patterns. 



7.3 Sediment Dispersion Due to Wind-Driven Currents 



We now present the results of sediment transport simulations under the 

 action of wind-driven currents due to a westerly wind as discussed in 

 Section 5.2. All simulations start with an otherwise zero concentration field 

 and a 500 mg/1 concentration within a 3 Km square area in the Biloxi Channel. 

 Results at the end of 24 hours are shown for three simulations: (1) a 

 dissolved species with zero settling and zero net flux at the bottom, 

 (2) sediments with settling (w5=-0.05 cm/sec) and deposition {V(j=0.01 cm/sec) 

 but entrainment for the newly deposited velocities only, and (3) sediments 

 with the same settling and deposition velocities while entrainment allowed for 

 both the old and new sediments. 



For the first case, the concentration distribution at a constant depth of 

 0.5 m is shown in Figure 7.12(a). Due to the relatively strong wind-driven 

 currents, center of the initial species concentration distribution has moved 

 towards the East by almost 20 Km. 



For the second simulation, deposition prevails and the suspended sediment 

 concentration at 24 hours later is on the order of 20 mg/1 or less 

 (Figure 7.12(b)). Net deposition up to 0.1 cm is found in Figure 7.12(c). 

 When entrainment is allowed for all the sediments, as shown in Figure 7.12(d), 

 simulation, suspended sediment concentration up to 1000 mg/1 is possible 

 within the Sound. As shown in Figure 7.12(e), net entrainment up to 2 cm is 

 found off the Pascagoula Channel and in other shallow areas. Although 

 entrainment is found in the area immediately off the West Pascagoula River, 

 field studies have reported the formation of a mound there. The formation of 

 the mound has apparently taken place during time periods when relatively low 

 wind existed in the Sound. With the increased compaction of bottom sediments, 

 the mound had become much harder to entrain than the entrainment relationship 

 used in the present simulation. 



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