Table 4 



Average Annual Alongshore Sediment Transport (WIS M50) 



Results from Single Grain Size and Multiple dSO's 



Profile 



Average Annual Alongshore Sediment Transport 



0.2 mm 



0.4 mm 



2.0 mm 



Offshore dSO = 0.2 mm 

 Beach dSO = 2.0 mm 



To the 

 South 



To the 

 North 



Net 



To the 

 South 



To the 

 North 



Net 



To the 

 South 



To the 

 North 



Net 



To the 

 South 



To the 

 North 



Net 



R12 



355,381 



-283,712 



71,669 



150,601 



-130,454 



20.147 



48,856 



-44,679 



4,176 



265,388 



-213,467 



51,921 



R14 



170,794 



-100,086 



70,708 



78,898 



-51,092 



28,705 



24,592 



-16,702 



7,890 



154,524 



-97,413 



57,111 



Note: 1. Positive transport is directed to the south. 



2. Transport calculations from average annual waves (WIS Station M50). 



sediment in the swash zone and beach for the new model runs (i.e., the coarse 

 sediment has a reduced potential for transport). 



The ability of C0SM0S-2D to estimate alongshore sediment transport rates 

 with multiple d5Q's improves the accuracy of the predictions for St. Joseph by 

 representing the natural distribution of sediment across the nearshore and beach 

 zones. In general, the 0.2-mm results in Table 4 were reduced by 25 percent 

 when coarse sediment was considered. For the protected sections of the 

 SL Joseph shore (such as the MDOT revetment) where no beach exists, the 

 reduction is less than 25 percent. 



In summary, these sediment transport calculations also indicate that perhaps 

 only 50 percent of the coarse sand which is eroded from the feeder beach area 

 (by storms with waves from the north) can be transported out of the study area 

 south of Line 23. 



Annual variation in potential alongshore sediment transport 



To investigate variation in the wave climate, yearly estimates of wave 

 energy and average direction were calculated for selected years from the WIS 

 data (see Figures 8 and 9). Figure 8 shows a large annual variation in total 

 wave energy ranging from a maximum in 1977 of 46.000 m~/s to a minimum 

 in 1986 of 17,000 m /s. The average annual wave direction presented in Fig- 

 ure 9 also shows considerable variation. From the 32 years of data, seven 

 individual years were selected to represent the wide range of actual combina- 

 tions of wave energy and direction. 



Alongshore sediment transport rates were calculated with C0SM0S-2D for 

 profiles R12 (sandy shore) and R14 (revetment). Multiple grain sizes were 

 considered for both profiles to represent the actual field conditions at 

 St. Joseph. Results are presented in Table 5. In 1964, the average wave 



22 



Chapter 4 Analyses of Coastal Processes and Geomorphology 



