Coastal Construction Manual - National Ready Mixed Concrete ...

IDENTIFYING HAZARDS 3
3.4.3 Waves
Waves can affect coastal buildings in a number of ways, including breaking waves, wave runup, wave
reflection and deflection, and wave uplift. The most severe damage is caused by breaking waves (see Figure
3-23). The force created by waves breaking against a vertical surface is often 10 or more times higher than
the force created by high winds during a storm event.
Figure 3‐23.
Storm waves breaking
against a seawall in front
of a coastal residence at
Stinson Beach, CA
SOURCE: LESLEY EWING,
USED WITH PERMISSION
Wave runup occurs as waves break and run up beaches, sloping surfaces, and vertical surfaces. Wave runup
(see Figure 3-24) can drive large volumes of water against or around coastal buildings, inducing fluid impact
forces (albeit smaller than breaking wave forces), current drag forces, and localized erosion and scour (see
Figure 3-25). Wave runup against a vertical wall generally extends to a higher elevation than runup on a
sloping surface and is capable of destroying overhanging decks and porches. Wave reflection or deflection
from adjacent structures or objects can produce forces similar to those caused by wave runup.
Figure 3‐24.
Wave runup beneath
elevated buildings at
Scituate, MA, during
the December 1992
nor’easter storm
SOURCE: JIM O’CONNELL,
USED WITH PERMISSION
COASTAL CONSTRUCTION MANUAL
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