This thesis investigates local and global scour processes around four-legged jacket (4LJ) foundations
for offshore wind turbines under current-only conditions using the 3D CFD Large Eddy Simulation (LES) model TUDflow3D. Jacket foundations, while increasingly deployed in deeper offshore environments, remain less studied than monopiles on local scour and scale effects and introduce new scour patterns like global scour. The research addresses this gap by evaluating the predictive performance of TUDflow3D against laboratory experiments, extending simulations to field scale, and assessing the applicability of monopile-based empirical scour relations to jacket configurations.

Laboratory-scale numerical simulations replicate the experimental study of Welzel et al. (2023) for both clear-water and live-bed regimes, validating the model for a 4LJ foundation. Model performance is assessed through morphodynamic comparison and time-averaged observation of the hydrodynamics, supplemented by a sensitivity analysis on numerical parameters: morphological acceleration factor, relaxation factors, numerical domain and grid resolution.

The validated model is then scaled to field conditions using a mobility similarity approach, enabling
investigation of scale effects on scour magnitude, spatial extent, and equilibrium timescales.
After the scaling up, both models are analyzed in order to enhance the knowledge that is known until now from 4LJ foundations.

For local scour, the spatial extent of scour was determined by adapting a formulation for monopiles and quantified throughout the entire scour evolution, revealing a consistent footprint over time. Scaling to field conditions demonstrated that the upstream–downstream scour pattern persists, but with reduced magnitudes in local scour depth due to scale effects, observed by the reduction of time-averaged bed shear stresses around the legs. This reduction in magnitude was approximately 30%–35% when compared in terms of dimensionless scour for both regimes and for both upstream and downstream piles. Timescale analysis showed that scour equilibrium occurs later at locations farther from the piles. When scaling, it was also found that scour on clear-water regimes
require months while live-bed regimes is in the order of magnitude of days to reach local scour equilibrium.

For global scour, live-bed conditions produced a footprint extending up to twice the jacket footprint
radius with rapid initial development, while clear-water conditions yielded slower, more confined scour. The order of magnitude for the global scour is variable depending on the location, but it reached values around 0.9 - 1 D on the center of the jacket and downstream of it.

Finally, empirical monopile scour formulas were evaluated, showing that they still provide reasonable order-of-magnitude estimates for upstream piles and capturing scale effects, as well it was proved that the scaling up from laboratory scale to field scale developed for monopiles can be useful also for 4LJ foundations.

The study demonstrates that CFD LES modeling is a robust and flexible tool for detailed, process based scour prediction around complex foundation geometries. Beyond validation, its ability to simulate field-scale morphodynamics and provide high-resolution temporal and spatial data makes it a valuable complement to laboratory testing,

Previous studies show that climate change effects and anthropogenic disturbances are having an increasingly strenuous effect on the performance of the coastal system of Sisal, a rural fishing village in the state of Yucatán, Mexico. Resilience has been a crucial component for these studies, as it presents the system's ability to react and adapt to environmental hazards and human interventions. In recent years, several research initiatives have aimed to assess the resilience of Sisal's coastal system through the use of previously identified resilience index calculations. However, these indices lack the ability to quantify disparities of resilience on a local scale. Furthermore, previous studies focus solely on the technical aspects of resilience, and therefore fall short on defining other relevant aspects of the term.

Consequently, this research project aimed to understand Sisal's coastline by understanding the multi-faceted definitions of resilience by analysing the socio-economic and technical factors impacting the coastal system. The study involved examining both its historical context, as well as potential future trends and developments.

This was done through a thorough evaluation of different aspects of the coast, a storm impact study and a social analysis. The findings of these studies are subsequently incorporated into a comprehensive web-tool, providing experts, policymakers, and community members with clear-cut and valuable information on the current resilience of Sisal's coastline.

The findings of the research present that the coastal resilience of Sisal is highly negatively impacted by human interventions along the coast, predominantly causing inadequate resilience performances on profiles with significant anthropogenic perturbations and generally along the coastline westwards of Sisal's port. Current coastal management policies are considered ineffective to deal with these developments, which is among others caused by exclusive decision-making processes and ambiguous governmental policies. Changes in coastal management strategies are therefore needed to effectively deal with future threats of environmental hazards and human interference. Ultimately, resulting in improved coastal and community resilience.