Fig. 3: Clay accumulation patterns for segregated and locked end states.

Images on the left are representative images of the two end states, while concentration profiles on the right reflect clay accumulation in the sediment bed (see methods). Red circles denote the median concentration and shading represents the interquartile range. a In the segregated end state (NU-3), clay accumulates in a defined layer just below the active layer of sand transport. The peak of the clay concentration profile occurs just below the most frequent bedform scour depth. Clay also deposits below the maximum scour depth (~0.075 m), as clay is actively pumped underneath bedforms by hyporheic exchange. b In the locked end state (NU-8), extensive clay accumulation within bedforms halts bed motion. The clay deposition patterns reflect bedform-induced hyporheic pumping into the stoss slope and through the bedform. In this case, there is no defined layer of buried clay and deposited clay concentration decreases monotonically with depth. Flow is from left to right in the images of bedforms. Images have been color matched to allow for easier visualization of clay accumulation.