Introducing Flashiness‐Intensity‐Duration‐Frequency (F‐IDF): A New Metric to Quantify Flash Flood Intensity

Abstract

AbstractFlash flooding is a damaging weather event, yet it remains challenging to quantify its severity. We propose a development—the Flashiness‐Intensity‐Duration‐Frequency (F‐IDF) curve—to quantify flash flood intensity based on the frequency and duration of the event. As a proof‐of‐concept, we mapped Contiguous US (CONUS)‐wide F‐IDF values at 3,722 stream gage locations and explored their relations with basin attributes. It is found that (a) The return periods of flash flood events are highly associated with the return peroids of rainfall events; (b) Climatological precipitation amounts exhibit the most positive correlation with flashiness while a basin's drainage area is the most negatively correlated; (c) Correlation of flashiness with basin attributes decreases with increasing F‐IDF return periods and shorter event durations. Both aspects are attributable to the rainfall signal overwhelming the underlying basin attributes as the intensities become more extreme. This new metric has implications for hydrology and emergency responders.