Number range CHAPTERCHAPTER 7

# HAZARD MITIGATION

This chapter will explain what hazard mitigation is, and how it fits in
with the other phases of emergency management. Next, the chapter will
describe the most widely used mitigation strategies and the ways they
are applied to the most common types of environmental hazards. The
following section will describe the legal basis for hazard mitigation as
it stands in the United States today. Problems in the adoption and
implementation of mitigation policies will be described and some methods
of addressing them will be offered. Finally, the chapter will conclude
with as discussion of the relationship between hazard mitigation and
sustainable development.

# Introduction

As noted in Chapter 1, FEMA long ago adopted the conception of emergency
management as four phases---mitigation, preparedness, response, and
recovery. Hazard mitigation takes place before disasters, along with
emergency preparedness and recovery preparedness. This makes it
important to coordinate mitigation with preparedness. Moreover,
disasters provide opportunities to rebuild communities that are more
resilient. This makes it important to integrate hazard mitigation into
disaster recovery (Schwab, et al., 1998).

FEMA's (1999, p. 1-1) Hazard Mitigation Grant Program Desk Reference
defines mitigation as "any sustained action taken to reduce or eliminate
long-term risk to people and property from natural hazards and their
effects". One limitation of this definition is its inclusion of a
diverse set of activities that have only an indirect relationship to the
reduction of disaster impacts. For example, FEMA's independent study
course on hazard mitigation (Federal Emergency Management Agency, 1998a)
lists emergency services and public information as mitigation measures
along with more logical candidates such as flood control works, land use
planning, and building codes. To overcome this limitation, Lindell and
Perry (2000) defined hazard mitigation as preimpact actions that provide
*passive* protection at the time of disaster impact. This definition
clearly distinguishes hazard mitigation from emergency preparedness,
which consists of preimpact actions that provide the resources
(personnel, plans, facilities, equipment, materials) needed to support
an *active* response at the time of disaster impact. It also
distinguishes hazard mitigation from recovery preparedness, which
consists of preimpact actions or policies that provide the resources
needed to return the community to its normal patterns of social
functioning after disaster impact occurs.

# Legal Framework for Hazard Mitigation

The federal government has no constitutional authority to directly
intervene in local land use or building construction practices. However,
it has a significant incentive to change these practices because it
faces an exponentially increasing annual cost for disaster recovery
(Mileti, 1999). The federal government first attempted to reduce
disaster losses by reducing hazard exposure. In the case of floods, this
led to an extensive program of dams and levees. As the limitations of
sole reliance on this approach became increasingly evident, Congress
provided a legal basis for the federal government to intervene
*indirectly* into local land use or building construction practices by
passing the Robert T. Stafford Disaster Relief and Emergency Assistance
Act of 1988. Under Section 409 of this act, states were required to
prepare and update state hazard mitigation plans within six months of a
Presidential Disaster Declaration *as a condition for receiving federal
disaster assistance.* Section 404 of the Stafford Act covered grants
made available for postdisaster hazard mitigation projects. The Disaster
Mitigation Act of 2000 (known as DMA2K) amended the Stafford Act. DMA
2000 substituted new (Section 322) mitigation planning requirements for
the old ones in Section 409. In order for a state to qualify for
disaster assistance, DMA 2000 requires one of two levels of hazard
mitigation plan---*standard* or *enhanced*
(www.fema.gov/plan/mitplanning/DMA.shtm). States that develop an
approved enhanced plan qualify for increased Hazard Mitigation Grant
Program (HMGP) funding. DMA 2000 also requires local mitigation plans
and authorizes a state to allocate as much as 7% of its HMGP funds for
developing state and local hazard mitigation plans. The current amount
of federal assistance for mitigation projects can be as much as 75% of
each project's cost, but the total amount of funding for all mitigation
projects must not exceed 7.5% of the federal assistance for a given
disaster.

The creation of a Mitigation Directorate in FEMA during 1993
significantly raised the level of attention given to hazard mitigation.
Hazard Mitigation Survey Teams comprising FEMA, state, and local
representatives are now formed after disasters to identify community
mitigation needs and opportunities. In addition, an Interagency Hazard
Mitigation Team comprising representatives from relevant federal
agencies is activated after flood disasters to coordinate hazard
mitigation efforts. Whenever a Presidential Disaster Declaration is
made, a Federal Hazard Mitigation Officer (FHMO) is appointed to manage
hazard mitigation programs. The FHMO serves as a liaison with the State
Hazard Mitigation Officer (SHMO), participates in the preliminary damage
assessment, helps assess local mitigation issues, develops a mitigation
strategy, and also evaluates state mitigation programs for the Regional
Analysis and Recommendation. FEMA and the affected state establish a
written agreement that defines the duties and responsibilities that the
federal, state, and local governments will assume after a disaster.
These and other requirements have increased the amount of effort that
state and local governments have put into hazard mitigation.

The SHMO, who coordinates the development of a Section 409 plan, serves
as a liaison between the federal and local levels. In addition, the SHMO
generally performs the same functions at the state level as the FHMO
does at the federal level. Local governments, in turn, are required to
evaluate hazards, adopt appropriate hazard mitigation measures, and
appoint local HMOs when necessary. They also participate on Hazard
Mitigation Survey Teams and Interagency Mitigation Teams when
appropriate and, finally, develop and implement Section 409 plans. The
legal justification for this organizational structure is founded on the
right of the federal government to offer or withhold its disaster relief
funds. Thus, the federal government provides an incentive for local
hazard mitigation policies, not a punishment for failure to adopt them.
There is a wide array of specific programs dealing with hazard
mitigation, particularly for flood and earthquake hazards. However,
these programs have typically been established in response to the
specific needs of historical disasters, so the result has been "an ad
hoc patchwork system" (May & Deyle, 1998) that is limited in focus and
even varies across hazards. In the case of flood hazard, federal
policies have worked against each other. On the one hand, they promote
occupation of flood prone areas through subsidized insurance and flood
control projects. On the other hand, they seek to limit occupation of
flood zones by regulating wetlands and development in coastal zones.

Local governments often feel that federal and state mandates are overly
restrictive and do not provide enough financial assistance to achieve
the goals of these mandates. Local governments, as the direct regulators
of land use and building construction practices, are politically
vulnerable to blame for withholding land from development and requiring
flood control or earthquake resistance measures that drive up local
development costs. States have attempted to support the local
governments and meet federal requirements in many different ways,
including mandates that local jurisdictions apply traditional land use
planning tools such as zoning and subdivision regulations. However,
states have also encouraged local governments to include hazard
mitigation objectives in their everyday investment policies, such as
open space acquisition and capital improvement plans, to reduce
community hazard vulnerability.

As the cost of disasters has risen, some insurers have stopped writing
policies in some hazard prone areas, but the insurance industry as a
whole has begun to promote mitigation for households. The Institute for
Business and Home Safety (IBHS), an insurance industry coordinating
organization, has been a leader in this effort, through its *Showcase
Communities* program (www.ibhs.org). IBHS also provides materials on
disaster planning to promote business continuity after disasters through
its *Open for Business* program.

Hazard mitigation faces important legal challenges in the United States.
Several "regulatory takings" cases have been heard in the Supreme Court,
the most famous of which was *Lucas v. South Carolina Coastal Council*
(112 S.Ct., at 2886, 1992). These cases have sought to clarify the
conditions under which jurisdictions can regulate the use of private
property in order to accomplish a public purpose. Government has
traditionally held the power of *eminent domain*, under which it can
compel private owners to sell their property to the government at a fair
market value. Historically, governments have used eminent domain to
acquire property for major public benefits such as roadways. In recent
years, some plaintiffs have successfully argued in the courts that some
government restrictions on the use of their property constitute a
"taking" of part of its value. The net effect of these cases has been to
limit, but not eliminate, the ability of local governments to regulate
land use for hazard mitigation. Governments must not remove all value of
a property ("total taking") without adequate compensation, regardless of
the purpose of the law. There must be a "rough proportionality" (*Dolan
v. City of Tigard, Oregon*, 114 S.Ct., at 2309, 1994) between the burden
on the property owner and the benefit to the public. Many states have
passed laws requiring an assessment of the impact that any proposed
governmental action has on private property. There also are laws
requiring governments to compensate property owners if any rule or
regulation causes a decrease in the fair market value of a property by
more than a specific percentage.

The principles established in previous case law were recently modified
by a Supreme Court decision that endorsed a broadened definition of
"public benefit" (*Kelo vs. City of New London*, No. 04-108 June 23,
2005). However, this does not change government's obligation to continue
to meet other established conditions when it "takes" private property.
Specifically, governments must provide adequate compensation for the
economic value of any property they acquire through the use of eminent
domain. Moreover, widespread opposition to the Supreme Court's decision
makes it likely that state legislatures will respond by tightening legal
restrictions on the use of eminent domain to condemn private property.
Such legislation is likely to reestablish the principle articulated in
*Dolan*, but the precise nature of the requirements will vary from one
state to another.

# Mitigation Strategies

Mitigation strategies have been classified in many different ways. One
of the most common is the distinction between structural and
nonstructural mitigation. As its name suggests, structural mitigation
involves the use of engineered safety features to provide protection
from disaster impacts. Unfortunately, the term *structural mitigation*
is ambiguous because engineers design structural protection at many
different scales and in structures that have many different functions.
The most common examples of structural mitigation are dams, levees,
seawalls, and other permanent barriers that prevent floodwater from
reaching protected areas. However, engineers also use building designs
and construction materials to increase the ability of an individual
structure's foundation and load bearing framework to resist
environmental extremes. They apply these building construction practices
to residential, commercial, and industrial structures as well as to
infrastructure facilities such as pipelines for potable water, waste
water, and fuel (e.g., oil and natural gas); roads and bridges; radio,
television, and cellular telephone towers; and electric transmission
lines.

The term *nonstructural mitigation* is also vague because it also
includes a broad set of mitigation strategies. These include activities
as diverse as reducing chemical quantities stored at water treatment
plants, purchasing undeveloped floodplains and dedicating them to open
space, installing window shutters for buildings located on
hurricane-prone coastlines, and bolting water heaters to walls in
earthquake zones. In fact, these have little in common other than that
they are not designed by engineers.

To reduce confusion about the meaning of the term structural mitigation,
this chapter uses it only to refer to design, construction, and retrofit
features of individual buildings that make them less vulnerable to
environmental hazards. Instead of classifying mitigation measures as
either structural or nonstructural, this chapter adapts a system used by
the Federal Emergency Management Agency (1986) to classify hazard
mitigation strategies in terms of five categories---hazard source
control, community protection works, land use practices, building
construction practices, and building contents protection. *Hazard source
control* involves intervention at the point of hazard generation to
reduce the probability or magnitude of an event. By contrast, *community
protection works* attenuate disaster impact by altering the hazard
transmission process, especially by confining or diverting materials
flows to reduce the hazard exposure of target locations and populations.
One feature that is common to both hazard source control and most
community protection works is that they are collective methods of hazard
mitigation. That is, they are usually constructed by government agencies
to provide protection for a large number of properties.

