Morphodynamic Modeling of Tidal Basins: The Role of Sand‐Mud Interaction

Abstract

The morphology of tide‐dominated systems is progressively influenced by human activities and climate change. Quantitative approaches aiming at understanding or forecasting the effects of interventions and climate change are often aggregated, thereby simplifying or schematizing the investigated area. In this work, we advance on the knowledge of sediment transport processes shaping tidal systems and on methodologies translating schematized model output into physically realistic variables. In terms of improved physics, we systematically evaluate the influence of sand‐mud interaction processes. Most tidal systems are shaped by a mixture of sand and mud. Morphological models typically compute transport of sand and mud independently, despite studies clearly demonstrating that their physical behavior is mutually dependent. We investigate the effects of two interaction mechanisms (erosion interaction and roughness interaction, applied with varying mud erodibility) with a schematized process‐based morphodynamic model. We convert model output into metrics that describe the meso‐scale configuration of the modeled systems, allowing a quantitative comparison of scenarios. Modeled patterns and intertidal flat shape, size and composition widely vary with mud erodibility settings, but equally depend on the evaluated sand‐mud interaction mechanisms (with erosion interaction having a larger effect than roughness interaction). Sand‐mud interaction thus needs to be accounted for from a physical point of view, but also to improve predictions of tidal basin evolution models, particularly the (bimodally distributed) sediment composition of intertidal flats.

Reservoir Mud Releasing May Suboptimize Fluvial Sand Supply to Coastal Sediment Budget: Modeling the Impact of Shihmen Reservoir Case on Tamsui River Estuary

“…To resolve the density stratification effects would require the model to be run in 3D mode. (b) Sand‐mud interaction, which affects sand erosion flux through the variations of erodibility (critical shear stress for erosion) and bed roughness (bed shear stress due to skin drag) as a function of bed mud content (Alonso et al., 2023; Braat et al., 2017). Sand erosion flux would decrease with the increase of bed mud content because of the reduced erodibility and bed shear stress, not just because of the reduced availability.…”