Objective Analysis of Envelope Curves for Peak Floods of European and Mediterranean Flash Floods

Flash floods rank highly among natural disasters in terms of number of affected people and number of fatalities. This paper analyzes the scaling of highest flash flood peaks at multiple spatial scales for different hydro-climatic regions in Europe and in the Mediterranean. The analysis is based on an integrated, high-resolution dataset of discharges concerning a number of high-intensity flash floods that occurred in these regions from 1991 to 2015. Quantile regression has permitted to define regional envelope curves of unit peak discharge versus drainage basin area, which summarize the current bound to extreme flash floods in a given region. Mean and standard error of the envelope curves' parameters are objectively derived, permitting to explore the similarities in the slopes of the regional envelope curves. Results show that the exponent of the envelope curves shows almost negligible variations among climatic region whereas the multiplier depends on the climatic regions.