FLOOD HAZARD MITIGATION HANDBOOK PUBLIC...
65
FLOOD HAZARD MITIGATION HANDBOOK FOR PUBLIC FACILITIES Produced By: FEMA Region 10 Response & Recovery Division Infrastructure Section June 2001
Transcript of FLOOD HAZARD MITIGATION HANDBOOK PUBLIC...
FLO
OD
HA
ZA
RD
MIT
IG
AT
IO
N
HA
ND
BO
OK
F
OR
PU
BLIC
FA
CILIT
IE
S
Pro
duced B
y:
FE
MA
Regio
n 1
0
Response &
Recovery
Div
isio
n
Infr
astr
uctu
re S
ecti
on
Jun
e 2
001
FLO
OD
HA
ZA
RD
MIT
IG
AT
IO
N
HA
ND
BO
OK
FO
R
PU
BLIC
FA
CILIT
IE
S
Federa
l E
merg
ency M
anagem
ent
Agency
Regio
n 1
0
June 2
001
TA
BL
E O
F C
ON
TE
NT
S
Intr
od
ucti
on
Pu
rpo
se o
f H
an
db
oo
k
Mit
igati
on
Alt
ern
ati
ves F
or
Flo
od
Dam
ag
ed
P
ub
lic F
acilit
ies
Flo
od
Dam
ag
e In
tro
du
cti
on
I.
RO
AD
S
A.
Ditch E
rosio
n..
....
....
....
....
....
....
....
....
....
....
....
....
....
....
..3
B.
Em
bankm
ent
Ero
sio
n..
....
....
....
....
....
....
....
....
....
....
....
.8
C.
Surf
ace a
nd S
hould
er
Ero
sion
................................
14
II.
CU
LV
ER
TS
A.
Insu
ffic
ient C
apacity &
/or
Ineff
icie
nt E
nd S
ections...2
0
B.
Plu
ggin
g..
....
....
....
....
....
....
....
....
....
....
....
....
....
....
....
...2
9
C.
Em
bankm
ent
Ero
sion
.............................................3
4
D.
Mis
alig
nm
ent.
....
....
....
....
....
....
....
....
....
....
....
....
....
....
.40
III.
BR
IDG
ES
A.
Mis
alig
nm
ent.
....
....
....
....
....
....
....
....
....
....
....
....
....
....
.48
B.
Insu
ffic
ient
Capacity (
Decks)
...................................5
3
C.
Ero
sion (
Appro
aches)
.............................................5
9
D.
Scour
(Pie
rs &
Abutm
ents
).....................................6
0
E.
Debris
Impact (P
iers
& A
butm
ents
).........................
64
IV
. B
UIL
DIN
GS
A.
Inundation
....
....
....
....
....
....
....
....
....
....
....
....
....
....
....
..71
B.
Hig
h V
elo
city F
low
s................................................
77
V
. U
TIL
ITIE
S
A.
Hig
h V
elo
city F
low
s................................................
81
B.
Soil
Settle
ment.
....
....
....
....
....
....
....
....
....
....
....
....
....
..85
V
I. IR
RIG
AT
ION
FA
CIL
ITIE
S
A.
Hig
h V
elo
city F
low
s................................................
89
VII.
MIS
CE
LL
AN
EO
US
FA
CIL
ITIE
S
A.
Inundation
....
....
....
....
....
....
....
....
....
....
....
....
....
....
....
..92
B.
Hig
h V
elo
city F
low
s................................................
96
Ap
pen
dic
es
A.
Regula
tions a
nd C
onsid
era
tions
................................
i B
. G
loss
ary
& K
eyw
ord
Index........................................
iii
C.
Acro
nym
s..
....
....
....
....
....
....
....
....
....
....
....
....
....
....
....
...x
i D
. R
efe
rences..
....
....
....
....
....
....
....
....
....
....
....
....
....
....
....
xii
E
. Lis
t of
Contr
ibuto
rs.................................................x
iii
Intr
oduction
INT
RO
DU
CT
ION
The F
edera
l E
merg
ency M
anagem
ent A
gency (
FE
MA
) continuousl
y s
triv
es
to im
pro
ve the d
eliv
ery
of
dis
ast
er
assi
stance to s
tate
s and local govern
ments
. T
his
Flo
od
Hazard
Mitig
ation H
andbook for
Public
Facili
ties (
Handbook)
assi
sts
those e
ntities
directly a
ffecte
d b
y n
atu
ral cata
stro
phic
events
and P
resi
dentially
-decla
red d
isast
ers
by p
rovid
ing
various
ideas
for m
itig
ation m
easu
res.
T
hese
measu
res
are
in
tended to h
elp
identify
options
and m
itig
ation ideas
for
local
jurisd
ictions
that can b
e u
sed a
t any tim
e, not only
aft
er
a
dis
ast
er.
FE
MA
is
charg
ed to p
rovid
e the f
ocal poin
t of
dis
ast
er
resp
onse
at th
e F
edera
l le
vel. F
EM
A’s
mis
sion to r
educe loss
of
life a
nd p
ropert
y c
ause
d b
y n
atu
ral dis
ast
ers
is
accom
plis
hed thro
ugh a
com
pre
hensi
ve e
merg
ency
managem
ent pro
gra
m.
Befo
re a
dis
ast
er
strikes,
FE
MA
pro
vid
es
fundin
g a
nd technic
al
assi
stance f
or
a r
ange o
f pre
pare
dness
and m
itig
ation
activitie
s. O
ne e
xam
ple
is flo
odpla
in m
anagem
ent, o
f w
hic
h
FE
MA
has
severa
l pro
gra
ms
that pro
vid
e incentives
for
com
munitie
s to
reduce futu
re flo
od r
isks.
Intr
oduction
During the d
isast
er,
FE
MA
work
s w
ith g
overn
menta
l and
volu
nte
er
agencie
s, s
uch a
s th
e R
ed C
ross
, to
meet th
e
imm
edia
te n
eeds
of
dis
ast
er
vic
tim
s by p
rovid
ing food, sh
elter,
and m
edic
al care
. T
hro
ugh the F
edera
l R
esp
onse P
lan, F
EM
A
coord
inate
s th
e r
eso
urc
es
of
oth
er
Federa
l agencie
s to
re
spond to e
merg
ency s
ituations
that are
beyond the
capabili
ties
of
Sta
te a
nd local re
sourc
es.
A
fter
a d
isast
er,
FE
MA
coord
inate
s lo
ng-t
erm
recovery
eff
ort
s th
rough a
num
ber
of
mitig
ation p
rogra
ms.
T
he P
ublic
A
ssis
tance P
rogra
m p
rovid
es
fundin
g o
pport
unitie
s fo
r im
ple
menting m
itig
ation m
easu
res
during the r
ebuild
ing o
f dis
ast
er-
dam
aged p
ublic
infr
ast
ructu
re. T
he H
azard
Mitig
ation
Pro
gra
m s
upport
s a n
um
ber
of
mitig
ation p
rogra
ms
that help
pro
tect com
munitie
s by w
ork
ing to r
educe o
r elim
inate
futu
re
dis
ast
er
dam
age.
Th
e P
rob
lem
: A
s dis
ast
ers
have g
row
n in fre
quency a
nd
severity
, th
e c
ost
s of
resp
onse
and r
ecovery
have e
scala
ted to
unsu
stain
able
levels
. In t
he P
acific
Nort
hw
est
, betw
een 1
996
and 1
998 a
lone, F
EM
A p
rovid
ed o
ver
$535 m
illio
n in d
isast
er
assi
stance. T
his
fig
ure
does
not in
clu
de a
ssis
tance p
aid
by
oth
er
Federa
l agencie
s, c
ost
s to
Sta
te a
nd local govern
ments
, or
direct in
div
idual or
busi
ness
losse
s.
Nationw
ide, natu
ral
dis
ast
ers
cost
over
$50 b
illio
n e
ach y
ear.
Intr
oduction
Th
e S
olu
tio
n:
The m
ost
eff
ective w
ay to r
educe these
excess
ive loss
es
is thro
ugh d
isast
er
pre
pare
dness a
nd
mitig
ation. T
o b
est
achie
ve this
goal, w
e a
s a s
ocie
ty n
eed to
vig
oro
usl
y p
urs
ue thre
e o
bje
ctives:
O
BJE
CT
IVE
1: T
o b
reak the d
isast
er–
rebuild
–dis
ast
er
cycle
.
This
cycle
of
repetitive loss
is
the h
isto
rical m
ode o
f dis
ast
er
recovery
. B
ut m
ere
ly r
epairin
g s
ubst
andard
facili
ties
to their
pre
-dis
ast
er
conditio
n d
oes
not pro
tect th
e c
om
munity fro
m
futu
re d
isast
er
dam
ages
or
reduce long-t
erm
cost
s.
Mitig
ation
betterm
ents
should
alw
ays
be c
onsid
ere
d in the r
ebuild
ing
pro
cess,
utiliz
ing a
multi-hazard
appro
ach w
henever
possib
le.
OB
JE
CT
IVE
2: T
o s
trength
en e
xis
ting infr
ast
ructu
re a
nd
facili
ties
to m
ore
eff
ectively
withsta
nd the n
ext dis
ast
er.
O
BJE
CT
IVE
3: T
o e
nsu
re that com
munitie
s addre
ss
natu
ral
hazard
s.
Com
pre
hensi
ve p
lans
should
acknow
ledge a
ll hazard
s th
at pose
a r
isk a
nd take s
teps
to a
void
these
hazard
s altogeth
er,
or
incre
menta
lly r
educe the c
om
munity’s
exposu
re
to its
hazard
s.
Th
e S
avin
gs:
The o
utc
om
e o
f achie
vin
g these
obje
ctives
will
be m
ore
resi
lient and e
conom
ically
sust
ain
able
com
munitie
s.
An a
naly
sis
of
FE
MA
-funded m
itig
ation m
easu
res
in the P
acific
N
ort
hw
est
has
est
ablis
hed that fo
r every
dolla
r sp
ent in
dam
age p
revention, tw
o to thre
e d
olla
rs a
re s
aved in f
utu
re
repairs.
P
urp
ose
PU
RP
OS
E O
F H
AN
DB
OO
K
The F
lood H
azard
Mitig
ation H
andbook for
Public
Facili
ties
(Handbook)
is inte
nded to a
id local ju
risd
ictions
in identify
ing a
variety
of
feasi
ble
mitig
ation ideas
that can b
e im
ple
mente
d
during the r
ebuild
ing p
rocess
. It fo
cuse
s on p
roje
cts
com
monly
elig
ible
for
hazard
mitig
ation f
undin
g u
nder
the P
ublic
A
ssis
tance P
rogra
m. F
requently, due to the u
rgency to r
epair
the f
acili
ty, lo
ng-t
erm
mitig
ation o
pport
unitie
s are
not fu
lly
explo
red. A
s a r
esu
lt, hazard
mitig
ation f
undin
g o
pport
unitie
s th
rough F
EM
A’s
Public
Ass
ista
nce p
rogra
m a
re n
ot fu
lly
utiliz
ed.
This
Handbook p
rovid
es
local ju
risd
ictions
with m
itig
ation ideas
that have d
em
onst
rate
d s
uccess a
nd c
an b
e tim
ely
im
ple
mente
d. T
hese
mitig
ation m
easu
res
rela
te to the m
ost
com
mon d
am
ages
sust
ain
ed b
y s
evere
flo
od e
vents
. T
his
H
andbook c
an b
e a
use
ful m
itig
ation tool re
gard
less
wheth
er
a
specific
pro
ject is
pro
pose
d f
or
FE
MA
fundin
g u
nder
either
the
Public
Ass
ista
nce o
r M
itig
ation p
rogra
ms.
M
itig
ation m
easu
res
in the H
andbook a
re p
rese
nte
d a
s h
elp
ful
ideas.
T
o learn
of
oth
er
mitig
ation m
easu
res,
see F
EM
A’s
M
itig
ation P
olic
y N
o. 9526.1
. T
his
Polic
y inclu
des
an a
ppendix
of m
easu
res
already d
ete
rmin
ed b
y F
EM
A to b
e c
ost
-eff
ective
when c
ert
ain
conditio
ns
are
met, s
uch a
s w
hen the c
ost
of
the
liste
d m
itig
ation m
easu
re d
oes
not exceed 1
00 p
erc
ent of
the
pro
ject cost
. N
one o
f th
e m
itig
ation m
easu
res
in this
H
andbook, how
ever,
should
be c
onsi
dere
d ‘pre
-appro
ved’ or
oth
erw
ise a
uto
matically
elig
ible
for
FE
MA
fundin
g. O
nly
FE
MA
st
aff
can d
ete
rmin
e e
ligib
ility
, once they h
ave r
evie
wed a
pro
ject pro
posa
l.
Mitig
ation A
ltern
atives
MIT
IGA
TIO
N A
LT
ER
NA
TIV
ES
FO
R F
LO
OD
DA
MA
GE
D
PU
BL
IC F
AC
ILIT
IES
Org
an
izati
on
of
mit
igati
on
measu
res in
th
is H
an
db
oo
k:
Dam
ages
to p
ublic
facili
ties
from
a d
isast
er
can v
ary
gre
atly,
dependent upon s
ite a
nd f
acili
ty c
onditio
n. T
his
Handbook is
org
aniz
ed first
by type o
f fa
cili
ty, th
en b
y failu
res
or
dam
ages
that are
com
monly
sust
ain
ed b
y that fa
cili
ty d
ue to a
flo
od.