*Land use practices* limit hazard exposure by minimizing development in
areas where the likelihood of hazard impact is high. By contrast,
*building construction practices* limit physical vulnerability by
building structures whose resistance to hazard impact is high. Finally,
*building contents protection* prevents furniture, equipment (e.g.,
furnaces, air conditioners, washers, dryers), and other building
contents from being damaged or destroyed. In many cases, but not all,
appropriate building construction practices protect building contents at
the same time as they protect the structure itself. For example,
preventing wind damage to a structure will also prevent damage to its
contents. However, seismic shaking can overturn water heaters and
refrigerators without causing any damage to the building structure
itself.

*Hazard Source Control*

For some hazards, it is possible to control the physical event system
that is the source of the danger. It is easy to understand how this is
true for technological hazards that are normally under human
control---structural fires/conflagrations, explosions, toxic chemical
releases, and radiological releases. As Chapter 5 indicated, fires can
occur only when there is fuel, oxygen, and an ignition source. Thus,
source control for structural fires and mass conflagrations can be
achieved by confining a fuel to prevent it from mixing with oxygen or by
keeping any fuel/air mixture that does develop away from an ignition
source. Source control for toxic chemical releases can be achieved by
substituting nontoxic chemicals, reducing chemical quantities, lowering
operating temperatures and pressures, and maintaining equipment to
prevent leaks from tank, pipes, and valves (Ashford, et al., 1993).

Hazard source control is generally not feasible for meteorological,
geophysical, or hydrological hazards. However, there are some
exceptions. Wildfire hazard can be controlled by limiting fuel loads in
woodlands and controlling ignition sources. Flood hazard can be
controlled by maintaining ground cover that decreases runoff by causing
rainfall to infiltrate the soil. Even when hazard source control is
feasible, local emergency managers rarely implement these measures
directly. Thus, they must work with others, such as facility operators
in the case of technological hazards, to implement this hazard
mitigation strategy. Nonetheless, such efforts are well worth the
investment of time and energy because this mitigation strategy can be
very simple, cheap, and effective.

*Community Protection Works*

Community protection works are most commonly used to divert flood water
past communities that are located in flood plains. They also can be used
to provide protection from other types of water flows such as tsunami
and hurricane storm surge inundation. Finally, community protection
works can protect against two types of geophysical hazards, landslides
and volcanic lava flows, and some industrial hazards involving hazardous
materials flows from storage tanks. Each of these is described in the
following sections.

*Flood control works.* The four major types of flood control works are
stream channelization, dams, levees, and floodwalls. Channelization is
achieved by deepening and straightening stream channels. Deepening a
channel prevents flooding by increasing the volume of water that the
channel can carry. Straightening a channel allows the water to move
downstream faster by shortening the distance it must travel.

Dams are elevated barriers sited *across* (perpendicular to) a streambed
that increase surface storage of flood water in reservoirs upstream from
the dam. These structures can be made of concrete, earth, or earth with
a rock core that provides additional strength. In addition, these
structures have floodgates and spillways that allow their operators to
release water from the reservoir. The water level in most reservoirs is
actively managed to achieve four conflicting objectives. Electric power
generation, water recreation, and irrigation are best achieved by full
reservoirs, whereas flood control is best achieved by empty reservoirs.
The solution is typically to fill partially, leaving some capacity for
floods. However, severe upstream flooding might require an emergency
release to protect the dam if the reservoir is so full that it cannot
store any more water. In a severe storm, a reservoir can fill so rapidly
that massive amounts of water must be released in a very short time. In
some cases, this can cause downstream flooding that is just as bad as if
the dam had never been built. Indeed, one community downstream from a
dam was flooded so frequently from emergency reservoir releases that
local residents and government authorities decided to relocate the
community (Perry & Lindell, 1997).

Downstream flooding can also occur if a dam fails catastrophically and,
of course, the extent of the flooding depends on the size of the
reservoir. Dam safety is an issue during routine operation because 20
major dam collapses occur each year worldwide and 83% of these collapses
occur in earth- or rock-filled dams. In a survey conducted after some
significant dam collapses in the late 1970s, the US Army Corps of
Engineers found that one third of the 9000 inspected dams were unsafe
and these threatened over 2000 US communities. As one might expect, most
of the risk comes from dams that were constructed with little or no
engineering supervision. One catastrophic dam failure occurred at
Buffalo Creek, West Virginia in 1972. There, a poorly designed dam
constructed by a coal company collapsed. The resulting flood killed 125
people, injured hundreds, and left thousands homeless (Gleser, Green &
Winget, 1981).

Detention basins are quite similar to dams, but are earth- or
rock-filled structures with dry reservoirs that fill only during floods.
Unlike dams, whose floodgates and spillways are actively managed,
detention basins have passive outflow. This is achieved by placing a
pipe through the dam at ground level. The water in the pipe can flow
through the dam unimpeded, but any amount that exceeds the capacity of
the pipe backs up into the reservoir. This effectively regulates
downstream discharge so it cannot exceed a predetermined rate of flow.
Very large detention basins can be constructed to provide a substantial
amount of storage capacity. Because the reservoir bottoms are dry most
of the time, they can be used for open space. Ball fields, hiking
trails, and even parking lots and picnic shelters are excellent uses for
detention basins because these facilities have such low development
intensity that they can be repaired quickly and cheaply after flooding
subsides.

Levees are elevated barriers sited *along* (parallel to) the streambed
that confine stream flow to the floodway. To be effective, a levee must
be built on soil that will provide a stable foundation and constructed
of impervious soil, such as clay, that is compacted to prevent it from
settling (Army Corps of Engineers National Floodproofing Committee,
1993). Its surfaces are usually planted with grass or other low
vegetation to prevent them from eroding. Additional protection from
erosion during flooding can be obtained by using *riprap* (large chunks
of concrete or stone) to line the surface exposed to river currents and
wave action. One convenient characteristic of an earthen levee is that
people can readily raise its height if the forecast depth of a specific
flood is greater than the levee elevation. For example, it is common to
see television coverage of volunteers stacking sandbags to raise a levee
as a river level rises. However, sandbagging operations conducted during
a flood are emergency response actions rather than (preimpact) hazard
mitigation actions.

Levees are susceptible to a number of design, construction, and
maintenance problems. The New Orleans levees that failed during
Hurricane Katrina, which were constructed by the Army Corps of
Engineers, were not adequately designed for the soils that existed in
that area. Many other levees have been constructed by local levee
districts that have limited budgets and, therefore, sometimes provide
inadequate maintenance. Levees have four basic types of failure
mechanisms (see Figure 7-1). These are wave action (Path A), overtopping
(Path B), piping (Path C), and seepage erosion (Path D).

# [Figure 7-1. Levee Failure Modes.]{.underline} 

*Wave action* causes failure by attacking the face of the levee and
scouring away the material from which it is constructed. *Overtopping*
occurs when the water level exceeds the height of the levee. Once this
happens, the flow of water over the top of the levee begins to erode a
path that allows increasing amounts of water to flow through the
opening. This can quickly cause a progressive failure that completely
floods the area behind the levee. *Piping* occurs when an animal burrow,
rotted tree root, or other disturbance in the levee creates a long
circular tunnel through or nearly through the levee. Once the water
reaches the "pipe", it has an open path toward the landward face of the
levee and can fail the levee. *Seepage erosion* occurs when the height
of the water in the river puts pressure on water that has seeped into
the riverbed, under the levee, and into the soil on the landward side of
the levee. The resulting flow of water can eventually cause boils of
muddy water that erode a path for the water to flow underneath and then
behind the levee.

Levees can have long-term effects on the river level by forcing silt to
accumulate on the river bottom rather than being deposited onto the
surrounding floodplain. Thus, levees can increase flood hazard while
simultaneously reducing soil fertility. The Hwang Ho (Yellow River) in
China is an especially good example of this because its bottom is now 25
feet above the surrounding floodplain.

Unlike the earthen construction of levees, floodwalls are built of very
strong materials such as concrete. Although this makes them more
expensive to construct than levees, such construction has the advantage
of providing an impermeable face that avoids piping or other water
infiltration into the structure. In addition, concrete structures can be
built with nearly vertical faces, whereas levees must be built with a
pitch of one foot of vertical elevation to two or three feet of
horizontal distance (Army Corps of Engineers National Floodproofing
Committee, 1993). This makes floodwalls attractive in urban areas where
space is limited by existing development and land values are high. Like
levees, floodwalls must also be constructed on stable soil to prevent
differential settling or collapse. In addition, construction on
impervious soil will avoid seepage erosion under the floodwall. Although
levees and floodwalls are typically constructed large enough to protect
entire neighborhoods or even communities, they also can be built small
enough to protect individual structures.

Dams, detention basins, and levees have saved many lives and prevented
untild damage from floods. Nonetheless, it is important to recognize
that these protection works can only protect against events up to the
magnitude of the *design basis event* (DBE). In the United States, the
DBE is typically the 100 year flood---a flood with a 1% chance of
occurrence in any given year. Dams, levees, and detention basins will
not protect against events that are more extreme than this, so the
entire area that was protected up to the 100 year flood will be
inundated when a more extreme event occurs.

Perhaps the biggest problem with community protection works is that
people overestimate their effectiveness. In some cases, people are
unaware that protection is provided only up to the DBE, so they assume
that protection works will eliminate *all* flood hazard. In other cases,
people have assumed their flood risk has been reduced by protection
works that have no effect on their property. For example, Harding and
Parker (1974) studied the risk perceptions held by people living along a
river. These researchers found that some people living in a town located
on one branch of the river thought they would be protected by a nearby
dam that was actually located on the other branch. Thus, these people
thought the dam eliminated their risk of flooding when, in fact, it did
not affect their risk at all. Of course, the problem with people
overestimating the level of protection provided by dams, detention
basins, and levees is that they further develop the protected area after
the protection work has been built. This increases the amount of
property at risk and, in the long term, increases rather than decreases
property losses. In such cases, communities can be worse off than they
were before the protection work was constructed.

Finally, community protection works can force riverside communities into
something like an "arms race". Stream channelization is effective in
protecting the area in the immediate vicinity of the channelized section
of river. However, it frequently transfers one community's flooding
problem to the next ones downstream. As a result, the downstream
communities face a higher flood risk than they did before their upstream
neighbor channelized the river. Of course, if they reduce their risk by
channelizing their section of the river, this will transfer the risk to
the communities downstream from them. A similar dynamic emerges when a
community builds a levee or floodwall, except the victim is across the
river rather than downstream. Preventing the flow of floodwater on one
bank will tend to force it onto the other bank. If the second community
attempts to reduce this increased risk with its own levee or floodwall,
the risk is then transferred to downstream communities.

