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An improved rainfall-threshold approach for robust prediction and warning of flood and flash flood hazards / Geraldo Moura Ramos Filho, Victor Hugo Rabelo Coelho, Emerson da Silva Freitas, Yunqing Xuan, Cristiano das Neves Almeida

Natural Hazards, Volume: 105, Issue: 3, Pages: 2409 - 2429

Swansea University Author: Yunqing Xuan

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Abstract

This paper presents an improved method of using threshold of peak rainfall intensity for robust flood/flash flood evaluation and warnings in the state of São Paulo, Brazil. The improvements involve the use of two tolerance levels and the delineating of an intermediate threshold by incorporating an e...

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Published in: Natural Hazards
ISSN: 0921-030X 1573-0840
Published: Springer Science and Business Media LLC 2021
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa55586
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Abstract: This paper presents an improved method of using threshold of peak rainfall intensity for robust flood/flash flood evaluation and warnings in the state of São Paulo, Brazil. The improvements involve the use of two tolerance levels and the delineating of an intermediate threshold by incorporating an exponential curve that relates rainfall intensity and Antecedent Precipitation Index (API). The application of the tolerance levels presents an average increase of 14% in the Probability of Detection (POD) of flood and flash flood occurrences above the upper threshold. Moreover, a considerable exclusion (63%) of non-occurrences of floods and flash floods in between the two thresholds significantly reduce the number of false alarms. The intermediate threshold using the exponential curves also exhibits improvements for almost all time steps of both hydrological hazards, with the best results found for floods correlating 8-h peak intensity and 8 days API, with POD and Positive Predictive Value (PPV) values equal to 81% and 82%, respectively. This study provides strong indications that the new proposed rainfall threshold-based approach can help reduce the uncertainties in predicting the occurrences of floods and flash floods.
Keywords: Flood hazards warning; Rainfall threshold method; Peak rainfall intensity; Antecedent precipitation index; Tolerance limits; Intermediate rainfall intensity threshold
College: College of Engineering
Issue: 3
Start Page: 2409
End Page: 2429