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Floods are extreme weather events that cause severe damages to human lives and properties. The present study aims to analyze and predict the effect of rainfall variability on the occurrence of floods in the Colombo District. The rainfall data of thirteen Divisional Secretariat Divisions (DSDs) from 1991 to 2020 was analyzed using the Standard Precipitation Index (SPI) and Rainfall Anomaly Index (RAI). According to the SPI 1 analysis, extreme wet periods (SPI > 2) were observed in 1997, 2005, 2008, 2014, and 2016 in all the DSDs, with an increase in flood events with the rise in extreme wet conditions after 2005. The SPI 3 and SPI 6 values also indicated historical flood events in June 2008, May 2016, and September 2019, followed by extreme wet periods due to Southwest-monsoon. The RAI analysis revealed the influence of extremely humid conditions (RAI > 4) on flood events in May 2016. The flood prediction analysis suggests an exceeding probability of ≥ 27% for extreme wet conditions leading to flood events in the Colombo District in 100 years. The results of this study are beneficial for decision-makers on future flood risk management in a disaster-resilient community.

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Analysis and Prediction of Flood Events in Colombo District, Sri Lanka Using Standard Precipitation Index (SPI) and Rainfall Anomaly Index (RAI)

  • 章节

  • 发表日期：

    2025年

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  • R. M. A. S. D. Rajakaruna,
  • B. G. N. Sewwandi

摘要

Floods are extreme weather events that cause severe damages to human lives and properties. The present study aims to analyze and predict the effect of rainfall variability on the occurrence of floods in the Colombo District. The rainfall data of thirteen Divisional Secretariat Divisions (DSDs) from 1991 to 2020 was analyzed using the Standard Precipitation Index (SPI) and Rainfall Anomaly Index (RAI). According to the SPI 1 analysis, extreme wet periods (SPI > 2) were observed in 1997, 2005, 2008, 2014, and 2016 in all the DSDs, with an increase in flood events with the rise in extreme wet conditions after 2005. The SPI 3 and SPI 6 values also indicated historical flood events in June 2008, May 2016, and September 2019, followed by extreme wet periods due to Southwest-monsoon. The RAI analysis revealed the influence of extremely humid conditions (RAI > 4) on flood events in May 2016. The flood prediction analysis suggests an exceeding probability of ≥ 27% for extreme wet conditions leading to flood events in the Colombo District in 100 years. The results of this study are beneficial for decision-makers on future flood risk management in a disaster-resilient community.