A real-time flood monitoring index based on daily effective precipitation and its application to Brisbane and Lockyer Valley flood events

A real-time flood monitoring index based on daily effective precipitation and its application to Brisbane and Lockyer Valley flood events

An objective index for flood monitoring is pragmatic tool for flood early warning systems. This study investigates a novel Flood Index (I F ) based on Effective Precipitation (PE) for quantifying floods in Brisbane and Lockyer Valley. Using daily precipitation (P) data as an input, the IF was determined by calculating PE using exponentially-decaying time-reduction function considering gradual depletion of water resources over the passage of time and comparing and normalizing the PE per day with the means and standard deviations of yearly maximums in the hydrological period. Start of flood was identified for IF ≥0, severity (IF acc ) assessed by running-sum on consecutively positive IF , duration (DF) as number of days with positive IF and peak danger (IF max ) as maximum I F . The ability of IF for flood warning was verified with river height and discharge rates. The most severe flood was recoded in January 1974 in Brisbane (IF acc =118, IF max =4.4, DF = 104 days) with return period (T) =106.2 years. Next was the December 2010–January 2011 event (I F acc =61.8, IF max =2.6, DF = 89 days) with T = 53 years. For Lockyer Valley, December 2010–January 2011 was the most severe (T = 104.4 years). Consequently, we advocate the practicality of the daily IF for flood risk assessments where severity, peak danger, duration or return periods are to be considered

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