Coastal Construction Manual - National Ready Mixed Concrete ...

IDENTIFYING HAZARDS 3
3.4.4 Flood‐Borne Debris
Flood-borne debris produced by coastal flood events and storms typically includes decks, steps, ramps,
breakaway wall panels, portions of or entire houses (see Figure 3-27), heating oil and propane tanks, vehicles,
boats, decks and pilings from piers (see Figure 3-28), fences, destroyed erosion control structures, and a
variety of smaller objects. Flood-borne debris is often capable of destroying unreinforced masonry walls,
light wood-frame construction, and small-diameter posts and piles (and the components of structures they
support). Figure 3-29 shows debris generated by destroyed buildings at Pass Christian, MS, that accumulated
approximately 1,000 feet inland from the highway. The debris from buildings closest to the Gulf of Mexico
undoubtedly accentuated damage to buildings in the area and contributed to their destruction. Debris
trapped by cross bracing, closely spaced pilings, grade beams, or other components or obstructions below the
BFE is also capable of transferring flood and wave loads to the foundation of an elevated structure. Parts of
the country are exposed to more massive debris, such as the drift logs shown in Figure 3-30.
Figure 3‐27.
A pile‐supported house
at Dauphin Island, AL,
was toppled and washed
into another house,
which suffered extensive
damage (Hurricane
Georges, 1998)
COASTAL CONSTRUCTION MANUAL
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