Avaliação das relações de frequência entre precipitações e enchentes raras por meio de séries sintéticas e simulção hidrológica

Abstract

It is an engineering practice to admit the equivalence between the return periods of rainfall depths and floods. According to this assumption, all randomness that is inherent to flood volumes is caused only by rainfall. However, it is also important to understand that there are other conditions, such as the initial soil moisture conditions that can modify the river basin response. This research aims to explore the impact caused by the wrong consideration of equality between return periods of precipitations and floods. In order to evaluate this impact a long series of daily average streamflows has been synthesized by means of models of random generation of synthetic precipitation series and evapotranspiration, and a deterministic conceptual model of the rainfall-runoff transformation. This methodology has been applied totwo river basins located in the Brazilian state of Minas Gerais, namely the Pará and Indaiá watersheds. The results show evidences that, as very large return periods are of concern, the consideration of equality of return periods is less critical. However, for smaller return periods, other factors that affect the rainfall-runoff transformation, such as the different soil moisture conditions, should be considered. As for flood peaks, the antecedent-precipitation index has been used to verify the effect of previous rainfall episodes on flood peaks.