Graduation of Daniel Dedina

Sea Turtle Nest Inundation in Ras Baridi: Improving Flood Risk Modeling in Data-Limited Coastal Regions

• Professor of graduation: Dr. Ir. J.A. Antolinez (TU Delft)

• Supervisors: Ir. J.C. Christiaanse (TU Delft), Prof. dr. ir. A. Reniers (TU Delft), Dr. A. Elshinnawy (Tanta University), Ir. F. Roelvink (Deltares)

Six out of seven sea turtle species are classified as endangered by the IUCN. They confront intensifying threats, notably from climate change. This report centers on sea turtle nesting beaches, which are highly susceptible to climate-induced flooding via wave runup. sea turtle eggs, sensitive to environmental fluctuations, face reduced viability and skewed sex ratios when inundated. Flood risk mitigation of sea turtle nests involves wave and water level reduction or nest relocation, with the optimal relocation height often undefined. This study aids responsible nesting relocation by providing flood risk assessments linked to beach elevation at Ras Baridi, a significant Green turtle nesting site in the Red Sea.

Two metamodels, BEWARE 2.0 and HyCReWW, designed for wave runup assessments in coral reef environments, were employed to evaluate flood risk. BEWARE 2.0 uses real bathymetry profiles and XBeach 1D Non-hydrostatic model runup results, generating ensemble runup values. HyCReWW schematizes reefs using four parameters, interpolating to an XBeach runup database. Results for Ras Baridi revealed stable runup values across the beach for HyCReWW: 0.9 ± 0.15 m to 1.95 ± 0.4 m for return periods of 1 and 40 years respectively. BEWARE 2.0 yielded variable results across the beach of 0.85-1.35 and 1.8-2.7 m for return periods of 1 and 40 years, respectively.

Comparing model runs with validated data from other reef locations revealed BEWARE 2.0's superiority. BEWARE 2.0 outperformed HyCReWW, even with low-resolution bathymetry data, albeit with increasing errors. Both models' Ras Baridi performance, while different, offered valuable flood risk estimates for coastal management, despite data limitations. Model uncertainty persisted due to the lack of validation data and parameter uncertainties within the metamodels.

In summary, this report addresses the pressing issue of sea turtle nest flooding, emphasizing the importance of responsible relocation. It leverages metamodels BEWARE 2.0 and HyCReWW to assess flood risk at Ras Baridi, aiding coastal managers in making informed decisions for the protection of these endangered species.