Operative procedure to derive changes of flood frequencies from projected extreme precipitation changes

Código

I-EBHE0047

Autores

Alberto Viglione, Luigi Cafiero, Miriam Bertola, Eleonora Dallan, Paola Mazzoglio, Francesco Laio, Marco Borga

Tema

WG 1.10: Hydrologic Design - Solutions & Communication

Resumo

Flood risk management institutions and practitioners need innovative and easy-to-use approaches that incorporate the changing climate conditions into flood predictions in ungauged basins. The traditional approach to regional flood frequency analysis enables the estimation of hydrological variables under stationary conditions. However, it is nowadays crucial to develop innovative techniques that consider the non-stationarity of climate variables. The present work aims at implementing an operative procedure to include the expected variation in precipitation extremes into regional flood frequency analysis. We relate Flood Frequency Curves (FFC) and Intensity-Duration-Frequency curves (IDF) through quantile-quantile relationships and assume that this relationship also quantifies the sensitivity of floods to changes in precipitation extremes. Under the assumption that the quantile-quantile relationship does not significantly change in time, we obtain modified FFC according to the variation of precipitation extremes. The methodology is tested assuming a simplified world based on the Rational Formula idea, where flood events are the result of the combination of two jointly distributed random variables: the extreme precipitation for the time of concentration of the catchment and the peak runoff coefficient. This methodology is then applied to more than 200 catchments of the Po River basin in northern Italy using projected percental changes of precipitation extremes from different sources (several CMIP 5 CORDEX simulations and a CMIP 6 Convection Permitting model). The percentage change of the 100-year floods over the next century obtained through the methodology are compared for the different models over the study area. This study was carried out within the RETURN Extended Partnership and received funding from the European Union Next-GenerationEU (National Recovery and Resilience Plan ? NRRP, Mission 4, Component 2, Investment 1.3 ? D.D. 1243 2/8/2022, PE0000005)