*Landslide controls.* For landslide mitigation, protection works focus
on reducing shear stress, increasing shear resistance, or a combination
of these strategies (Alexander, 1993). Reducing shear stress decreases
the pressure pushing one soil stratum over the top of another whereas
increasing shear resistance enhances the ability of the two strata to
remain in place. Thus, landslide protection works stabilize slopes by
hardening the soil surface to prevent water infiltration, installing
drain fields to remove water from the soil, and building retaining
structures such as buttresses, retaining walls, or tie-rods. It also is
possible to reduce the risk of landslides by controlling the timing of
construction on slopes, especially by leaving them undisturbed during
periods of heavy rainfall. Landslide risk can also be reduced by
minimizing the loads they carry. For example, limiting the extent of
development prevents the weight of additional houses and roads from
causing further slides.

*Industrial storage failures.* Community protection works can also be
used to confine hazardous materials flows. For example, dikes can be
constructed around storage tanks at industrial facilities to confine any
liquid releases that might occur. Such protection works are especially
common around petroleum storage tanks. Risk analyses are used to
determine the likely volume of any releases that might occur under
different failure modes (slow leak versus catastrophic shell failure)
and the rate at which the oil can be pumped from the damaged tank into
other intact tanks. The expected release volume and release rate can
then be used to determine the required storage capacity within the dike.

*Land Use Practices*

Land use practices are defined by the ways people use the land. These
include woodlands; livestock grazing; farmland; residential, commercial,
and industrial structures; and infrastructure facilities. Most of the
property in United States is controlled by households and businesses,
not governments. Consequently, local government must attempt to
influence the land use practices of households and businesses through
the use of risk communication, incentives, and sanctions. *Risk
communication* attempts to change land use practices voluntarily by
providing property owners with a more accurate understanding of hazard
vulnerability and hazard adjustments (Lindell & Perry, 2004). Similarly,
*incentives* attempt to change land use practices voluntarily through
property owners' free choice whether to accept compensation for
restrictions on development. One incentive for foregoing development of
a hazard-prone property is the sale of development rights. If the
incentive adequately compensates the property owners for their
opportunity cost (the profit they think they would have made from
developing the land), they are likely to accept it. If the incentive is
too small, they can proceed with development. By contrast, *regulations*
attempt to change land use practices involuntarily by subjecting
property owners to legal penalties such as fine and possibly jail
sentences for engaging in prohibited land use practices. The differences
among risk communication, incentives, and regulations can be illustrated
by developers that are planning to develop a subdivision at the edge of
a 100-year flood plain. They might change their minds if a local
emergency manager informs them about the flood risks they and their
customers will face (risk communication). Alternatively, the developers
might voluntarily choose to avoid building homes there if the city will
allow them to build to a higher density in a portion of the subdivision
that is located outside the floodplain (an incentive). Finally, they
might comply with a city ordinance that makes it illegal to build in the
floodplain because they are concerned about the legal consequences of
violating the ordinance (a sanction for violation of the regulation).

Local governments have a variety of land use management practices
available to them that can be used to reduce hazard exposure---as well
as many other land use objectives such as sustainable economic growth
and a greater quality of life. Chief among these is land use planning, a
well-recognized tool for natural hazard mitigation (Burby, 1998;
Godschalk, Kaiser & Berke, 1998). Under the United States Constitution,
states delegate the land use planning function to local governments
under the police power to protect public health, safety, and welfare.
States vary significantly in the levels of planning they mandate, so
local reliance on land use regulation as a method of hazard mitigation
varies tremendously. Some states require local governments to develop
comprehensive plans that include land use elements and environmental
hazards elements. Florida and California are leaders in this regard.
Other states allow, but do not require, comprehensive or land use plans,
so fewer local jurisdictions in these states have such plans. Among the
other tools available to local governments for hazard mitigation are
zoning, subdivision regulations, capital improvements programs,
acquisition of property or development rights, and fiscal policies.
Local governments should explore these practices for their potential to
mitigate natural and technological hazards. In some cases, multiple
jurisdictions might collaborate in developing a mitigation plan for a
watershed or other ecological unit whose boundaries are broader than
those of political jurisdictions.

*Acquisition of land and development rights.* In some cases, a community
might decide to purchase land outright in order to preclude development
in hazardous areas. Such land is often located along rivers, lakes, and
seashores---which makes it a good location for low impact public uses
such as hiking and bicycle trails, golf courses, or picnic areas. It is
also possible to purchase development rights rather than the property
itself. Purchasing only the development rights allows landowners to
continue the current use of their property. An example of this is
farmers who want to continue to raise crops and livestock. In exchange,
the community ensures the land is not developed for a higher density use
as residential, commercial, or industrial structures that increase
physical vulnerability to hazard impacts.

*Capital improvements programs.* A capital improvements program (CIP) is
used to plan the placement of community infrastructure (water, sewer,
and natural gas pipelines; roads and bridges; electric power, telephone,
and cable television lines) and critical facilities (police and fire
stations, hospitals, schools, jails, and city offices). These elements
of the built environment all represent a significant investment of
public capital, so CIPs carefully assess the need for these facilities.
CIPs plan what type of facilities will be built, where they will be
built, and how they will be financed. The amount of infrastructure local
government controls is small in some communities. However, these local
governments can ensure the facilities they do control will be built in
locations that limit hazard exposure. The facilities will also be built
according to construction practices that limit their physical
vulnerability.

*Fiscal policy.* Local governments have some discretion in their use of
fiscal policy and taxation to distribute the public costs of private
development on hazardous property. Impact fees for provision of
infrastructure such as streets and sewers can be used to offset the
increased cost of their construction and maintenance in hazardous areas.
On the other hand, cities can offer tax incentives for reductions in the
intensity of development in hazard areas. The property tax burden can be
reduced for undeveloped land in order to reduce the pressure for
developing it in more intensive (and lucrative) uses. This is usually
done by assessing property taxes at the current use value rather than at
the market value. Of course, the owners are required to sign a written
agreement to keep the property at its current level of development or
they must forfeit the lower tax rate and compensate the jurisdiction for
the difference between the taxes that were actually paid and the amount
that would have been paid at the higher level of development.

*Hazard mitigation planning.* Hazard mitigation plans can be developed
as part of a comprehensive plan or as a stand-alone plan. A
comprehensive plan is the product of a process that is designed to help
communities develop strategies for managing changes in the built
environment. As the name implies, comprehensive plans are based on a
thorough assessment of a community's geography and history, economy,
demographic trends, transportation, housing, historic preservation, and
environmental protection, as well as its land use practices. The data
from this assessment is used in conjunction with community goals to
define strategies for achieving the kinds of growth and development that
are desired by local residents. In turn, these broad strategies guide
specific decisions about the siting of residential, commercial, and
industrial development and location of infrastructure and critical
facilities.

In some cases, it is advantageous to have a stand-alone mitigation plan.
Some communities have no comprehensive plan, or have weak and outdated
plans, yet face significant hazards. As noted earlier, DMA 2000 directed
FEMA to require all local governments to establish mitigation plans as a
condition for receiving federal assistance for disaster recovery. This
requirement could increase the prominence of hazard mitigation on the
community agenda and provide an opportunity to connect hazard mitigation
to land use policy through a planning process. In response to this
requirement, some states have developed model local hazard mitigation
plans (e.g., Arizona Division of Emergency Management, 2003).

Whether it is part of a community's comprehensive plan or is developed
as a stand-alone plan, a hazard mitigation plan should be based on the
hazard/vulnerability analysis, as described in Chapter 6. This analysis
provides a factual basis and a rational framework for setting feasible
goals and measurable objectives for mitigating hazard exposure. The
information in the hazard exposure section of the hazard assessment can
be communicated to public officials to help them devise more reasonable
and efficient land use policies (Burby, et al., 1985). Such hazard
information can also be communicated to private individuals (developers,
householders, and business owners) so they can make better decisions
about the location and type of development on their land (Milliman,
1983). As discussed in Chapter 4, local officials can disseminate this
information through a variety of communication channels. These include
the plan itself, other city publications, the planning process and
public meetings, and the news media.

Moreover, the hazard mitigation plan should establish specific policies
for meeting these objectives and define a method for evaluating progress
toward the stated goals on a regular schedule. In this regard, it is
important to remember that the planning process is just as important as
the document itself. As Chapter 3 indicated is the case with EOPs,
hazard mitigation plans are all too frequently placed in thick binders
to gather dust on shelves. However, an effective planning process
involves all affected sectors of the community in discovering what needs
to be done and how to go about doing it. This process requires the
participants to articulate community objectives for hazard mitigation
and develop specific policies the community can use to reach these
objectives. Thus, the written mitigation plan derives its significance
from the fact that it records the participants' consensual vision of
their community's future development. The "paper plan" is actually
implemented through other, more specific, mechanisms.

One advantage of incorporating hazard mitigation into a comprehensive
plan rather than adopting a stand alone plan is the increased likelihood
that hazard mitigation measures will be area wide rather than
site-based. Flood management is particularly amenable to regional
approaches such as the "No Adverse Impact" policy advocated by the
Association of Floodplain Managers (www.floods.org/home/). Moreover,
comprehensive plans can be used to evaluate land suitability and
indicate appropriate locations for development (Burby, 1998; White &
Haas, 1975). Including hazard mitigation goals in a comprehensive plan
can increase the likelihood that local government will adopt workable
policies that are consistent with residents' personal values (Godschalk,
et al., 1998). Linking hazard mitigation to other goals in the plan,
such as environmental protection or preservation of open space for
recreational use, might also enhance support for policies limiting
development because of natural hazards. (For an example of such
policies, see the San Antonio River Authority's Web site at
www.sara-tx.org/).

*Zoning.* Zoning originally was designed to separate "incompatible land
uses". For example, heavy industry, with its noise and pollution, is
kept away from residential neighborhoods. Of course, such uses of zoning
also mitigate the risk of technological disasters by keeping chemicals,
radiological and nuclear materials, and explosives away from those who
could be harmed. The same idea can be used to keep residential and
commercial property from hazardous areas such as earthquake fault lines
and floodplains. Moreover, communities can use zoning to avoid
permitting hazardous development near special facilities (for example,
preventing the siting of a chemical facility within one mile of an
elementary school). However, as noted at the beginning of this chapter,
problems can arise when zoning "takes" some or all of the value of
private property without establishing a clear basis in the protection of
the public health and safety. Thus, zoning ordinances must be related to
a city's comprehensive land use plan in order to be effective and
legally defensible.

