Principles of Sediment Transport Applicable in Tidal Environments - Principles of Tidal Sedimentology - page 25

Fig. 2.3 The Shields diagram for initiation of motion under
steady currents. In order to calculate the critical shear stress, it is

the critical Shields parameter is the intersection between this
value and the Shields curve

D ¤ ³

¥ ¦ µ

r

first necessary to determine the value of 0.1

s

1 gD ,

n r

Fig. 2.4 The revised Shields diagram relating the critical Shields stress directly with dimensionless grain diameter (Modified from
Soulsby 1997)

sediment deposition and morphology change. In most
tidal environments and excluding few local areas
(e.g., nearshore breaker zone), most of the sediments
that are coarser than fine sand tend to be transported as
bedload. The definition of bedload is not always clear.

Theoretically, the Bagnold ( 1956 ) definition, defined
as the part of the total load that is supported by inter-
granular forcing, is commonly used. This definition is
convenient for mathematical modeling. However, from
a measurement point of view, especially during field