Vulnerability Assessment of Levee Failure Due to Underseepage in the Szigetköz Floodplain Area

Analysis of the likelihood of structural or hydraulic failures of levees is a crucial part of flood risk assessment and is affected by many uncertainties. This paper evaluates a critical area along the Danube River in the Szigetköz floodplain, where hydraulic risk has been increasing due to rising flood levels. Blanket theory approaches demonstrated the probability of failure relative to erosional failure, and Monte Carlo simulations generated fragility curves. The results of the case study show that the thickness of the aquifer layer has a slight effect if it is deeper than 30 m. The research also reveals that the probability of failure is highly affected by the distance from the river to the riverside levee toe; the shorter this distance, the higher the hydraulic risk. Sensitivity analyses emphasize the effect of variable inhomogeneity; as the leakage factor increases, the probability of failure due to underseepage increases. Comparing coefficients of variation across different floodwater levels showed that at low floodwater levels, a lower coefficient of variation corresponds to a lower probability of failure. In contrast, at higher floodwater levels, the same coefficient produced a higher probability of failure.