*Subdivision regulations.* Subdivision regulations, which can serve
either as an alternative or as a supplement to zoning regulations, are
used to control the way "raw" (undeveloped) land is converted into
smaller parcels suitable for building. Subdivision regulations can be
used in many ways that include elevating properties to a prescribed
level above the base flood elevation, limiting development density in
sensitive lands such as dunes or wetlands, or clustering of housing to
minimize the impact on environmentally sensitive areas. Subdivision
regulations can also require setbacks from faults, slopes, or
floodplains---just as they routinely require setbacks from streets or
adjacent structures. In areas prone to wildfire, such regulations can
require the construction of *defensible space* by clearing a 30-foot
perimeter around any structure of vegetation, choosing fire-resistant
plant varieties and maintaining landscapes to reduce the buildup of
flammable materials such as dead leaves and fallen branches (Partners in
Protection, 1999). There is usually a site-plan review process
associated with these regulations that provides an opportunity for local
government agencies and the developer to discuss how the proposed
development will affect the hazard exposure of structures on the
property as well as other structures throughout the community.

*Building Construction Practices*

As is the case with land use practices, property owners can change their
building construction practices voluntarily because of risk
communication or incentives, or involuntarily because of building code
requirements. Thus, it is important to recognize the distinction between
building construction practices, which might or might not be freely
adopted by property owners, and a building code, which is a mechanism
for requiring specific building construction practices by all property
owners in a jurisdiction. This section will begin by describing the
basic components of a building, with a brief discussion of the major
differences among types of structures (see Ching & Adams, 1991, for
further details). This will be followed by a discussion of ways in which
building construction practices can reduce vulnerability to five
different types of hazards: hydrological, wildfire, wind, seismic, and
airborne toxic chemicals. Finally, this section will conclude with a
discussion of the process of building code adoption and implementation.

*Building components.* As previous chapters have indicated, buildings
can be classified as residential, commercial, and industrial. In turn,
residential structures can be classified as single family, multifamily
(apartment buildings), and mobile homes. Commercial structures can be
classified as low rise or high rise, but industrial structures comprise
so many different types that they will not be discussed here. The
typical residential or commercial building consists of three structural
systems---the foundation, the walls, and the roof. In addition, it has a
number of ancillary systems that include the electric, plumbing, and
HVAC (heating, ventilating, and air conditioning) systems. It is the
structural systems that are of primary concern in this section because
they support the weight of the building; the other systems will be
addressed in the section on building contents protection.

A building's foundation rests on soil that is either naturally or
artificially compacted so the building's weight will not cause it to
sink into the ground. The foundation itself is usually either a thick
slab of concrete that is poured directly onto the ground to support the
floor or a basement that is installed in an excavated pit. A basement
also has a concrete slab but, because it is below ground level (referred
to as *below grade*), it also has walls that are either made of a
vertical concrete slab or (in some older houses) concrete blocks. In
some cases, as will be discussed later, a building is constructed on
pilings that are sunk deep into the ground.

Most residential structures are currently built with walls that are
constructed in the shape of a frame that is made out of 2x4 inch wooden
studs. As Figure 7-2 indicates, each wall has a long horizontal stud,
called a sill plate, that runs the length of the wall's bottom. The wall
has another long horizontal stud located at the top, called a top plate.
The sill plate and top plate are connected by vertical studs that are
customarily spaced at 16 inch intervals. Rough openings are left in the
walls so window and door frames can be installed after the structural
frame has been completed.

[**Figure 7-2**. Wall Frame for a Small Residential
Structure.]{.underline}

The wall frame is usually constructed lying flat on the ground because
this makes it easy to assemble. Once the four walls have all been
assembled, they are tilted up and nailed together at the corners of the
building. The wall system is nailed to the foundation to secure it in
place and 4x8 foot sheets of plywood sheathing are nailed to the wall
frame. After a vapor barrier of plastic sheet is tacked over the entire
surface of the sheathing to make it impermeable to water, an exterior
veneer is attached. This veneer can be plywood siding, clapboard
(overlapping planks of wood, aluminum, or vinyl), or stucco (a mortar
that is spread over a wire mesh).

It is also common to see houses whose walls appear to be built entirely
of brick but are actually only brick veneer over a wooden frame. A true
brick wall is made of many horizontal layers (called *courses*) of
bricks that are held in place by mortar. Although this is not visible
from the outside, a brick wall actually consists of two adjacent wythes
(parallel walls) to make the wall thick enough to support the weight of
the upper floors and roof. These brick walls are strong enough to
support loads in *compression* (the weight of the upper stories pushing
downward due to gravity). However, brick walls perform poorly when they
are subjected to forces that are *shear* (pushing them sideways),
*torsional* (twisting them), or *tensile* (stretching them apart by
forcing them upward). As will be discussed further in the section on
seismic construction, ordinary brick walls are called unreinforced
masonry (URM) because they have no steel reinforcing bars to help them
resist these latter types of forces.

In a small multistory building, the floors are created by nailing 2x6
inch floor joists at 16 inch intervals to connect two of the opposite
walls of the building. Once the joists have been installed, they are
covered with a rough particle board or plywood subfloor and then a
better grade of plywood that has a smoother surface. Multiple layers of
subfloor are used to make the floor stiff enough to resist sagging under
the weight of occupants, furniture, and appliances. The visible
floor---which might be wall-to-wall carpet, wood, or tile---is installed
over the subfloor.

The roof is usually constructed according to one of three designs---a
flat roof, a gable end roof, or a hip roof. The name, *flat roof*, would
seem to imply that this type of roof is exactly horizontal. However,
such roofs usually have a slight slope toward the back of the building
and some have low parapets (6-24 inch walls) that surround the roof on
the front and sides. This method of construction confines the rain and
forces it run off toward a gutter in the back. Panel *a* of Figure 7-3
illustrates a small residential structure with a flat roof.

[**Figure 7-3**. Flat, Gable-end, and Hip Roofs.]{.underline}

![](media/image1.png){width="1.8346456692913387in"
height="1.4074803149606299in"}![](media/image2.png){width="2.0346456692913386in"
height="1.2570866141732284in"}![](media/image1.png){width="2.0346456692913386in"
height="1.4074803149606299in"}

A *gable end roof* is built so it has two angled surfaces that are
joined at the roof ridge---a long 2x6 inch board that runs the length of
the roof---and each side slopes downward toward the walls on opposite
sides of the house (see Panel *b*). The fact that the two surfaces of a
gable end roof connect to only two of the four walls would leave open
triangles over the other two end walls unless there is something to fill
them. This triangle, which has the top of the wall as the base, the two
sections of roof as the two sides, and the ridge as the peak, is the
gable end. Of course, the gable is filled in with a structural frame,
sheathed, and covered with veneer just like the rest of the wall. A *hip
roof* is a logical extension of a gable end roof that has four angled
roof surfaces instead of two and each of the four surfaces slopes toward
one of the four walls (see Panel *c*). The principal difference of the
hip roof from the gable end roof is that the "vertical gable" has been
tilted away from the vertical and, because it is now exposed to
rainfall, is covered with roof decking and shingles rather than wall
veneer.

Each of these three different roof designs requires a different form of
bracing. A flat roof is essentially just a floor braced with horizontal
joists that has an impermeable surface installed to prevent rain from
entering. This surface is often a *built up roof* that has 4x8 foot
sheets of plywood decking nailed to the joists and successive layers of
tarpaper and hot asphalt applied to provide the necessary weather
protection. Gable end and hip roofs require a different form of support
because their surfaces are sloped. As indicated in Figure 7-4, this
support consists of rafters that extend from the walls up to the roof
ridge. Sometimes buildings that have very wide spans from one wall
connection to the other have trusses rather than rafters. *Trusses*
(shown in the figure by the structural members in dotted lines) are
engineered systems that are internally braced to provide maximum
strength at minimum weight. Unlike a rafter system that is constructed
onsite, trusses are manufactured offsite and hoisted into place by
crane. Gable end and hip roofs also have 4x8 foot sheets of plywood
decking that are nailed to the rafters (or trusses, if these were used
instead). Moreover, gable end and hip roofs usually have a single layer
of tarpaper tacked to the decking and shingles nailed through the
tarpaper into the decking.

Very large multifamily and commercial buildings use materials that are
much stronger than the wood or brick that is used in single family
residences and small multifamily and commercial buildings. Because the
large buildings are much heavier, they have much sturdier
foundations---sometimes on concrete pilings that extend down to bedrock.
These structures support the weight of the upper stories on an internal
frame made from either steel girders or concrete columns that contain
steel reinforcing bars. Moreover, these very large buildings typically
have floors that are made from poured concrete and also have flat roofs
with penthouses where the machinery is located that is needed to run the
elevators.

[**Figure 7-4**. Simplified Roof System.]{.underline}

*Structural protection from hydrological hazards.* There are four major
methods for providing structural protection from hydrological hazards,
especially inland flooding and hurricane storm surge (Federal Emergency
Management Agency, 1998a). The most cost-effective method typically is
to raise the house so the lowest floor is elevated above the level of
the DBE (the 100 year flood is usually the *base flood*). The two most
common techniques for elevating structures are to elevate on continuous
foundation walls and to elevate on an open foundation.

When *elevating on continuous foundation walls*, a contractor uses a set
of jacks to raise the house slightly higher than the base flood, builds
the existing foundation walls up to the desired level, and then lowers
the structure back onto the new (higher) foundation. This method
increases the height of the basement walls so this area can provide
secure storage, but is only suitable in locations where the risks of
high velocity flow and wave action are low. If flood depth is expected
to be greater than about one foot, openings in the foundation must be
provided to allow water to flow in and out. This will prevent
hydrostatic pressure, the pressure of water outside the foundation, from
pushing the walls in.

When *elevating on open foundations*, the foundation supports the
structure only at critical points. The purpose of an open foundation,
such as cross-braced pilings, is to allow high velocity water flow and
breaking waves to pass under the structure with minimal resistance. Both
methods of elevation must have foundations that are deep enough to avoid
having water currents scour the ground beneath them. Naturally, both
methods of elevation are easier and cheaper for small wooden structures
than for large brick, steel, or reinforced concrete structures.

Another method for providing structural protection from hydrological
hazards is *dry floodproofing*, which seals the structure so flood water
cannot enter. Walls are sealed with an impermeable coating, penetrations
such as windows and doors are protected by shields, and backflow valves
are installed in sewer drains so water cannot enter the structure. A
simple backflow valve has a rubber ball that usually rests in the bottom
of the drain pipe but floats up to block the drain when flood water
backs up through the sewer system into the basement. Dry floodproofing
is not recommended where the expected flood depth is three feet or more
because hydrostatic pressure can collapse unreinforced masonry walls and
buoyancy can fracture a slab floor or even cause the structure to
"float".