Each c
ate
gory
of fa
ilure
or
dam
age lis
ts a
sele
ction o
f m
itig
ation ideas
to c
onsi
der.
T
he e
ffectiveness
, lim
itations,
and
consi
dera
tions
for
each m
itig
ation m
easu
re a
re a
lso identified.
En
gin
eeri
ng
, d
esig
n, an
d p
erm
itti
ng
req
uir
em
en
ts:
The H
andbook d
oes
not deta
il si
te-s
pecific
requirem
ents
, as
the e
ngin
eering a
naly
sis,
desi
gn, and p
erm
itting o
f each p
roje
ct
will
vary
wid
ely
. In m
any inst
ances,
the a
pplic
ant is
well
qualif
ied to c
onduct th
e e
ngin
eering a
nd d
esi
gn, as
well
as
const
ruction s
pecific
ations,
in-h
ouse
. In o
ther
case
s, it w
ill b
e
necessa
ry to c
ontr
act w
ith o
uts
ide s
ourc
es.
P
ub
lic A
ssis
tan
ce e
lig
ibilit
y:
As
with a
ll agencie
s th
at pro
vid
e federa
l fu
ndin
g, F
EM
A
requires
specific
crite
ria b
e m
et re
gard
ing e
ligib
ility
befo
re it
appro
ves
pro
posed p
roje
cts
. O
NLY
FE
MA
CA
N D
ET
ER
MIN
E
AN
AP
PLIC
AN
T’S
ELIG
IBIL
ITY
. E
ligib
ility
crite
ria a
re d
eta
iled
in the P
ublic
Assis
tance G
uid
e, F
EM
A P
ublic
ation 3
22.
Additio
nal in
form
ation c
an a
lso b
e o
bta
ined thro
ugh F
EM
A’s
w
ebsite a
t w
ww
.fem
a.g
ov o
r th
e F
EM
A R
egio
nal O
ffic
e.
M
itig
ation A
ltern
atives
Reg
ula
tio
ns a
nd
Co
nsid
era
tio
ns:
The f
ollo
win
g c
onsi
dera
tions
may b
e r
efe
renced in e
ach
mitig
ation m
easu
re. D
efinitio
ns
are
in A
ppendix
A,
“Regula
tions
and C
onsi
dera
tions.
”
National E
nvironm
enta
l P
olic
y A
ct
Endangere
d S
pecie
s A
ct
National H
isto
ric P
rese
rvation A
ct
US
Arm
y C
orp
s o
f E
ngin
eers
/ C
lean W
ate
r A
ct
Flo
odpla
in / W
etlands
Rig
ht of W
ay C
onst
rain
ts
Main
tenance R
equired to M
ain
tain
Eff
ectiveness
Pro
ject M
ay b
e C
ost
-Pro
hib
itiv
e
Dow
nst
ream
or
Upst
ream
Eff
ects
E
ngin
eer
Needed
Mit
igati
on
Keyw
ord
s:
The “
Glo
ssary
and K
eyw
ord
Index,”
found a
t A
ppendix
B,
pro
vid
es
a g
loss
ary
of
term
s and identifies
keyw
ord
s w
hic
h a
re
italic
ized a
nd b
old
ed in the text. A
keyw
ord
is
a m
itig
ation
ele
ment use
d in tw
o o
r m
ore
mitig
ation m
easu
res
in the
Handbook, and is
inte
nded to h
elp
the r
eader
becom
e fam
iliar
with the m
itig
ation e
lem
ent by u
nders
tandin
g its
use
in a
diffe
rent m
easu
re.
Flo
od D
am
age I
ntr
oduction
FL
OO
D D
AM
AG
E IN
TR
OD
UC
TIO
N
Sin
ce 1
994, each s
tate
within
Regio
n 1
0 h
as
incurr
ed a
t le
ast
th
ree P
resi
dentially
-decla
red d
isast
ers
for
flood e
vents
.
Betw
een 1
994 a
nd 2
000, R
egio
n 1
0’s
Public
Ass
ista
nce
pro
gra
m p
rovid
ed $
397.5
mill
ion to m
unic
ipalit
ies,
counties,
and o
ther
elig
ible
applic
ants
for
the r
epair a
nd r
est
ora
tion o
f flood d
am
aged p
ublic
facili
ties.
N
ort
hw
est
flo
od d
am
ages
are
most
com
monly
cause
d b
y
excess
ively
heavy r
ain
s, s
uccess
ive r
ain
storm
events
, or
rapid
m
eltin
g o
f heavy s
now
accum
ula
tions.
W
ith these
events
, peak
flood levels
are
reached a
nd r
ecede r
ela
tively
rapid
ly.
Assessin
g t
he C
au
se o
f D
am
ag
e
Mitig
ation m
easu
res
are
desi
gned to r
educe o
r elim
inate
futu
re
dam
age to f
acili
ties.
D
ete
rmin
ation o
f th
e a
ppro
priate
m
itig
ation m
easu
re d
epends,
in p
art
, on a
n a
ssessm
ent of
the
cause
of
dam
age. A
pro
per
ass
ess
ment is
critical, a
s m
itig
ation a
pplie
d inappro
priate
ly c
ould
actu
ally
incre
ase r
isk t
o
the f
acili
ty o
r oth
er
stru
ctu
res
in the flo
odpla
in. A
ssessm
ents
sh
ould
: •
be m
ade a
s so
on a
s possib
le a
fter
the flo
od e
vent;
•
be b
ase
d o
n technic
ally
sound f
ield
obse
rvations;
•
inclu
de d
iscussi
ons
with m
ain
tenance p
ers
onnel, local
citiz
ens,
and o
ther
pers
ons
who o
bse
rved w
hen a
nd h
ow
dam
age o
ccurr
ed; and
•
be v
erified, w
hen p
ossib
le, by r
ecord
s of
past
dam
ages
such a
s p
hoto
gra
phs.
D
eta
ils o
n a
ssess
ing the c
ause
s o
f dam
age a
re d
iscusse
d a
t th
e “
Intr
oductions”
for
each f
acili
ty w
here
appro
priate
.
F
lood D
am
age I
ntr
oduction
The follo
win
g s
ections identify
the types o
f
flood d
am
age m
ost ty
pic
ally
susta
ined b
y
public
facili
ties. V
arious m
itig
ation m
easure
s
are
then p
rovid
ed w
hic
h r
espond to the
specific
dam
ages to e
ach facility
. M
itig
ation
measure
s h
ave b
een identified for
com
mon
flood d
am
ages to the follo
win
g facili
ties:
� R
oads .................................................p
. 1
� C
ulv
ert
s ...............................................p. 17
� B
ridges ................................................p
. 46
� B
uild
ings .............................................p
. 70
� U
tilit
ies ................................................p. 81
� Ir
rigation F
acili
ties .
...............................p
. 89
� M
iscella
neous F
acili
ties .......................p
. 93
Roads
1
ROADS
RO
AD
S
Roads a
re the m
ost com
monly
dam
aged f
acili
ty in a
flo
od
event.
Dam
age to r
oads m
ay b
e c
aused b
y flo
odw
ate
rs
overt
oppin
g a
nd e
rodin
g r
oad s
urf
aces, should
ers
, and
em
bankm
ent slo
pes, and b
y w
ashin
g o
ut ro
adw
ay p
rism
s.
Mitig
ation m
easure
s identified m
ay a
lso b
e a
pplicable
to
railr
oads o
r oth
er
em
bankm
ent fa
cili
ties d
am
aged b
y flo
od
events
. D
am
ages to r
oads a
nd o
ther
em
bankm
ent fa
cili
ties
can b
e m
itig
ate
d b
y:
•
Pro
tecting d
itches f
rom
ero
sio
n a
nd incre
asin
g the c
apacity
for
ditches to c
arr
y s
ide flo
w;
•
Constr
ucting p
rote
ction fro
m e
mbankm
ent slo
pe e
rosio
n;
and
•
Pro
tecting r
oad s
urf
aces a
nd s
hould
ers
fro
m e
rosio
n.
Assessin
g t
he C
au
ses o
f R
oad
Dam
ag
e
Sele
ction o
f appro
priate
mitig
ation m
easure
s f
or
dam
aged r
oad
facili
ties d
epends u
pon the f
low
conditio
ns that caused the
dam
age. S
om
e o
bserv
ations o
f th
ese f
low
conditio
ns c
an b
e
made d
uring o
r im
media
tely
after
the d
am
age o
ccurr
ence.
If the e
levations o
f th
e u
pstr
eam
and d
ow
nstr
eam
hig
h w
ate
r
mark
s a
re n
early the s
am
e, th
e flo
w c
onditio
ns a
cro
ss the r
oad
were
tra
nquil o
r str
eam
ing, and s
cour
of
the e
ntire
road s
urf
ace
2
Roads
and s
hould
ers
will be e
vid
ent. E
rosio
n o
f th
e u
pstr
eam
em
bankm
ent m
ay h
ave a
lso o
ccurr
ed a
nd there
may b
e
depositio
n o
f gra
vel acro
ss t
he r
oad s
urf
ace. A
ppro
priate
mitig
ation f
or
this
flo
w c
onditio
n inclu
des:
•
Hard
enin
g the e
ntire
road s
urf
ace a
nd s
hould
ers
in the
road o
verf
low
section, and
•
Arm
oring the top o
f th
e u
pstr
eam
em
bankm
ent.
If the u
pstr
eam
and d
ow
nstr
eam
hig
h w
ate
r m
ark
s a
re
sig
nific
antly d
iffe
rent, the flo
od flo
w w
as lik
ely
in a
‘superc
ritical’
sta
te (
rapid
and turb
ule
nt flow
) at th
e d
ow
nstr
eam
sid
e o
f th
e
road, and s
cour
of
the d
ow
nstr
eam
road s
hould
er
and
em
bankm
ent w
ill b
e e
vid
ent.
Appro
priate
mitig
ation for
this
flow
conditio
n inclu
des:
•
Hard
enin
g the d
ow
nstr
eam
road s
hould
er,
and
•
Arm
oring the e
ntire
dow
nstr
eam
face o
f th
e e
mbankm
ent.
If the r
oad p
rism
was w
ashed o
ut, a
dete
rmin
ation o
f th
e f
low
conditio
ns w
ill be c
ritical in
ord
er
to a
ppro
priate
ly d
esig
n the
resto
ration a
nd m
itig
ation. T
o identify
the flo
w c
onditio
ns that
caused d
am
age to r
oads a
nd their e
mbankm
ents
, dete
rmin
e:
•
The u
pstr
eam
and d
ow
nstr
eam
wate
r surf
ace e
levations,
and
•
The s
cour
and e
rosio
n f
eatu
res o
n the r
em
ain
ing r
oad
surf
aces, should
ers
, and e
mbankm
ents
.
This
section d
iscusses m
itig
ation m
easure
s for
com
mon flo
od d
am
ages to r
oads, w
hic
h a
re
caused b
y:
A.
Ditch E
rosio
n .
......................................p. 3
B.
Em
bankm
ent E
rosio
n ...........................p. 8
C.
Surf
ace a
nd S
hould
er
Ero
sio
n...............p
. 14
Ditch E
rosio
n
3
ROADS
A.
Dit
ch
Ero
sio
n
Intr
od
ucti
on
Pro
ble
m:
Severe
roadw
ay a
nd d
itch e
rosio
n d
ue to w
ate
r
velo
citie
s e
rodin
g the d
itch a
nd o
verf
low
are
as.
Mit
igati
on
Ob
jecti
ve:
To s
trength
en e
roded a
reas a
nd/o
r
redirect floodw
ate
rs a
way f
rom
ditch a
reas v
uln
era
ble
to
ero
sio
n.
Mit
igati
on m
easu
res t
o p
rote
ct
road
s f
rom
flo
od
d
am
ag
e c
au
sed
by d
itch
ero
sio
n in
clu
de:
1.
Incre
ase D
itch C
apacity .
...........................p. 4
2.
Insta
ll Lin
ing in the D
itch .
..........................
p. 5
3.
Insta
ll A
dditio
nal C
ross C
ulv
ert
s ................p. 6
4.
Insta
ll C
heck D
am
s ..................................
p. 7
4
Ditch E
rosio
n
A.1
In
cre
ase D
itch
Cap
acit
y
Incre
ase the c
apacity o
f th
e r
oadw
ay d
itch b
y incre
asin
g its
depth
and/o
r w
idth
.
Eff
ecti
ven
ess:
•
Very
eff
ective in a
reas o
f lo
w to m
odera
te flo
w v
elo
city
where
overt
oppin
g o
f th
e r
oadw
ay d
itch c
auses the
dam
age.
•
Eff
ectiveness in h
igh flo
ws c
an b
e incre
ased b
y lin
ing
the
ditch, em
ban
km
en
t slo
pe p
rote
cti
on
, or
insta
lling c
heck
dam
s.
Lim
itati
on
s:
•
In a
reas o
f hig
h v
elo
city flo
ws, or
if d
itch is c
onstr
ucte
d
from
fin
e, hig
hly
ero
deable
mate
rials
, additio
nal m
easure
s
may b
e n
eeded.
•
May r
equire incre
ased s
lope a
ngle
s o
n e
ither
sid
e o
f ditch.
Co
nsid
era
tio
ns:
Ditch E
rosio
n
5
ROADS
A.2
In
sta
ll L
inin
g in
th
e D
itch
Lin
e th
e d
itch w
ith r
ock,
concre
te, asphalt, or
vegeta
tion to
pre
vent ditch e
rosio
n. U
se larg
er
and c
oars
e-g
rain
ed m
ate
rials
to p
rote
ct again
st hig
h v
elo
city flo
ws.
