Estimating vegetation drag on bore propagation using a high-resolution, non-hydrostatic shallow water model with turbulence closure

In this study, we estimated vegetation drag forces exerted on a propagating bore, represented by arrays of emergent cylinders in the experimental setup, by accounting for free-surface and bottom pressure fluctuations around the cylinders. To capture these fluctuations, we employed NUFSAW2D, our in-house non-hydrostatic shallow-water solver with turbulence closure, where the cylinders were fully resolved using fine-resolution meshes of up to 7.5 mm. Three initial Froude numbers (1.32, 1.53, and 3.98) were considered to generate the bore. Within the vegetated zone, complex wave-vortex-vegetation interactions were observed, and our fully resolved model accurately predicted water-level fluctuations under medium and high Froude number conditions. For the low Froude number case, the amplitude was well captured; however, slight discrepancies in wave period indicated significant non-hydrostatic effects. To quantify vegetation drag, we compared the fully resolved model with several drag-force formulations. Results revealed notable discrepancies between the two approaches under conditions of strong water-level fluctuations.