Channel refraction, a process in which obliquely incident waves are turned by navigation channel slopes and effectively reflected away from the channel, can significantly influence nearshore hydrodynamics and sediment transport. This thesis investigates how well phase-averaged and phase-resolving numerical models capture these effects. A comparative study was conducted using SWAN-FINEL (phase-averaged) and XBeach non-hydrostatic (phase-resolving). First, model performance in simulating wave transformation was assessed using a physical model of Taman Port. Both models reproduced general wave patterns and showed comparable performance based on the wave measurements. XBeach offered slightly improved accuracy in energetic conditions and on the lee side of the channel. Second, an idealized numerical experiment was used to explore sediment transport differences. Offline sediment transport calculations using an intra-wave and phase-averaged model based on the Meyer-Peter-Müller formulations revealed very similar longshore transport gradients and infilling patterns, but notable differences in cross-shore transport due to the inclusion of wave skewness, asymmetry, and swash-zone processes in XBeach. The findings highlight that while SWAN-FINEL performs well in longshore-dominated systems at low computational cost, phase-resolving models offer added value for short-term cross-shore-dominated settings, albeit at higher computational demand. Model choice should therefore depend on the dominant transport direction and project scope.

Sea turtle nesting beaches are under increasing pressure from climate change, rising sea levels, and human activity, making the protection of critical habitats like Ostional Beach, Costa Rica, an urgent priority. This study integrates the analysis of wave runup dynamics, groundwater behavior, stakeholder collaboration, and coastal squeeze mitigation to address the unique challenges at this vital olive ridley turtle nesting site.

Wave runup was examined using timestack imagery analysis. Two automated extraction models— entropy-only and entropy-saturation—were compared against manually digitized data. Results show that the entropy-only model is more reliable in capturing peak wave run-up values, a critical measure for understanding inundation risks. Challenges in accuracy, particularly for the entropy-saturation model, were linked to the site’s unique environmental conditions, such as dark volcanic sand. The findings fill a gap in understanding how specific extraction methods perform under unique site conditions, with implications for improving future modeling efforts.

Groundwater dynamics were studied using pressure sensors installed in custom-built wells, revealing significant interactions with tidal forces. These measurements highlighted the role of tidal cycles in influencing groundwater levels, providing crucial insights into the potential for nest inundation. These findings extend existing knowledge by combining tidal and hydrodynamic factors specific to turtle nesting sites.

Collaboration within the TURTLE project was analyzed through semi-structured interviews and structural evaluation of partner interactions. A tailored framework was developed to enhance communication and coordination among stakeholders, addressing identified gaps and leveraging existing strengths. This framework contributes to more effective project management and the application of scientific insights in conservation strategies.

To mitigate coastal squeeze—a phenomenon where natural habitats are compressed by rising sea levels and human development—the study evaluated strategies such as foreland restoration and managed retreat. Findings suggest that integrating habitat restoration with community involvement is critical to preserving the ecological and social balance at Ostional Beach.

This study takes an interdisciplinary approach to explore how wave runup, groundwater behavior, and collaboration strategies can be effectively combined to support conservation efforts. The results stress the need for tailored, site-specific solutions that blend engineering, ecological, and social perspectives to protect endangered species and their habitats. By bridging knowledge gaps and offering practical recommendations, the research bolsters both local and global initiatives aimed at preserving vulnerable coastal ecosystems.