investigated 1n a laboratory flume (Sheng 1981; Sheng et al . 1982). 

 To prepare the bed, sediments are introduced into the flume, 

 resuspended, and allowed to settle for a period of 1 to 10 days. A 

 given bottom shear stress is then applied and the time history of 

 sediment concentration recorded until an equilibrium concentration is 

 reached, at which the resuspension balances the deposition. As shown 

 in Figure 11, resuspension as indicated by the equilibrium 

 concentration depends strongly on the applied shear stress. More than 

 an order of magnitude increase in equilibrium concentration can be 

 expected when the shear stress is increased by a factor of 5. Salinity 

 affects the aggregation of particles and hence the erodability of the 



'o'r Site # 



Salinity (ppt) = 

 % H = 



lOV 



Setthng Time (days)= 3 



Site # 



Settling Time(doys)= 3 

 — TjjCdyne/cm*) = 3 



2 3 4 



rjj (dynes /cm* ) 



Site # 3 



Sahnify (ppt) : 30 

 j-jj (dyne/cm') = 3 3 



Salinity (ppt ) 



Site # 3 I 



Salinity (ppt) = 30 

 rj^(dyne/cm*) =3 3 



2 4 6 8 



Settling Time (days) 



2 4 6 6 



Settling Time ( days) 



Figure 11(a). Equilibrium Suspended Sediment Concentration in 

 Laboratory Flume as a Function of Applied Shear Stress, 



(b). Effect of Salinity, 



(c). Effect of Time History of the Bed, and 



(d). Resuspension Rate as a Function of Time History of the 

 Bed. 



283 



Sheng 



