Charleston Harbor Jetties
The Charleston Harbor jetties were constructed by the US Army Corps of Engineers between 1882 and 1895. The purpose of these three-mile-long jetties was to allow safe transit of ships into and out of Charleston Harbor. The construction of these jetties was an engineering marvel at that time and has not needed many repairs over the past 130 years. However, these jetties disrupted longshore currents resulting in increased erosion on barrier islands south of the jetties. One of the most significant landmarks of this area is the Morris Island lighthouse on Morris Island. When it was first constructed in 1876, it was more than 1200 ft inland from the coastline. Following the construction of the jetties, the ocean currents shifted and caused increased erosion on Morris Island. By 1938, the coastline had receded to the base of the lighthouse. Eventually, multiple coastal storms and structural damage led to its decommissioning and its addition to the National Register of Historic Places. There are continuing efforts to stabilize the base of this lighthouse.
Exercise 5 – Charleston Harbor Jetties
Below are additional resources needed to answer the following questions:
- Beach erosion affects residents, wildlife and economy (sc.edu)
- Folly Beach reflects state’s battle to save coastal towns
- Edisto residents worry about coastal erosion
- Google Earth link to the area
- According to Paul Gayes of USC in the article above, what are the two drivers for coastal erosion?
- According to Leslie Sautter of CofC in the article above, which two barrier islands have lost sediment to erosion since the jetties were built?
- Based on the pattern of sediment loss, what is the general direction of the longshore current in the Charleston harbor?
- From 1876 to 1938, 1200 ft of coastline was eroded near the Morris Island lighthouse. At what rate (in ft/yr) is the coast eroding here?
- Given that the jetties are causing the erosion of Folly Beach, what is the continuing rationale for keeping the jetties in place?
- What is the hard structural approach implemented by the Town of Folly Beach to arrest the erosion on the northern end of the island?
- What is the soft structural approach implemented by the Town of Folly Beach to arrest the erosion on the rest of the island?
- What is the main reason towns such as Folly Beach and Edisto Beach spending large sums of money to restore or stabilize their beaches?
