Benjamin Beylard

Preparation of public tenders and assistance in the management and monitoring of environmental regulation projects within the project ownership department of the Directorate of Infrastructure of the Gironde Departmental Council.

Title: Morphodynamic modelling of a nourished beach The focus of this study is to introduce and evaluate the performance of the 2DH coastal process-based model COAST2D that incorporates a novel engineering approach to multi-fractional sediment dynamics. This new method assumes that sediments of similar size adopt similar behaviours (mixing) when exposed to given hydrodynamic forcing. It is expected to improve computational efficiency while accurately predicting beach nourishment evolution. To assess the performance of the mixed sediment algorithm, the morphodynamic evolution of the Sandscaping Bacton gas terminal (UK), is computed under different hydrodynamic conditions. A series of tests are conducted under both calm and storm conditions of different intensities between the 20th of September 2019 and the 05th of February 2020. The model results are then compared with field data to determine the magnitude of model error. Additional tests are also performed to identify the origin of these errors and evaluate the model's sensitivity. Overall, COAST2D model captures properly the early-life evolution of the Bacton nourished beach (6 months). the steep artificial beach slope transitions towards a more dissipative state and shore-parallel sand bars appear in the surf zone. Comparisons with field data reveal that the model predicts accurately the trend of erosion along the Sand- scaping's wider area as well as the redistribution of the eroded sand downstream although globally underestimating the erosion/accretion volumes. Assumptions made or potential errors in model set-up or data manipulations contribute to these differences. Nevertheless, the results of the study at hand remain encouraging regarding the capabilities of the mixed sediment approach to accurately represent the evolution of a nourished beach.

Within a multidisciplinary team, my role consisted of conducting one-hour lectures (in English and French); supervising groups ashore (driving Zodiacs®, marking the area, explanations...) and more generally creating a privileged relationship of trust with passengers, acting as a scientific and field referent.