HEAVY RAINFALL EVENTS IN VOLTA REDONDA

Abstract

Most Brazilian cities do not manage urban drainage in a proper manner, due to lack of planning in the sector or of easy-to-consult literature about local hydrology to enable hydrological modeling. Volta Redonda County fits this statistic, since it experiences events associated with flood and inundation in some specific sites. The aims of the present study are: (i) to record a series of maximum annual daily rainfall events in Volta Redonda County and to investigate whether their intensity has increased over the years; (ii) to adjust the maximum daily annual rainfall to a probability distribution model and to generate a heavy rainfall table for Volta Redonda County to enable dimensioning surface drainage systems. Seventy-seven years of rainfall data from a local station were used in the current study - maximum daily annual rainfall was calculated. Mann-Kendell test was applied to this series in order to check its stationarity over time. Then, Gumbel distribution was adjusted to the maximum annual data to allow its extrapolation. Finally, daily data were transformed into shorter rainfall values, at return period ranging from 2 to 500 years. Volta Redonda rainfall series can be considered stationary; results in the present research can be used to build rainwater drainage systems in Volta Redonda County; it is recommended using mean intensity of 150 mm h^-1 for small urban drainage structures, whenever it is not possible determining their surface runoff concentration time.