The hydraulic study, carried out by GIT on behalf of the Unione Montana Langa Astigiana Val Bormida, of a stretch of the Bormida di Millesimo river extended between the municipalities of Vesime and Bistagno, by means of 1D and 2D numerical modeling, has laid the foundations for the hydraulic risk mitigation project in the territory of the Municipality of Bubbio, which historically suffers major flooding.

The design of the interventions followed the following steps:

• acquisition of topographical data using GPS technology along road routes adjacent to the Bormida river for about 70 km, in order to prepare strongholds, then used to georeference the aero-photogrammetric surveys carried out with SAPR technology on the territories of Vesime, Bubbio, Monastero Bormida, Sessame and Bistagno;
• integration of the photogrammetric surveys with Digital Terrain Models (DTM) provided by the Ministry of Environment;
• hydrological study to determine the design flow rate for Tr= 200 years, by setting up two different hydrological models (HEC-HMS and IdroPrev) calibrated in back-analysis on the 2016 event;
• preparation of 1D and 2D hydraulic models then calibrated in back-analysis on the 24-25 November 2016 event, for which observed hydrograms of the Bormida di Millesimo at Cessole and of the Bormida di Spigno at Mombaldone were available, as well as ground effects surveys by Arpa Piemonte;
• hydraulic simulations for different scenarios of pre-works overflow and post verification with the inclusion of design hypotheses pile walls.