and for 1<Z)*<60, 



n = l-0.243ln(D.) 

 A = 0.14 + 0.23/jD, 



(?) 

 m = 1. 34 + 9.66 J D« 



C, =exp(2.86]n(D*)-0.434(\n(D,)f -8. J i) 



Output from the hydrodynamic model supplied the velocity and depth variables. 

 Sediment sampling suggested an estimate of 0.3 mm for Z) 35 . Assumed values account 

 for water density and viscosity. 



Figures 26 through 29 show contours of sediment transport (in cfs/ft) at the shoaling 

 hot spots. As a visual aid, vectors were overlaid on the contours. The vectors have the 

 magnitude equal to the calculated sediment transport, but a direction equal to that of the 

 ambient currents. The assumption is that the sediment is transported in the direction of 

 flow (this is usually the case). As mentioned previously, the appropriate indicator of 

 sediment deposition is the negative gradient of sediment-transport magnitude. 



Figures 26 and 27 show the sediment transport during spring flood and ebb near the 

 channel bend. They confirm the previous conclusion that shoaling in this area results 

 from the horizontal expansion of the channel. Figure 26 illustrates how sediment is 

 transported from south to north along the axis of the channel on flood tide. This analysis 

 has also yielded an unexpected result. Figure 27 also exhibits the behavior associated 

 with a horizontal channel expansion on ebb tide. Sediment is transported along the axis 

 of the northern section of the channel. This result solidifies the selection of this 

 classification for shoaling in this area. 



Solutions to remedy this type of shoaling vary widely in cost. Shoaling from 

 shoreline recession causes the channel to meander within the inlet throat. The least- 

 costly solution is surveying the area regularly to designate the position of the channel by 

 the location of the meandering thalweg. Another possible solution involves altering the 

 geometry causing the expansion. The construction of flow-training walls would constrain 

 the flood jet as it enters the inlet throat. This action would maintain stronger flows 

 through the throat and hence mitigate shoaling. Notably, a "soft" solution in the same 

 vein is to build out the shoreline on either side of the throat through the placement of 

 dredged material. Either of these costly solutions would require a comprehensive 

 cost/benefit analysis before implementation. One final solution is to treat the source of 

 the sediment creating the shoal. The east jetty is presently at its sediment-storage 

 capacity. Sediment that likely bypasses the tip of this jetty gets transported into the throat 

 on flood tide. Once deposited, it contributes to shoaling. Extension of this jetty or 

 mining the updrift filet would reduce the contribution from this sediment source. 



Figures 28 and 29 illustrate sediment-transport contours and vectors during spring 

 flood and ebb near Old Pass. These figures show much less variation than the previous 

 example. Except for a small region to the west of the area during flood (Figure 28), the 

 contours of sediment-transport magnitude are constant (solid) in almost every area within 

 and surrounding this shoal. Near-constant sediment-transport magnitude indicates that 

 little sediment deposits in these areas. This result suggests a need to reevaluate the 

 classification of this shoal. Examination of the wave climate in this area helps to clarify 

 the classification. 



Chapter 4 DMS-Analytical Toolbox 45 