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Suitable
for
hig
h-f
low
velo
city,
and h
igh-f
low
conditio
n.
•
Gra
ss lin
ed d
itches p
rovid
e b
io-f
iltra
tion a
nd s
edim
ent
reduction.
Lim
itati
on
s:
•
Gra
ss lin
ing r
equires tim
e f
or
the g
rass to b
ecom
e
esta
blished p
rior
to u
se.
•
Concre
te lin
ed d
itches incre
ase r
un-o
ff a
nd d
ecre
ase tim
e
of floodw
ate
rs c
oncentr
ation.
Co
nsid
era
tio
ns:
6
Ditch E
rosio
n
A.3
In
sta
ll A
dd
itio
nal C
ross C
ulv
ert
s
Insta
ll ad
dit
ion
al ro
adw
ay c
ross c
ulv
ert
s t
o c
ut
off
the flo
w s
o
as n
ot to
exceed the c
apacity o
f th
e r
oadw
ay d
itch. T
his
measure
will addre
ss the p
roble
m o
f ditch e
rosio
n w
hen
excessiv
e flo
w in the d
itch is e
ither
overt
oppin
g the r
oad o
r is
causin
g e
rosio
n o
f th
e r
oad p
rism
. C
ross c
ulv
ert
s a
re u
sually
sm
all-
siz
ed, ra
ngin
g fro
m 1
8 to 2
4 inches in d
iam
ete
r.
Eff
ecti
ven
ess:
•
Very
eff
ective in r
educin
g the v
olu
me o
f ru
noff
in the d
itch
line.
Ditch E
rosio
n
7
ROADS
A.4
In
sta
ll C
heck D
am
s
Insta
ll lo
w-h
eig
ht barr
iers
(ch
eck d
am
s),
usually m
ade o
f lo
ose
rock, to
slo
w the v
elo
city o
f th
e s
torm
wate
r and r
educe the
scouring a
ction o
f th
e flo
w.
Eff
ecti
ven
ess:
•
Very
eff
ective in r
educin
g flo
w v
elo
city a
nd e
rosio
n.
Lim
itati
on
s:
•
Difficult to m
ain
tain
.
•
May b
e m
ore
appro
priate
for
tem
pora
ry e
rosio
n a
nd s
ilt
contr
ol.
Co
nsid
era
tio
ns:
8
Em
bankm
ent
Ero
sio
n
Mit
igati
on m
easu
res t
o p
rote
ct
road
s f
rom
flo
od
dam
ag
e c
au
sed
by e
mb
an
km
ent
ero
sio
n in
clu
de:
1.
Bio
-Engin
eere
d E
mbankm
ent S
lope P
rote
ction
...p
. 9
2.
Insta
ll H
alf-R
ound o
r S
pill
way P
ipes, or
R
ock C
hannels
...............................................p
. 10
3.
Change G
eom
etr
y o
f R
oadw
ay S
ection
..............
p. 11
4.
Constr
uct a W
all
................................................
p. 12
5.
Pla
ce R
ipra
p A
long E
roded S
lope.......................p
. 13
B.
Em
ban
km
en
t E
rosio
n
Intr
od
ucti
on
Pro
ble
m:
Dam
age c
aused b
y e
rosio
n o
f in
adequate
ly
pro
tecte
d s
lopes.
Mit
igati
on
Ob
jecti
ve:
Hard
en the d
am
aged e
mbankm
ent
slo
pe o
r re
direct flow
s to a
void
hig
her velo
citie
s.
Em
bankm
ent
Ero
sio
n
9
ROADS
B.1
B
io-E
ng
ineere
d E
mb
an
km
en
t S
lop
e P
rote
cti
on
Pro
vid
e b
io-e
ngin
eere
d e
mb
an
km
en
t slo
pe p
rote
cti
on
by
covering the s
lope w
ith d
eep r
ooting v
egeta
tion a
nd w
here
it is
adja
cent to
and in c
onta
ct w
ith a
liv
e s
tream
, str
ate
gic
ally
anchor
larg
e w
oody d
ebris (
i.e. ro
ot w
ads)
that w
ill h
old
the s
oil
in p
lace a
nd p
rote
ct it fro
m e
rosio
n.
Eff
ecti
ven
ess:
•
Very
eff
ective in a
reas o
f lo
w f
low
velo
city.
•
Environm
enta
lly friendly
.
•
Contr
ibute
s to s
ettling o
f part
icula
te m
atter.
Lim
itati
on
s:
•
Vegeta
tion m
ust have s
uff
icie
nt tim
e to b
ecom
e
esta
blished p
rior
to b
ein
g e
xposed to flo
odw
ate
rs.
•
Genera
lly n
ot suitable
for
are
as o
f susta
ined h
igh v
elo
city
flow
s.
Co
nsid
era
tio
ns:
10
Em
bankm
ent
Ero
sio
n
B.2
In
sta
ll H
alf
-Ro
un
d o
r S
pillw
ay P
ipes,
o
r R
ock C
han
nels
Concentr
ate
flo
ws in a
colle
ction s
tructu
re a
nd insta
ll half-r
ound
or
spill
way p
ipes, or
rock c
hannels
dow
n s
teep s
lopes to
elim
inate
ero
sio
n.
Eff
ecti
ven
ess:
•
Most eff
ective for
inte
rmitte
nt str
eam
s o
r surf
ace w
ate
r
collection.
•
Pip
es v
ery
eff
ective w
hen p
roperly c
onnecte
d to d
rain
age
collection s
tructu
res o
r ro
adw
ay d
itches.
Lim
itati
on
s:
•
Requires g
ood a
nchors
to e
limin
ate
failu
re b
y s
lippage o
f
the p
ipes o
n the s
teep s
lope.
•
Consid
er
constr
ucting a
n e
nerg
y d
issip
ate
r at
bottom
of
slo
pe.
Em
bankm
ent
Ero
sio
n
11
ROADS
B.3
C
han
ge G
eo
metr
y o
f R
oad
way S
ecti
on
Alter
the a
ngle
of
an e
mbankm
ent slo
pe thro
ugh s
hould
er
roundin
g a
nd s
lope r
eduction to r
educe e
rosio
n. R
educin
g the
angle
of
slo
pe g
enera
lly r
educes the v
elo
city o
f th
e w
ate
r
runnin
g a
cro
ss it.
Eff
ecti
ven
ess:
•
Very
eff
ective in a
reas o
f ro
adw
ay o
vert
oppin
g w
ith low
velo
city flo
ws.
•
Part
icula
rly e
ffective if
com
bin
ed w
ith a
rmoring o
f th
e
dow
nstr
eam
em
bankm
ent slo
pe a
nd r
oad s
hould
er.
Lim
itati
on
s:
•
May r
educe c
arr
yin
g c
apacity o
f ditch o
r str
eam
.
Co
nsid
era
tio
ns:
12
Em
bankm
ent
Ero
sio
n
B.4
C
on
str
uct
a W
all
Constr
uct a w
all to p
rote
ct th
e s
lope fro
m e
rosio
n a
nd
consequent slo
ughin
g a
nd s
lum
pin
g. W
alls
can b
e c
onstr
ucte
d
of various m
ate
rials
inclu
din
g r
ock, gabio
ns, sheet pile,
concre
te, etc
. E
ffecti
ven
ess:
•
Very
eff
ective.
•
Suitable
for
hig
h v
elo
city,
hig
h v
olu
me flo
od e
vents
.
•
May b
e d
esig
ned to a
ccom
modate
repla
nting o
f a
dam
aged r
iparian a
rea.
Lim
itati
on
s:
•
May p
reclu
de r
egro
wth
of
riparian a
reas.
Co
nsid
era
tio
ns:
Em
bankm
ent
Ero
sio
n
13
ROADS
B.5
P
lace R
ipra
p A
lon
g E
rod
ed
Slo
pe
Pla
ce a
ppro
priate
ly s
ized r
ipra
p a
long the e
roded
em
bankm
ent slo
pe in s
uff
icie
nt quantities to r
esis
t scouring
eff
ects
of
hig
her
velo
city flo
ws a
nd p
rote
ct th
e e
mbankm
ent
slo
pe f
rom
futu
re flo
od d
am
age.
Eff
ecti
ven
ess:
•
Very
eff
ective in a
reas o
f m
odera
te flo
w v
elo
city a
nd
volu
me w
hen a
ppro
priate
ly g
raded m
ate
rial is
pla
ced in
suff
icie
nt quantity
and layere
d s
o fin
es a
re n
ot ero
ded.
•
Wate
r velo
city w
ill d
ete
rmin
e s
ize a
nd v
olu
me o
f ripra
p.
Lim
itati
on
s:
•
Exte
nsiv
e u
se o
f ripra
p m
ay p
reclu
de r
e-g
row
th o
f riparian
are
as.
•
Access m
ay lim
it w
here
rip
rap c
an b
e p
laced.
Co
nsid
era
tio
ns:
14
Surf
ace a
nd S
hould
er
Ero
sio
n
Mit
igati
on m
easu
res t
o p
rote
ct
road
s f
rom
flo
od
dam
ag
e c
au
sed
by s
urf
ace a
nd
sho
uld
er
ero
sio
n
inclu
de:
1.
Incre
ase R
oadw
ay E
levation
..............................
p. 15
2.
Constr
uct S
hould
er
Pro
tection............................
p. 16
3.
Incre
ase C
apacity o
f D
rain
age S
tructu
re....
See b
elo
w
C.
Su
rface a
nd
Sh
ou
lder
Ero
sio
n
Intr
od
ucti
on
Pro
ble
m:
Road s
urf
ace a
nd s
hould
er
ero
sio
n c
aused b
y w
ate
r
flow
ing o
ver
the top o
f th
e r
oadw
ay, due to low
roadw
ay
ele
vation o
r in
adequate
dra
inage s
tructu
re c
apacity.
Mit
igati
on
Ob
jecti
ve:
Hard
en the top o
f th
e r
oadw
ay o
r div
ert
floodw
ate
r fr
om
the top o
f th
e r
oadw
ay to p
revent ero
sio
n o
f
the r
oad s
urf
ace a
nd s
hould
er.
3.
Ad
d M
ultip
le P
ipe
Cu
lvert
s
(p. 24)
Surf
ace a
nd S
hould
er
Ero
sio
n
15
ROADS
C.1
In
cre
ase R
oad
way E
levati
on
Incre
ase the r
oadw
ay e
levation b
y a
ddin
g s
uitable
fill
mate
rial
to r
ais
e the r
oadw
ay s
urf
ace a
bove the d
esig
n f
lood e
levation.
Eff
ecti
ven
ess:
•
Very
eff
ective in a
reas w
here
the f
lood e
levations a
re
above the r
oadw
ay s
urf
ace f
or
a s
hort
dis
tance.
•
Pre
vents
futu
re d
am
age a
nd k
eeps the r
oadw
ay in s
erv
ice
during flo
od e
vents
. L
imit
ati
on
s:
•
May n
ot be justified if fr
equent flood e
levations a
re too h
igh
above the r
oadw
ay.
•
May incre
ase u
pstr
eam
flo
od e
levation a
nd c
reate
a
dam
min
g e
ffect.
•
Should
be u
sed in c
onju
nction w
ith e
mb
an
km
en
t slo
pe
pro
tecti
on
measure
s.
Co
nsid
era
tio
ns:
16
Surf
ace a
nd S
hould
er
Ero
sio
n
C.2
C
on
str
uct
Sh
ou
lder
Pro
tecti
on
To p
rote
ct th
e r
oad s
hould
er
from
ero
sio
n, pave d
ow
nstr
eam
should
er
with a
sphalt c
oncre
te p
avem
ent, c
oncre
te, ri
pra
p, or
oth
er
appro
priate
revetm
ents
.
Eff
ecti
ven
ess:
•
Very
eff
ective w
hen d
rain
age s
tructu
re c
apacity c
annot be
incre
ased to p
revent overt
oppin
g.
Lim
itati
on
s:
•
The tre
atm
ent m
ust be c
om
patible
with the s
oil
type a
nd
roadw
ay c
onditio
ns.
•
Asphalt c
oncre
te m
ay h
ave a
lim
ited life o
n s
lopes.
•
May h
ave a
dvers
e im
pacts
on r
iparian a
reas. W
illow
s a
nd
oth
er
pla
ntings c
an b
e s
taked w
ithin
the s
hould
er
pro
tection.
Co
nsid
era
tio
ns:
Culv
ert
s
17
CULVERTS
CU
LV
ER
TS
D
am
age to c
ulv
ert
s is c
aused p
rim
arily
by flo
odw
ate
rs e
rodin
g
culv
ert
entr
ances o
r outlets
and r
oad e
mbankm
ents
, and
usually r
esults in a
full
or
part
ial w
ashout or
mis
alignm
ent of
the
culv
ert
. T
hese d
am
ages m
ay b
e d
ue to insuff
icie
nt desig
n
capacity o
r end tre
atm
ents
, in
adequate
slo
pe p
rote
ction, or
inadequate
pro
tection f
rom
flo
ating d
ebris. C
are
ful
dete
rmin
ation o
f th
e c
ause f
or
the d
am
age is n
ecessary
, as
diffe
rent causes r
equire d
iffe
rent m
itig
ation.
