The ADCP current data collected during the fall 1997 field-data collection 

 effort at Port Huron was reduced to extract the near-bottom fluid velocity vectors. 

 Proximal vectors for the multiple transect runs and/or days of collected data were 

 averaged to obtain a representative vector field for each transect. Each resulting 

 flow vector was used to calculate a Shield's parameter that then was compared 

 with a critical Shield's parameter for a set of representative sediments. If the 

 Shield's parameter exceeded the critical Shield's parameter for that sediment size, 

 then transport occurred and Equation 3 was used to calculate a unit-transport rate. 

 This unit-transport rate was converted to a total-transport rate by assuming the 

 flow vectors described above occurred across a given length defined as the 

 distance between the midpoints of two vectors. 



The characteristic sediments used in computing transport potential were 

 chosen to represent the sediment population of the study area (Figure 13). These 

 sediments (listed in Table 3) are those that were found inside or along the entrance 

 to the boat basin and identified as being available for transport. 



The unidirectional transport rates calculated as described above are 

 represented in Figure 14. Comparing Figure 14 with the velocity vectors from 

 Figures 10 and 11 shows the correlation of sediment transport to bottom velocity. 

 Figure 14, however, indicates that the majority of transport occurs south of the 

 boat basin where the currents are strongest. Even for the finest sediment (BB4, 

 D50 =0.17 mm), little transport potential exists to the north of the basin. This 

 suggests that the unidirectional flow alone is not sufficient to transport significant 

 quantities of sediment from the north to fill in the boat basin. Anecdotal evidence 

 supports this conclusion during calm wave days when the unidirectional currents 

 remain strong, yet water clarity indicates little if any material is in suspension. 



Table 3 



Representative Sediments from Inside and Near Boat Basin 



Location' 



D50 grain size, mm 



BB1 



0.21 



BB2 



9.7 



BB3 



15.0 



BB4 



0.17 



CL1 



0.62 



CL2 



19.0 



CL3 



25.5 



CL4 



20.0 



CL5 



8.9 



CL6 



40.0 



'SB nos. are samples taken within the boat basin; CL nos. are samples taken along the center line of 

 the boat basin entrance. 



24 



Chapter 5 Sediment Transport 



