Hydrological and hydrodynamic reconstruction of a flood event in a poorly monitored basin: a case study in the Rolante River, Brazil

Mel Oliveira Guirro () and Gean Paulo Michel
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Mel Oliveira Guirro: Universidade Federal do Rio Grande do Sul
Gean Paulo Michel: Universidade Federal do Rio Grande do Sul

Natural Hazards: Journal of the International Society for the Prevention and Mitigation of Natural Hazards, 2023, vol. 117, issue 1, No 31, 723-743

Abstract: Abstract Flash floods are natural hazards and often occur in small and mountainous river basins with low monitoring. The hydrological and hydrodynamic reconstruction of past rainfall events is useful for understanding the phenomena that led to a flood. This study aims to reconstruct a rainfall event that triggered landslides and floods in 2017 in the Rolante basin (771 km2), southern Brazil, a region with low monitoring. Due to the large magnitude of the flood event, a question was raised whether only the basin response to intense rainfall could have caused that flood. Therefore, different rainfall scenarios were tested with the use of official rain gauges and unofficial rainfall information from local farmers to determine the spatial and temporal distribution of rainfall. The reconstruction of the rainfall event was performed with the use of a hydrologic model (HEC-HMS) to define hydrographs and a hydrodynamic model (Nays2D Flood) to simulate flood propagation, with adjusted methods for the poorly monitored basin. The maximum flood depth and extent were analysed for three rainfall scenarios. The results showed that, with the information provided by the residents, it was possible to determine that extreme and concentrated rainfall occurred in the mountainous area and the basin ordinary response to that rainfall may have caused a flood of that great magnitude. The analysis of past extreme events can contribute to verifying if there are changes in the rainfall patterns and can assist in risk mitigation and disaster management, primarily in ungauged basins.

Keywords: Flash flood; Extreme event; Hydrological and hydraulic reconstruction; Ungauged basin (search for similar items in EconPapers)
Date: 2023
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DOI: 10.1007/s11069-023-05879-1

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