The Effect Of Clogging, Bed-Forms And Bioturbation On Hyporheic Exchange-Experimental Studies At The Flume Scale

The biophysical processes influencing rates of hyporheic exchange are nuanced and not well understood. On the one hand, bedforms are known to promote advective pumping, increasing exchange rates in systems with bedforms compared to those without. By contrast, fine sediment infiltration into stream beds decreases permeability and porosity by clogging, reducing exchange. Benthic macroinvertebrates may either increase or decrease exchange through bioturbation activities, which have the potential to increase porosity, but may also redistribute sediments leading to surface clogging. However, streams are dynamic systems, and it is likely that bedforms, suspended sediments, and bioturbation affect hyporheic exchange in an interactive manner. To date, the interaction between bedforms, suspended sediments and bioturbation has not been quantified. This study considered these interactions in several flume experiments in which flux across the sediment water interface was quantified by measuring tracer concentration over time in the water column. The experiments used a fully crossed design with presence of bedforms, presence of suspended sediment, and presence of bioturbators as factors.