Estudo de frequência das cotas máximas anuais do Rio Negro, em Manaus-AM, antes e depois do evento extremo de 2021 e efeitos em risco e segurança nas obras de engenharia na área de inundação

Abstract

The disorderly urbanization process causes several social, economic, and behavioral problems over time. A very clear example of this situation is Manaus city. One of the main consequences of this increase is the concentration of people on the city's outskirts, which favors irregular and unprepared housing construction for the adversities caused by natural phenomena. The clearest examples are Negro river's extreme events level rise, which reached exceptional levels in 2012 and 2021. It is necessary to study each record of the historical series within a context, which would be the compilation of all registered quotas, selecting the maximums and thus understanding the recurrence of such phenomenon through the frequency of occurrence, using statistical means, also defining the safety or risk in hydraulic/civil works. The objective of this work is to evaluate how the extreme event of Negro river's maximum level, in Manaus city, which occurred in 2021, affects the frequency analysis of the historical series of annual maximums. To this end, data were collected on the levels reached by the Negro river, in Manaus, at the bases of the National Water Agency (ANA) and the Port of Manaus, to be studied through Probability Distribution Functions (PDF) and to define the best fit for the historical series of annual maximums of the Negro river. In addition, the influences of each extreme event on the recurrence time, risk, and safety of project quotas were evaluated. For a greater representation of the risk assessment, we sought to understand the influence of each share on the return period through an impact factor - or impact index - (ξ*). The quantification was performed before and during the year of each extreme event. The results achieved the expected objectives, which allow us to offer design engineers and hydraulic contractors information and tools for analysis and reference of the levels reached by the Negro river, recurrence times and associated risks, and their variations, to such events to Manaus city. Finally, the techniques developed in this work are of interest to students and professionals in engineering and other related areas. The applied methodology can be used in academic activities of teaching, research, and extension, as well as by development agencies for studies and projects, in addition to guiding the execution of services and future works.