Submitted as: model description paper
27 Sep 2023
Submitted as: model description paper |  | 27 Sep 2023
Status: a revised version of this preprint is currently under review for the journal GMD.

LOCATE v1.0: Numerical Modelling of Floating Marine Debris Dispersion in Coastal Regions Using Nested Hydrodynamic Grids and Parcels v2.4.2

Ivan Hernandez, Leidy M. Castro-Rosero, Manuel Espino, and Jose M. Alsina Torrent

Abstract. The transport mechanisms of floating marine debris in coastal zones remain poorly understood, primarily due to the complex geometry and influence of coastal processes which pose difficulties in incorporating them into Lagrangian numerical models at coastal scales. The numerical model presented in this study addresses these challenges using nested grids of varying hydrodynamic resolutions (2.5 km, 350 m, and 70 m). The model couples Eulerian hydrodynamic data with a Lagrangian particle solver to accurately simulate the motion of plastic particles in coastal regions. A Lagrangian validation of the model was conducted using drifter data to assess the model’s skill and confidence in simulation predictions. The results demonstrated high skill and stability in 72-hour forecast horizons and high skill score values close to the shoreline. Additionally, a beaching sensitivity analysis was performed to determine particle beaching parameterisations suitable for coastal zones. This analysis demonstrated that the real-time distance of particles to the shore during simulations was the most accurate method for detecting the land-water boundary at coastal scales, accurately representing residence times and spatiotemporal beaching patterns. Simulations were conducted using nested grids and a single coarse grid, both using the same plastic input from river outflows in a pilot test at the Barcelona coastline with a complex morphology due to coastal structures, two major river mouths, and a large harbour. The simulations revealed marked differences in beaching amounts and residence times. Both simulations exhibited high levels of beaching, with the nested grid simulation registering 91.5 % beaching and the low-resolution grid simulation showing 95.8 % beaching, surpassing other studies conducted at larger scales. Beaching amounts exhibited high levels of variability within demarcated areas between simulations, with the highest flux observed near the Llobregat River mouth release point. The inner port area showed that particles have 18 times longer residence times when using high-resolution data, demonstrating the model’s ability to solve complex coastal geometrical structures. By using nested grids, the model can resolve coastal processes with high-resolution hydrodynamic data and accurately simulate potential accumulation zones and litter hot-spots at coastal scales.

Ivan Hernandez et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2023-160', Anonymous Referee #1, 24 Oct 2023
    • AC2: 'Reply on RC1', Ivan Hernandez, 16 Nov 2023
      • RC3: 'Reply on AC2', Anonymous Referee #1, 21 Nov 2023
        • AC3: 'Reply on RC3', Ivan Hernandez, 24 Nov 2023
  • RC2: 'Comment on gmd-2023-160', Joseph Harari, 09 Nov 2023
    • AC1: 'Reply on RC2', Ivan Hernandez, 10 Nov 2023

Ivan Hernandez et al.

Ivan Hernandez et al.


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Short summary
A numerical model, LOCATE, has been developed to use high-resolution hydrodynamic data simulate the transport of marine debris at coastal scales. Simulations were conducted using nested grids and a low resolution grid. Very high beaching amounts were recorded (> 90 %), the model was able to solve some coastal processes (limited by hydrodynamic data resolution), solve complex geometrical structures (port area) and successfully predict particle trajectories by using drifter data to compare.