An approach for flood hazard modelling and mapping in the medium Valtellina

Abstract. In the Lombardy Region, as in many other contexts all over the world, hazard maps do not have a precise legislative confirmation. Despite this, they are necessary to support several institutional activities, and among these, local urban planning. An approach to hazard analysis and mapping that fits the Lombardy Region legislative framework is presented here that introduces a level of experimental modelling, making use of SOBEK 1-D–2-D as a tool for hydrodynamic simulations. A stretch of 17 km of the Adda river in Valtellina has been modelled, referring to twelve scenarios characterised by different temporal probabilities, and comprising the main sources of uncertainty. The results were compared with available local hydraulic studies, and combined to obtain two complementary flood hazard maps which could usefully support urban planning. Advantages and drawbacks of this modelling approach, together with considerations related to flood hazard mapping are discussed.