Laboratory Manual for Introductory Geology 4e

FIGURE 17.19 Examples of seawall construction.
(a) A section of the Galveston, Texas, seawall.
(b) Concrete blocks of a seawall.
is protected from storm surge by an extensive seawall (FIG. 17.19a). Seawalls can
be made with different designs and different materials, such as the concrete blocks
shown in FIGURE 17.19b.
17.4.2 Beach Nourishment
A single storm can erode vast amounts of sand from an unprotected beach, as
shown in FIGURE 17.20a. The most common remedy is to do in a short time what
it would take nature decades to do: replace the eroded beach by dredging sand
from offshore, pumping it onto the beach, and spreading it out with bulldozers
(FIG. 17.20b) This process is known as beach nourishment.
17.4.3 Jetties
Communities on barrier islands often use their knowledge of the longshore drift
that built those islands to try to preserve their beaches. They build structures perpendicular
to the shoreline in an attempt to trap moving sand and prevent its loss
FIGURE 17.20 Beach erosion and nourishment.
(a) Effect of erosion along a sandy shore.
(b) Beach nourishment: sand pumped from offshore replaces a
beach whose sand has been eroded away.
456 CHAPTER 17 SHORELINE LANDSCAPES