Scour, fill, and burial depth of coarse material in gravel bed streams

Scour, fill, and burial depths of coarse particles were examined in two ephemeral streams using magnetically‐tagged particles and scour chains. The burial depth varied within a bedform and from one bedform to another. The maximum burial depth was recorded in bars, but differences in the mean burial depth in the pools, bar, and thalweg were insignificant. Mean burial depth was three to six times the median size of material on bar surfaces and ten to thirty times that in the pools and thalweg. More than eighty per cent of the tagged particles which were located on, or close to, the bed surface moved in each event. Although previously buried particles were moved by flood events, others which were initially exposed remained stationary on the surface or were buried in situ . The data indicate that the mean burial depth was intermediate between the mean depths of scour and fill. Deeply buried particles probably reflect the development of scour holes during flood flows. Aggradation and degradation changed the recorded burial depth, relative to the local bed surface, of stationary tracer particles. These observations indicate that scour and fill processes during a flow event are sporadic and change with water discharge.