Methods to measure sedimentation of spawning gravels

Sediment transport occurring after spawning can cause scour of incubating embryos and infiltration of fine sediment into spawning gravel, decreasing intergravel flow and preventing hatched fry from emerging from the gravel. Documentation of these effects requires measuring gravel conditions before and after high flow periods and combining methods to record scour and fill and sediment infiltration by different grain sizes at different depths in the streambed. Scour and fill is best measured with scour chains, which can record the depth of maximum scour that occurs during high flow. Repetitive sampling of bed material with bulk-core or freeze-core samplers can be hindered by the large size of sample required to adequately characterize gravelmixtures compared to the size of fish redds. Freeze tubes, porous and solid-walled containers, and infiltration bags can be used to recover experimental gravel of known grain size after it has been infiltrated with fine sediment. An array of devices is suggested to measure both scour and fill and sediment infiltration.