Rain Storm Severity Index RSI to categorize heavy rainfall events in terms of their spatial peculiarity

Abstract

The expected increase of extreme torrential rainfall and urban flooding requires a systematic risk management as a joint mu-nicipal effort. The characterization of heavy rainfall events with Rain Storm Severity Index RSI has become a valuable tool of urban flood risk communication. RSI values allow a general event categorization based on single rainfall depths and their statistical return periods. Besides, a more specific evaluation of the spatial extension of extreme rainfall intensities would pro-vide additional information to classify extreme rainfall events. For that purpose a methodical approach has been developed with the parameter RAS as a measure of spatial rainfall extension in the range between 0 and 5. The computation of RAS is based on RSI values that are assigned to grid-based radar-measured ranked rainfall depths.