Identifying robust large-scale flood risk mitigation strategies: a quasi-2D hydraulic model as a tool for the Po river

This paper focuses on the identification of large-scale flood risk mitigation strategies for the middle-lower reach of River Po, the longest Italian river and the largest in terms of streamflow. This study develops and tests the applicability of a quasi-2D hydraulic model to aid the identification of large-scale flood risk mitigation strategies relative to a 500-year flood event other than levee heightening, which is not technically viable nor economically conceivable for the case study. Different geometrical configurations of the embankment system are considered and modelled in the study: no overtopping; overtopping and levee breaching; overtopping without levee breaching. The quasi-2D model resulted in being a very useful tool for (1) addressing the problem of flood risk mitigation from a global - perspective (i.e., entire middlelower reach of River Po), (2) identifying critical reaches, inundation areas and corresponding overflow volumes, and (3) generating reliable boundary conditions for smaller scale studies aimed at further analyzing the hypothesized flood mitigation strategies using more complex modelling tools (e.g., fully 2D approaches). These are crucial tasks for institutions and public bodies in charge of formulating robust flood risk management strategies for large European rivers, in the light of the recent Directive 2007/ 60/EC on the assessment and management of flood risks (European Parliament, 2007).