Drag and Reconfiguration of Aquatic Plant Patches: Roles of Patch Size, Density and Plant Flexural Stiffness

The reconfiguration of flexible structures such as submerged aquatic plants is a key mechanism for reducing drag in environments with high variation in water velocities. In flowing water, submerged aquatic vegetation can form patches, which are discrete structures formed by many individuals at high density. While most studies have focused on isolated shoots, drag and reconfiguration remain largely unstudied in aquatic plant patches.

We studied the drag and reconfiguration of patches and tested the effects of patch size, density, and plant flexural stiffness on reconfiguration. We investigated three aquatic plant species presenting contrasting properties in a flume experiment.

Our results demonstrated that the reconfiguration of patches is similar to previous findings on isolated shoots, indicating a high reconfiguration capacity for patches. Moreover, the reconfiguration capacity differed between species, suggesting that a single reconfiguration coefficient cannot accurately estimate drag in models. Overall, patch reconfiguration was linked to patch fresh mass and density but not to plant flexural stiffness.

By providing the first measurements of drag and reconfiguration of small patches in flumes, our results provide an initial basis for the large‐scale numerical modelling of patch drag in fluvial environments.