Levee body seepage: A refinement of an expeditious procedure for fragility curves and vulnerability diagrams' assessment

Extensive flooding can be the result of levee system failures most frequently caused by the piping process due to seepage. The proper description of the seepage line is affected by the difficulty of estimating the hydraulic parameters, mainly the soil hydraulic conductivity. Therefore, the development of simple methods for a quick analysis of extended levee systems is fundamental to identify critical points. In this context, a practical procedure, recently proposed, based on a simple vulnerability index is here enhanced and used to derive diagrams easily applicable for seepage vulnerability estimate, taking the hydraulic parameters' uncertainty into account. The procedure is applied for the Tiber River, in central Italy, and the Tanaro River, in northern Italy, by analyzing 67 and 6 levees, respectively. The results show that the method provides the highest seepage probabilities for levees affected by failures in the past. Therefore, the procedure seems to be able to identify the levees that require detailed investigations. Finally, the Italian levee database (DANTE) is presented as a dynamic geospatial tool for collecting all the available data/information on levee systems to usefully support authorities with the charge of hydraulic risk mitigation for identifying the most vulnerable levees.