Channel Processes: Suspended Sediment Transport

Suspended sediment is that portion of the total sediment load of rivers that is carried in the water column. It contains the portion termed "wash load" or that portion of the suspended load not represented in the bed material. In practice, wash load usually comprises the silt/clay or colloidal fraction that is more controlled by supply than energy. Most of the suspended sediment transport and wash load relations are derived from measured sediment rating curves and flow-duration curves. Bedload and bed-material suspended load transport are often termed "total-load equations" where a portion of the bed material is composed of sand that is transported as both bedload and suspended load. Total-load equations do not include wash load. A detailed listing and evaluation of total bed-material load or suspended bed-material load equations appears in Reid and Dunne (1996). Ackers/White (1973), Bagnold (1966) and Yang (1979) are commonly used total bed-material load or suspended bed-material load equations. A computer program that offers the user a selection of various sediment transport equations is GSTARS 2.0 (Yang et al. 1998).

Dimensionless suspended sediment rating curves were developed and tested against an independent data set of the same stream type/stability class as in the bedload example (Troendle, 2001), (Figure 13). Once reference suspended sediment rating curves are established for a region, dimensioned sediment rating curves can be established by the methods previously described.

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