Regional Analysis of Intensity-Duration-Frequency of Heavy Storms Over the Brazilian State of Rio de Janeiro

Storm rainfall often cause considerable material damage and human losses. In order to mitigate such disasters, the design of hydraulic structures and flood plain occupation planning must take into account the risks associated with the occurrence of heavy storms. These risks are estimated by statistical analysis of temporal series of recording raingauge data, from which the intensity and duration of events can be estimated. This paper is a summary of an extensive study aiming to estimate regional intensity-duration-frequency (IDF) curves for the Brazilian state of Rio de Janeiro. Such a study has been motivated by recent episodes of extensive damages caused by heavy storms in the state of Rio de Janeiro and by realizing that the last state-wide statistical study has been carried out in the late fifties; the quality of that previous study has been limited by the number of recording raingauge stations available at the time. The present study has been carried out with partial duration series abstracted from data recorded at 34 raingauge stations, spread throughout the state's territory. In addition to this expressive volume of data, contemporary methodologies of regional analysis, based on the so-called L-Moments, have improved parameter and quantile estimates of extreme rainfall intensities. By defining homogeneous regions over the state of Rio de Janeiro and taking into account local characteristics, the IDF curves are estimated for each region, from which one can define quantiles for designing hydraulic structures and stormwater drainage systems.