Validating floc settling velocity models in rivers and freshwater wetlands

• DOI: 10.5194/egusphere-2024-524
• Publication Date: 2024-02-27T06:20:30Z
• Authors: Justin A. Nghiem; Gen K. Li; Joshua P. Harring...; Gerard Salter; Cédric G. Fichot; Luca Cortese; Michael P. Lamb
• Keywords: Settling; Sedimentation; Particle (ecology)

Abstract. Flocculation controls mud sedimentation and organic carbon burial rates by increasing settling velocity. Floc velocity can be predicted using a semi-empirical model that depends on turbulence, sediment concentration, geochemical variables or an explicit Stokes law-type floc diameter, permeability, fractal properties. However, validation of the models with direct field measurements is lacking. We employed camera, in situ particle sizing, analysis grain size-specific suspended concentration profiles to measure flocs freshwater channels wetlands Wax Lake Delta, Louisiana. Sediment finer than ~20 50 μm flocculates median diameter 30 90 μm, bulk solid fraction 0.05 0.3, ~0.1 1 mm s-1, little variation along depth. These values are consistent model, which indicates turbulence limits flood-to-seasonal time scales. In effective primary commonly assumed differs factor ~2 6 smaller better described simple theory. Flow through increases explained parameterizing as effectively permeable clusters particles. Our results provide first full permeability theories, improve predictions model.