Collection and analysis of the reactivation data of the historical sand boils in the po river levees

A recent study (Aielli et al. 2017) about sand boil reactivations in the major Po river banks (Italy) has demonstrated how a structured database of historic information can significantly contribute to better understanding of seepage phenomena and provide a practical tool for safe management of hydraulic works. The primary aim of the present work is to enhance the information collected in the database (DB), which cover the whole course the Po river, to the beginning of the delta. In particular, an improved estimation of the critical height (i.e. height of the water level in the river which causes a sand boil reactivation) for sand boil phenomena is discussed herein. The maximum height without reactivation and the minimum height with reactivation have been evaluated for each recorded sand boil. The DB information and processing of the available data allow defining how the values of the critical heights are distributed along the course of the river. The DB information, connected to the alert thresholds and to the early warning system, can provide an indication of the possible reactivations of the piping phenomena in advance, enabling efficient coordination of the emergency actions against backward erosion piping progression.