Fluvial suspended sediment dynamics: Implications for particulate organic carbon transport modeling

Abstract

The effect of fluvial suspended sediment aggregation on the hydrodynamic transport properties of particulate organic carbon (POC) was investigated using a combination of field measurement and numerical modeling. Field‐based settling tube experiments were conducted to obtain particle settling velocity frequency distributions of a 4‐km‐long section of a lake outlet river at two distinct discharge levels (6.8 and 29.7 m3 s−1). Results of field studies conducted in April 2001 and April 2002 showed that the lacustrine settling velocity frequency distributions of suspended particulate matter (SPM) and POC were altered owing to the formation of riverine aggregates having comparatively higher settling velocities. Data suggest that aggregation promoted deposition fluxes of POC; these fluxes were in turn closely tied to the processes that controlled deposition of SPM. Data interpretation was aided by the employment of a hydrodynamic sediment transport model. The approach used to integrate aggregation in the sediment transport simulations represents the interaction of multiple settling velocity mass fractions. Both field data and modeling demonstrated the effect of aggregation on the increase in deposition fluxes of POC.