Risk Assessment of Levee Seepage Failure Based on the Levee Seepage Failure Probability $P_f$ and the Levee Vulnerability Index $t^{*}$

This study presents scientific methods for risk assessment of levee seepage failure. First, the levee seepage failure probability, $P_f$, was calculated by reliability analysis considering muddying and slope sliding due to the development of the seepage line and uncertainty in the soil index. $P_f$ is useful for estimating levee sites with a high seepage risk. Next, the seepage flow number, SFn, which is a dynamic dimensionless number governing general seepage flow, was derived by nondimensionalizing Richards’ equation. Then, the levee vulnerability index, $t^{*}$, was obtained by applying SFn to the phenomena of levee seepage and failure. Values of $t^{*}$ were determined by applying it to damage results of model levees and field levees. Because $t^{*}$ and $P_f$ corresponded well in the field levees in which considerable damage such as levee breaching and slope sliding or collapse have occurred, the risk of levee seepage failure can be estimated by $t^{*}$. Finally, $t^{*}$ can provide a dynamic similarity condition to describe the phenomenon of levee seepage and failure and can be a useful tool for understanding levee seepage failure.