Measuring bedload transport rates usually involves measuring the flux of sediment or collecting sediment during a certain interval of time Δt . Because bedload transport rates exhibit significant non‐Gaussian fluctuations, their time‐averaged rates depend a great deal on Δt . We begin by exploring this issue theoretically within the framework of Markov processes. We define the bedload transport rate either as the particle flux through a control surface or as a quantity related to the number of moving particles and their velocities in a control volume. These quantities are double averaged; that is, we calculate their ensemble and time averages. Both definitions lead to the same expression for the double‐averaged mean rate and to the same scaling for the variance's dependence on the length of the sampling duration Δt . These findings lead us to propose a protocol for measuring double‐averaged transport rates. We apply this protocol to an experiment we ran in a narrow flume using steady‐state conditions (constant water discharge and sediment feed rates), in which the time variations in the particle flux, the number of moving particles, and their velocities were measured using high‐speed cameras. The data agree well with the previously defined theoretical relationships. Lastly, we apply our experimental protocol to other flow conditions (a long laboratory flume and a gravel‐bed river) to show its potential across various contexts.

中文翻译：

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估计平均床载运输率及其不确定性

测量推移质传输速率通常涉及测量一定的时间间隔期间的沉积物或收集沉淀的通量Δ吨。由于泥沙输沙率表现出显著非高斯的波动，他们的时间平均速率取决于大量的Δ ŧ。我们首先在马尔可夫过程的框架内从理论上探讨这个问题。我们将床载运输速率定义为通过控制表面的粒子通量，或者定义为与运动粒子的数量及其在控制体积中的速度有关的数量。这些数量是两倍的平均值；也就是说，我们计算它们的合奏和时间平均值。这两个定义导致对双平均平均速率，并为方差的上采样持续时间的长度依赖相同的缩放相同的表达Δ吨。这些发现促使我们提出了一种测量双重平均运输速率的协议。我们将此协议应用于使用稳态条件（恒定的出水量和沉积物进料速度）在狭窄水槽中运行的实验，其中使用以下方法测量了粒子通量，运动粒子的数量及其速度的时间变化高速相机。数据与先前定义的理论关系非常吻合。最后，我们将实验方案应用于其他流量条件（长长的实验室水槽和砾石床河），以显示其在各种情况下的潜力。