Assessin
g t
he C
au
ses o
f C
ulv
ert
Dam
ag
e
Sele
ction o
f appro
priate
mitig
ation d
epends u
pon the c
ulv
ert
flow
conditio
ns a
t th
e tim
e o
f dam
age. S
urv
eys o
f hig
h w
ate
r
mark
s locate
d u
pstr
eam
and d
ow
nstr
eam
fro
m the c
ulv
ert
, and
surv
eys o
f th
e inle
t and o
utlet ele
vations a
re n
ecessary
to
identify
the flo
w c
onditio
ns.
Flo
w thro
ugh a
culv
ert
may b
e c
ontr
olle
d b
y its
entr
ance o
r
outlet conditio
ns, or
by d
ow
nstr
eam
channel fe
atu
res. A
culv
ert
will
flo
w f
ull
if its
outlet is
subm
erg
ed o
r if the d
epth
of
wate
r above the top o
f its e
ntr
ance is g
reate
r th
an 1
.5 tim
es its
dia
mete
r.
Dam
age to a
culv
ert
flo
win
g full
usually o
ccurs
when
the r
oad e
mbankm
ent is
overt
opped a
nd is f
ully
or
part
ially
washed o
ut.
Appro
priate
mitig
ation m
easure
s inclu
de:
•
Incre
asin
g c
ulv
ert
siz
e;
•
Incre
asin
g e
ffic
iency o
f th
e e
ntr
ance; and/o
r
•
Rais
ing the c
ulv
ert
. If
rais
ing the c
ulv
ert
causes it to
flo
w p
art
ially
full,
adju
st th
e
slo
pe to r
etu
rn it to
full
flow
conditio
ns.
A c
ulv
ert
may flo
w p
art
ially
full
when the w
ate
r depth
is a
bove
the t
op o
f th
e c
ulv
ert
’s e
ntr
ance a
nd b
elo
w the top o
f th
e o
utlet,
or
when the w
ate
r surf
ace is b
elo
w the top o
f th
e c
ulv
ert
at both
entr
ance a
nd o
utlet. D
am
age to a
culv
ert
flo
win
g p
art
ially
full
usually o
ccurs
when e
mbankm
ent ero
sio
n h
as o
ccurr
ed.
Appro
priate
mitig
ation f
or
these c
onditio
ns inclu
de:
18
Culv
ert
s
•
Incre
asin
g c
ulv
ert
entr
ance e
ffic
iency, and/o
r
•
Decre
asin
g the s
lope o
f th
e c
ulv
ert
. If
the c
ulv
ert
was f
low
ing p
art
ially
full
and the flo
w a
t th
e o
utlet
was in a
subcritical or
tranquil
sta
te, th
e d
am
age w
ill lik
ely
be
confined to its
entr
ance. In this
case, appro
priate
mitig
ation
inclu
des:
•
Incre
asin
g the e
ffic
iency o
f th
e e
ntr
ance, and
•
Arm
oring the e
ntr
ance e
mbankm
ent.
If the c
ulv
ert
was f
low
ing p
art
ially
full
and the flo
w a
t th
e o
utlet
was in a
superc
ritical or
turb
ule
nt sta
te, dam
age m
ay h
ave
occurr
ed to e
ither
the e
ntr
ance o
r outlet
or
both
. A
ppro
priate
mitig
ation w
ould
then inclu
de:
•
Incre
asin
g e
ffic
iency o
f entr
ance a
nd o
utlet conditio
ns, and
•
Arm
oring the e
ntr
ance a
nd o
utlet em
bankm
ents
. If
, as a
result o
f th
ese c
onditio
ns, ero
sio
n o
f th
e s
tream
bed w
ith
subsequent head c
uttin
g a
nd e
mbankm
ent
ero
sio
n o
ccur,
appro
priate
mitig
ation w
ould
be:
•
Insta
llation o
f a s
tilli
ng b
asin
, and/o
r
•
Arm
oring o
f th
e s
tream
channel and r
oad e
mbankm
ent.
To identify
the flo
w c
onditio
ns that caused the d
am
age,
dete
rmin
e:
•
Wate
r surf
ace e
levations u
pstr
eam
and d
ow
nstr
eam
fro
m
the c
ulv
ert
at th
e tim
e o
f dam
age;
•
Ele
vations o
f th
e c
ulv
ert
entr
ances a
nd o
utlets
;
•
Wheth
er
dow
nstr
eam
channel ero
sio
n a
nd h
ead c
uttin
g
occurr
ed; and
•
Evid
ence o
f ro
ad e
mbankm
ent ero
sio
n.
Culv
ert
s
19
CULVERTS
Flo
odw
ate
rs f
requently c
arr
y d
ebris b
oth
as the flo
ws r
ise o
r
recede. D
ebris c
arr
ied b
y r
isin
g flo
od flo
ws m
ay b
ecom
e
caught or
wedged in c
ulv
ert
s, plu
ggin
g the flo
w. C
ulv
ert
s c
an
then b
e w
ashed o
ut or
dam
aged d
ue to incre
ased s
urf
ace flo
w
ele
vations. M
itig
ation m
easure
s s
hould
be d
esig
ned to p
rote
ct
again
st debris im
pact and a
ccum
ula
tion, and to a
ssis
t in
passin
g d
ebris thro
ugh the s
tructu
re o
penin
gs. D
ebris c
arr
ied
by r
ecedin
g flo
od flo
ws w
ill genera
lly b
e d
eposited o
n the
str
eam
overb
anks a
nd d
raped o
ver
culv
ert
entr
ances. D
am
age
to c
ulv
ert
s w
ill m
ost lik
ely
occur
due to facto
rs o
ther
than
floating d
ebris, and m
itig
ation s
hould
be d
evelo
ped b
ased u
pon
the m
ost pro
bable
cause o
f dam
age.
This
section d
iscusses m
itig
ation m
easure
s for
com
mon flo
od d
am
ages to c
ulv
ert
s, w
hic
h a
re
caused b
y:
A.
Insuffic
ient C
apacity &
/or
In
effic
ient E
nd S
ections......................p. 20
B.
Plu
ggin
g...............................................p
. 29
C.
Em
bankm
ent E
rosio
n............................p. 34
D.
Mis
alig
nm
ent.
.......................................p
. 40
20
Insuffic
ient
Capacity &
/or
Ineffic
ient
End S
ections
A.
Ins
uff
icie
nt
Cap
acit
y a
nd
/or
Ineff
icie
nt
En
d S
ecti
on
s
In
tro
du
cti
on
Pro
ble
m:
Dam
age o
r fa
ilure
of
a c
ulv
ert
resultin
g fro
m
overt
oppin
g a
nd/o
r ero
sio
n o
f em
bankm
ents
due to insuff
icie
nt
culv
ert
capacity a
nd/o
r in
eff
icie
nt end s
ections. T
he inadequate
capacity m
ay b
e a
result o
f in
appro
priate
hydro
logic
analy
sis
of
flood p
eaks a
nd v
olu
mes, and/o
r application o
f in
appro
priate
culv
ert
desig
n c
rite
ria.
Mit
igati
on
Ob
jecti
ve:
To p
revent fu
ture
dam
age to a
pip
e
culv
ert
by incre
asin
g the d
esig
n c
apacity a
nd a
ddin
g e
ffective
end s
ections; re
desig
nin
g the c
ulv
ert
insta
llation; re
pla
cin
g the
culv
ert
with a
n a
ltern
ate
dra
inage s
tructu
re(s
); a
nd/o
r addin
g
an o
verf
low
channel.
Mit
igati
on m
easu
res t
o p
rote
ct
culv
ert
s f
rom
flo
od
dam
ag
e d
ue t
o in
su
ffic
ien
t cap
acit
y o
r in
eff
icie
nt
en
d
secti
on
s in
clu
de:
1.
Repla
ce W
ith L
arg
er
Pip
e C
ulv
ert
..........................
p. 21
2.
Incre
ase E
ffic
iency o
f E
ntr
ance &
/or
Outlet D
esig
n.p. 22
3.
Change C
ulv
ert
Alig
nm
ent.....................................
p. 23
4.
Add M
ultip
le P
ipe C
ulv
ert
s....................................
p. 24
5.
Repla
ce W
ith a
Box o
r A
rch C
ulv
ert
.......................p. 25
6.
Repla
ce W
ith a
Bridge...........................................p. 26
7.
Repla
ce W
ith o
r A
dd a
Low
Wate
r C
rossin
g...........p. 27
8.
Insta
ll a H
igh W
ate
r O
verf
low
Cro
ssin
g..................
p. 28
Insuffic
ient
Capacity &
/or
Ineffic
ient
End S
ections
21
CULVERTS
A.1
R
ep
lace W
ith
Larg
er
Pip
e C
ulv
ert
A larg
er
culv
ert
allo
ws f
or
the p
assage o
f a g
reate
r volu
me o
f
wate
r.
Eff
ecti
ven
ess:
•
Very
eff
ective if, a
t th
e tim
e o
f fa
ilure
the c
ulv
ert
was
flow
ing f
ull.
(S
ee “
Assessin
g C
ulv
ert
Dam
age,”
pp. 17-1
9)
Lim
itati
on
s:
•
Ineff
ective if
dam
age w
as d
ue to o
rigin
al culv
ert
’s
ineff
icie
nt end s
ections r
ath
er
than inadequate
capacity.
•
Consid
er
culv
ert
en
dw
alls, w
ing
walls, en
erg
y
dis
sip
ate
rs, d
eb
ris b
arr
iers
, em
ban
km
en
t slo
pe
pro
tecti
on
, and a
hig
h w
ate
r o
verf
low
cro
ssin
g for
maxim
um
eff
ectiveness.
Co
nsid
era
tio
ns:
22
Insuffic
ient
Capacity &
/or
Ineffic
ient
End S
ections
A.2
In
cre
ase E
ffic
ien
cy o
f E
ntr
an
ce &
/or
Ou
tlet
Desig
n
Cu
lvert
en
tran
ce r
ou
nd
ing
, entr
ance b
evel rings, w
ing
walls,
flare
d e
nd
secti
on
s, p
avin
g t
he c
ulv
ert
en
tran
ce b
ott
om
, and/o
r “U
” shaped e
nd
walls m
ay incre
ase the e
ffic
iency o
f a
pip
e c
ulv
ert
.
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Tre
atm
ents
can incre
ase e
ffic
iency u
p to 2
0 p
erc
ent.
•
Consid
er
em
ban
km
en
t slo
pe p
rote
cti
on
, en
erg
y
dis
sip
ate
rs, and e
ntr
ance d
eb
ris b
arr
iers
for m
axim
um
eff
ectiveness.
Lim
itati
on
s:
•
The least eff
ective o
f th
ese tre
atm
ents
are
entr
ance
win
gw
alls a
nd f
lare
d e
ntr
ance e
nd s
ections.
•
Eff
ectiveness is less f
or
endw
alls a
nd w
ingw
alls w
hen
cente
rlin
e o
f culv
ert
is a
t an a
ngle
to that of th
e s
tream
.
Co
nsid
era
tio
ns:
Insuffic
ient
Capacity &
/or
Ineffic
ient
End S
ections
23
CULVERTS
A.3
C
han
ge C
ulv
ert
Alig
nm
en
t
Change c
ulv
ert
horizonta
l and v
ert
ical alig
nm
ent to
matc
h
cente
rlin
e a
nd s
lope o
f str
eam
. D
irect entr
ance a
nd e
xit
alignm
ent to
maxim
ize c
ulv
ert
eff
icie
ncy. (
See a
lso “
Culv
ert
s-
Mis
alig
nm
ent,”
pp. 40-4
5)
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Consid
er
culv
ert
en
tran
ce a
nd
ou
tlet
treatm
en
ts, en
erg
y
dis
sip
ate
rs a
nd d
eb
ris b
arr
iers
, em
ban
km
en
t slo
pe
pro
tecti
on
, lo
w w
ate
r cro
ssin
g, or
hig
h w
ate
r o
verf
low
cro
ssin
g f
or m
axim
um
eff
ectiveness.
Lim
itati
on
s:
•
A c
ulv
ert
bottom
slo
pe less t
han t
hat
of
the s
tream
may
cause b
ackw
ate
r conditio
ns w
ith d
ecre
ased e
ffic
iency a
nd
pote
ntial silt
ation.
•
A c
ulv
ert
bottom
slo
pe g
reate
r th
an that
of
the s
tream
may
cause s
cour
of
the s
tream
bed a
t th
e o
utlet and e
rosio
n
dow
nstr
eam
.
Co
nsid
era
tio
ns:
24
Insuffic
ient
Capacity &
/or
Ineffic
ient
End S
ections
A.4
A
dd
Mu
ltip
le P
ipe C
ulv
ert
s
Mu
ltip
le c
ulv
ert
s m
ay b
e insta
lled w
ith a
n e
xis
ting c
ulv
ert
at a
sin
gle
cro
ssin
g s
ite a
t either
the s
am
e o
r at diffe
ring e
levations.
The c
ulv
ert
s s
hould
be p
laced a
t diffe
rent ele
vations in the
em
bankm
ent and s
hould
be s
epara
ted b
y m
ore
than o
ne-t
enth
th
e d
iam
ete
r of
the indiv
idual culv
ert
s to m
inim
ize the p
ote
ntial
for
sedim
enta
tion b
uild
-up.
Eff
ecti
ven
ess:
•
Genera
lly v
ery
eff
ective.
