Hyporheic exchange in a riverbed affected by fine particle clogging

Fine particles exist in river water. Transport of these particles into the riverbed driven by the hyporheic flow can lead to clogging of the bed, which in turn affects the flow and exchange processes. Results from numerical simulations show that clogging of fine particles led to the formation of a low permeability area (LPA) near the bed surface. This reduced the fluxes between the bed and river water significantly. A dimensionless variable (A*) for the LPA was introduced to evaluate changes of the hyporheic exchange induced by clogging. The exchange flux was found to decrease linearly with A*. In contrast, the mean circulation time of the hyporheic flow increased exponentially with A*. The results also showed that effects of the particle collision efficiency and particle diameter on the particles clogging were significant. An increase in the fine particle collision efficiency would weaken total clogging, whereas an increase in the particle diameter would form a very low-permeability layer near the bed surface, intensifying following clogging.