Page 420 - Laboratory Manual in Physical Geology

ACTIVIT Y 15.3 Shoreline Modification at Ocean City, Maryland

Name: ______________________________________ Course/Section: ______________________ Date: ___________

Ocean City is located on a long, narrow barrier island called Fenwick Island. During a severe hurricane in 1933, the island was
breached by tidal currents that formed Ocean City Inlet and split the barrier island in two. Ocean City is still located on what
remains of Fenwick Island. The city is a popular vacation resort that has undergone much property development over the past
50 years. The island south of Ocean City Inlet is called Assateague Island. It has remained undeveloped, as a state and national
seashore.
Rising sea level at Ocean City has increased the risk of beach erosion there. Therefore, Ocean City constructed barriers to trap
sand. Examine the portion of the Ocean City, Maryland, topographic quadrangle map provided in FIGURE 15.7 . Purple features

show changes made in 1972 to a 1964 map, so you can see how the coastline changed from 1964–1972. Also note the black and
red outlines of the barrier island as it appeared in 1849 and 2010 according to the U.S. Geological Survey.

A. After the 1933 hurricane carved out Ocean City Inlet, the Army Corps of Engineers constructed a pair of jetties on each side
of Ocean City Inlet to keep it open. The southern jetty is labeled “seawall” on the map. Sand filled in behind the northern
jetty, so it is now a seawall forming the straight southern edge of Ocean City on Fenwick Island (a straight black line on the
map). Based on this information, would you say that the longshore current along this coastline is traveling north to south, or
south to north? Explain your reasoning.

B. Notice that Assateague Island has migrated landward (west), relative to its 1849 position ( FIGURE 15.7 ). This migration began

in 1933.

1. Why did Assateague Island migrate landward?

2. Field inspection of the west side of Assateague Island reveals that muds of the lagoon (Sinepuxent Bay) are being covered
up by the westward-advancing island. What was the rate of Assateague Island’s westward migration from 1933–1972 in
feet/year and meters/year? (Show your work.)

3. Based on your last answer above (B2), and extrapolating from 1972, in what approximate year should the west side of

Assateague Island have merged with saltmarshes around Ocean City Harbor? (Show your work.)

4. Notice from the 2010 position of Assateague Island (red outline on FIGURE 15.7 ) that it has not merged with saltmarshes

of the mainland. What natural processes and human activities may have prevented this?

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