Fine particles (0.1–100 microns) are ubiquitous within the water column. Observations on the interactions between suspended fine particles and sediment beds remain limited, reducing our ability to understand the interactions and feedbacks between fine particles, morphodynamics, and hyporheic flow. We performed laboratory experiments to explore changes in bedform morphodynamics and hyporheic flow following the progressive addition of kaolinite clay to the water column above a mobile sand bed. We characterized these interactions by taking high‐frequency time series measurements of bed topography and freestream clay concentration combined with solute injections and bed sediment cores to characterize subsurface properties. Deposition of initially suspended clay resulted in a decrease of bedform height, celerity, and sediment flux by 14%, 22%, and 29% when 1000 g was accumulated within the bed (equal to clay/sand mass ratio of 0.4% in the bed). The hyporheic exchange flux decreased by almost a factor of 2 for all clay additions, regardless of the amount of clay eventually deposited in the bed. Post experiment sediment cores showed clay accumulation within and below the mobile layer of the bedforms, with the peak concentration occurring at the most frequent bedform scour depth. These results demonstrate the tight coupling between bed sediment morphodynamics, fine particle (clay) deposition, and hyporheic exchange. Suspended and bed load transport rates are diminished by the transfer of suspended load to the sediment via hyporheic exchange. This coupling should be considered when estimating sediment transport rates.

中文翻译：

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悬浮粘土颗粒沉积对砂床形态动力学的影响

细颗粒（0.1–100微米）在水柱内无处不在。关于悬浮细颗粒和沉积物床之间相互作用的观察仍然有限，这降低了我们了解细颗粒之间的相互作用和反馈，形态动力学和流动性的能力。我们进行了实验室实验，以探索将高岭石粘土逐步添加到流动沙床上方的水柱后，床层形态动力学和低渗流的变化。我们通过对床形貌和自由流粘土浓度进行高频时间序列测量，并结合溶质注入和床沉积物核来表征地下相互作用，从而表征了这些相互作用。最初悬浮的粘土的沉积导致床形高度，速度和沉积物通量下降了14％，22％，当床内累积1000 g时为29％（等于床中粘土/砂的质量比为0.4％）。对于所有添加的粘土，无论最终沉积在床中的粘土量如何，流变交换通量几乎都降低了2倍。实验后的沉积物岩心显示出粘土堆积在床形活动层之内和之下，峰值浓度出现在最频繁的床形冲刷深度处。这些结果证明了床沉积物形态动力学，细颗粒（粘土）沉积和流变交换之间的紧密耦合。通过流变交换将悬浮负荷转移到沉积物中，从而降低了悬浮负荷和床负荷的输送速度。在估算泥沙输送速率时应考虑这种耦合。