One of the great challenges of natural disaster monitoring and early warning systems is to predict when and under what conditions landslides are triggered. Intensity-duration rainfall thresholds use rainfall events’ duration and intensity to estimate which of them are capable of triggering landslide and have practical applicability. They have been extensively applied worldwide in analyzing landslides triggered by rain. Thus, seeking to expand the possibilities of forecasting landslides in Brazil and taking advantage of temporal and spatial resolution of rainfall data of rain gauges from Brazil’s National Center for Monitoring and Early Warning of Natural Disasters (Cemaden), this paper aimed to define intensity-duration rainfall thresholds for the municipality of Jaraguá do Sul (Santa Catarina state, Brazil). Ten events with records of landslides were used to calculate rainfall intensity — I (mm/h) and duration — D (h). A rainfall event was defined by rains with an interval of up to 12 hours with no precipitation. Rainfall thresholds were created plotting I and D data in a log-log graph and adjusted using a Power Function with the same exponent as the regression line of the data. Two rainfall thresholds were developed: A, which comprises any landslide occurrences, and B, which embraces rainfall events capable of triggering ten or more landslides. With average success rates of up to 29.8% and 62.5%, respectively, it was estimated that 3.2% of the rainfall events that occurred between 2016 and May 2022 overcame threshold A and that 0.4% overcame threshold B. Results encourage an increase in research on intensity-duration rainfall thresholds in other Brazilian regions in order to improve the capacity of predicting disasters caused by landslides. Um dos grandes desafios dos sistemas de monitoramento e alerta de desastres naturais é prever em que momento e sob quais condições os deslizamentos ocorrem. Os limiares intensidade-duração, ao utilizar a duração e a intensidade média dos eventos de chuva para estimar quais deles são capazes de deflagrar deslizamentos, têm potencial prático e têm sido extensivamente aplicados mundialmente na análise de deslizamentos deflagrados pela chuva. Consequentemente, buscando ampliar as possibilidades de previsão de deslizamentos no Brasil e explorar a boa resolução temporal e espacial das informações de chuva dos pluviômetros do Centro Nacional de Monitoramento e Alertas de Desastres Naturais (Cemaden), esta pesquisa teve como objetivo definir limiares de chuva do tipo intensidade-duração para o município de Jaraguá do Sul (SC). Para isso, foram utilizados dez eventos de chuva com registro de deslizamentos, definidos por chuvas com um intervalo de até 12 horas com ausência de precipitação, para os quais foram calculadas a intensidade (I), medida em mm/h, e a duração (D), medida em horas. Para a construção dos limiares os dados de I e D dos eventos de chuva com deslizamentos foram plotados em gráfico log-log e ajustados a partir de uma Função Potência com o mesmo expoente da linha de regressão dos dados. Foi possível elaborar dois limiares de chuva: o Limiar A que abrange quaisquer ocorrências de deslizamento e o Limiar B que delimita os eventos de precipitação capazes de deflagrar dez ou mais deslizamentos. Com taxas de acerto médias de até 29,8% e 62,5%, respectivamente, estimou-se que 3,2% dos eventos de chuva ocorridos entre 2016 e maio/2022 estão acima do Limiar A e que 0,4% superam o Limiar B. Os resultados encorajam a expansão de estudos de limiares intensidade-duração para outros municípios e regiões de maneira a aperfeiçoar o potencial de previsão de desastres causados por deslizamentos no território brasileiro.

High-magnitude landslides are natural processes that shape steep slopes and valleys in southern and southeastern Brazil, while also being responsible for some of the most devastating natural disasters recorded in recent years. To improve disaster prevention strategies, this study aimed to analyze the geomorphodynamics of high-magnitude landslides in the Paraitinga Plateau (SP) associated with the extreme 2009/2010 event. The research adopted a detailed approach based on high-resolution geomorphological mapping, integrating multitemporal photointerpretation techniques, fieldwork, and analysis of erosional and depositional features. Results revealed that deeper landslides, linked to weathering mantle ruptures, were frequently associated with debris flows that reshaped valleys, forming depositional lobes in debris cones. Scouring from these flows was marked by plucking features in bedrock channels, contrasting with fluvial abrasion in downstream sections. Past deposits indicate historical recurrence of these processes, potentially intensified by anthropogenic changes like native vegetation removal. The study demonstrates that high-magnitude events, though rare, play a fundamental role in landscape as agents of slope and channel remodeling. Results highlight the importance of considering the integration of geomorphodynamic analyses into risk assessment, enhancing the understanding of mass movement dynamics and supporting forecasting in data-scarce regions, thereby contributing for more effective public policies for disaster prevention in humid tropical regions.

A parte alta dos vales, junto às cabeceiras de drenagem e às vertentes de alta declividade têm uma geomorfodinâmica particular, dependente da natureza dos processos nessa zona de interação entre vertente...