(3) From 147th Avenue to a point approximately 1,900 feet south 
of 146th Avenue (Fig. 12, reach 4). Reach 4, about 4,500 feet long, 
is characterized by eroding sand dunes up to 225 feet high. Figure 
12 shows that erosion is greater at the northern end of the reach and 
decreases progressively southward. At the southern end of the reach 
the shoreline before construction of the navigation structures coin- 
cides closely with that of the 1929 and 1944 surveys. Erosion appears 
to be greatest at a point about 800 feet south of 147th Avenue where 
the shoreline receded about 220 feet from 1866 to 1945, or an average 
of 3 feet per year. 
The rates of movement of the shoreline near the harbor have decreased 
(1945-73) but the trends of accretion on the north side and erosion on the 
south side have continued. The present lower rates of shoreline movement 
are due to several factors: 
(a) The rate of shoreline movement due to the navigation structures 
decreases with time. 
(b) Local interests have built more shore protection structures as 
their property was threatened. The consequence of these structures is 
to reduce the apparent rate of erosion locally, but this is accomplished 
at the expense of steepening of the offshore bottom profiles and in- 
creased erosion downdrift. The shoreline protective structures now 
extend almost continuously from 1,000 feet to about 4,600 feet south 
of the harbor. 
(c) The bluffs, currently under erosive wave attack between 5,000 
and 7,000 feet south of the harbor, are very high so that erosion rates 
measured in feet per year are low but the corresponding volume rates 
(in cubic yards per foot) are high. 
The shorelines apparently have become comparatively stabilized since about 1933. 
2. Geomorphology. 
Figure 13 shows the nearshore bathymetry determined by a survey in April 
1973. Beach profiles from this survey and one in May 1945 are summarized in 
Figure 14. Three or four lines of longshore bars are prominent most of the 
time and occur in water depths to approximately 30 feet. The first bar, in 
depths of 1 to 4 feet, can change rapidly from storm to storm and is often 
broken into short segments from 200 to 1,000 feet long by rip channels. Adja- 
cent to the breakwaters, the rip channels tend to elongate lakeward as far as 
the second bar. The second and third bars, occurring in depths of 6 to 14 feet, 
appear to be affected only by larger storm waves and are relatively continuous 
along the shore. Aerial photos show that these bars tend to lose their promi- 
nence as they approach the breakwaters from both sides, suggesting that pre- 
vailing erosion exists across the bar crests near the breakwaters. Tie fourth 
bar occurs at depths of 15 to 20 feet about 1,500 feet offshore and is charac- 
terized by crescentic crests displaying wavelengths between 3,000 and 5,000 
feet. A crescentic fourth bar with an average wavelength of about 5,000 feet 
existed north of Holland Harbor, but none existed on the south side. 
Although the general bathymetry follows the coastline, significant departure 
from this trend occurs in a region offshore of the Holland Harbor breakwaters 
(Fig. 15). The 24-, 27-, and 29-foot-depth contours meander sharply off the 
33 
