Estimativa de chuvas intensas no Rio Grande do Sul a partir das relações genéricas de Bell e Chen

Abstract

The knowledge of the relationship between intensity-duration-frequency (IDF relationship) of intense rainfall is of enormous importance for the design of engineering works. However, the availability of this data is limited, due to the scarcity of pluviographs data in Rio Grande do Sul (RS) or, when these exist, generally encompass small observation periods and/or with failures, which makes them useless to the determination of IDF relationships. In this scenario, we propose here to analyze the applicability in RS of the methodology suggested by Bell (1969) and Chen (1983). Bell (1969) proposed an equation for the entire planet, where intense rainfall, for any duration and return period, is determined based only on precipitation with return period of 10 years and duration of 1 hour, from anywhere we want determine. Bell (1969) is based on the fact that heavy rainfall are usually produced by convective systems that behave in a similar way regardless of the local of the precipitation. Numerous modifications of the methodology presented by Bell (1969) have already been carried out and presented as reliable results as Back (2009), Chen (1983), Ueahara et al. (1980) among others. In this study, the application of Bell s (1969) original equation, and some of his modifications was analyzed, introducing extra modifications still allowing its use with the rainfall data in RS. The results show that the methodologies of Bell (1969) and Chen (1983) are complementary because we obtained if good fits for durations shorter than 2 hours when applied Bell (1969) and when applied Chen (1983) presented best settings in durations greater than 2 hours. The biggest errors were found in the rainfall estimation for 2 years return period, because we also observed that both methodologies go through a heating process of the equation. To try and fill the entire State on the issue of intense rainfall, the regionalization of heavy rains in order to make more practical and reliable use, which presented good results only for the regions B, D and F, and in the other regions (A, C and E) the results were positive in only 60% of the sites studied.