Estimativa de vazões máximas de projeto por métodos determinísticos e probabilísticos

Abstract

Flood is a natural phenomenon that can cause inundation of river valleys and serious economic and social problems. Estimates of flood peak flows are essential for planning and implementation of measures for minimizing flood impacts. There are several methods for estimating design peak flows. The aim of this study is to analyze deterministic and probabilistic methods used in practice for estimating maximum flows for different return periods. For estimating maximum flows there were utilized the following hydrologic methods: Rational, Modified Rational, Soil Conservation Service and adjustment of Gumbel, Pearson III, Log Pearson III and Log Normal II and III probability distributions . GIS technology was applied for obtaining parameters involved in the deterministic methods. Nine rainfall and nine river flow gauging stations installed in medium-size basins located in the Espirito Santo state were selected for application of the methodologies. The design flows were estimated for return periods 10, 20, 50, 100, 200, 500 and 1000 years. The results obtained from the probabilistic methods were much closer than those obtained by deterministic methods. The SCS method, in general, estimated lower values than those obtained by probabilistic methods Rational and Modified. Rational methods overestimated the maximum flow values. The analysis of results showed that the practical application of the methods should be very careful. It was also concluded that deterministic methods application may cause very significant oversize or undersize of civil works and overestimation or underestimation of parameters related to non-structural measures for flood control