All of the littoral drift computations show a large gross drift of 300,000 
to 500,000 cubic yards, defined as the sum of all north and south movement, 
regardless of direction, whereas the net drift is much smaller. Individual 
yearly predictions show a wide variability in net littoral drift quantities. 
The littoral drift is predicted to be from south to north with a mean value 
of more than 265,000 cubic yards. The SSMO data and Coles and Hilfiker's wave 
statistics lead to the prediction of 61,000 and 76,000 cubic yards, respectively, 
from north to south. This direction is consistent with the observed growth of 
the fillets on each side of the harbor, the north side showing a much greater 
accretion. 
Figure 22 summarizes the monthly fluctuations of littoral drift based on 
the SSMO data. The figure shows that the monthly drift is large during late 
fall when the activity of extratropical cyclones intensifies in these regions, 
and small during the summer months, especially in June, when wave heights are 
generally smaller. 
MONTHLY GROSS DRIFT 
x10" (yd?/mo) 
MONTHLY NET DRIFT 
s 
& 
io 0 JAN BEDE MAR APR MAY JUNE UG SEPY OCT NOV DEC 
es iI‘ JULY 
ee yj 
ted 10 / 7 
° 
251210 
imal AVG. ICE-FRE® PERIOD 
Y AVG. ICE PERIOL 
Figure 22. Monthly variations of eo of computed 
gross and net littoral drifts 
for Holland, Michigan. 
7. Analysis of Aerial Photos. 
A sequence of eight sets of aerial photos of Holland Harbor taken over the 
interval 27 July 1950 to 5 October 1973 was analyzed to assess the long-term 
evolutionary development of the shoreline. A regression analysis was verformed 
to correct the shoreline for lake level variations and to determine the long- 
term erosion-accretion rates along the coast. 
45 
