Avaliação de limiares críticos de inundação para implementação de sistema de alerta em região urbana com monitoramento hidrológico limitado e interação fluvial

Abstract

The study aimed to define critical rainfall and hydraulic thresholds to support a flood warning system in Itabuna, Bahia, an urban region with limited hydrological monitoring. To achieve this, hydrological and hydrodynamic modeling was used to simulate flood events under different rainfall scenarios. Rainfall data, from a grid, and flow data, obtained from a fluviometer, applied for model calibration, underwent a prior consistency analysis. It was found that the grid rainfall was representative for the study area based on the applied statistical metrics. However, the flow data showed discontinuity and overestimation, compromising the accuracy for modeling. The applied hydrological model was satisfactorily calibrated for two flood events in the study area, with one of the calibrations chosen for the continuation of the study. With the calibrated hydrological model, ten hydrographs were generated, corresponding to ten different accumulated rainfall amounts, which were propagated in the hydrodynamic model, resulting in flood scenarios for the municipality. The methodology enabled the identification of accumulated rainfall amounts that led to the exceedance of alert levels, associated with peak flows in different monitored sections. In the most intense event, all alert thresholds in the areas of interest were exceeded. Maps representing the extent of floods and wave propagation time demonstrated the evolution and severity of the events, indicating a significant increase in the affected area in proportion to the rainfall intensity. Additionally, maps of body instability risk (such as overturning and slipping) revealed dangerous situations in areas near watercourses from a certain level of event severity, with the expansion of higher-risk zones. This work highlights the feasibility of a methodology to analyze and correlate accumulated rainfall with hydraulic parameters in locations with limited hydrological monitoring capacity. Such an approach can contribute to the development of flood preparedness and response plans in municipalities with restricted monitoring infrastructure, offering support to civil defense agencies in defining alert levels and communicating risks to the population.