• Extended gravity-driven sediment transport theory with a power-law rheology model. • A perturbation analysis simplifies Navier–Stokes equations for numerical solution. • Bed slope dominates transport velocity and thickness redistribution patterns. • Rheology (Viscosity and flow index) control motion initiation and duration. fluid-mud is widely distributed in weak hydrodynamic environments such as estuaries and reservoirs where hydrodynamic conditions are weak. Its motion, governed by complex rheological properties and gravity-induced forces, plays a crucial role in sediment redistribution and morphological evolution. This study investigates the gravity-driven transport dynamics of fluid-mud through the development of a one-dimensional numerical model based on a power-law rheological model. The governing equations are derived from the N-S equations and simplified via perturbation expansion, then solved using an explicit finite difference method. Laboratory flume experiments were conducted under mild slope conditions to validate the model and to quantify the effects of mud density, viscosity coefficient, flow behaviour index, and bed slope on flow velocity and layer redistribution. The results show that the model effectively reproduces the initiation, motion, and deposition processes of fluid-mud under gravity, highlighting the dominant role of bed slope in controlling flow velocity and redistribution patterns. Increased viscosity and flow index suppress motion initiation and shorten transport duration. These findings provide new insights into the gravity-driven depositional behaviour of cohesive fine sediments in weakly dynamic aquatic systems, offering implications for bed evolution, sediment stability, and the management of fine-sediment accumulation under weak hydrodynamic conditions.
Liu et al. (Wed,) studied this question.