The third method of structural protection from hydrological hazards is
*wet floodproofing*, which allows water to enter uninhabited portions of
the structure during flooding. During wet floodproofing, water
vulnerable equipment (e.g., service equipment such as the furnace,
washer, and dryer) is moved to a higher location or protected in place
by a floodwall. In addition, water vulnerable materials, such as
ordinary gypsum wallboard, are replaced by flood resistant materials.
The fourth method of structural protection from hydrological hazards is
*relocation* of the structure to higher ground out of the floodplain.
This requires jacking up the structure, supporting it on steel beams
while it is being transported, and lowering it onto another foundation
at the new site. As is the case with elevating on continuous or open
foundations, relocating wood structures is cheaper than relocating
brick, steel, or reinforced concrete structures.

Protection from tsunami or hurricane surge hazards is more difficult
than protection from most inland flooding because the two coastal
hazards have breaking waves. In the case of hurricane storm surge, the
waves are usually small enough that they mostly threaten wood
structures. However, buildings located on open coastline should be built
on pilings sunk deep enough to prevent the structure from toppling if
topsoil or sand is scoured away by strong currents or breaking waves.

Tsunamis are so powerful that they can threaten even sturdy masonry
structures. Indeed, one tsunami so thoroughly destroyed the Scotch Cap
lighthouse located on an Alaskan shoreline that the entire structure
above the rock foundation was washed away. Thus, structures located
directly on the shoreline of tsunami-prone coasts risk total
destruction. Structures that are located farther back from the
shoreline, but still in the runup zone, are safe if they are built of
steel-reinforced concrete and have floors that are elevated above
anticipated wave height. In most cases, the high cost of such
construction is only reasonable for public facilities, such as schools
and town halls, that are intended for use as safe havens during a
tsunami warning.

*Structural protection from wildfire hazard.* Wildfires threaten
structures with airborne firebrands that can land on roofs, radiant heat
from burning trees and brush, and convective heat from direct flame
contact (National Wildland/Urban Interface Protection Program, no date;
see also www.firewise.org). Thus, property owners should not build on
sites that are at the top of a slope or near a canyon draw because these
will be exceptionally vulnerable to fire. In addition, they should build
with a 30 foot setback to eliminate vegetation near the structure.
Moreover, a structure should be built with its exterior walls or roof
constructed of nonflammable materials. Consequently, property owners
should replace wood siding with metal, concrete, or masonry. Similarly,
they should replace wood or composition (asphalt) shingles on the roof
with metal or tile. Finally, property owners should replace wooden doors
with metal ones and install tempered glass to protect the windows.

*Structural protection from wind hazard.* As noted in Chapter 5, the
pressure of the wind on structures is proportional to the square of the
wind speed. Thus, a 150 mph wind speed produces four times as much
pressure as a 75 mph wind. However, wind speed, and thus wind pressure,
varies over the different surfaces of a building. Structures are
vulnerable to wind forces in different ways at their walls, roof, and
penetrations such as windows and doors. The windward wall (the one
facing the wind) experiences positive pressure that tends to push it
inward, whereas the leeward wall (the one opposite the wind direction)
and side walls experience negative pressure ("suction") that tends to
pull them outward. Similarly, the part of a gable end or hip roof that
is windward of the ridge experiences positive pressure that tends to
push it downward, whereas the part of the roof that is leeward of the
ridge experiences negative pressure that tends to pull it upward.
Penetrations such as windows (unless protected by shutters) and doors
(especially the overhead doors in attached garages) are known as "soft
spots" because they are the most likely parts of the building to fail
from wind pressure or flying debris that has been entrained in the wind
field. When windows or doors do fail, the wind pressurizes the house
from the inside. This internal pressure forces the walls out and the
roof up, which adds to the external pressures and initiates a
catastrophic structural failure.

The reason structures fail is that wind causes lateral (sideways) and
upward forces on structures that are ordinarily designed only to resist
the downward force of gravity. These forces sometimes break the wooden
studs in the wall and roof systems. However, their more common effect is
to pull out the nails that hold the structure together. Many nailed
connections are weak because many of them are driven into the wood at a
45 degree angle (which is called *toe-nailing*) that provides a weaker
connection than nails driven at a 90 degree angle.

Structures can be significantly protected from wind damage by installing
stronger than normal connections among the foundation, walls, rafters or
roof trusses, and roof decking (American Institute of Architects, 1995).
The process begins by embedding the bottom ends of bolts in a concrete
foundation while it is still wet. After the wall sections have been
built, holes are drilled into the sole plates so the threaded ends of
the bolts can pass through. The nuts are then tightened to secure the
sole plate to the foundation, thus making a very strong connection.

In turn, the roof system is connected to the wall system by *hurricane
straps*. These metal straps have holes at each end through which
carpenters pound nails at a 90 degree angle. One end of the hurricane
strap is nailed to a rafter (or roof truss) and the other end is nailed
to a wall stud. Installing hurricane straps at many locations around the
perimeter of the roof makes a very strong connection between the roof
and walls. The roof decking, usually a layer of plywood, should be
attached to the rafters by screws instead of nails because screws bind
the two pieces of wood more tightly together than nails do.

In addition to strengthening the connections, a good installation
provides wind resistant shingles and also strengthens the gable end
wall. The structure can be further strengthened by installing permanent
shutters for all windows. The most convenient shutters slide on tracks
and can be raised or lowered using an electric motor. Other permanent
designs include the familiar bifold shutters having two leaves, one
attached to each side of the window. These can be closed and latched
quickly when a storm threatens. Alternatively, inexpensive temporary
shutters can be cut from plywood sheets and screwed (not nailed) to the
window frame. It also is possible to replace the glass with wind (and
debris) resistant materials such as plexiglas.

Many of these wind resistant mitigation measures can be performed as
retrofits to existing structures, but the cost is higher than in new
construction because retrofitting requires removing exterior wall
sheathing, performing the retrofit, and reinstalling the sheathing.
Moreover, installing wind resistant mitigation measures in new
construction has the added advantage of being able to use wind resistant
designs as well as wind resistant construction materials and methods.
For example, new construction can use hip roofs instead of gable end or
flat roofs. In addition, new construction can avoid large roof overhangs
that tend to catch the wind and pull the roof off the structure.
Finally, new construction can avoid double-wide garage doors, which tend
to fail even at relatively low wind speeds because wind pressure against
the wide surface causes the glider wheels to pop out of their tracks.
This is a major problem for attached garages because failure of the
garage door increases the wind pressure on the door from the garage into
the house. This door is not designed for wind resistance, so it becomes
the next building component to fail. Finally, kitchen door failure
allows wind to pressurize the inside of the house which, as noted
earlier, is usually the last step before the entire structure collapses.

The methods used to protect buildings from hurricane wind also can be
used to protect them from tornado wind forces. As Chapter 5 indicated,
the core of a tornado produces a devastating wind speed that, for the
most severe tornadoes, can destroy everything down to ground level.
However, buildings on the edge of the storm will have reduced damage if
they are constructed using the mitigation principles described in this
section. In addition, building occupants can be protected by
constructing a safe room that will withstand even the most severe
tornadoes (Federal Emergency Management Agency, no date, b). This manual
describes alternative designs from which homeowners can choose,
depending on their space and budget constraints.

*Structural protection from seismic hazard.* Many of the basic
principles for protecting buildings from wind hazard also apply to
seismic protection because seismic shaking can exert lateral and upward
forces that are similar to those caused by wind (American Institute of
Architects, 1992). An important difference is that seismic forces come
in periodic waves, so buildings sway rhythmically with a period (the
length of time to complete an entire cycle of back and forth motion)
that is determined by building height. However, this makes little
difference in the mitigation measures used to reduce structural
vulnerability.

One of the basic sources of seismic vulnerability in building design is
irregularity in the building configuration. As a result, T-shaped,
L-shaped and U-shaped buildings (as they appear from above) are much
more vulnerable than rectangular buildings because each leg of the
building reacts in a different way to the seismic forces and the stress
is concentrated at the "hinges" where adjacent legs join. Moreover,
"soft-story" buildings that are supported by piers at the ground level
are also vulnerable. Such designs are usually found in large public and
commercial buildings, but apartment buildings with second story living
quarters located over carports or garages at ground level also have this
vulnerability.

Another source of seismic vulnerability comes from the construction
materials, especially URM. Buildings constructed from brick, stone, or
concrete masonry units ("cinder block") respond poorly to earthquakes
because they are too rigid to bend as the seismic waves rock them back
and forth. URM buildings are very common in some areas of the country
such as the New Madrid Seismic Zone in the Central US URM buildings can
be retrofitted by adding reinforced concrete walls, steel braces, wall
ribs, or buttresses (American Institute of Architects, 1992). It is
common for URM structures to have flat roofs with parapets.
Unfortunately, these nonstructural architectural elements are very
unstable, so they must be secured or removed to prevent them from
falling on passers-by on the sidewalks below. Unlike URM buildings,
wooden structures are relatively strong and flexible. Nonetheless, it is
often wise to strengthen older wooden houses by bolting the wall system
to the foundation and strapping the wall system to the roof system.

Window protection is also important in earthquakes because broken glass
is a major source of injury to building occupants. This can be avoided
by replacing conventional glass with Plexiglas, which will not break.
Alternatively, property owners can apply plastic film over conventional
glass to stabilize it. The glass will shatter during seismic shaking but
the film will hold the pieces in place within the window frame. The
glass will need to be replaced for aesthetic reasons, but will continue
to maintain the building envelope, thus avoiding injuries to building
occupants until it is replaced.

*Structural protection from airborne hazmat.* Buildings can provide
protection from inhalation of hazmat such as radiological materials or
toxic chemicals, as well as ash and gas from volcanic eruptions. People
can find protection against these airborne pollutants if they can take
refuge within a temporary "safe haven" that is closed tightly enough to
keep out the hazardous material and has enough oxygen to sustain those
within it until the danger has passed. Because most structures are
leaky, there is an exchange of indoor and outdoor air that comes from
*exfiltration* of indoor air to the outdoors and *infiltration* of
outdoor air to the indoor area. The principal points of exfiltration are
usually the furnace flue, ventilation fans and leakage sites near the
ceiling. Infiltration is typically dispersed over a large number of
small openings including cracks around windows and doors, electrical
outlets, and gaps between building walls and foundations. The mitigation
measures for airborne hazmat are identical to some of those used to
increase energy efficiency in home space heating. Sealing cracks saves
energy by reducing a home's loss of warm air during the winter and cool
air during the summer. At the same time as it conserves energy, sealing
cracks reduces the potential for infiltration of airborne pollutants in
an emergency. Newly built structures typically are well sealed, but
older structures will require retrofitting to reduce the rate of air
exchange. It is more difficult and expensive to retrofit existing
structures, but sealing structures more completely will eventually pay
for itself in reduced energy bills.

*Building codes*. The process of establishing local building codes
begins with model building codes that are developed by nongovernmental
organizations using a consensus approach that is slow and careful. Code
development is substantially influenced by engineering analyses, but
political and economic factors also play a major role. The resulting
model building codes are guidance documents that do not become legal
requirements until they are adopted by local jurisdictions (Nordenson,
1993). During the process of adoption by local jurisdictions, a model
code is modified to accommodate local environmental conditions such as
seasonal snow loads and local construction conditions. However,
political and economic constraints play an important role at this level
too (Jirsa, 1993).

