A dearth of field measurements exists from sandy gravel-bed rivers. Laboratory experiments suggest that sediment mixtures with a large sand component are particularly efficient at transporting bedload downstream. To evaluate transport processes in these environments, we constructed a sediment monitoring research facility with the ability to continuously monitor sediment fluxes. The Arroyo de los Pinos is a gravel-bed ephemeral channel with a large (>30%) sand component in New Mexico, USA. This field station incorporates direct measurements of bedload flux using Reid-type slot samplers with high quality measurements of suspended sediment, water depth, water velocity, and grain size. Measurements are collected at a stable cross section constructed for long-term, consistent monitoring.

Instantaneous bedload flux is high compared to global averages, as high as 12 kg s⁻¹ m⁻¹. Suspended sediment is also high, peaking at 100,000 mg L⁻¹, with evidence of clockwise hysteresis. The Pinos nondimensional bedload flux rates are similar to those in other ephemeral channels, but the high sand content allows equal mobility at relatively shallow water depths and high rates of bedload transport during hydrograph recession. Bedload flux responded hysteretically, higher at equal shear stresses during stage rise. This is likely caused by an inadequate use of the depth-slope product for calculation of bed shear, steeper friction slopes during the rising limb, or both.

These first monitored sediment transporting flash flood events reveal a channel that is very active during short periods of time. On average, the Arroyo de los Pinos flows 12–24 h during 3–5 events every year. However, in these brief periods, the channel is hyper-efficient at transporting bedload and suspended sediment at rates that are orders of magnitude higher than perennial counterparts.

砂砾石床河流缺乏实地测量数据。实验室实验表明，含沙大的沉积物混合物在向下游输送床荷方面特别有效。为了评估在这些环境中的运输过程，我们建立了具有连续监测沉积物通量能力的沉积物监测研究设施。Arroyo de los Pinos是美国新墨西哥州的砾石层短暂通道，含大量沙（> 30％）。该现场站使用Reid型槽式采样器直接测量了床荷通量，并对悬浮物，水深，水流速度和粒度进行了高质量测量。在稳定的横截面中收集测量数据，以进行长期，一致的监控。

与全球平均水平相比，瞬时床荷通量高，高达12 kg s ^-1  m ^-1。悬浮沉积物也很高，峰值为100,000 mg L ^-1，有顺时针方向的滞后现象。Pinos无量纲的地基通量速率与其他短暂通道的通量速率相似，但是高含砂量允许在相对浅的水深下具有相同的流动性，并且在水文衰退期间可以实现高的基层输运速率。在阶段上升过程中，在相同的剪应力下，床载通量产生了滞后响应。这可能是由于未充分使用深度-坡度积来计算床层剪切力，上升肢体期间较陡的摩擦坡度或两者兼而有之。

这些首先监测的泥沙输送山洪暴发事件揭示了一个在短时间内非常活跃的通道。平均来说，每年3至5次活动期间，Arroyo de los Pinos流量为12​​至24小时。然而，在这短暂的时期内，该河道以比多年生对应物高几个数量级的速率高效地运输床荷和悬浮泥沙。