Modeling Hydro‐Morphodynamic Processes During the Propagation of Fluvial Sediment Pulses: A Physics‐Based Framework

Abstract

AbstractFluvial sediment pulses are associated with a sudden and major increase in sediment supply to riverine environments. Their occurrence can be triggered by natural or anthropogenic factors or processes, including landslides, debris flows from tributaries, volcanic eruptions, dam removals, and mining‐related activities. To predict their propagation, decoupled (clear‐water) models are commonly used, despite shortcomings identified when simulating the initial propagation phase and the existence of coupled (sediment‐laden) models. Herein, a framework for improving the accuracy of modeling efforts that simulate fluvial sediment pulse propagation dynamics is presented. The framework is centered on a physics‐based criterion formed by a dimensionless parameter ξ and its threshold condition ξcr. Comparison with laboratory and field studies shows that ξ indicates the relative importance of the terms neglected in decoupled models and that its threshold condition ξcr effectively sets an upper limit for their application. Results show that decoupled models are inaccurate when ξ > ξcr but become sufficient when ξ < ξcr. When applied to well‐monitored fluvial sediment pulses, the framework quantifies the two‐phase propagation dynamics observed in the field, showing an initial phase characterized by ξ > ξcr and a subsequent phase characterized by ξ ≤ ξcr. Overall, the framework provides a physics‐based quantitative approach that addresses the limitations of decoupled models by setting an upper limit for their range of validity.