A Critical Analysis Hydrograph Maximum Most Probable (Hmmp) Method Applied to Design Peak Discharge Estimates in Large River Basins (PAP014909)

Código

PAP014909

Autores

Daysy Lira Oliveira Cavalcanti, Luisa Fernanda Ribeiro Reis

Tema

Flood forecasting and early warning systems

Resumo

The failures of hydraulic structures and the lack of water resources management has been identified as causes of floods in large river basins. In cases of dam failures, for example, there are several evidences that the magnitudes of floods occurring have exceeded the design capabilities of their discharge structures. Thus, the statistical method (Local Frequency Analysis) and the deterministic method (Probable Maximum Flood - PMF), widely used in current practice, have received severe criticism related to their ability to estimate design flows. The method of Hydrograph Maximum Most Probable (HMMP) was recently proposed by Conte [1] in order to overcome the difficulties imposed by the referred methods. It has its conceptual basis on the analogy between the maximum entropy theory and the behavior of large river basins and uses the relations of Curvilinear Unit Hydrograph (UH) developed by Victor Mockus. This paper evaluates the applicability of the HMMP method and influence of factors such as the length of the data series, the presence of outliers and lower values of the series on the estimated maximum values. The HMMP method was applied to Sobradinho and Três Marias, in the basin of the São Francisco River, both belonging to the Brazilian hydroelectric power plants system, and to fluviometric station of Paso de Los Libres, located in the basin of the Uruguay River. The removal of outliers and influence of lower values of the series, for example, caused maximum variations in the estimate values of 6%, considered little relevant. The main difficulty met to use the HMMP method was to determine the time base, defined by the method, which revealed itself characteristic of decisive influence on the estimates. For the case studies analyzed, the HMMP has demonstrated advantages over the methods of analysis of local frequency. Besides that, the HMMP method has proved to be more reliable, estimating values always above the maximum recorded to the flood of 10000 years. At the same time, the HMMP proved to be prone to overestimate the flow of project. The results obtained allow concluding that the HMMP is a promising method for adding stability and security to the determination of design flows. [1] CONTE, A. E. Aspectos de um Hidrograma Máximo Mais Provável (Aspects of a Hydrograph Maximum Most Probable). São Paulo: CreateSpace, 2012. p. 1-180. (in Portuguese)