Modelling water flow in presence of various obstructions: description and validation of a generic module for 2- and 3-dimensional simulations

In coastal areas, various types of biological and anthropogenic structures significantly influence the flow and related sediment dynamics. In this paper, we describe a new generic flow-obstruction module, designed to represent both upward or downward, rigid or flexible structures. This module provides a particularly accurate representation of flow velocities in the presence of flexible obstructions, due to a thorough description of their bending. The obstruction/flow interaction module can operate either in 3D or 2D mode. It also offers the possibility of incorporating multiple types of obstructions within a single mesh, which is invaluable when modeling realistic ecosystem dynamics. Module validation was carried out using flume experiments on seagrasses, as well as using numerical studies involving two anthropogenic structures: mussel long-lines and oyster tables. The coupled hydrodynamic/obstruction model yielded excellent results for 2D/3D velocity fields with minimal calibration efforts. This module can be integrated into any hydrodynamic coastal model and is aimed at being upscaled to a regional scale, offering the potential to explore future trajectories regarding the vulnerability of coastal systems in response to global change, or to identify restoration measures in engineered coastal systems. • New Flow-Obstructions module for upward/downward and rigid/flexible obstructions • Possibility of simulating multiple obstructions within a single grid cell • This module is validated for various seagrass species and anthropogenic structures • Minimum calibration effort is required as long as obstructions are properly described • This module can be coupled with any hydrodynamic coastal model