•
Part
icula
rly e
ffective w
hen c
om
bin
ed w
ith c
ulv
ert
en
tran
ce
an
d o
utl
et
treatm
en
ts a
nd e
mb
an
km
en
t slo
pe
pro
tecti
on
.
•
May b
e m
ore
suitable
than a
sin
gle
, la
rge d
iam
ete
r culv
ert
pip
e f
or
low
fill
are
as.
•
Sedim
enta
tion c
an b
e m
inim
ized b
y u
se o
f th
e s
cour
eff
ect
from
hig
her
velo
city flo
ws.
Lim
itati
on
s:
•
Sm
alle
r pip
e c
ulv
ert
s w
ill r
estr
ict debris p
assage.
Co
nsid
era
tio
ns:
Insuffic
ient
Capacity &
/or
Ineffic
ient
End S
ections
25
CULVERTS
A.5
R
ep
lace W
ith
a B
ox o
r A
rch
Cu
lvert
A b
ox o
r arc
h c
ulv
ert
pro
vid
es a
dditio
nal capacity in low
fill
situations. C
an b
e d
esig
ned f
or very
min
imal fill
heig
ht.
Eff
ecti
ven
ess:
•
Genera
lly v
ery
eff
ective.
•
Ro
un
din
g c
ulv
ert
en
tran
ces, in
sta
lling w
ing
walls,
pavin
g c
ulv
ert
en
tran
ce b
ott
om
s, and/o
r in
sta
lling f
lare
d
ou
tlets
may a
lso incre
ase c
ulv
ert
capacity.
Co
nsid
era
tio
ns:
26
Insuffic
ient
Capacity &
/or
Ineffic
ient
End S
ections
A.6
R
ep
lace W
ith
a B
rid
ge
Repla
ce c
ulv
ert
with a
bridge.
Eff
ecti
ven
ess:
•
Very
eff
ective in incre
asin
g flo
w c
apacity thro
ugh
em
bankm
ent.
Lim
itati
on
s:
•
May r
equire e
ngin
eering a
naly
sis
and d
esig
n.
Co
nsid
era
tio
ns:
Insuffic
ient
Capacity &
/or
Ineffic
ient
End S
ections
27
CULVERTS
A.7
R
ep
lace W
ith
or
Ad
d a
Lo
w W
ate
r C
rossin
g
Repla
ce c
ulv
ert
with a
depre
ssio
n in the r
oadw
ay that w
ill
accom
modate
the a
nticip
ate
d flo
ws (
low
wate
r cro
ssin
g),
or
add a
roadw
ay d
epre
ssio
n o
ver
a c
ulv
ert
.
Eff
ecti
ven
ess:
•
Genera
lly v
ery
eff
ective in s
easonal in
term
itte
nt dra
inages
and a
s a
n e
merg
ency s
pill
way.
Lim
itati
on
s:
•
Not appro
priate
if
roadw
ay p
rovid
es a
ccess to a
critical
facili
ty.
•
Road im
passable
during f
loodin
g e
vents
.
•
Adequate
sig
nage a
nd b
arr
icades a
re n
ecessary
when
wate
r depth
exceeds a
safe
level fo
r vehic
les.
•
Roadw
ay a
nd e
mbankm
ents
should
be d
esig
ned a
nd
constr
ucte
d to w
ithsta
nd a
nticip
ate
d flo
ws.
•
The p
rofile
of
the c
rossin
g s
hould
matc
h the s
hape o
f th
e
str
eam
cro
ssin
g a
s c
lose a
s p
ossib
le.
Co
nsid
era
tio
ns:
28
Insuffic
ient
Capacity &
/or
Ineffic
ient
End S
ections
A.8
. In
sta
ll a
Hig
h W
ate
r O
verf
low
Cro
ssin
g
Insta
ll overf
low
section (
hig
h w
ate
r o
verf
low
cro
ssin
g)
in the
roadw
ay that w
ill a
ccom
modate
flo
ws f
rom
the o
verb
ank a
reas
of
the s
tream
. T
his
eff
ectively
reduces a
nd p
rovid
es a
n
em
erg
ency s
pill
way. H
igh w
ate
r overf
low
cro
ssin
gs s
hould
be
locate
d a
t natu
ral sid
e c
hannels
and/o
r in
lin
e w
ith h
eavy flo
w
are
as locate
d o
n the s
tream
overb
anks.
Eff
ecti
ven
ess:
•
Genera
lly v
ery
eff
ective, and p
art
icula
rly w
hen the r
oad
must re
main
passable
during n
orm
al flow
s a
nd topogra
phy
makes a
lo
w w
ate
r cro
ssin
g infe
asib
le.
Lim
itati
on
s:
•
Not appro
priate
if
roadw
ay p
rovid
es a
ccess to a
critical
facili
ty.
•
Road im
passable
during f
loodin
g e
vents
.
•
Adequate
sig
nage a
nd b
arr
icades a
re n
ecessary
when
wate
r depth
exceeds a
safe
level fo
r vehic
les.
•
Roadw
ay a
nd e
mbankm
ents
should
be d
esig
ned a
nd
constr
ucte
d to w
ithsta
nd a
nticip
ate
d flo
ws.
Co
nsid
era
tio
ns:
Plu
ggin
g
29
B.
Plu
gg
ing
Intr
od
ucti
on
Pro
ble
m:
Dam
age o
r fa
ilure
of
a c
ulv
ert
caused b
y
overt
oppin
g a
nd e
rosio
n o
f th
e e
mbankm
ent due to p
luggin
g o
f
the c
ulv
ert
with d
ebris a
nd/o
r silt
. D
ebris d
epositio
n a
cro
ss the
culv
ert
entr
ance, or
debris c
aught or
wedged in the c
ulv
ert
,
restr
icts
the w
ate
r flow
. A
culv
ert
can then b
e w
ashed o
ut or
dam
aged d
ue to incre
ased w
ate
r surf
ace e
levations u
pstr
eam
.
Mit
igati
on
Ob
jecti
ve:
To p
revent fu
ture
dam
age to a
culv
ert
by p
reventing it fr
om
becom
ing p
lugged.
Mit
igati
on m
easu
res t
o p
rote
ct
culv
ert
s f
rom
flo
od
dam
ag
e c
au
sed
by p
lug
gin
g in
clu
de:
1.
Insta
ll an E
ntr
ance D
ebris B
arr
ier.
...............p. 30
2.
Insta
ll a S
edim
ent C
atc
h B
asin
....................
p. 31
3.
Insta
ll a R
elie
f C
ulv
ert
.................................p. 32
4.
Insta
ll a P
erf
ora
ted S
tandpip
e.....................p. 33
30
Plu
ggin
g
B.1
In
sta
ll a
n E
ntr
an
ce D
eb
ris B
arr
ier
Insta
ll an e
ntr
ance d
eb
ris b
arr
ier
(deb
ris d
efl
ecto
r o
r debris
crib)
to p
revent blo
ckage o
f th
e c
ulv
ert
or
deb
ris f
ins d
esig
ned
to o
rient th
e flo
ating d
ebris f
or
easy p
assage thro
ugh the
culv
ert
. In
sta
ll a “
V”
shaped o
r sem
i-circula
r ra
ck a
t th
e c
ulv
ert
entr
ance o
r a s
traig
ht ra
ck a
t th
e e
nd o
f w
ing
walls to a
llow
for
overt
oppin
g o
f ra
ck b
y the flo
w w
hen d
ebris a
ccum
ula
tes
aro
und the r
ack. In
sta
ll debris d
eflecto
r or
debris fin
s a
t
upstr
eam
entr
ance to the c
ulv
ert
and insta
ll a d
ebris c
rib o
ver
the e
ntr
ance w
ith a
dro
p inle
t.
Eff
ecti
ven
ess:
•
Genera
lly v
ery
eff
ective in a
reas that have s
ignific
ant
debris loadin
g in the u
pstr
eam
dra
inage.
•
Consid
er
em
ban
km
en
t slo
pe p
rote
cti
on
, culv
ert
en
tran
ce a
nd
ou
tlet
treatm
en
ts, and e
nerg
y d
issip
ate
rs
where
appro
priate
for
maxim
um
eff
ectiveness.
Lim
itati
on
s:
•
Adequate
str
eam
channel sto
rage f
or
debris a
ccum
ula
tion
must
be a
vaila
ble
.
Co
nsid
era
tio
ns:
Plu
ggin
g
31
CULVERTS
B.2
In
sta
ll a
Sed
imen
t C
atc
h B
asin
In
sta
ll a s
edim
ent catc
h b
asin
upstr
eam
of
the c
ulv
ert
. T
he
basin
should
be locate
d f
ar
enough u
pstr
eam
and the o
penin
gs
should
be s
ized to a
llow
the s
uspended s
edim
ent suff
icie
nt
tim
e to s
ettle
out prior
to e
nte
ring the c
ulv
ert
.
Eff
ecti
ven
ess:
•
Genera
lly v
ery
eff
ective.
•
Part
icula
rly e
ffective in a
reas w
here
heavy s
ilt a
nd/o
r sand
loadin
g o
ccurs
during flo
od e
vents
and v
elo
city levels
do
not pro
vid
e for
scouring o
f th
e s
tream
bed a
nd c
ulv
ert
.
Lim
itati
on
s:
•
Requires a
dequate
sto
rage in b
asin
.
•
Must be e
asily a
ccessib
le f
or
sedim
ent cle
an o
ut.
Co
nsid
era
tio
ns:
32
Plu
ggin
g
B.3
In
sta
ll a
Relief
Cu
lvert
Relief
culv
ert
(s)
should
be locate
d a
t th
e c
rossin
g s
ite a
nd in
the e
mbankm
ent above the flo
w lin
e o
f th
e p
rim
ary
culv
ert
.
This
configura
tion p
rovid
es a
n a
ltern
ate
route
for
the flo
w, if the
main
culv
ert
gets
plu
gged, and p
revents
sedim
enta
tion thro
ugh
the h
igh flo
w s
couring a
ction.
Eff
ecti
ven
ess:
•
Genera
lly v
ery
eff
ective.
•
Desig
n o
f re
lief
culv
ert
(s)
should
inclu
de a
ppro
priate
en
tran
ce a
nd
/or
ou
tlet
treatm
en
t(s)
and e
mb
an
km
en
t
slo
pe p
rote
cti
on
.
Lim
itati
on
s:
•
Em
bankm
ent
geom
etr
y m
ay lim
it a
bili
ty to locate
culv
ert
(s)
above flo
w lin
e o
f prim
ary
culv
ert
.
Co
nsid
era
tio
ns:
Plu
ggin
g
33
CULVERTS
B.4
In
sta
ll a
Perf
ora
ted
Sta
nd
pip
e
Insta
ll a p
erf
ora
ted s
tandpip
e in lie
u o
f th
e tra
ditio
nal culv
ert
entr
ance. T
he s
tandpip
e a
llow
s d
ebris to f
loat up w
ith the
risin
g flo
odw
ate
rs w
ithout im
pacting flo
w into
the c
ulv
ert
. T
he
sta
ndpip
e s
hould
be a
rmore
d a
t its b
ase b
y c
onstr
ucting a
cone
of fr
ee d
rain
ing g
ravel aro
und it. T
he a
rea u
pstr
eam
of th
e
entr
ance s
hould
be s
uitable
for
sto
ring flo
odw
ate
rs.
Eff
ecti
ven
ess:
•
Genera
lly v
ery
eff
ective.
Lim
itati
on
s:
•
Sta
ndpip
e m
ay b
e v
uln
era
ble
to d
am
age fro
m h
igh v
elo
city
flow
s.
Co
nsid
era
tio
ns:
34
Em
bankm
ent
Ero
sio
n
C.
Em
ban
km
en
t E
rosio
n
Intr
od
ucti
on
Pro
ble
m:
Dam
age o
r fa
ilure
of
a c
ulv
ert
caused b
y e
rosio
n o
f
the e
mbankm
ent at its e
ntr
ance a
nd/o
r outlet, o
r aro
und the
outs
ide o
f th
e c
ulv
ert
. T
he e
mbankm
ent ero
sio
n a
nd
subsequent culv
ert
dam
age o
r fa
ilure
may b
e a
result o
f
inadequate
culv
ert
end s
ections.
Mit
igati
on
Ob
jecti
ve:
To p
revent fu
ture
dam
age to a
pip
e
culv
ert
by a
ddin
g a
ppro
priate
end s
ections.
Mit
igati
on m
easu
res t
o p
rote
ct
culv
ert
s f
rom
flo
od
dam
ag
e c
au
sed
by e
mb
an
km
ent
ero
sio
n in
clu
de:
1.
Shape C
ulv
ert
Entr
ance
.................................p. 35
2.
Constr
uct a C
uto
ff W
all
..................................
p. 36
3.
Insta
ll A
ppro
priate
Culv
ert
End S
ections
.........p. 37
4.
Constr
uct an E
nerg
y D
issip
ate
r......................
p. 38
5.
Exte
nd C
ulv
ert
Inle
t or
Outlet.
.........................p. 39
Em
bankm
ent
Ero
sio
n
35
CULVERTS
C.1
S
hap
e C
ulv
ert
En
tran
ce
Sh
ap
e (
bevel/skew
) cu
lvert
en
tran
ce t
o m
atc
h the
em
bankm
ent slo
pe o
r str
eam
alig
nm
ent. C
ulv
ert
eff
icie
ncy w
ill
be incre
ased, and turb
ule
nce a
t th
e e
ntr
ance a
nd thro
ugh the
culv
ert
will
be d
ecre
ased, re
ducin
g e
rosio
n o
f th
e b
ank.
