Análise de chuvas extremas e a relação com eventos de alagamentos na cidade de são paulo – SP.
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Data
2021-10-08
Autores
Carvalho, Raissa Barreto de
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Universidade Estadual Paulista (Unesp)
Resumo
Os eventos extremos de chuva no município de São Paulo são cada vez mais frequentes e intensos, esses eventos aliados ao mal planejamento das cidades e à vulnerabilidade da população se tornam um fator decisivo na ocorrência de desastres, como deslizamentos, inundações, enxurradas e alagamentos. Os alagamentos são um dos problemas mais recorrentes nas grandes cidades. O município de São Paulo, o mais populoso do Brasil, com uma densidade populacional de 7.398,26 hab/km², é uma das cidades que mais são afetadas por alagamentos. Os danos provocados por alagamentos são de magnitude pequena, porém têm interferência na vida cotidiana da população, causando, por exemplo, transtornos na movimentação de pessoas e automóveis, afetando o crescimento econômico e o bem-estar da população. Portanto, o objetivo deste trabalho foi analisar os eventos extremos de chuva na cidade de São Paulo - SP e associá-los com os sistemas atmosféricos de frente fria e ZCAS, selecionados com base nos boletins gerados pelo CPTEC, e identificar a relação desses eventos com os episódios de alagamentos na cidade. Por fim foram quantificados os danos e impactos causados pelos eventos extremos. Para isso foram utilizados dados de precipitação de 5 estações pluviométricas instaladas na cidade de São Paulo, referentes ao período que varia de 1985 a 2019. Para encontrar o limiar e identificar os eventos extremos foi aplicado o percentil de p(0,99) e como condição para ser considerado chuva extrema pelo menos 2 postos pluviométricos devem ter chuva acima do limiar encontrado. Os resultados mostraram que os limiares sazonais de chuva extrema p(0,99) em todos os postos foram maiores na estação de verão com variação entre 62,1 e 75,5 mm, já os menores limiares ocorreram no inverno (com variação entre 31 e 37,5 mm). Foi identificado uma ocorrência de 60 eventos extremos de chuva entre os anos 2005 e 2019, onde apresentaram pontos de alagamentos em quase todos os dias, apenas 11 dias não tiveram episódios de alagamentos, porém 6 deles tiveram alagamentos no dia anterior ao evento. Durante os episódios de eventos extremos, a ZCAS e as frentes frias contribuíram para ocorrência de chuvas intensas no município de São Paulo tendo ocorrido em 68,3% dos casos das chuvas analisadas, a ZCAS foi mais frequente no verão e as frentes frias no outono e inverno. A contabilização dos danos causados pelas chuvas extremas demonstrou que os principais impactos ocorridos foram congestionamentos e interdições de vias, desabamentos, danos em imóveis, queda de muro e danos em veículos e o total de pessoas afetadas foram de 21 feridas, 20 desalojadas, 19 ilhadas, 15 vítimas fatais, 7 desabrigadas e 6 pessoas arrastadas pelas enxurradas. Os principais danos associados aos alagamentos verificados nas notícias foram de congestionamentos e pessoas ilhadas.
Extreme rain events in the city of São Paulo are increasingly frequent and intense, these events, combined with poor planning in cities and the vulnerability of the population, become a decisive factor in the occurrence of disasters, such as landslides and flooding. Flooding is one of the most recurrent problems in big cities. The city of São Paulo, the most populous in Brazil, with a population density of 7,398.26 inhabitants/km², is one of the cities that are most affected by flooding. The damage caused by flooding is of small magnitude, but it interferes in the daily life of the population, causing, for example, disturbances in the movement of people and cars, affecting economic growth and the population's well-being. Therefore, the objective of this work was to analyze the extreme rain events in the city of São Paulo - SP and associate them with the atmospheric cold front systems and ZCAS, selected based on the bulletins generated by CPTEC, and to identify the relationship of these events with the episodes of flooding in the city. Finally, the damage and impacts caused by extreme events were quantified. For this, precipitation data from 5 pluviometric stations installed in the city of São Paulo were used, referring to the period ranging from 1985 to 2019. To find the threshold and identify the extreme events, the percentile of p(0.99) was applied and how condition to be considered extreme rain, at least 2 pluviometric stations must have rain above the threshold found. The results showed that the seasonal extreme rainfall thresholds p(0.99) in all stations were higher in the summer season, with a variation between 62.1 and 75.5 mm, and the lowest thresholds occurred in the winter (with a variation between 31 and 37.5 mm). An occurrence of 60 extreme rain events was identified between the years 2005 and 2019, which showed flooding points on almost every day, only 11 days had no flooding episodes, but 6 of them had flooding the day before the event. During episodes of extreme events, ZCAS and cold fronts contributed to the occurrence of heavy rains in the city of São Paulo, occurring in 68.3% of the analyzed rain cases, ZCAS was more frequent in summer and cold fronts in autumn it's winter. The accounting of damages caused by extreme rains showed that the main impacts that occurred were traffic jams and interdictions, landslides, damage to buildings, falling walls and damage to vehicles and the total number of people affected was 21 injured, 20 homeless, 19 islands, 15 fatal victims, 7 homeless and 6 people dragged by the floods. The main damages associated with the flooding verified in the news were from traffic jams and stranded people.
Extreme rain events in the city of São Paulo are increasingly frequent and intense, these events, combined with poor planning in cities and the vulnerability of the population, become a decisive factor in the occurrence of disasters, such as landslides and flooding. Flooding is one of the most recurrent problems in big cities. The city of São Paulo, the most populous in Brazil, with a population density of 7,398.26 inhabitants/km², is one of the cities that are most affected by flooding. The damage caused by flooding is of small magnitude, but it interferes in the daily life of the population, causing, for example, disturbances in the movement of people and cars, affecting economic growth and the population's well-being. Therefore, the objective of this work was to analyze the extreme rain events in the city of São Paulo - SP and associate them with the atmospheric cold front systems and ZCAS, selected based on the bulletins generated by CPTEC, and to identify the relationship of these events with the episodes of flooding in the city. Finally, the damage and impacts caused by extreme events were quantified. For this, precipitation data from 5 pluviometric stations installed in the city of São Paulo were used, referring to the period ranging from 1985 to 2019. To find the threshold and identify the extreme events, the percentile of p(0.99) was applied and how condition to be considered extreme rain, at least 2 pluviometric stations must have rain above the threshold found. The results showed that the seasonal extreme rainfall thresholds p(0.99) in all stations were higher in the summer season, with a variation between 62.1 and 75.5 mm, and the lowest thresholds occurred in the winter (with a variation between 31 and 37.5 mm). An occurrence of 60 extreme rain events was identified between the years 2005 and 2019, which showed flooding points on almost every day, only 11 days had no flooding episodes, but 6 of them had flooding the day before the event. During episodes of extreme events, ZCAS and cold fronts contributed to the occurrence of heavy rains in the city of São Paulo, occurring in 68.3% of the analyzed rain cases, ZCAS was more frequent in summer and cold fronts in autumn it's winter. The accounting of damages caused by extreme rains showed that the main impacts that occurred were traffic jams and interdictions, landslides, damage to buildings, falling walls and damage to vehicles and the total number of people affected was 21 injured, 20 homeless, 19 islands, 15 fatal victims, 7 homeless and 6 people dragged by the floods. The main damages associated with the flooding verified in the news were from traffic jams and stranded people.
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Palavras-chave
Eventos extremos de precipitação, Alagamentos, ZCAS, Frentes frias., Extreme precipitation events, Floods, SACZ, Cold fronts