On the effect of hydrometric water level time-variability on riverbank stability evaluation

High water event is one of the most impacting threats affecting embankment stability. In the current practice, the geotechnical assessment of retaining water infrastructures stability against high water events is performed by assuming steady state conditions in equilibrium with the design level. Although on the safe side, the approach does not allow for proper evaluation of the associated risk, as it may largely overestimate the occurrence of instability mechanisms. This study is conceived to address the time dependent response of dykes and levees, in an attempt to improve the present models for their vulnerability evaluation. Data collected from the Secchia river stream gauges, north of the city of Modena (Italy), are processed through spectral analysis, with the aim to identify the principal component frequencies, and to create a hydrometric spectrum for the site under investigation. The waveforms are analysed in the time-domain space, to identify relevant features of the hydrometric water level. Numerical analyses are performed to determine the riverbank stability indicators for different scenarios, representative of specific initial and boundary conditions. The final purpose of this study is to underline the effect of the water level time-variability on the riverbanks stability evaluation, providing preliminary indications and suggestions, which can eventually be implemented in the standard engineering practice.