Numerical modelling of turbidity currents in the Xiaolangdi reservoir, Yellow River, China

SummaryTurbidity currents play a critical role in effective sediment and reservoir management in alluvial rivers. Yet previous estimations of reservoir turbidity currents are mostly based on simple empirical relations and it remains unclear how and to what extent physically based numerical models can resolve current evolution as compared against field observations. This paper presents a physically-based, process-resolved computational study of turbidity currents in the Xiaolangdi reservoir in the lower Yellow River, China. A coupled layer-averaged 2D numerical model is applied, which explicitly incorporates the interactions between the current, sediment transport and morphological evolution, and features a new well-balanced numerical scheme dealing with irregular topography. Two turbidity current events in July 2004 are numerically simulated to calibrate and validate the model. The current advance and the sediment transport rate computed by the model compare favourably with field measurements. These suggest the present model is a viable tool for determining the timing for operating the bottom outlets, which is critical for effective reservoir sediment management. The sediment entrainment flux and bed resistance are key factors dictating the evolution of turbidity current and warrant further investigations.

► Turbidity currents in a real reservoir are investigated using a process-resolving model. ► The model is well-balanced and explicitly accounts for the current-sediment interactions. ► Two turbidity current events are simulated to calibrate and validate the model. ► The current advance and transport rate are reproduced favourably well by the model. ► The model is a viable tool for determining the timing for operating bottom outlets.