Multi-model approach in flood forecasting systems and flood hazard mappreparation at the local and regional scale

As stated by the new EU flood directive “Member States should base their assessments, maps and plans on appropriate 'best practice' and 'best available technologies' ....” From an hydrological point of view this could suggest the use of the 'best model' both in the simulation of prefixed flood scenarios and in flood forecasting systems. Actually plenty of hydrological models were created and applied for this purpose in the past, especially in the last decades, but the definition of an 'optimal model' is still an unresolved problem. The multi model approach, considering a weighted combination of hydrological models to define the most probable response of the basin, might be a suitable solution. The application of this approach and its advantages were investigated in this work, focusing on the mountain areas of Northern Apennines (Italy), contributing to the Po river. To this aim, the Taro river watershed was selected as a case study. The drained area is about 2˙000 km2 wide at the junction with the Po river. In the last decade the basin has been monitored through a dense hydro-meteorological network. Distributed, semi-distributed and lumped hydrological models were used to simulate or hind-cast (using real time meteorological forecasts) the flood events that occurred during the monitoring period and their performance was measured.