EM 1110-2-1100 (Part I)
30 Apr 02
Figure I-3-4. Converging jetty system designed by James Buchanan Eads for the mouth of the St. Johns
River, Florida. Figure courtesy of USAED, Jacksonville
Colonel Quincy Gillmore, familiar with Eads' plan for Jacksonville, used a similar plan to construct the jetties
at Charleston Harbor, South Carolina, between 1878 and 1893. From the barrier islands on each side of the
harbor entrance, the USACE constructed two converging jetties followed by a parallel section. The near
shore portion of the jetties was constructed to just below the low tide water surface, thereby serving as a weir
and allowing the flood tide to come in normally. During the ebb tide, the bottom currents were channeled
through the parallel section (constructed higher, with the seaward quarter above high tide) toward the bar and
this scouring action kept the new channel clear (Moore 1982). A similar plan was used at the mouth of the
St. Mary's River at the Florida-Georgia border. Major George L. Gillespie, District Engineer in Portland,
OR, submitted a plan for a dike at the mouth of the Columbia River to concentrate river currents and tides
to scour a deep channel. Construction commenced on the south jetty in 1884, a project that had to overcome
fierce winter storms and hazardous working conditions (Willingham 1983).
c. Early coastal development and shore protection. From the early days of settlement to the present,
Americans have built in the coastal area. During the 1600 and 1700s, the original colonies owed their
prosperity largely to the availability of good natural harbors, rich nearby fishing grounds, and active trade
with the Caribbean and Europe. As the giant continent was explored and settled in the 1800s, rivers and the
Great Lakes became the prime mode of moving goods and people to and from distant towns. In the 20th
century, a new social phenomena arose that resulted in an ever-increasing interest in the coastal zone: more
and more Americans achieved the economic means and leisure time to enjoy the beach for recreational
purposes. Even before beaches became popular vacation destinations, engineers constructed structures to aid
navigation, to halt erosion, and to protect shore front development from storm surge. They designed
bulkheads, revetments, and seawalls to hold the shoreline in place. Generally, these designs were successful,
with Galveston, Texas, and San Francisco, California, being two examples of early seawall construction.
Other structures, such as groins and jetties, impeded longshore transport of sand. Groins are intended to
I-3-12
History of Coastal Engineering
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