Abstract
Establishing a geotechnical rationale for an embankment overflow is challenging. The occurrence of embankment overflow is deemed unlikely since the initial highest water level of the embankment is assumed to be fixed as a designed flood water level or a seasonal flood-limited water level when calculating the rainfall amount in the hydrological stability analysis. However, the possibility of overtopping can be assessed by employing copula functions. This approach takes into account the return frequency of overflow and the fluctuation of probable water levels due to climate change rather than relying on the fixed highest water levels of an embankment. This study examined the effect of tensile cracks leading to the shallow failure of embankment slopes during drawdown and placed an emphasis on the vulnerability of embankment slopes due to extreme rainfall events. Throughout the comprehensive numerical simulations, it was found that the critical period for embankment slope collapse was immediately after drawdown for the upstream slope and during the initial stages of overflow for the downstream slope.