Code adoption by local jurisdictions is only the first step in reducing
structural vulnerability. The second step is to train building
contractors and building trades personnel in the methods for meeting the
new code requirements and also the reasons why the requirements have
been established (Earthquake Engineering Research Institute, 1996).
Finally, code enforcement is essential because there are numerous
examples of building failures in disasters caused by inadequate design,
construction materials, and construction methods that violated the local
building code. Thus, changes to model codes are only as good as local
adopting agencies are willing to enforce. The extent to which building
officials enforce codes by checking plans and inspecting construction
depends upon local laws and the availability of budget support
(Nordenson, 1993).

Building codes are in a continuous state of reconsideration even after
they have been adopted, but changes are often made after a major
disaster (Martin, 1993). For example, the 1971 San Fernando, 1985 Mexico
City, and 1989 Loma Prieta earthquakes all led to major modifications to
seismic codes, particularly in earthquake prone areas (Nordenson, 1993).
Thus, building age is important because older structures were built
under outdated codes. Moreover, the building inventory in the Eastern
and Central United States is different from that on the West Coast; with
the former regions having many more unreinforced masonry structures
(Jirsa, 1993).

*Building Contents Protection*

For most hazards, protecting buildings from damage will also protect the
contents from harm. One exception is flooding when the property owner
has elected to protect a structure by wet floodproofing. As indicated in
the section on structural protection for hydrological hazards, wet
floodproofing allows water to enter a structure so the basement walls
will not collapse from hydrostatic pressure. Thus, the building contents
will be sacrificed unless they are protected in some other manner.
Similarly, earthquake shaking can cause damage to contents even if the
structure is not compromised. For example, seismic shaking can cause
fluorescent light fixtures to tear loose from their mountings, heavy
items with high centers of gravity (e.g., refrigerators and bookcases)
to topple, and glass windows and doors to fracture. These unrestrained
objects can cause damage to other building contents and injury to
building occupants. Building contents strategies can be implemented in
three different ways. Internal movement involves moving property to a
safer location, usually a higher elevation, within a building.
Protection in-place involves shielding contents from hazards that have
entered the structure. Contents stabilization is used to prevent
property from moving.

Internal movement is the primary method for protecting contents from
hydrological hazards. This includes elevation within the structure
(i.e., on a platform on the same floor or movement to a higher floor)
and relocation to higher locations out of the structure. However,
building contents can also be protected from hydrological hazards by
protection in-place. This includes building a floodwall around a
furnace, anchoring aboveground tanks, and installing backflow valves to
prevent the reverse flow of water from the river up through floor drains
(Army Corps of Engineers National Floodproofing Committee, 1993).

Although these are not, strictly speaking, building contents (i.e.,
located inside a building), outdoor furniture, sheds, storage tanks, and
air conditioners can also become hazards in high wind if they are
located outdoors. Light materials can become deadly missiles when
propelled by a strong wind. For example, a 2x4 inch stud can penetrate a
concrete masonry wall when traveling at 100 mph (Federal Emergency
Management Agency, no date, b). Other items are too heavy to fly through
the air but are significant rollover hazards whose moderate speed is
compensated by their heavy weight to breach windows, doors, and even
walls (State of Florida Department of Community Affairs/Division of
Emergency Management and University of Florida School of Building
Construction, 1997). Thus, light items can be moved indoors whereas
heavier items can be protected in place by anchoring them securely to
the ground. Securing items also protects light fixtures, furniture,
plant machinery, storage tanks, generators, air conditioners, and
heaters from seismic hazard. Such mitigation measures can significantly
reduce human casualties as well as property damage (American Institute
of Architects, 1992). For a more comprehensive list of methods for
contents protection, see the American Red Cross lists of household
mitigation measures
(www.redcross.org/services/prepare/0,1082,0_77\_,00.html).

# Applicability of Hazard Mitigation Measures

The five hazard mitigation measures discussed in the previous section
differ in their applicability to the natural and technological hazards
described in Chapter 5. Table 7-1 indicates source control is suitable
for eight of the hazards---flood, landslide, structural
fire/conflagration, explosion, toxic chemical release, radiological
release, and biological incident.

**Table 7-1. Applicability of Mitigation Measures, by Hazard.**

  -------------------- ---------- ------------ ----------- -------------- ------------
  Hazard               Source     Community    Land use    Building       Building
                       control    protection   practices   construction   contents
                                  works                    practices      protection

  Severe storms/cold                                       X              X

  Extreme heat                                             X              

  Tornado                                                  X              

  Hurricane                                    X           X              

  Wildfire             X          X            X           X              

  Flood                X          X            X           X              X

  Storm surge                     X            X           X              X

  Tsunami                         X            X           X              X

  Volcanic eruption               X            X           X              X

  Earthquake                                   X           X              X

  Landslide            X          X            X           X              

  Structural           X                       X           X              
  fire/conflagration                                                      

  Explosion            X                       X           X              

  Chemical spill or    X                       X           X              
  release                                                                 

  Radiological release X                       X           X              

  Biological incident  X                                   X              
  -------------------- ---------- ------------ ----------- -------------- ------------

Flood and landslides can be controlled at the source by reforestation
and other measures that increase infiltration into the soil. Floods also
can be controlled by measures, such as detention ponds, that delay
overland flow from impervious surfaces---roofs, parking lots, and
streets. Accidental industrial fires/conflagrations, explosions, toxic
chemical releases, and radiological release can be controlled at the
source by system designs and operating procedures that reduce the
likelihood of extreme temperatures and pressures that will overwhelm
containment systems. Moreover, deliberate radiological, chemical, or
biological incidents caused by sabotage or terrorist attacks can be
controlled by preventing the perpetrators from implementing their plans.

Community protection works are suitable for six of the
hazards---wildfire, flood, storm surge, tsunami, volcanic eruption, and
landslide. In the case of wildfire, this takes the form of fire breaks
that subdivide areas with large amounts of fuel. For inland floods,
storm surges, tsunamis, mudflows, and lava flows from volcanic
eruptions, appropriate protection works include dams that impede the
flow and dikes that confine it. In addition, inland floods can be
mitigated by channelization. Landslides can be mitigated by installing
drain fields that remove ground water from unstable slopes and retaining
walls that stabilize the toe of the slope.

Land use practices are suitable for twelve hazards---hurricane wind,
wildfire, flood, storm surge, tsunami, volcanic eruption, earthquake,
landslide, structural fire/conflagration, explosion, toxic chemical
release, and radiological release. Hurricane wind and all of the
hydrological hazards---flood, storm surge, and tsunami---produce
significant variations in hazard exposure within most jurisdictions.
Consequently, land use practices can prove to be quite useful in
reducing vulnerability to these hazards. Land use practices can also
play an important role in reducing vulnerability to all of the
geophysical hazards. In the case of volcanic eruptions, vulnerability
can be reduced by limiting development in areas subject to lava flows,
lahars (mudflows), and pyroclastic flows. The first two of these threats
generally follow river valleys whereas the third is generally limited to
areas close to the volcano. In the case of earthquakes, land use
practices can restrict the construction of residential, commercial, and
industrial buildings in close proximity to known faults, on unstable
slopes, or on soils that are prone to failure. Of course, land use
practices cannot avoid the vulnerability of infrastructure (water,
sewer, fuel, electric power, transportation, and land-based
telecommunications) that must inevitably cross these faults. Similarly,
land use practices can control the type and density of housing
development and the number of roads in landslide-prone areas, thus
reducing the loading on unstable slopes.

Land use practices are also quite relevant for the technological hazards
(structural fire, explosion, toxic chemical releases, and radiological
releases) by reducing population densities in the vicinity of
technological facilities and, perhaps, major transportation routes. In
addition, land use practices can be used to avoid siting critical
facilities such as school, hospitals, and nursing homes in areas close
to hazardous technological facilities.

Building construction practices are suitable for all of the
hazards---severe storms/cold, extreme heat, tornado, hurricane wind,
wildfire, flood, storm surge, tsunami, volcanic eruption, earthquake,
landslide, structural fire/conflagration, explosion, toxic chemical
release, radiological release, and biological incident. People and
property can be protected from severe storms/cold and extreme heat by
requiring levels of thermal insulation appropriate to the prevailing
climate. Physical vulnerability to these hazards can also be reduced by
decreasing air infiltration into buildings, which also can significantly
decrease inhalation exposure to toxic chemical and radiological
releases. Protection from high wind (tornado and hurricane wind), the
seismic shaking of earthquakes, and the blast effects of explosions can
be achieved by better building designs, stronger materials, and better
connections among building systems. Vulnerability to flood, storm surge,
tsunami, and volcanic mudflow can be achieved by elevating structures or
floodproofing them. Protection from volcanic ashfall specifically
focuses on strengthening support for the roof system. Building
construction practices can reduce vulnerability to wildfire and
structural fire/conflagration by using fire resistant materials.
Landslide protection can be increased by anchoring foundations in
deeper, more stable soil layers.

Building contents protection is applicable to six hazards---severe
storms/cold, flood, storm surge, tsunami, volcanic eruption, and
earthquake. People and property can be protected from severe storms/cold
by providing additional insulation to plumbing and other systems
containing water that might freeze. Physical vulnerability to flood,
storm surge, tsunami, and mudflows following volcanic eruption can be
reduced by elevating furniture, appliances, and HVAC systems or by
building flood walls within the structure. Content can be protected
against earthquakes by bolting heavy objects, installing latches on
cabinets, and providing lips on shelves. Building contents strategies
can also be effective for fires if the building contents are constructed
of flame-resistant or nonflammable materials.

*Limitations in the applicability of hazard source control*. Some of the
physical event systems that produce hazards simply cannot be controlled
by current technology. These include most of the meteorological hazards
(severe storms/cold, extreme heat, tornadoes, and hurricane wind) and
two of the hydrological hazards (storm surge and tsunami). Similarly,
volcanic eruptions (with the specific threats of ashfall, lava flow, mud
flows, and pyroclastic flows) and earthquakes (with the specific threats
of seismic shaking and ground failure) are caused by tectonic plate
motion that also is beyond technological control. Thus, alternative
methods of mitigation are required for these hazards.

*Limitations in the applicability of community protection works*.
Exposure to meteorological hazards (severe storms/cold, extreme heat,
tornadoes, hurricane wind, and wildfire) and the technological hazards
that are propagated through the atmosphere (toxic chemicals and
radiological materials) cannot be controlled using community protection
works. Thus, alternative methods of mitigation are required for these
hazards.

*Limitations in the applicability of land use practices*. Land use
practices have no practical application if there is no significant
variation in hazard exposure throughout a jurisdiction. This is
especially true for severe storms, extreme heat, and tornadoes.
Moreover, there is no obvious way in which land use practices can
control exposure to biological incidents.