Eff
ecti
ven
ess:
•
Very
eff
ective w
ith larg
e c
ulv
ert
s.
•
Modera
tely
eff
ective f
or
sm
alle
r culv
ert
s.
•
A c
uto
ff w
all a
nd/o
r p
aved
cu
lvert
en
tran
ce b
ott
om
should
be c
onsid
ere
d to p
revent underm
inin
g o
f th
e
entr
ance.
•
Consid
er
culv
ert
en
dw
alls,
win
gw
alls, d
eb
ris b
arr
iers
, and/o
r em
ban
km
en
t slo
pe p
rote
cti
on
to
maxim
ize
eff
ectiveness.
Lim
itati
on
s:
•
Cuttin
g a
culv
ert
to b
evel or
skew
its
entr
ance m
ay w
eaken
a larg
e d
iam
ete
r culv
ert
’s a
bili
ty to r
esis
t ring c
om
pre
ssio
n;
flanges m
ay b
e r
equired to s
tiff
en it.
Co
nsid
era
tio
ns:
36
Em
bankm
ent
Ero
sio
n
C.2
C
on
str
uct
a C
uto
ff W
all
Constr
uct sheet ste
el, low
heig
ht, c
uto
ff w
all to p
revent
underm
inin
g o
f culv
ert
entr
ance. T
he s
heeting s
hould
exte
nd
belo
w the c
ulv
ert
entr
ance to a
t le
ast one h
alf tim
es the c
ulv
ert
dia
mete
r and a
bove the c
ulv
ert
entr
ance to a
poin
t w
here
it
meets
the junction o
f th
e e
mbankm
ent w
ith o
ther
end
treatm
ents
.
Eff
ecti
ven
ess:
•
Very
eff
ective, part
icula
rly for
larg
e c
ulv
ert
s a
nd w
hen u
sed
with a
sh
ap
ed
cu
lvert
en
tran
ce a
nd/o
r p
aved
cu
lvert
en
tran
ce b
ott
om
.
•
Eff
ectiveness incre
ases if
com
bin
ed w
ith c
ulv
ert
en
dw
all
s,
win
gw
alls, d
eb
ris b
arr
iers
, and/o
r em
ban
km
en
t slo
pe
pro
tecti
on
.
Lim
itati
on
s:
•
Str
eam
bed g
eolo
gy m
ay p
rohib
it insta
llation o
f cuto
ff w
all.
C
on
sid
era
tio
ns:
Em
bankm
ent
Ero
sio
n
37
CULVERTS
C.3
In
sta
ll A
pp
rop
riate
Cu
lvert
En
d S
ecti
on
s
Constr
uct an e
nd
wall, w
ing
walls, and/o
r fl
are
d e
nd
secti
on
to d
irect flow
into
and o
ut of
the c
ulv
ert
and p
rote
ct
em
bankm
ent slo
pes. S
traig
ht or
“U”
shaped e
ndw
alls o
r flare
d
win
gw
alls m
ay b
e u
sed w
hen the c
ente
rlin
e o
f th
e s
tream
is
aligned w
ith the c
ulv
ert
. A
“U
” shaped e
ndw
all o
r w
ingw
all m
ay
be u
sed w
hen a
n a
bru
pt change in the flo
w d
irection is
necessary
. A
n “
L”
shaped e
ndw
all m
ay b
e c
onstr
ucte
d to
redirect th
e flo
w to the a
ngle
of
the c
ulv
ert
.
Eff
ecti
ven
ess:
•
Very
eff
ective. G
enera
lly s
uitable
for
hig
h v
elo
citie
s.
•
Win
gw
alls are
pre
ferr
ed w
hen b
oth
flo
w v
olu
mes a
nd
velo
citie
s a
re h
igh.
•
Consid
er
culv
ert
en
erg
y d
issip
ate
rs, d
eb
ris b
arr
iers
and
em
ban
km
en
t slo
pe p
rote
cti
on
. L
imit
ati
on
s:
•
Str
aig
ht endw
alls m
ay d
ecre
ase c
ulv
ert
capacitie
s, but
rou
nd
ing
of
the e
ntr
an
ce c
orn
ers
may o
ffset it.
•
If s
tream
velo
citie
s a
re h
igh, la
tera
l scour
of
em
bankm
ents
may r
esult fro
m e
ddie
s a
t th
e c
ulv
ert
end s
ections.
•
Attachin
g f
abricate
d fla
red e
nd s
ections to c
ulv
ert
entr
ances a
nd o
utlets
may c
ause s
epara
tion o
f culv
ert
join
ts if
the c
ulv
ert
cannot support
additio
nal w
eig
ht.
Co
nsid
era
tio
ns:
38
Em
bankm
ent
Ero
sio
n
C.4
C
on
str
uct
an
En
erg
y D
issip
ate
r
Constr
uct an e
nerg
y d
issip
ate
r to
min
imiz
e s
couring a
t th
e
culv
ert
outlet.
Energ
y d
issip
ate
r desig
ns m
ay inclu
de c
oncre
te
or
rock s
lopin
g a
pro
ns, “b
ucket”
outlets
that th
row
the jet
dow
nstr
eam
, stilli
ng b
asin
s, or
oth
er
more
ela
bora
te s
tructu
res.
Eff
ecti
ven
ess:
•
Very
eff
ective. E
specia
lly e
ffective w
hen there
is a
sig
nific
ant dro
p fro
m the b
ottom
of
the o
utflo
w e
nd o
f th
e
culv
ert
to the d
rain
age flo
w lin
e, or
when the g
radie
nt of
the
culv
ert
is s
teep.
•
If s
tream
velo
citie
s a
re h
igh, m
ay b
e n
eeded to e
limin
ate
late
ral scour.
Lim
itati
on
s:
•
Str
eam
channel geom
etr
y m
ay d
icta
te the d
esig
n o
f energ
y
dis
sip
ate
rs.
•
Dependin
g o
n e
xis
ting c
onditio
ns, str
eam
velo
city, and
depth
of
pool, m
easure
may h
ave c
onsid
era
ble
im
pacts
on
fish.
Co
nsid
era
tio
ns:
Em
bankm
ent
Ero
sio
n
39
CULVERTS
C.5
E
xte
nd
Cu
lvert
In
let
or
Ou
tlet
Exte
nd c
ulv
ert
entr
ance a
nd/o
r outlet past th
e e
mbankm
ent
face.
Eff
ecti
ven
ess:
•
Modera
tely
eff
ective in r
educin
g turb
ule
nce a
t culv
ert
entr
ance.
•
Modera
tely
eff
ective in r
educin
g e
rosio
n o
f th
e d
ow
nstr
eam
em
bankm
ent, b
ut can c
ause e
rosio
n to u
pstr
eam
em
bankm
ent due to e
ddie
s.
•
Consid
er
en
erg
y d
issip
ate
rs, em
ban
km
en
t slo
pe
pro
tecti
on
, and d
eb
ris b
arr
iers
to
maxim
ize
eff
ectiveness.
Lim
itati
on
s:
•
Exte
nsio
ns c
an c
ause s
cour
of
the s
tream
bed d
ow
nstr
eam
.
•
Exte
nsio
ns a
re v
uln
era
ble
to flo
w a
nd d
ebris im
pacts
.
Co
nsid
era
tio
ns:
40
Mis
alignm
ent
D.
Mis
alig
nm
en
t
Intr
od
ucti
on
Pro
ble
m:
Dam
age to a
culv
ert
caused b
y its
horizonta
l and/o
r
vert
ical m
isalig
nm
ent w
ith the s
tream
channel and s
ubsequent
ero
sio
n o
f th
e e
mbankm
ent. T
he m
isalignm
ent m
ay b
e a
result
of
origin
al desig
n m
iscalc
ula
tions a
nd/o
r subsequent str
eam
mig
ration.
Mit
igati
on
Ob
jecti
ve:
To p
revent fu
ture
dam
age to a
culv
ert
by a
lignin
g the c
ulv
ert
to the a
xis
of
the s
tream
; to
pre
vent
futu
re m
igra
tion o
f th
e s
tream
aw
ay f
rom
the c
ulv
ert
; and to
desig
n s
upple
menta
ry d
rain
age s
tructu
res to a
ccom
modate
futu
re m
igra
tion o
f th
e s
tream
channel.
Mit
igati
on m
easu
res t
o p
rote
ct
culv
ert
s f
rom
flo
od
dam
ag
e c
au
sed
by t
heir
mis
alig
nm
ent
inclu
de:
1.
Insta
ll A
dditio
nal C
ulv
ert
s...................................p
. 41
2.
Realign C
ulv
ert
..................................................
p. 42
3.
Insta
ll A
ppro
ach B
erm
s......................................
p. 43
4.
Insta
ll F
low
Div
ert
ers
..........................................
p. 44
5.
Realign the S
tream
Channel...............................
p. 45
6.
Insta
ll A
ppro
priate
Culv
ert
End S
ections
.....S
ee b
elo
w7.
Pla
ce R
ipra
p..............................................S
ee b
elo
w
7.
Pla
ce R
ipra
p (
p. 13)
6.
Insta
ll A
pp
rop
ria
te C
ulv
ert
End S
ections (
p. 37)
Mis
alignm
ent
41
CULVERTS
D.1
In
sta
ll A
dd
itio
nal C
ulv
ert
s
Locate
ad
dit
ion
al cu
lvert
s a
t pre
vio
us a
nd/o
r pote
ntial str
eam
alignm
ents
at ro
ad c
rossin
g s
ite. T
he a
dditio
nal culv
ert
s
should
be locate
d s
om
e d
ista
nce f
rom
the m
ain
str
eam
culv
ert
. E
ffecti
ven
ess:
•
Very
eff
ective.
•
Consid
er
em
ban
km
en
t slo
pe p
rote
cti
on
and c
ulv
ert
en
erg
y d
issip
ate
rs, en
dw
alls, w
ing
wall
s, and d
eb
ris
barr
iers
for
maxim
um
eff
ectiveness.
Lim
itati
on
s:
•
Pote
ntial fo
r sedim
enta
tion o
f culv
ert
s that are
not carr
yin
g
hig
her
floodw
ate
r velo
citie
s.
•
Consid
er
vary
ing the c
ulv
ert
s’ ele
vations.
Co
nsid
era
tio
ns:
42
Mis
alignm
ent
D.2
R
ealig
n C
ulv
ert
Alig
n c
ente
rlin
e o
f th
e c
ulv
ert
(either
vert
ically
or
horizonta
lly)
to
the c
ente
rlin
e o
f th
e s
tream
to e
limin
ate
ero
sio
n a
long the
em
bankm
ent and s
ubsequent dam
age to the c
ulv
ert
.
Alig
nm
ent m
ay r
equire r
elo
cating c
ulv
ert
to p
resent lo
cation o
f str
eam
channel.
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Consid
er
em
ban
km
en
t slo
pe p
rote
cti
on
, culv
ert
en
dw
alls, w
ing
wall
s, en
erg
y d
issip
ate
rs, and d
eb
ris
barr
iers
for
maxim
um
eff
ectiveness.
•
Str
eam
and/o
r ro
ad g
eolo
gy m
ay p
reclu
de a
ltera
tion o
f
culv
ert
alig
nm
ent.
Co
nsid
era
tio
ns:
Mis
alignm
ent
43
CULVERTS
D.3
In
sta
ll A
pp
roach
Berm
s
Insta
ll appro
ach b
erm
s o
n the s
tream
overb
anks. B
erm
s
should
be a
ligned s
o that flow
is d
irecte
d into
and a
t th
e s
am
e
angle
as the c
ulv
ert
and a
way f
rom
the e
mbankm
ent.
Eff
ecti
ven
ess:
•
Eff
ective a
t hig
h flo
ws, but no e
ffect
at lo
w flo
ws.
•
Consid
er
em
ban
km
en
t slo
pe p
rote
cti
on
, culv
ert
en
dw
alls, w
ing
wall
s, en
erg
y d
issip
ate
rs, and d
eb
ris
barr
iers
fo
r m
axim
um
eff
ectiveness.
Lim
itati
on
s:
•
Overb
ank g
eom
etr
y m
ay p
reclu
de this
option.
•
Berm
s n
eed to b
e p
laced o
n the s
tream
overb
anks n
ear
or
at th
e e
dge o
f th
e flo
odw
ay s
o that w
ate
r-surf
ace
ele
vations a
re n
ot sig
nific
antly incre
ased a
t th
e c
ulv
ert
or
upstr
eam
. C
on
sid
era
tio
ns:
44
Mis
alignm
ent
D.4
In
sta
ll F
low
Div
ert
ers
Insta
ll flow
div
ert
ers
(barb
s)
in the s
tream
. D
esig
n b
arb
s to
redirect th
e flo
w a
way f
rom
the e
mbankm
ent and into
the
culv
ert
.
Eff
ecti
ven
ess:
•
Part
icula
rly e
ffective d
uring r
ela
tively
low
flo
ws.
•
May n
ot
be e
ffective a
t hig
h flo
ws.
•
May h
elp
pre
vent channel m
igra
tion a
t all
flow
levels
.
•
Consid
er
culv
ert
en
dw
alls, w
ing
walls, d
eb
ris b
arr
iers
,
and e
nerg
y d
issip
ate
rs f
or
maxim
um
eff
ectiveness.
•
Consid
er
usin
g n
atu
ral m
ate
rials
such a
s r
oot balls
or
anchore
d logs.
