An integrated hydrological and hydraulic modelling 1 approach for the flood risk assessment over Po river 2 basin. 3 Rita Nogherotto 1 , Adriano Fantini 1 , Francesca Raffaele 1 , Fabio Di 4 Sante 1 , Francesco Dottori 2 , Erika Coppola 1 , and Filippo Giorgi 1 5 1 International Centre for Theoretical Physics,Trieste, Italy 6 2 European Commission, Joint Research Centre, Ispra, Italy 7 Abstract 9 Identification of flood prone areas is instrumental for a large number of applications, ranging 10 from engineering to climate change studies, and provides essential information for planning 11 effective emergency responses. In this work we describe an integrated hydrological and hy- 12 draulic modeling approach for the assessment of flood-prone areas in Italy and we present 13 the first results obtained over the Po river (Northern Italy) at a resolution of 90m. River 14 discharges are obtained through the hydrological model CHyM driven by GRIPHO, a newly- 15 developed high resolution hourly precipitation dataset. Runoff data is then used to obtain 16 Synthetic Design Hydrographs (SDHs) for different return periods along the river network. 17 Flood hydrographs are subsequently processed by a parallelized version of the CA2D hy- 18 draulic model to calculate the flow over an ad hoc re-shaped HydroSHEDS digital elevation 19 model which includes information about the channel geometry. Modeled hydrographs and 20 SDHs are compared with those obtained from observed data for a choice of gauging sta- 21 tions, showing an overall good performance of the CHyM model. The flood hazard maps 22 for return periods of 50, 100, 500 are validated by comparison with the official flood hazard 23 maps produced by the River Po Authority (Adbpo) and with the Joint Research Centre’s 24 (JRC) pan-European maps. The results show a good agreement with the available official 25 national flood maps for high return periods. For lower return periods the results and less 26 satisfactory but overall the application suggests strong potential of the proposed approach 27 for future applications. 28 29 Keywords: Flood hazard; Flood mapping; CHyM hydrologic model; CA2D hydraulic model. 30 1 8 https://doi.org/10.5194/nhess-2019-356 Preprint. Discussion started: 29 November 2019 c  Author(s) 2019. CC BY 4.0 License.