Coastal Construction Manual - National Ready Mixed Concrete ...

IDENTIFYING HAZARDS 3
3.3.4.7 Wildfire
Wildfires can occur virtually everywhere in the United States and can threaten buildings constructed in coastal
areas. Topography, the availability of vegetative fuel, and weather are the three principal factors that influence
wildfire hazards. FEMA has produced several reports discussing the reduction of the wildfire hazard and
the vulnerability of structures to wildfire hazards, including Wildfire Mitigation in the 1998 Florida Wildfires
(FEMA 1998) and FEMA P-737, Home Builder’s Guide to Construction in Wildfire Zones (FEMA 2008b).
Some communities have adopted the International Wildland-Urban Interface Code (ICC 2012c), which includes
provisions that address the spread of fire and defensible space for buildings constructed near wildland areas.
Experience with wildfires has shown that the use of fire-rated roof assemblies is one of the most effective
methods of preventing loss of buildings to wildfire. Experience has also shown that replacing highly
flammable vegetation around buildings with minimally flammable vegetation is also an effective way of
reducing possible wildfire damage. Clearing vegetation around some buildings may be appropriate, but this
action can lead to slope instability and landslide failures on steeply sloping land. Siting and construction
on steep slopes requires careful consideration of multiple hazards with sometimes conflicting requirements.
3.3.4.8 Floating Ice
Some coastal areas of the United States are vulnerable to problems caused by floating ice. These problems can
take the form of erosion and gouging of coastal shorelines, flooding due to ice jams, and lateral and vertical
ice loads on shore protection structures and coastal buildings. On the other hand, the presence of floating
ice along some shorelines reduces erosion from winter storms and wave effects. Designers should investigate
potential adverse and beneficial effects of floating ice in the vicinity of their building site. Although this
Manual does not discuss these issues in detail, additional information can be found in Caldwell and Crissman
(1983), Chen and Leidersdorf (1988), and USACE (2002).
3.3.4.9 Snow
The principal hazard associated with snow is its accumulation
on roofs and the subsequent deflection and potential failure of
roof trusses and supports. Calculation of snow loads is more
complicated than rain loads, because snow can drift and be
distributed non-uniformly across a roof. Drainage of trapped
and melted snow, like the drainage of rain water, must be
addressed by the designer. In addition, particularly in northern
climates such as New England and the Great Lakes, melting
snow can result in ice dams. Ice dams can cause damage to roof
coverings, drip edges, gutters, and other elements along eaves,
leaving them more susceptible to future wind damage.
3.3.4.10 Atmospheric Ice
Ice can sometimes form on structures as a result of certain
atmospheric conditions or processes (e.g., freezing rain or drizzle
or in-cloud icing—accumulation of ice as supercooled clouds
or fog comes into contact with a structure). The formation and
CROSS REFERENCE
Chapter 7 of ASCE 7 includes
maps and equations for
calculating snow loads. It also
includes provisions for additional
loads due to ice dams (ASCE
2010).
CROSS REFERENCE
State CZM programs (see Section
5.6, in Chapter 5) are a good
source of hazard information,
vulnerability analyses, mitigation
plans, and other information
about coastal hazards.
COASTAL CONSTRUCTION MANUAL
3-27