Lim
itati
on
s:
•
Requires a
dditio
nal str
eam
em
ban
km
en
t slo
pe
pro
tecti
on
for
hig
h flo
ws.
•
Desig
n s
hould
inclu
de m
easure
s, such a
s s
heet ste
el
pili
ng, to
elim
inate
wash-o
ut of
landw
ard
end o
f barb
s.
•
Heig
ht of
barb
s s
hould
not cause s
ignific
ant in
cre
ase in
wate
r-surf
ace e
levations f
or
hig
h flo
ws a
t or
upstr
eam
of
the c
ulv
ert
.
Co
nsid
era
tio
ns:
Mis
alignm
ent
45
CULVERTS
D.5
R
ealig
n t
he S
tream
Ch
an
nel
Channel flow
should
be d
irecte
d into
and a
t sam
e a
ngle
as the
culv
ert
and a
way f
rom
the e
mbankm
ent
to r
educe e
rosio
n
alo
ng the e
mbankm
ent and c
onsequent dam
age to the c
ulv
ert
.
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Consid
er
em
ban
km
en
t slo
pe p
rote
cti
on
, culv
ert
en
dw
alls, w
ing
wall
s, e
nerg
y d
issip
ate
rs, and d
eb
ris
barr
iers
for
maxim
um
eff
ectiveness.
Lim
itati
on
s:
•
Str
eam
may r
ecla
im o
rigin
al channel over
tim
e d
ue to
natu
ral m
eandering.
Co
nsid
era
tio
ns:
Bridges
45
BRIDGES
46
Bridges
BR
IDG
ES
F
lood d
am
age to b
ridges a
re typic
ally
caused b
y w
ate
r
overt
oppin
g d
ecks, ero
sio
n o
f th
e s
tream
bed u
nder
pie
rs a
nd
abutm
ent fo
otings, ero
sio
n o
f th
e e
mbankm
ents
, and im
pact
and a
ccum
ula
tion o
f floating d
ebris o
n the d
ecks, pie
rs, and
abutm
ents
. T
hese d
am
ages m
ay b
e r
ela
ted to the inadequate
hydra
ulic c
apacity o
f th
e b
ridge, m
isaligned p
iers
and/o
r
abutm
ents
, or
accum
ula
tion o
f debris.
Assessin
g t
he C
au
ses o
f B
rid
ge D
am
ag
e
Inadequate
hydra
ulic c
apacity o
f a b
ridge m
ay r
esult in
str
eam
bed s
cour
on b
oth
sid
es o
f th
e p
iers
and a
butm
ent.
Mis
alig
nm
ent of
the p
iers
and/o
r abutm
ents
may r
esult in
str
eam
bed s
cour
on the e
xposed s
ide o
f th
e p
iers
, and
depositio
n o
f str
eam
bed m
ate
rials
on the lee s
ides. T
o h
elp
identify
excessiv
e flo
od flo
w v
elo
citie
s that caused u
nderm
inin
g
and s
ubsequent dam
age to b
ridge p
iers
and a
butm
ents
,
dete
rmin
e:
•
The location o
f str
eam
bed s
cour,
and
•
Depositio
n o
f str
eam
bed m
ate
rials
.
Bridges
47
BRIDGES
Debris c
an thre
ate
n b
ridge f
acili
ties, w
heth
er
it is c
arr
ied in
flood flo
ws that are
ris
ing o
r re
cedin
g. In r
isin
g w
ate
rs, debris
may b
ecom
e c
aught on b
ridge p
iers
and a
butm
ents
, w
hic
h
decre
ases the s
ize o
f th
e b
ridge o
penin
g. T
he b
ridge c
an then
becom
e d
am
aged b
y flo
w im
pacting the d
ecks, pie
rs, and
abutm
ents
, and b
y w
ashouts
of
pie
rs a
nd a
butm
ents
due to
str
eam
bed s
cour.
Dam
age c
aused b
y d
ebris im
pact and a
ccum
ula
tion is v
erified
by o
bserv
ing d
ebris jam
med into
bridge m
em
bers
, debris p
iles
deposited a
round the u
pstr
eam
sid
e o
f pie
rs a
nd a
butm
ents
,
and s
tream
bed s
cour
belo
w a
nd a
dja
cent to
debris p
iles. If
debris w
as c
arr
ied thro
ugh r
ecedin
g flo
od flo
ws, th
e d
ebris w
ill
be d
eposited o
n the s
tream
overb
anks o
r aro
und the b
ase o
f
pie
rs a
nd a
butm
ents
, but are
usually n
ot th
e c
ause o
f dam
age.
This
section d
iscusses m
itig
ation m
easure
s for
com
mon flo
od d
am
ages to b
ridge facili
ties,
whic
h a
re c
aused b
y:
A.
Mis
alig
nm
ent.
....................................p.
48
B.
Insuffic
ient
Capacity (
Decks).............p
. 53
C.
Ero
sio
n (
Appro
ache).
.........................p
. 59
D.
Scour
(Pie
rs &
Abutm
ents
)................p.
60
E.
Debris Im
pact (P
iers
& A
butm
ents
)....p
. 64
48
Mis
alignm
ent
A.
Mis
alig
nm
en
t
Intr
od
ucti
on
Pro
ble
m:
Dam
age to a
bridge c
aused b
y its
mis
alig
nm
ent w
ith
the s
tream
channel. T
he m
isalig
nm
ent m
ay b
e a
result o
f
origin
al desig
n m
iscalc
ula
tions a
nd/o
r subsequent str
eam
mig
ration. (
See “
Culv
ert
s-M
isalignm
ent,”
pp. 40-4
5)
Mit
igati
on
Ob
jecti
ve:
To p
revent fu
ture
dam
age to a
bridge
by a
lignin
g its
abutm
ents
and p
iers
to the c
ente
rlin
e o
f th
e
str
eam
, by p
reventing f
utu
re m
igra
tion o
f th
e s
tream
aw
ay f
rom
th
e b
ridge, and/o
r by insta
lling a
dditio
nal bridge o
penin
gs to
accom
modate
futu
re m
igra
tion o
f th
e s
tream
channel.
Mit
igati
on m
easu
res t
o p
rote
ct
bri
dg
es f
rom
flo
od
dam
ag
e c
au
sed
by m
isalig
nm
en
t in
clu
de:
1.
Constr
uct B
ridge W
ingw
alls
............................
p. 49
2.
Constr
uct S
pur
Dik
es......................................
p. 50
3.
Insta
ll A
dditio
nal B
ridge O
penin
gs o
r S
pans
....
p. 51
4.
Realign P
iers
and A
butm
ents
..........................
p. 52
5.
Insta
ll A
ppro
ach B
erm
s...........................S
ee b
elo
w
6.
Insta
ll F
low
Div
ert
ers
..............................S
ee b
elo
w7.
Realign the S
tream
Channel.
..................
See b
elo
w
5.
Insta
ll A
ppro
ach B
erm
s
(p
. 43)
6.
Insta
ll F
low
Div
ert
ers
(p
. 4
4)
7.
Realign the S
tream
Chan
nel
(p
. 45)
Mis
alignm
ent
49
BRIDGES
A.1
C
on
str
uct
Bri
dg
e W
ing
walls
Insta
ll bridge e
ntr
ance a
nd o
utlet w
ing
walls. D
esig
n w
ingw
alls
to r
edirect th
e flo
w into
the b
ridge o
penin
g a
nd e
limin
ate
ero
sio
n u
nder
the b
ridge p
iers
, abutm
ents
and e
mbankm
ent.
Use f
lare
d w
ingw
alls a
ngle
d to c
oin
cid
e w
ith the s
tream
. (
See
“Culv
ert
s-E
mbankm
ent E
rosio
n,”
pp. 34-3
9)
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Flo
w v
olu
mes m
ay b
e incre
ased u
p to 3
0 p
erc
ent
dependin
g o
n a
ngle
of
win
gw
alls.
•
Roundin
g o
r bevelin
g o
f abutm
ent
corn
ers
may incre
ase
flow
volu
mes b
y 2
0 p
erc
ent.
•
Consid
er
deb
ris d
efl
ecto
rs a
nd e
mb
an
km
en
t slo
pe
pro
tecti
on
for m
axim
um
eff
ectiveness.
Lim
itati
on
s:
•
If s
tream
velo
citie
s a
re h
igh, la
tera
l scour
of
em
bankm
ents
may r
esult fro
m e
ddie
s a
t th
e e
nds o
f w
ingw
alls. D
esig
n
win
gw
all s
hapes a
nd their a
ngle
s to the s
tream
to m
inim
ize
the d
evelo
pm
ent of
eddie
s.
•
Desig
n o
f debris d
eflecto
rs n
eeds to a
ccount fo
r eff
ect of
str
eam
and b
ridge p
ier
and a
butm
ent alig
nm
ent.
Co
nsid
era
tio
ns:
50
Mis
alignm
ent
A.2
C
on
str
uct
Sp
ur
Dik
es
Spur
dik
es a
re e
mbankm
ents
desig
ned to d
irect flood flo
ws into
a b
ridge o
penin
g. T
hey a
re ‘tied into
’ th
e r
oad e
mbankm
ent at
an a
ppro
priate
poin
t la
ndw
ard
fro
m the b
ridge o
penin
g a
nd
then e
xte
nd u
pstr
eam
. T
he u
sual shape o
f a s
pur
dik
e is e
ither
str
aig
ht or
elli
ptical.
Spur
dik
es s
hould
be insta
lled a
t an a
ngle
to r
edirect th
e flo
w into
the b
ridge o
penin
g, th
ere
by e
limin
ating
the p
ote
ntial fo
r ero
sio
n a
long a
nd u
nder
the b
ridge p
iers
and
abutm
ents
and a
long the b
ridge e
mbankm
ent.
Eff
ecti
ven
ess:
•
Very
eff
ective. C
onsid
er
deb
ris d
efl
ecto
rs a
nd
em
ban
km
en
t slo
pe p
rote
cti
on
for m
axim
um
eff
ectiveness.
Lim
itati
on
s:
•
Spur
dik
es s
hould
be p
laced o
n the s
tream
overb
anks s
o
wate
r-surf
ace e
levations a
re n
ot in
cre
ased s
ignific
antly.
•
If s
tream
velo
citie
s a
re h
igh, scour
of
spur
dik
e
em
bankm
ents
may r
esult fro
m e
ddie
s a
t th
eir u
pstr
eam
ends a
nd a
long their s
ides. D
esig
n s
pur
dik
e s
hapes a
nd
angle
s to the s
tream
to m
inim
ize d
evelo
pm
ent of
eddie
s.
Co
nsid
era
tio
ns:
Mis
alignm
ent
51
BRIDGES
A.3
In
sta
ll A
dd
itio
nal B
rid
ge O
pen
ing
s o
r S
pan
s
Insta
ll additio
nal bridge o
penin
gs o
r bridge s
pans. T
hese
additio
nal openin
gs o
r spans s
hould
be locate
d a
t his
torical
and/o
r pote
ntial str
eam
alig
nm
ents
at a c
rossin
g s
ite. T
his
measure
can b
e e
mplo
yed to m
itig
ate
for
the e
ffects
of
a
bra
idin
g s
tream
bed, or
a w
idenin
g s
tream
bed.
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Consid
er
bridge e
ntr
ance a
nd o
utlet w
ing
walls, d
eb
ris
defl
ecto
rs, and e
mb
an
km
en
t slo
pe p
rote
cti
on
for
maxim
um
eff
ectiveness.
Lim
itati
on
s:
•
Cro
ssin
g g
eom
etr
y m
ay p
reclu
de this
option.
Co
nsid
era
tio
ns:
52
Mis
alignm
ent
A.4
R
ealig
n P
iers
an
d A
bu
tmen
ts
Realig
n the b
ridge p
iers
an
d a
bu
tmen
ts to b
e p
ara
llel to
the
cente
rlin
e o
f th
e s
tream
, th
ere
by e
limin
ating the p
ote
ntial fo
r
ero
sio
n a
long a
nd u
nder
the b
ridge p
iers
and a
butm
ents
and
alo
ng the e
mbankm
ent.
Realig
nm
ent of
the b
ridge m
ay inclu
de
relo
cati
ng
it
to the v
icin
ity o
f th
e p
resent str
eam
channel
and/o
r alig
nin
g the b
ridge o
penin
g to the c
ente
rlin
e o
f th
e
str
eam
.
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Flo
w v
olu
mes m
ay b
e incre
ased u
p to 3
0 p
erc
ent w
hen
pie
rs a
re a
ligned.
•
Consid
er
bridge e
ntr
ance a
nd o
utlet w
ing
walls, d
eb
ris
defl
ecto
rs, and e
mb
an
km
en
t slo
pe p
rote
cti
on
for
maxim
um
eff
ectiveness.
Co
nsid
era
tio
ns:
Insuff
icie
nt
Capacity (
Decks)
53
BRIDGES
B.
In
su
ffic
ien
t C
ap
ac
ity (
De
ck
s)
Intr
od
ucti
on
Pro
ble
m:
Dam
age to b
ridge d
ecks a
nd a
ssocia
ted
supers
tructu
res (
raili
ngs a
nd tru
ss)
as a
result o
f overt
oppin
g
due to insuff
icie
nt capacity f
or flow
thro
ugh the b
ridge o
penin
g.
