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, 203-211

1 National Research Council, CNR-IRPI, Via Madonna Alta, I-126 06124 Perugia, Italy

2 Department of Hydraulics, Transportation and Highways, University of Rome "La Sapienza", Via Eudossiana 18, I-00184 Rome, Italy

Abstract A design hyetograph is a synthetic rainfall temporal pattern associated with a return period. Usually it is determined by means of statistical analysis of observed rainfall mean intensity through intensity–duration–frequency (IDF) curves. The other characteristics of a rainfall event, such as the peak, total depth and duration, are found indirectly throughout several phases of hydrological analysis, and trigger suitable work assumptions. The aim of this paper is to apply a multivariate approach in order to analyse jointly observed data of rainfall critical depth, maximum intensity and total depth. In particular, bivariate analysis of intensity–total depth conditioning to critical depth is developed using a 3-copula function to define the trivariate joint distribution function. Following the proposed procedure, once a design return period and related critical depth are selected, it is possible to determine, in a probabilistic way, the intensity and total depth, without advancing a priori hypotheses on the design hyetograph pattern. In a case study, the results obtained with the proposed procedure are compared with those deduced from standard design hyetographs usually applied in practical hydrological applications.

Key words copula; multivariate analysis; rainfall; synthetic hyetographs