Análise das áreas de risco associadas aos processos hidrológicos na área urbana de Candelária, RS

Abstract

In recent years, Brazil has faced significant material losses and an increasing number of fatalities due to natural disasters, with floods being the most frequent events. Several municipalities in the state of Rio Grande do Sul have been severely affected by major floods, impacting thousands of people. In this context, identifying and mapping risk areas become essential, as they enable more efficient public management and the implementation of preventive measures and proper management in these vulnerable regions. The municipality of Candelária experiences numerous episodes of flooding, flash floods, and inundation. In this regard, this research aims to determine and assess the risk areas associated with hydrological processes. The study was conducted in stages. The first stage involved compiling an inventory of hydrological processes that occurred between 2000 and 2024, organizing and tabulating information on different disasters in the municipality based on the National Disaster Registry and a local newspaper. To evaluate flood-prone areas, a heat map was created, highlighting the most affected streets. The flood analysis involved mapping susceptibility, hazard, vulnerability, and risk within the municipality. Susceptibility was determined based on terrain characteristics, identifying floodplains using the AHP method. Hazard was assessed by considering high and medium susceptibility classes, integrated with the flood extent of the 2024 event and data collected through fieldwork. Vulnerability was analyzed using social data from the 2022 IBGE Census and the structural characteristics of the urban area. Finally, risk was determined by cross-referencing vulnerability and hazard data, resulting in four risk classes: low, medium, high, and very high. Over the past 24 years, the most recurrent events in Candelária have been flooding, with a total of 30 occurrences. Most of these events took place in January and November and were associated with torrential rainfall. Inundations, on the other hand, occurred approximately 16 times, being more frequent in October and November, linked to accumulated precipitation during spring. The urban area of Candelária showed that 92.06% of its territory has high or medium susceptibility, a factor directly related to the city's proximity to the river and other watercourses. Regarding hazard and vulnerability, the neighborhoods with the highest indices were Costa Norte, Esmeralda, and Rincão Comprido. Flood risk in Candelária classified as High Risk accounts for approximately 50.54% of the total risk area, encompassing 371 households, most of them located near the Rio Pardo. The Very High-Risk class corresponds to the areas with the highest vulnerability and hazard, where floods are frequent and cause significant material damage to the population. This category includes 100 households, representing 13.62% of the total risk area, with the highest concentration in the Centro and Esmeralda neighborhoods.Hydrological processes in Candelária exhibit a complex dynamic, particularly due to the interaction between flooding and inundation phenomena, which can occur simultaneously in certain regions during extreme events.