Coastal Construction Manual - National Ready Mixed Concrete ...

IDENTIFYING HAZARDS 3
Erosion during storms sometimes occurs despite the presence of erosion control devices such as seawalls,
revetments, and toe protection. Storm waves frequently overtop, damage, or destroy poorly designed,
constructed, or maintained erosion control devices. Lands and buildings situated behind an erosion control
device are not necessarily safe from coastal flood forces and storm-induced erosion.
Narrow sand spits, barrier islands and low-lying coastal lands
can be breached by tidal channels and inlets—often originating
from the buildup of water on the back side (see Figure 3-39)—
or washed away entirely (see Figure 3-40). Storm-induced
erosion damage to unconsolidated cliffs and bluffs typically
takes the form of large-scale collapse, slumping, and landslides,
with concurrent recession of the top of the bluff.
CROSS REFERENCE
FIRMs incorporate the effects
of dune and bluff erosion during
storms (see Section 3.6.7).
BEFORE
AFTER
Figure 3‐39.
Breach through barrier island at Pine Beach, AL, before Hurricane Ivan (2001) and after (2004)
SOURCE: USGS
BEFORE
AFTER
Figure 3‐40.
Cape San Blas, Gulf County, FL, in November 1984, before and after storm‐induced erosion
COASTAL CONSTRUCTION MANUAL
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