Reservoir sustainability is strongly impacted by the reservoir sedimentation processes. Most of the substantial sedimentation processes occur in non‐stationary flows such as in the case of flash floods, surges and tidal waves. However, a stationary probability assumption is normally adopted to reduce mathematical model complexity. This work develops a non‐stationary Gambler's ruin model using the Monte‐Carlo simulation method. Daily water‐level data for the Xia‐Yun station are used to predict the effective risk that the maximum capacity of the water treatment plant in the Shihmen Reservoir is reached. This non‐stationary model yields fairly accurate probabilities of sedimentation by the transitional probability of a reservoir reaching different levels of turbidity, and the average time to reach a designated reservoir maximum handling turbidity. The extended capacity of the proposed model demonstrates the major particle processes during non‐stationary flows. Such analytical results offer water resources agency to scientifically evaluate the dredging/remediation strategies with the existing reservoirs. Transport capacities of rivers and streams, and the potential consequences of flood risks in response to reservoir sedimentation can then be comprehensively estimated in order to allow effective contingency planning for public safety.

Sediment transport in open channel flow has a significant impact on the siltation of rivers, reservoirs, and artificial channels, and it is one of the major topics studied in the water resources realm. Despite the intensive investigation done in the past, the transport mechanism of sediment particles seems to have reached a stage where further progress may depend on a more comprehensive understanding of the chaotic and intermittent behavior of turbulence instead of the temporally averaged streamwise momentum of a boundary layer that exhibits a smooth profile with no evidence of sharp changes in momentum. Among others, the existence of coherent structures in wall-bounded turbulent flows has been confirmed (

No abstract

<p>Abstract</p><p>Recent experiments have established that the sediment particle motion, especially for particles near the bed, may not follow the normal (Fickian) diffusion behavior. To modify the diffusion equation where the fluctuation velocity is based on the normal distribution, this investigation hypothesizes that the fluctuation velocity based on bivariate probability distributions and particle-bed collision in open channel can provide some physical insight into the particle diffusion behavior. The distribution of fluctuation velocity is obtained using the Gram-Charlier expansion which considers the first four statistical moments of turbulent fluctuation velocity. The correlation between two-dimensional fluctuation velocities is modeled by performing Monte Carlo simulations. Besides, the uniform momentum zones (UMZ) are further identified and consequently the spatial locations of the edges that demarcate UMZs can be estimated. Once UMZs in the turbulent boundary layers can be characterized, the streamwise momentum deficit, and occurrences of ejection events and sweep events in the vicinity of UMZ edges under different Reynolds numbers can be simulated. The spatial influence of turbulent coherent structures on sediment particle trajectory can be demonstrated.</p>