*Limitations in the applicability of building contents protection*. The
vulnerability of building contents can be reduced in the case of flood
and, to a significantly lesser extent, storm surge by providing a
capability for moving them to upper floors of a structure or moving them
out of the risk area. However, such actions almost always require active
intervention in response to forewarning of disaster impact, so this is
more appropriately classified as an emergency preparedness strategy.
There are no obvious ways in which building contents selection or
stabilization can reduce vulnerability to explosions, toxic chemical
releases, radiological releases, or biological incidents.

*Hazard Mitigation Implementation Mechanisms*

This section will examine the degree to which different implementation
mechanisms are being used to promote hazard mitigation. The discussion
will begin by examining the technological hazards (structural
fire/conflagration, explosion, toxic chemical release, radiological
release, and biological incident) and then turn to the natural hazards
(severe storms/cold, extreme heat, tornado, hurricane wind, wildfire,
flood, storm surge, tsunami, volcanic eruption, earthquake, and
landslide). For each of these types of hazards, this section will
discuss the ways in which hazard mitigation is promoted through risk
communication, incentives, sanctions, and technological advances
(Lindell & Perry, 2004).

*Technological hazards*. Mitigation of structural fires and
conflagrations is achieved principally through building codes and
standards that control the hazard source and limit the physical
vulnerability of buildings to fires. As discussed earlier in this
chapter, building codes are adopted by local jurisdictions and rely on
sanctions for their implementation. In addition, the insurance industry
adopts standards of evaluation for fire risks and charges premiums for
insurance policies that are a function of the risk. Consequently, fire
and smoke detectors, alarms, and sprinkler systems earn the policy
holders reduced premiums.

The federal approach to mitigating the other technological
hazards---especially explosion, toxic chemical release, and radiological
releases---is typified by SARA Title III, which emphasizes local
emergency planning and the community right-to-know (RTK). RTK provisions
require a facility that handles extremely hazardous substances (a set of
about 400 especially dangerous chemicals) in amounts that are greater
than thresholds set by the US EPA to notify its local fire department,
Local Emergency Planning Committee, State Emergency Response Commission,
and the EPA. In turn, these organizations were required to make the
information available to citizens. This notification requirement
prompted many facilities to undertake a systematic accounting of their
chemical inventories and, in some cases, reduce the quantity stored on
site or switch to less hazardous chemicals. Thus, the (implicit)
sanction of adverse public opinion served as the implementation
mechanism for hazard source reduction. Laws and regulations adopted
since the terrorist attacks of 9/11 have significantly weakened RTK
provisions. This is, of course, because of the legitimate concern that
readily available information about toxic chemical inventories might be
used by terrorist organizations to identify the best targets for
attacks. Unfortunately, weaker RTK provisions also hamper local
residents' information access and, thus, their ability to pressure
industry to mitigate chemical hazards.

The European Union's *Seveso II Directive* and the Organization for
Economic Cooperation and Development (OECD, or Common Market)
*Principles* include emergency planning and RTK, just as in the United
States. However, the European Union also specifically includes land use
planning for mitigation purposes. In the United States, local
governments are expected to develop standards on hazardous facility
siting in their land use plans, but there is no systematic federal
guidance or incentives to do so, or sanctions for failure to do so. Nor
has there been any systematic federal encouragement to promote more
hazard resistant building construction practices. This is a missed
opportunity because chemical hazard mitigation could be achieved by
adopting more stringent energy conservation practices (Lindell, 1995).

*Natural hazards*. During the decade of the 1990s, the federal
government was actively involved in promoting mitigation approaches to
natural hazards, especially tornadoes, hurricane winds, wildfires,
floods, storm surges, and earthquakes. FEMA, in particular, engaged in
or funded programs that provided information about these hazards (e.g.,
risk communication about the results of hazard/vulnerability analyses).
The federal government also supported the development and dissemination
of technological innovations such as the tornado safe room (Federal
Emergency Management Agency, no date, b) and methods of floodproofing
(Army Corps of Engineers National Floodproofing Committee, 1993).

The federal government also created a systematic program of hazard
mitigation during the latter part of the 1990s. Project Impact was
conceived as a way to encourage local governments, citizens, businesses,
and NGOs to work together in a locally controlled program to reduce the
potential for losses of life and property due to natural disasters. The
idea was to fill some of the holes left in hazard mitigation by the
current "patchwork" of federal, state, and local regulations (Mileti,
1999, p. 7). Project Impact was a program based on small incentives and
large amounts of persuasion, with no real sanctions for nonperformance.
At its peak, there were more than 250 Project Impact communities in the
United States.

Communities seeking to participate in the program were required to apply
through their state emergency management agency, and the states
nominated communities for consideration by the FEMA Regional office.
Upon completion of review by FEMA Regional offices, nominations were
sent to FEMA Headquarters for acceptance and invitations to join the
program were issued. A "community" could be an incorporated city, a
county, a Council of Governments or a tribal government. In cases where
two or more governments applied jointly, they were required to agree
which one would serve as the project administrator. One of the criteria
for selection was that the community show a history of mitigation
effort; in other words, Project Impact was meant to accelerate rather
than a initiate a community's hazard mitigation efforts. The project
normally ran for two years, but extensions were available.

The three guiding principles for Project Impact were that preventive
actions must be decided at the local level, private sector participation
is vital, and long-term efforts and investments in prevention measures
are essential (Prater, 2001). Approved activities for Project Impact
fell into four phases: Partnership, Assessment, Mitigation, and Success.
Phase One was meant to involve private sector organizations as publicly
committed partners in the program. At this point, Project Impact
managers were expected to line up local businesses to contribute money,
products, services, space, staff time, or other resources to Project
Impact projects. The partners received positive publicity, and could
increase their own disaster resistance through their participation.
There were many Project Impact National Corporate Partners, including
Associated Builders and Contractors, Bell Atlantic, Bell South, Compaq,
Environmental Systems Research Institute, International Code Council,
National Association of Broadcasters, Portland Cement Association, Visa,
and others. In addition, several federal agencies, including the USGS,
Fannie Mae, and NASA joined Project Impact as National Partners. Project
Impact communities were also encouraged to sign up local NGOs as Project
Impact partners.

In Phase Two, communities were expected to perform a hazard assessment.
In fact, many Project Impact communities had already done this by the
time they had joined the program. In any case, the assessment was
expected to be completed, the data put into a GIS or other useful
computerized format, and public education materials that promote hazard
awareness developed for use by citizens and decisionmakers. Phase Three
was a crucial stage, when specific mitigation and preparedness projects
were selected and implemented. In Phase four, the success of Project
Impact projects was to be communicated to all citizens, thus building
the political will to continue Project Impact projects beyond the
two-year program period. Despite its promise, Project Impact was never
given a thorough evaluation and a new administration discontinued this
program after it took control of the executive branch in 2001.

Even though Project Impact no longer exists, local governments can
devise their own hazard mitigation programs by using the same basic
principles. Incentives for hazard mitigation measures could include the
provision of government grants, loans, tax deductions, and tax credits
for money that households and businesses spend on mitigation measures in
new or retrofitted structures. It is clear that government cannot afford
to support a major hazard mitigation program through grants alone
because of the tremendous expenditure this would involve. Loans for
repayment of principal only would be substantially less expensive. This
would limit the subsidy to the amount of interest the government would
have to pay for the use of the money. Tax deductions would allow
taxpayers to deduct all or part of the cost of hazard mitigation
projects from their income before taxes and tax credits would allow them
to deduct all or part of the cost of hazard mitigation projects from
their actual tax obligations. Unfortunately, none of these mechanisms
seem to have been explored. Indeed, given the country's current military
commitments and economic circumstances, such incentives are unlikely to
be adopted for the foreseeable future.

The only market mechanism that seems to have any prospect of success in
promoting hazard mitigation is hazard insurance, because banks and other
mortgage holders have exhibited little interest in managing hazard
exposure or physical vulnerability. One of the consequences of recent
disasters has been that the insurance industry has taken an increasingly
active political role in pressuring individuals, businesses, and
governments to undertake mitigation measures in order to reduce
insurers' financial exposure.

Insurance has sometimes been identified as a mitigation strategy, but
this is not accurate. Instead, it is a mechanism for spreading the
financial risk posed by hazards. Thus, it is a *recovery preparedness*
measure that reimburses the policyholder for the monetary value of
property that has been damaged or destroyed. This is in contrast to land
use practices and building construction practices that prevent damage
from occurring in the first place. Moreover, insurance spreads the risk
over time and people. If a policyholder incurs a loss in the first year
of coverage, the money to pay for this loss comes from the insurance
company's reserves that have been accumulated from the premiums paid by
other policyholders. In this case, the loss is completely spread over
persons. In later years of coverage, a policyholder's payoff for a loss
is increasingly covered by the premiums he or she has paid in previous
years. In this case, the loss is spread over time (for that
policyholder) as well as persons. As some point in time, the
policyholder's premium payments could well exceed any claims that will
ever be made. For example, a policyholder might pay \$400 per year for
20 years on flood insurance and never have a loss that justifies making
a claim (i.e., either there are no losses at all or there are no losses
that exceed the deductible).

Even though hazard insurance is not a method of mitigation, it can
provide an incentive for hazard mitigation if insurance premiums are
structured to reflect the actual risk of a given building in a hazard
prone area. That is, hazard mitigation is promoted when insurance
premiums are lower for buildings that are located in low risk areas
(e.g., in the 500-year flood plain rather than in the 100-year flood
plain) or are constructed to experience less damage if they are located
in high risk areas. That is, policies could give points for constructing
buildings using hazard resistant designs (e.g., hipped roofs rather than
flat roofs in hurricane zones), hazard resistant techniques (e.g.,
connecting the roof to the walls using hurricane straps), hazard
resistant materials (e.g., steel-reinforced concrete rather than
unreinforced masonry in seismic zones), and contents protection (e.g.,
water heaters bolted to the walls in seismic zones).

These features are incorporated into the National Flood Insurance
Program (NFIP), which was introduced in 1968 as a way to encourage local
governments to reduce the overall amount of development in floodplains.
The program imposes planning requirements on local jurisdictions in
exchange for allowing local homeowners to buy subsidized flood
insurance. The technical basis of the NFIP is a set of Flood Insurance
Rate Maps (FIRMs) that delineate flood risk zones. Table 7-2 shows
definitions of the various flood zones.

There are several problems with the NFIP approach to flood mitigation.
First, homeowners in flood zones are required to purchase insurance
policies when they receive their mortgages, but they often let these
policies lapse in later years because neither the government nor the
banks verify that the policies are continued. Second, some scholars have
argued that the NFIP has induced a false sense of security, leading
people to build in more hazardous areas because they have developed
exaggerated expectations of insurance industry and federal government
assistance after a disaster (Mileti, 1999). Finally, FIRMs are not
updated frequently enough to keep pace with the amount of upstream
development occurring in flood basins. Upstream development causes
downstream flood plains to increase in size but, because FIRMs are not
updated frequently enough (revising them costs the federal government a
lot of money), people are not aware that their hazard exposure has
increased.

