Experimental fi eld assessment of suspended sediment pathways for characterizing hydraulic habitat

摘要

The distribution of particulate matter within river channels, including sediments, nutrients and pollutants, is fundamental to the survival of aquatic organisms. However, the interactions between fl ow and sediment transport at the patch scale of river systems represents an under-researched component of physical habitat studies, particularly those concerning the characterization of ‘physical biotopes’ (riffl es, runs, pools, glides). This paper describes a fi eld methodology for exploring the transfer of particulate matter at small scales within river channels, which may be used to aid hydraulic habitat characterization. The fi eld protocol combines fi eld measurement of high frequency fl ow properties, to characterize hydraulic habitat units, and deployment of spatial arrays of turbidity probes, to detect the passage of artifi cially-induced sediment plumes through different biotope units.Sediment plumes recorded by the probes are analysed quantitatively in the manner of the fl ood hydrograph, and qualitative inferencesare made on the dominant mixing processes operating within different parts of the channel. Relationships between the nature of spatio-temporal hydraulic variations within glide, riffl e and pool biotopes, and the character and mixing behaviour of sediment plumes within these habitat units are identifi ed. Results from these preliminary experiments suggest that investigating and characterizing the transfer and storage of sediments, nutrients and pollutants within and between different biotopes is a viable avenue for further research, with potential to contribute to improved physical habitat characterization for river management and habitat restoration. The experiments are also an illustration of the value of neglected synergies between process geomorphology,ecology and river hydraulics.