics to improve the evalu ation of rainfall frequency in urban areas and the adoption of cluster analysis for reducing the n umber of simulations needed for flooding frequency analysis. The proposed approaches were applied to a real case study (the city of Palermo, Italy) using a historical flooding dataset for assessing the reliability of the analysis.

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