The design code Eurocode 7 relies on semi-probabilistic calculation procedures, through utilization of the soil parameters obtained by in situ and laboratory tests, or by the means of transformation models. To reach a prescribed safety margin, the inherent soil parameter variability is accounted for through the application of partial factors to either soil parameters directly or to the resistance. However, considering several sources of geotechnical uncertainty, including the inherent soil variability, measurement error and transformation uncertainty, full probabilistic analyses should be implemented to directly consider the site-specific variability. This paper presents the procedure of developing fragility curves for levee slope stability and piping as failure mechanisms that lead to larger breaches, where a direct influence of the flood event intensity on the probability of failure is calculated. A range of fragility curve sets is presented, considering the variability of levee material properties and varying durations of the flood event, thus providing crucial insight into the vulnerability of the levee exposed to rising water levels. The procedure is applied to the River Drava levee, a site which has shown a continuous trend of increased water levels in recent years.

When constructing flood protection structures such as river levees, oftentimes due to various factors engineers must design composite structures, i.e., reinforced earthen structures which comply with all the stability criteria. The most common way of reinforcing such structures is the usage of geosynthetics, or mostly geogrids when talking about stability. Since geosynthetics are man-made materials produced in a controlled environment and go through quality control measures, their characteristics contain a negligible amount of uncertainty compared to natural soils. However, geosynthetic handling, their installation in the levee, and their long-term degradation can all have significant effects of variable magnitude on geosynthetic characteristics. These effects and their variability can be considered as random variables, which can then be used in probabilistic analyses together with soil properties. To investigate the effects of the geogrid’s resistance variability on slope stability compared to soil properties variability, probabilistic analyses are conducted on a river levee in northern Croatia. It is found that the geogrid’s variability generally has very little effect on the total uncertainty compared to the friction angle’s variability, but out of the three geogrid layers used the top grid has the most influence.

Levees are linear structures that are continuously reconstructed throughout the years and whose construction and behavior depends on local soil conditions, as well as requirements regarding impermeability and mechanical resistance. This results in various levee cross sections, even within the same levee. In situations of extreme water events, when timely actions are required, this variability poses a problem for decision-making based on observed behavior, which is highly dependent on the specific section parameters. Creating models for each problematic section becomes impractical, and because of that, in this study, 91 different cross sections from 16 levees are considered to identify the key levee parameters with the largest effects on three observed mechanisms: deformations, exit hydraulic gradients, and factors of safety. The implemented factor screening methodology is based on the sequential bifurcation method (SB) and numerical analyses. The SB method successively investigates groups of factors and uses their cumulative effects to identify the important groups and to discard the unimportant based on a previously selected parameter $\Delta$, until the groups are reduced to single factors that may be deemed important. It is found that approximately 30% of all the factors used to describe the most complex sections are considered important by at least one of the investigated mechanisms.

This study investigates cross-border cascading hazards and infrastructure vulnerabilities in the Sava River Basin, a seismically active and flood-prone region spanning the Slovenia–Croatia border. Conducted within the CROSScade project, the research focuses on assessing cross-border hazards and the vulnerabilities of levees and bridges. Key earthquake and flood scenarios were identified using advanced hydraulic and seismic modelling, forming the basis for evaluating the cascading effects of these events, including the potential failure of hydropower plants and associated flood protection systems. The analysis reveals that levees are particularly vulnerable to failure during the recession phase of flooding that follows an earthquake. At the same time, bridges are primarily affected by seismic loading, with minimal structural impact from flood forces. These findings underscore the pressing need for enhanced cross-border collaboration, updated design standards, and the reinforcement of critical infrastructure. The study provides essential insights for multi-hazard resilience planning and emphasises the importance of integrated risk assessments in managing cascading disaster impacts across national boundaries.

This paper presents a numerical analysis of liquefaction-induced lateral spreading at Brest Pokupski in Croatia, observed during the 2020 M_w6.4 Petrinja earthquake. The site is composed of Holocene alluvial deposits consisting of loose to medium-dense sands, silty sands, and sandy silts with high groundwater levels, locally confined by low-permeability cohesive layers, which together created favourable conditions for excess pore pressure generation, liquefaction and lateral spreading. During the 2020 Petrinja earthquake, the area experienced large-scale ground failures, including widespread soil deformations, sand ejecta, ground cracking and settlement, making it one of the most prominent manifestations of earthquake-induced liquefaction in the affected region. The study applies dynamic analyses using the advanced constitutive models and soil parameters derived from laboratory tests and CPT investigations. The model simulates excess pore water pressure development and resulting ground deformations, with displacements evaluated at advanced stages of dissipation. During the dissipation phases, the model exhibits a high sensitivity to hydraulic conductivity, which may be attributed to slight residual numerical imbalances at the end of shaking. Consequently, scaling factors of 100 and 1000 result in horizontal displacements of approximately 20–30 cm and 60–70 cm, respectively, within the liquefiable layer. Trends of ground displacement with distance along the profile, however, remain consistent regardless of the applied scaling factors, and can therefore be used in conjunction with displacement measurements to assess the response. Numerical results are used in conjunction with InSAR observations from the European Ground Motion Service (EGMS) and geodetic benchmark measurements to assess the displacement field changes along the profile. The comparison from two points showed a shift in the displacement direction towards the river by about 14^∘.

Levees are vulnerable to a multitude of hazards which may cause their partial or complete failure, thus leading to loss of their main purpose of protection against floods. As earthen structures, levees are also highly susceptible to earthquakes. A major concern arises in the unlikely case that these two events occur at the same time with extreme magnitudes. A similar situation occurs when an earthquake damages upstream components of the same flood protection network, such as dams, causing water waves to propagate downstream. The loads are not simultaneous, but within the short delay the damage to the levees would not have yet been identified/repaired to prevent flooding of the surrounding area. This paper analyses cascading scenarios of strong earthquakes followed by water waves resulting from damaged dams, acting upon the downstream levees. The levees in the cross-border area of Croatia and Slovenia, sharing the seismic and flooding hazards, are selected for validation of the vulnerability assessment methodology. The vulnerability of levees was modelled considering the influence of earthquakes on both the levee network and the upstream hydropower plant. Probabilities of failure are derived, enabling the categorization of the levee network, and giving valuable information to infrastructure managers and first responders on the criticality of the network whose overall efficiency is controlled by the weakest link. <!----> <!----> <!----> <!---->