Turbulence-Driven Clogging of Hyporheic Zones by Fine Particle Filtration

Hyporheic exchange (HE), fine particle deposition and clogging are tightly coupled processes that control ecosystem services in rivers. While HE is assumed to be induced primarily by riverbed topography, surface flow turbulence also drives significant exchange. We show that turbulence-driven HE produces large interfacial fluxes and drives long-term feedback between HE and fine suspended particles via bed clogging. Turbulence significantly increases total HE fluxes as it rapidly delivers suspended particles into porewater over the entire interface, whereas advective pumping exchange only delivers particles into focused downwelling regions on the upstream side of bedforms. While turbulence is associated with rapid fluctuations and shallow HE, it is key on longer-timescale outcomes, namely bed clogging. However, beyond the general effect of clogging in attenuating HE, turbulence-driven HE will also be important for other river-borne materials that are retained and transformed within hyporheic zones, such as nutrients and organic pollutants.