Potentialities of intensity-duration rainfall thresholds in the forecast of landslides in Jaraguá do Sul (SC)

Abstract

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.