Table 5
Colorado River Jetties
Mouth of the Colorado River, Texas
Date(
Construction and Rehabilitation History
1984-
As part of navigational improvements, two rubble-mound jetties were
1986
viding protection for the 15- by 200-ft entrance channel. The south
jetty is 1,450
long, and the north jetty, which contains a rubble-
mound weir, is 2,650
long. The north jetty weir section begins
410 ft from landward end, at about the mlt contour, and extends
1 0 0 ft seaward to about the -8
mlt contour. The seaward ends of
,0
the north and south jetties are about 1,800 ft apart and situated in
water depths of approximately -12 and -5
mlt, respectively. The
jetty design incorporated an impoundment basin on the channel side of
the north jetty to trap littoral drift material passing over the
weir. The basin, initially dredged to a capacity of 740,000 cu
will be dredged periodically and the material deposited downdrift of
the jetties. The crown elevations of the weir section and remaining
ft mlt, respectively. The design crown
jetty sections are 0 and
width and side slopes are 16
and
respectively. The typical
jetty trunk section (Figure 7) consisted of a 2- to 3-ft-thick
bedding layer of 0.5-in. to 200-lb stone, 200- to 1,000-lb core stone
(2,000-lb maximum on the seaward leg of the north jetty), and a
single layer of rectangular granite cover stone. The 200-ft-long
head sections (at the seaward ends) were similar to the trunk sec-
tions except for a double layer of cover stone on the side slopes and
a 5-ft-thick bedding layer on the north jetty. The cover stone
varied in size from to 6 tons at the landward ends to maximums of
1 to 18 tons and 1 to 12 tons at the seaward ends of the north and
6
0
south jetties, respectively. To buttress the armor layer at the
slope toes, the outer two to three cover stones were to be placed
horizontally on the bedding layer. Cover stone sizes were selected
using design wave heights of up to 1 . ft (north jetty head) and
76
Hudson's slope stability formula. The permeability of the jetties
was decreased by chinking a section of the core stone, extending the
full width of the crown and downward on
slide slopes, with
to 4-in. filler stone. The absence of a core stone section was the
only difference between the weir and trunk sections. Toe protection
stone was placed on all sections of the jetties, buttressing the
bedding layer and outermost cover stone (thus the thickness varied
from 5 to 9.5 ft). The width of the toe protection section was 5 ft
except on the head sections where it was 1 ft, and the design outer
0
The stone size was the same as the adjacent
side slope was
core stone (weir section used 200- to 2,000-lb stone). Transition
sections, 1 0 ft long, were provided for changes in grade (or stone
0
geometry) among weir, trunk, and head sections. Approximately
490,000 cu yd of material from the channel and deposition basin were
to be used as fill on the west side of the channel and shoreline
(Continued)
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