Charleston Harbor Jetties
Construction and Rehabilitation History
Rubble-mound jetties (Figure 18) with a shoreward submerged weir
section and seaward raised section were constructed at Charleston
Harbor to provide (in conjunction with dredging) for a navigation
channel 2 1 ft mlw deep. The total lengths of the north and south
jetties were 15,400 ft and 19,100 ft, respectively. The distance
between the parallel seaward sections of the jetties was 2,900 ft.
Shoreward portions of both jetties, each approximately 6,000 ft
long, were built up to typical depths of -4 to - 12 ft mlw (rising
only a few feet above the bottom, with low sections as deep as 15 ft
and 28 ft on the north and south jetties, respectively). The outer
7,200 ft of the north jetty was raised to an average of
ft mlw, the outer 9,200 ft of the south jetty was raised to an
ft mlw, and shoreward of this section an additional
ft mlw. A typical section of the raised
2,400 ft was raised to
jetties consisted of a log and brush mattress foundation loaded with
30 to 60 tons of small stone weighing 10 to 250
narrow course of small stone was placed, and 1- to 7-ton granite
blocks were placed as cover stone. Typical crest widths were 1 2 to
1 5 ft.
Only minor dredging between the jetties has been required since the
project depth was increased in 1917 to - 30 ft mlw. Field survey
showed very little deterioration to the submerged or raised portion
of the jetties.
Present channel depth of -35 ft mlw has been maintained since 1961.
An inspection survey in August 1966 indicated a general subsidence
to 3.5 ft along the raised portion of the jetties, with maxi-
mums of 5 and 6 ft over short sections of the north and south jet-
Present channel depth (-35 ft mlw) extends approximately 13,000 ft
beyond the end of the jetties. There has been no history of mainte-
nance or repair to the jetties since their completion.