The
upper Texas coast was severely eroded during Tropical Storm Frances in
September 1998. In response to this erosion and in an effort to prevent
further storm damage to structures along the Gulf of Mexico shoreline,
geotextile-tube (geotube) shore protection projects have been constructed.
The geotubes consist of sediment-filled sleeves of geotextile fabric with
an oval cross section of approximately 4 m (12 ft). The geotubes rest
on a fabric scour apron that has sediment-filled anchor tubes along each
edge. Geotubes are placed in a trench dug parallel to shore along the
back beach or foredunes, and project designs call for sand and natural
beach vegetation to cover them.
Since
1998, nine geotube projects have been installed along the Gulf of Mexico
Shoreline of Galveston and Brazoria Counties (Fig.
1, Fig.
2, Fig.
3). A total of 10.2 km (6.3 mi) of shoreline has the tubes, and extensions
of projects on Bolivar Peninsula were in progress during June 2001. There
is concern that the geotubes may eventually cause the fronting beach to
unnaturally narrow and steepen and the adjacent shorelines to retreat
at a higher rate than they would without the geotubes in place. Even if
the geotubes do not cause changes in the dynamics of the environment,
they may eventually form an unacceptable landward boundary to the public
beach because of natural, long-term shoreline retreat. This study is providing
a quantitative evaluation of these extensive geotube projects. The results
will also aid the design of future erosion control projects, such as beach
nourishment and other geotube projects in the area.
Parameters
that are being measured include beach and dune topography, vegetation
and shoreline positions, geotube exposure and damage, vegetation cover,
and wave and water levels. From these measurements, the effects of the
geotubes on the beaches and dunes will be evaluated as well as their ability
to slow erosion and prevent storm damage.
