Introduction
Problem:
Damage
to
buildings,
equipment,
and other
components
are most
commonly
caused by
floodwater
inundation.
Floodwater
inundates
the
building,
saturating
the
building
materials
and its
contents.
The
floodwater
is usually
contaminated
by a
number of
substances,
such as
sewage and
other
hazardous
materials.
Mitigation
Objective:
The
most
effective
mitigation
is fully
protecting
the
building
facility
from
floodwaters,
such as
through
relocating
or
elevating
the
building.
A.1
Relocate
Building
Relocate
the entire
building
out of the
area
subject to
flooding
and to a
safe area,
outside
the
100-year
floodplain
or a
500-year
floodplain
if a
critical
facility.
Effectiveness:
- The
most
effective
mitigation
possible,
as
the
structure
will
no
longer
be
subject
to
flooding.
Limitations:
- Appropriate
receiving
site
must
be
obtained
Considerations:
A.2
Elevate
Building
Elevate
the
building
facility
on fill or
a
structure
above the
design
flood
elevation
or above
the
100-year
flood.
Buildings
can be
elevated
on
perimeter
walls,
piers,
piles, or
fill. If
walls are
used to
elevate,
they must
be vented
to
accommodate
hydrostatic
forces.
Effectiveness:
- Very
effective
- Area
under
the
building
(if
built
on
piers)
may
be
used
for
storage,
parking,
or
access.
Limitations:
- Building
access
will
be
impeded
during
flood
events.
- Fill
should
be
compacted
and
protected
from
erosion.
- May
require
additional
mitigation
considerations
for
areas
of
heavy
debris
loading.
Considerations:
A.3
Wet
Flood-Proof
Building
Allow
floodwater
to
inundate
selected
portions
of the
facility
in areas
that are
not
vulnerable
to damage
from
floodwater
saturation
by using
water-resistant
construction
methods,
designing
openings
for flood
water
passage,
and elevating
vulnerable
systems,
such as
electrical
equipment
above the
design
flood
elevation.
Design
should
include
the
construction
of
openings
to
equalize
hydrostatic
pressure,
and
construction
of the
walls to
resist
hydrostatic
pressure.
Effectiveness:
Limitations:
- Portions
of
building
vulnerable
to
floodwater
will
be
inaccessible
during
flood
event.
- Not
practical
in
areas
of
high
velocity
or
debris
impact.
- Advance
warning
needed
so
that
stored
materials
can
be
removed
Considerations:
A.4
Dry
Flood-Proof
Building
Seal
the
building
so that
floodwater
does not
enter.
Components
of dry
flood
proofing
may
include:
1)
Constructing
exterior
floodwalls;
2)
Constructing
an
impermeable
berm
around the
facility;
and/or 3)
Sealing
the
building
with
water-proof
material.
The
buoyancy
of the
building
must be
considered.
Hydrostatic
and
hydrodynamic
forces
must be
taken into
account.
effectiveness:
- Very
effective
in
preventing
damage
to
building
contents.
- Berms
and
floodwalls
can
be
integrated
into
landscaping.
Limitations:
- May
not
be
practical
in
areas
of
high
velocity
flows
or
heavy
debris
loading.
- May
require
access
gates
be
maintained
and
closed
prior
to
floodwaters
reaching
structure
- Site
should
be
designed
to
resist
the
forces
of
floodwaters
and
accommodate
on-site
drainage
needs.
- Slopes
exposed
to
moderate
or
high
velocity
flows
should
be
armored
Considerations:
A.5
Install
Backflow
Devices on
Sewer
Drains
Install
backflow
devices,
including
one-way
and
ordinary
valves, on
sewer
lines and
floor
drains.
These
devices
prevent
sewage
and/or
storm
water from
being
forced
back into
the
facility.
effectiveness:
- Very
effective,
particularly
for
buildings
outside
of
the
floodplain.
Limitations:
- One-way
valves
may
become
blocked
by
debris
and
fail
to
close
- Gate
valves
require
that
the
valve
be
manually
closed
prior
to
inundation.
Considerations:
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