island that separates East Bay from the Gulf of Mexico. The peninsula was breached under the
direction of the Texas Game and Fish Commission (now the Texas Parks and Wildlife
Department) at a low, narrow area to allow fish migration and to improve water quality.
Dredging of the breach cut began in October of 1954 and was completed by February, 1955. A
channel was to be dredged across the peninsula to a depth of 8 ft at mlw and 80 ft wide. The cut
was to be flared on the Gulf side and extended into the Gulf to a depth of 3 ft mlw, and to a depth
of 4 ft mlw on the bay side. The plan also called for the construction of a sheet pile retaining
wall on the southwest bank of the cut that extended from the middle of the barrier island to the
Gulf to resist erosive wave action in this area. A complete discussion of the Rollover Pass
project is given by the U.S. Army Engineer District, Galveston (1958).
Breaching of barrier islands will cause significant change to the local circulation and sediment
transport, and care must be exercised to avoid unwanted erosion. Rollover Pass is an example of
a purposeful breach that produced an excessive tidal current and caused unwanted and
uncontrolled rapid erosion of the channel banks. Before the work was completed, the breach
channel had eroded to 30 ft below mean tide level at the centerline of the barrier island, and the
Gulf side entrance widened to nearly 500 ft. A bridge spanned the cut and the current through
the breach caused erosion that threatened to undermine the bridge abutments. Immediate
protective measures constructed included additional pilings to protect the bridge abutments, a
groin along the northeast side to stop the breach from widening, and a revetment of the exposed
banks with broken concrete, shell, stone, and other rubble.
Despite the additional measures taken, erosion of the breach cut and the adjacent Gulf shore
continued. In 1955, shoreline recession on the southwest side of the breach cut continued for
approximately 1 mile down the coast. Four houses had to be moved by the owners. The bridge
abutments showed signs of undermining by scour. To protect the bridge, a sheet pile bulkhead
was constructed across the cut on the Gulf side of the bridge to a depth of about 2 ft below meant
tide level (mtl) to permit some exchange of water while controlling the erosion. The pass was
inspected in October 1956, and evidence of shoaling was found, including a bar that had formed
across the mouth of the cut. The Galveston District evaluated the pass and surrounding area, and
published a report in April of 1958. Based on the recommendations in that report, sills were
constructed at the centerline of the barrier near the bridge and at the Gulf entrance to reduce tidal
current velocity. Bulkheads were also constructed along both banks across the barrier to halt
erosion within the breach. Following construction of the improvements, the pass has not
exhibited the large-scale widening that characterized the initial cut.
Redwood Creek, Northern California.
Artificial breaching has been conducted at several
California river entrances for purposes such as improvement of water quality, mitigation of
flooding, and opening of fish migration paths. One example is Redwood Creek. The mouth of
Redwood Creek is located in Redwood National Park, west of the town of Orick in northern
California. The creek mouth is located in the park, but upstream portions of the estuary lie
outside the park boundary and private lands flood if the creek mouth closes and water levels rise.
A sand spit created by longshore sand transport typically builds across the mouth of the creek in
late spring and early summer, causing the mouth to migrate and forming an embayment. The
southward migration increases the length of the outflow channel and reduces the flow gradient,
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