Territorial recognition of existing stream crossings to assess hydraulic and structural vulnerability

Among the extreme climatic events, flooding after heavy rainstorms, such as flash flood in both urban and rural areas, is nowadays an ever more frequent occurrence in Italy, leading to substantial damage to property and infrastructure, and sometimes entailing loss of human lives. A significant aspect relates to road network vulnerability in suburban areas, in particular the existing stream crossing structures, whether they are pipe culverts or bridges. A large number of existing crossings may be at full capacity for many of the possible floods, causing significant backwater upstream off the structure. This situation might exacerbate during upstream flooding, causing road overflow in many cases. In this circumstance, a structural failure of small masonry or reinforced concrete bridges may also occur, enhanced and accelerated by the original structural weakness. A suitable identification of the watercourse and road network with the stream crossing and retaining structures is a key tool to provide the needed database for both hydraulic and structural vulnerability assessment on a territorial scale. For this reason, the main tools employed in this work are the Geographical Information System (QGIS) and the database (MySQL) for data storing and processing. All surveyed information regarding both crossing structures and the riverbed are collected through suitable evaluation forms. These contribute to creating an initial opinion on the aptitude of the stream crossing to damage users or to undergo collapse during an extreme rainfall event. The ability of accepting exposure data, such as traffic intensity, and the prospect of inserting vulnerability data into hazard maps may successively help to highlight the intervention priorities, making this work a valuable tool for risk mitigation.