Process Modeling and its Applications of Fine-Grained Sediments

Key words: 
• Fine-grained sedimentation /
• process modeling /
• flocculation /
• cohesive sediment /
• sediment dynamics

Abstract: Fine-grained sedimentation differs fundamentally from conventional coarse-grained sedimentation in terms of its dynamic mechanisms. It is therefore necessary to move beyond qualitative descriptions and establish quantitative dynamic models specifically for fine-grained materials. Based on the authors’ simulation results, this paper systematically reviews process modelling of fine-grained sediment across three hierarchical levels: (1) The grain scale represented by the floc mean-size model. The Winterwerp flocculation dynamics equation and the influence of fractal dimension are elucidated, revealing the evolution of floc size under the equilibrium of collision–flocculation–breakup processes; (2) The depositional-body scale, represented by Delft3D. Cohesive and noncohesive sediments are differentiated explicitly. It employs the Partheniades–Krone erosion–deposition formulation and salinity-controlled settling velocity, and effectively reproduces the impact of flocculation on deltaic depositional patterns; and (3) The basin scale, represented by Dionisos (Diffusion), Badlands (Stream Power), and Lecode (Marker-in-Cell). They are evaluated in terms of their applicability to fine-grained sediment simulation, parameterization strategies distinguishing fine- and coarse-grained sediments, and their ability to reproduce spatial patterns of various fine-grained depositional processes such as suspended settling, turbidity currents, debris flows, hillslope processes, and fluvial transport. This study deepens the understanding of the intrinsic dynamics of fine-grained sedimentation and provides perspectives for improving the adaptability of numerical models in fine-grained sediment research.