**Table 7-2.** Flood Insurance Rate Map Zones.

+-------------+--------------------------------------------------------+
| #           | Definition                                             |
|  Flood Zone |                                                        |
+-------------+--------------------------------------------------------+
| A           | 1 % annual chance of flood conditions, based on        |
|             | approximate analysis. Mandatory insurance purchase. No |
|             | Base Flood Elevations (BFEs) included.                 |
+-------------+--------------------------------------------------------+
| AE & A1-A30 | 1 % annual chance of flood conditions, based on        |
|             | detailed analysis. BFEs shown.                         |
+-------------+--------------------------------------------------------+
| AH          | 1 % annual chance shallow flooding (1-3 feet). BFEs    |
|             | shown.                                                 |
+-------------+--------------------------------------------------------+
| AO          | 1 % annual chance shallow flooding & alluvial fan      |
|             | hazard.                                                |
+-------------+--------------------------------------------------------+
| AR          | Protected by flood control structures (levees) under   |
|             | repair. BFEs variable.                                 |
+-------------+--------------------------------------------------------+
| A99         | To be protected by flood control structures. No BFEs.  |
+-------------+--------------------------------------------------------+
| D           | Possible but undetermined flood hazards. Insurance     |
|             | available, but not mandatory.                          |
+-------------+--------------------------------------------------------+
| V           | 1 % annual chance coastal flooding, based on           |
|             | approximate analysis.                                  |
+-------------+--------------------------------------------------------+
| VE          | 1 % annual chance coastal flooding, based on detailed  |
|             | analysis.                                              |
+-------------+--------------------------------------------------------+
| B, C, X     | No insurance required, no BFEs.                        |
+-------------+--------------------------------------------------------+

In response to these problems, the Association of State Flood Plain
Managers (ASFPM) has developed a *No Adverse Impact Strategy* to assist
local governments in the management of flood plains. The ASFPM position
is that current federal standards are insufficient because, as noted
earlier in this chapter, they allow for floodwater to be diverted onto
others, channel conveyance areas to be reduced, essential valley areas
to be filled, and stream velocities to be changed without regard to the
effects on others. "No adverse impact floodplain management is where the
action of one property owner does not adversely impact the rights of
other property owners." (ASFPM NAI White Paper 2002,
www.floods.org/home/default.asp).

### *Mitigation and Sustainable Development: Creating Disaster Resilient Communities*

Several challenging trends have become apparent in recent years that
have prompted a reconsideration of approaches to hazard mitigation. One
of these is increased hazard exposure. Global climate change is
beginning to be felt as changes in weather patterns, an increase in the
number of extreme weather events, and a rise in sea levels that
threatens the viability of coastal cities. Increasing hazard exposure is
compounded by a global drive toward urbanization, increasing
industrialization of agriculture, and decreasing fertility of
agricultural land due to environmental degradation. As a result, there
is a global tendency for small farms to be consolidated into large
agribusinesses. The displaced farmers are absorbed into large pockets of
poverty in cities where they have little access to jobs, education, or
health care. Many of the largest and fastest growing cities are located
in areas, such as coastal areas of the Pacific Rim, that are exposed to
multiple hazards.

Another trend is increased social vulnerability. Some of these trends
involve demographic shifts; the wealthiest countries are seeing a rapid
increase in the median age of their populations, whereas the poorest are
still experiencing rapid population growth. In addition, many countries
have experienced a general increase in income inequality, and the United
States is no exception. These trends bode ill for the future because, as
discussed in Chapter 6, the elderly and the poor are among the most
vulnerable groups in disasters.

In response to these problems, the concept of *sustainable development*
has become recognized by local governments throughout the world as
development that meets the needs of the present without compromising the
ability of future generations to meet their own needs (U.N. World
Commission on Environment and Development, 1987---the "Brundtland
Report"). Sustainable development emphasizes the principle of ecological
limits, which are based on natural ecological, meteorological, and
geological cycles. Accordingly, the earliest formulations of sustainable
development focused on environmental pollution and resource depletion
that threatened future generations. At this stage, however,
sustainability advocates failed to address the issues of hazard
mitigation, emergency preparedness, recovery preparedness, emergency
response, and disaster recovery---despite the close link between
sustainability and emergency management (Berke, 1995).

In the sustainable development perspective, disasters are a sign that
current development practices are probably not viable over the long
term. Instead, development will be sustainable to the extent that
preimpact recovery planning and postimpact recovery actions involve
diverse population segments in the planning process, recognize
ecological limits, and seek equitable outcomes for all stakeholders.
This formulation logically led to the concept of *disaster resistant*
(Geis, 1996, 2000) or *disaster resilient* (Beatley, 1998; Godschalk, et
al., 1998) communities. These perspectives emphasize the creation of
communities that are less likely to experience major disasters, and are
better able to respond and recover from one if it does occur. Just as
sustainable development does not displace problems onto others
(economists call these *externalities*), sustainable mitigation does not
displace hazards across space or time. The United States has become more
concerned with sustainability as the costs of disaster response and
recovery have risen. The President's Council on Sustainable Development
and the National Science and Technology Council issued reports in 1996
that made an explicit connection between disaster reduction and
sustainable development. These reports called for ending subsidies to
development in floodplains (President's Council on Sustainable
Development, 1996) and proposed that development should take into
account the natural variability of our planet, including seasonal and
longer term cycles (National Science and Technology Council, 1996).

In order to change development styles, people need to reorient their
understanding of development. The first change is to realize development
is not the same as growth (Daly, 1996). An organic unit (plant, animal,
person, city) grows in size until it reaches the optimum for its
species. At that point, it ceases to increase in size, but this does not
necessarily mean it stops changing, improving, and developing its
capacities. The current economic system is built on the satisfaction of
consumers' desires, but human desires are basically infinite and the
resources of the planet are not. What is needed is a system that
preserves the fundamental advantages of free market economies, yet
places increased emphasis on the satisfaction of human *needs* (rather
than wants) and equity or fairness across space and time. Such a system
would promote increased investment of resources in improving society's
ecological, social, and economic stability.

One measure of sustainability is the "ecological footprint" described by
William Rees (1992; Wachernagel & Rees, 1996). This is an estimate of
the land and water needed to support a particular pattern of consumption
and development. Societies differ in the amount of land used to support
each individual. For example, each North American has an ecological
footprint of 5 hectares (12.5 acres), and this amount of resources is
only available to us because other countries' citizens have much smaller
ecological footprints.

Sustainability is a holistic concept, including environmental
conservation and the reduction of hazard vulnerability in a network of
principles focused on improving the chances of future generations'
survival on this planet. Other social and economic principles are
included in sustainability, but our society and its economy will not be
sustainable without reducing its exposure to natural and technological
disasters. After all, extreme events in the physical environment are
*normal*, even if they are not *common*.

It is important to recognize that principles of sustainability and
hazard mitigation can sometimes conflict. Such conflicts will occur if
poorly designed hazard mitigation programs reduce the standard of living
for poorer sectors of society. For example, public acquisition of
properties in floodplains and mandatory seismic retrofit programs can
lead to increases in rental fees that, in turn, reduce the supply of
affordable housing. Such conflicts must be addressed through
comprehensive approaches and open decisionmaking processes that seek
answers to the root problems. In this case, a lack of ability to pay
market rental rates can be addressed by offering rental vouchers to low
income households. This would maintain social equity while ensuring an
adequate supply of labor to local businesses. In addition, it would
avoid burdening the public transportation systems with workers who are
forced to commute to jobs in communities where they cannot afford to
live.

Although changing public policies to produce sustainable development is
a difficult challenge, recent progress is encouraging. There is an
increasingly sophisticated understanding of the relationships between
natural processes and human activities. In many areas, a "culture of
prevention" is arising as people become more aware of the ways in which
they have increased their hazard vulnerability by ignoring the long term
costs of public policies. This increasing hazard awareness has been
supported by technical assistance from NGOs such as the Federal Alliance
for Safe Homes (www.flash.org), which provides technical information
about methods for strengthening homes from hazard impact. Other active
organizations include the Institute for Business and Home Safety
(www.ibhs.org), which provides information about community hazard
exposure and structural hazard resistance for homes and businesses, and
the Association of State Floodplain Managers (www.floods.org), which is
is very active in developing and analyzing government policy.

Knowledge and experience are increasingly shared across national
boundaries, and governments at all levels are attempting to grapple with
these problems. The most vulnerable population segments are the focus of
many programs aimed at increasing economic resilience through
ecologically sustainable development. These efforts are likely to reduce
disaster vulnerability as local governmental and personal resources
increase and settlements are increasingly located in less dangerous
areas. Alternatively, when economic or other considerations warrant
remaining in these risky areas, human activities will be located in less
dangerous structures within those risk areas.

**Case Study: Hazard Mitigation**

Kinston is a small community located on the Neuse River in eastern North
Carolina's Lenoir County. Most of the town is located in the 50 year
flood plain, so 400 homes and many businesses were damaged at a total
cost of tens of millions of dollars when Hurricane Fran inundated the
Neuse River basin with 16 inches of rain in September 1996. Three years
later, while Kinston was still recovering from Hurricane Fran, Hurricane
Floyd struck in September 1999. Once again, there was major damage to
approximately 400 homes, but this time there was also major damage to
approximately 200 businesses (North Carolina Division of Emergency
Management, 2001).

At the time Floyd struck, a recovery strategy had already been
formulated to eliminate repetitive flood losses by acquiring 400 homes,
three mobile home parks, and 68 vacant lots for about \$31 million.
Funding came from the Hazard Mitigation Grant Program (\$15 million),
Community Development Block Grant and HUD Disaster Recovery Initiative
funds (\$12 million), and state funds (\$4 million). When Floyd struck,
the first 100 homes had already been acquired. An estimated 95 of these
would have been flooded and 75 substantially damaged if they had not
already been acquired and removed. The purchase price of these homes
(approximately \$2.1 million) was about one third of the \$6 million it
would have cost to repair or rebuild these structures. There were also
another 150 Kinston homes that were earmarked for acquisition, but had
not yet been purchased when Floyd struck. Of these, 99 were damaged---84
of them substantially so.

After Hurricane Floyd, the Kinston city council officially adopted the
*Greater Kinston Urban Growth Plan.* This comprehensive plan addresses
Housing and Residential Development, Economic Development, Public
Facilities and Utilities, Agriculture and Rural Development, Parks and
Open Space, and Natural Resources and the Environment. Local officials
consider acquisition of flood prone properties to be an important part
of the strategy of revitalizing community by reducing future flood
losses.