Identification of flood-prone areas for future urban planning choices: the Val Seriana case study (Lombardy-northern Italy)

This case study examines 10 municipal areas of the Pioverna River valley bottom (Valsassina, Northern Italy). Flood-prone areas were identified using historical research and geomorphological analysis. The historical research for different areas utilized records from the State technical office archives, Ministry of Public Works, Hydrographical Offices of the Po River, Civil Engineers, Record Office, public libraries, local and national newspapers archives, and municipal archives. Large amounts of historical data on past floods were collected, reviewed and validated to map flood-damaged locations. A geomorphological analysis was also conducted in which multi-temporal aerial photographs were studied and field surveys conducted to verify the reliability of the historical data and the planform changes of the Pioverna River course. The analysis of historical and geomorphological data produced a flood-prone area map with two different hazard zones identified along the Pioverna River. Aerophotogrammetric and cadastral maps were used to verify and update the urban planning of 10 municipalities studied. The mosaic map of the urban plannings shows four classes of land-use destinations, as defined according to the different levels of building exposure. On a matrix, the four land-use classes were matched to flood hazard sites of the two zones along the Pioverna River. The resulting map defines five classes of different flood risk. The results of the study have been used to verify present land-use planning and to start a review process of the existing urban plans and/or their general changes.