Definition of direct and indirect types of landslide-bridge interference and a checklist for identifying and characterizing potential landslides

According to the new Italian Guidelines on existing bridges (LLG) the evaluation of the landslide susceptibility, vulnerability, and exposure, is based on the collection of the data necessary to fill the Field Sheet Form during the Periodic Field Surveys. Based on the knowledge and expertise gained during the inspections of the surrounding areas of a relevant number of existing bridges located in different geomorphological and geological contexts (i.e., Northern and Southern Apennines of Italy), the Authors recognized several difficulties in the accurate evaluation of the parameters to assess susceptibility and vulnerability according to LLG. In particular, the evaluation of the secondary parameters, namely extent of the interference and overall reliability of the assessment, depends greatly on the arbitrariness of the inspector. The main objectives of this work are: (a) to provide useful elements to distinguish between two types of landslide-bridge interference (direct and indirect) and evaluate the extent of the interference parameter (available options are: Total, Partial, and Approach Zone); (b) to propose an Additional Field Sheet Form aimed to improve the identification and characterization of Potential Landslides and to make more objective the self-evaluation of the inspector about the overall reliability of the assessment (two options: good, limited) of the primary parameters characterizing the landslide (activity, velocity, and magnitude).