Table 2. Summary of cross-sectional changes and computed 
volumetric changes for 1945 and 1973 surveys. ! 
[ Above LD { ___below LWD lee observed shoreline 
Line ||Distance |} Cross section | Avg. rate of }/ Cross section | Avg. rate of || Total mean v | accretion- i 
g ' g ol. | erosion 
No. || between area change vol. change area change | vol. change change rate change rate 
profiles (1945-73) (1950-73) 
(ft) (£2), (yd?/yr/ft) || (ft?) | (ya /yr/ ft) (yd3/yr/ft) (ft/yr) 
1 2,298 1,528 z 
1,150 +1.47 +1.10 +2.57 +2.0 
2 -78 134 
800 +0.84 +0.65 +1.49 7113) 
3 1,347 855 
Harbor 
4 2,144 928 
740 +1.16 +0.30 +1.46 -0.3 
§ 391 -479 
880 +0.17 -0.53 -0. 36 -0.6 
6 642 -324 
1,210 -0.24 -0.72 -0.96 -0.9 
7 821 -761 
605 -0.91 -2.80 -3.71 -1.0 
8 -562 -3,480 
830 -1.59 -3.39 -4.98 -1.2 
8) -1,848 -1,660 
815 +0.39 -0.88 -0.49 -0.9 
One| +2,431 I 305 | 
poet a ee Nee ee ee | | 2 = 
lL = accretion; - = erosion 
As demonstrated previously in the analysis of the aerial surveys, the har- 
bor influence on the north side extends about 4,200 feet. Farther north it is 
assumed that the observed erosion rate will be close to the natural erosion 
rate for this area of the Lake Michigan coast. At 4,200 to 15,400 feet to the 
north of Holland Harbor, the average erosion rate during the 1950-73 period 
(from aerial photos) was 1.28 feet per year per foot of shoreline. If the 
approximation of 1 cubic yard of volume per square foot of beach is used, the 
corresponding sediment volume loss is 1.28 cubic yards per year per foot of 
shoreline plus the erosion rate of the dunes. The bluffs which have an average 
height of about 40 feet in this area would contribute an additional sediment 
loss of 40 x 1.28/27 = 1.90 cubic yards per year per foot. Hence, the total 
sediment loss to the offshore in this area is estimated to be averaging 1.90 
+ 1.28 = 3.18 cubic yards per year per foot of shoreline during the past 23 
years. This rate of loss is considered to represent the natural rate of loss 
for littoral sediments in the Holland area due to all factors except the navi- 
gation structure. It must be remembered that the erosion rate of 3.18 cubic 
yards per year per foot of shoreline is an average rate for the past 23 years 
(1950-73). Since lake levels have been much higher during the past few years, 
the present erosion rate must be expected to be higher than the average and 
therefore will probably exceed 3.18 cubic yards per year per foot of beach. 
9. Sediment Budget. 
a. North Side. An independent evaluation of the net littoral drift has 
been obtained from various surveys as summarized below in which a sand budget 
analysis is made for the north side of Holland Harbor. The shoreline changes 
shown in Figure 25 provide information for an area measurement of accretion. 
An approximation for volumetric accretion can subsequently be made from the 
relationship, wherein 1 square foot of change in beach surface area equals 1 
cubic yard of beach material. This relationship has previously been shown to 
be reasonably valid for the north side. Subsequent corrections may be neces- 
sary because of the dune-building phenomenon. 
50 