Mit
igati
on
Ob
jecti
ve:
To p
revent dam
age to b
ridge d
ecks a
nd
associa
ted s
upers
tructu
res b
y incre
asin
g the d
esig
n c
apacity
for
the b
ridge o
penin
g, and/o
r m
odifyin
g the b
ridge d
eck d
esig
n
to a
llow
for
contr
olle
d o
verf
low
.
Mit
igati
on m
easu
res t
o p
rote
ct
bri
dg
e d
ecks f
rom
flo
od
d
am
ag
e c
au
sed
by in
suff
icie
nt
cap
acit
y in
clu
de:
1.
Ele
vate
the B
ridge D
eck ..............................................
p. 54
2.
Repla
ce S
teel T
russ B
ridge W
ith a
n O
pen D
eck B
ridge
.p. 55
3.
Repla
ce M
ulti-S
pans W
ith S
ingle
Span B
ridge...............p
. 56
4.
Incre
ase B
ridge O
penin
g S
ize.......................................p
. 57
5.
Constr
uct a R
elief O
penin
g...........................................p
. 58
6.
Constr
uct B
ridge W
ingw
alls
.................................S
ee b
elo
w7.
Insta
ll H
igh W
ate
r O
verf
low
Cro
ssin
g...................S
ee b
elo
w8.
Realign P
iers
and A
butm
ents
...............................S
ee b
elo
w9.
Insta
ll A
dditio
nal B
ridge O
penin
gs o
r S
pans
.........S
ee b
elo
w
6.
Co
nstr
uct
Bri
dg
e W
ing
wa
lls
(p. 49)
7.
Insta
ll H
igh W
ate
r O
verf
low
Cro
ssin
g (
p.
28
)
8.
Realign P
iers
and A
butm
ents
(p. 52)
9.
Insta
ll A
dd
itio
na
l B
rid
ge
Openin
gs o
r S
pans (
p. 51)
54
Insuff
icie
nt
Capacity (
Decks)
B.1
E
levate
th
e B
rid
ge D
eck
The b
ridge d
eck a
nd a
ssocia
ted s
upers
tructu
re s
hould
be
ele
vate
d t
o a
level suffic
ient to
pass a
nticip
ate
d flo
od flo
ws.
Appro
ach s
ections to the b
ridge m
ay lik
ew
ise n
eed to b
e
rais
ed.
E
ffecti
ven
ess:
•
Most eff
ective m
itig
ation f
or
passin
g f
lood flo
ws.
Lim
itati
on
s:
•
The p
ier
and a
butm
ent support
s m
ay n
eed to b
e
redesig
ned to a
ccom
modate
and s
upport
the e
levate
d
bridge d
eck a
nd a
ssocia
ted s
upers
tructu
re.
Co
nsid
era
tio
ns:
Insuff
icie
nt
Capacity (
Decks)
55
BRIDGES
B.2
R
ep
lace a
Ste
el T
russ B
rid
ge W
ith
an
O
pen
Deck B
rid
ge
Repla
cin
g a
ste
el tr
uss b
ridge w
ith a
n o
pen d
eck b
ridge w
ill
reduce the b
ackw
ate
r conditio
ns u
pstr
eam
, and e
limin
ate
the
accum
ula
tion o
f debris s
hould
the b
ridge b
ecom
e o
ver-
topped
during flo
od e
vents
.
Eff
ecti
ven
ess:
•
Genera
lly v
ery
eff
ective.
•
An o
pen d
eck b
ridge d
oes n
ot tr
ap flo
ating d
ebris to the
sam
e e
xte
nt th
at a s
teel tr
uss b
ridge w
ill w
hen o
vert
opped.
•
Eff
ectiveness is incre
ased if
open d
eck b
ridge is e
levate
d.
Lim
itati
on
s:
•
Bridge p
iers
and a
butm
ents
may r
equire e
xte
nsiv
e
redesig
n to a
ccom
modate
open d
eck b
ridge.
Co
nsid
era
tio
ns:
56
Insuff
icie
nt
Capacity (
Decks)
B.3
R
ep
lace M
ult
i-S
pan
s W
ith
a
S
ing
le S
pan
Bri
dg
e
Rep
lace t
he m
ult
iple
sp
an
s o
f a b
rid
ge w
ith
a s
ing
le c
lear-
sp
an
to e
limin
ate
the n
eed f
or
pie
rs. T
his
will in
cre
ase the flo
w
thro
ugh the b
ridge a
nd r
educe u
pstr
eam
backw
ate
r conditio
ns.
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Incre
ases the e
ffective s
ize o
f th
e b
ridge o
penin
g a
nd flo
w
capacity.
•
Reduces d
ebris a
ccum
ula
tion.
•
Decre
ases the b
ackw
ate
r conditio
ns u
pstr
eam
fro
m the
bridge a
nd the e
ffects
of
dra
wdow
n thro
ugh it.
•
Consid
er
relief
op
en
ing
s, w
ing
walls, re
alig
nm
en
t o
f
pie
rs a
nd
ab
utm
en
ts, em
ban
km
en
t slo
pe p
rote
cti
on
,
and a
butm
ent d
eb
ris d
efl
ecto
rs fo
r m
axim
um
eff
ectiveness.
Lim
itati
on
s:
•
Length
of
span m
ay b
e lim
ited b
y s
trength
of m
ate
rials
. C
on
sid
era
tio
ns:
Insuff
icie
nt
Capacity (
Decks)
57
BRIDGES
B.4
In
cre
ase B
rid
ge O
pen
ing
Siz
e
Incre
ase the s
ize o
f th
e b
ridge o
penin
g(s
) by length
enin
g the
openin
g o
r ra
isin
g the b
ridge d
eck. Incre
asin
g b
ridge o
penin
g
siz
e w
ill decre
ase a
ny b
ackw
ate
r conditio
ns u
pstr
eam
fro
m the
bridge a
nd r
educe the e
ffects
of
dra
wdow
n thro
ugh the b
ridge.
Eff
ecti
ven
ess:
•
Very
eff
ective. P
art
icula
rly e
ffective w
here
dam
age w
as
caused b
y o
vert
oppin
g o
f th
e b
ridge d
ue to e
xcessiv
ely
hig
h w
ate
r surf
ace e
levations u
pstr
eam
or
by e
xcessiv
ely
hig
h w
ate
r velo
citie
s e
rodin
g the p
ier
and a
butm
ent
foundations.
•
Degre
e o
f eff
ectiveness v
aries w
ith the d
iffe
rence o
f th
e
wate
r surf
aces u
pstr
eam
and d
ow
nstr
eam
fro
m the b
ridge,
and w
ith the w
ate
r velo
citie
s thro
ugh the b
ridge.
•
Consid
er
relief
op
en
ing
s, w
ing
walls, re
alig
nm
en
t o
f p
iers
an
d a
bu
tmen
ts, em
ban
km
en
t slo
pe p
rote
cti
on
,
and d
eb
ris d
efl
ecto
rs f
or
maxim
um
eff
ectiveness.
Lim
itati
on
s:
•
Cro
ssin
g a
nd s
tream
channel geom
etr
y m
ay p
reclu
de this
option.
Co
nsid
era
tio
ns:
58
Insuff
icie
nt
Capacity (
Decks)
B.5
C
on
str
uct
a R
elief
Op
en
ing
Constr
uct one o
r m
ore
relief
op
en
ing
s thro
ugh the r
oad p
rism
at a location that w
ill c
arr
y e
xcess f
loodw
ate
rs. T
he r
elie
f
openin
g m
ay b
e a
culv
ert
or
bridge, or m
ultip
le c
ulv
ert
s o
r
bridges. T
he o
penin
gs s
hould
be locate
d a
t natu
ral sid
e
channels
and in lin
e w
ith h
eavy flo
w a
reas locate
d o
n the
str
eam
overb
anks. (
See “
Culv
ert
s-P
luggin
g,”
pp. 29-3
3)
Eff
ecti
ven
ess:
•
Genera
lly v
ery
eff
ective, part
icula
rly if
com
bin
ed w
ith
appro
priate
culv
ert
and/o
r bridge e
ntr
an
ce a
nd
ou
tlet
treatm
en
ts.
•
Consid
er
win
gw
all
s, em
ban
km
en
t slo
pe p
rote
cti
on
, and
deb
ris d
efl
ecto
rs f
or m
axim
um
eff
ectiveness.
Lim
itati
on
s:
•
Geom
etr
y o
f dra
inage a
rea m
ay p
reclu
de this
option.
Co
nsid
era
tio
ns:
Ero
sio
n (
Appro
aches)
59
BRIDGES
C.
Ero
sio
n (
Ap
pro
ac
he
s)
In
tro
du
cti
on
Pro
ble
m:
Dam
age to b
ridge a
ppro
aches r
esultin
g fro
m
overt
oppin
g w
ith s
ubsequent ero
sio
n o
f th
e r
oad s
urf
ace,
should
er
and e
mbankm
ent, a
nd f
rom
im
pact of flood flo
ws a
nd
debris w
ith s
ubsequent ero
sio
n o
f th
e e
mbankm
ent.
Mit
igati
on
Ob
jecti
ve:
To p
revent fu
ture
dam
age to b
ridge
appro
aches (
em
bankm
ents
, ro
ad s
hould
er,
and r
oad s
urf
ace)
by e
limin
ating o
vert
oppin
g a
nd e
rosio
n.
Mit
igati
on m
easu
res d
eta
iled in
oth
er
secti
on
s, such
as
“C
ulv
ert
s” a
nd “
Ro
ads,”
th
at
can b
e e
mp
loyed
to
pro
tect
bri
dg
e a
ppro
ach
es f
rom
flo
od
dam
ag
e in
clu
de:
1.
Insta
ll H
igh W
ate
r O
verf
low
Cro
ssin
g...................S
ee b
elo
w
2.
Constr
uct a R
elief O
penin
g..................................
See b
elo
w3.
Realign S
tream
Channel......................................S
ee b
elo
w4.
Constr
uct R
oad S
urf
ace &
Should
er
Pro
tection
....
See b
elo
w5.
Bio
-Engin
eere
d E
mbankm
ent S
lope P
rote
ction
....
See b
elo
w6.
Insta
ll Lin
ing in the D
itch
......................................
See b
elo
w
1.
Insta
ll a
Hig
h W
ate
r O
verf
low
Cro
ssin
g (
p.
28
)
3.
Realign the S
tream
Chan
nel
(p. 45)
5.
Insta
ll L
inin
g in
th
e D
itch
(p
. 5)
4.
Constr
uct S
hould
er
Pro
tection (
p. 16)
2.
Constr
uct a R
elief O
penin
g
(p. 58)
6.
Bio
-Engin
eere
d E
mbankm
ent
Slo
pe P
rote
ction (
p. 9)
60
Scour
(Pie
rs &
Abutm
ents
)
D.
Sco
ur
(Pie
rs &
Ab
utm
en
ts)
In
tro
du
cti
on
Pro
ble
m:
Dam
age to b
ridge p
iers
and a
butm
ents
resultin
g
from
scouring o
f th
e s
tream
bed a
long a
nd u
nder
their footings.
Mit
igati
on
Ob
jecti
ve:
Reduce flo
od flo
w v
elo
citie
s a
long
bridge p
iers
and a
butm
ents
, th
ere
by e
limin
ating s
couring o
f th
e
str
eam
bed a
long a
nd u
nder
their footings.
Mit
igati
on m
easu
res t
o p
rote
ct
bri
dg
e p
iers
an
d a
butm
ents
from
flo
od
dam
age d
ue t
o s
co
ur
inclu
de:
1.
Incre
ase F
ooting D
epth
.............................................p
. 61
2.
Insta
ll F
low
Deflecto
rs...............................................p
. 62
3.
Insta
ll S
em
icircula
r or
Triangula
r E
ndnoses
...............p
.63
4.
Constr
uct B
ridge W
ingw
alls
..............................
See b
elo
w5.
Realign P
iers
and A
butm
ents
............................
See b
elo
w6.
Repla
ce M
ulti-S
pans W
ith S
ingle
Span B
ridge...S
ee b
elo
w7.
Insta
ll A
dditio
nal B
ridge O
penin
gs o
r S
pans
......
See b
elo
w
4.
Constr
uct B
ridge W
ingw
alls
(p. 49)
5.
Realign P
iers
and A
butm
ents
(p. 52)
6.
Repla
ce M
ulti-
Spans W
ith
Sin
gle
Span B
ridge (
p. 56)
7.
Insta
ll A
dd
itio
na
l B
rid
ge
O
penin
gs o
r S
pans (
p. 51)
Scour
(Pie
rs &
Abutm
ents
) 61
BRIDGES
D.1
In
cre
ase F
oo
tin
g D
ep
th
The d
epth
of
pie
r and a
butm
ent fo
otings s
hould
be e
xte
nded
belo
w the e
xpecte
d d
epth
of
str
eam
bed s
cour
or
to b
edro
ck.
The e
xpecte
d d
epth
of
scour
depends o
n the f
lood flo
w
velo
citie
s a
long the f
ooting a
nd the n
atu
re o
f th
e s
tream
bed
mate
rials
.
Eff
ecti
ven
ess:
•
Very
eff
ective, part
icula
rly w
hen f
lood flo
w v
elo
citie
s a
re
rela
tively
hig
h.
•
Consid
er
flo
w d
efl
ecto
rs, d
eb
ris d
efl
ecto
rs, or
rep
lacin
g
mu
lti-
sp
an
s w
ith
a s
ing
le s
pan
for
maxim
um
eff
ectiveness.
Lim
itati
on
s:
•
The d
epth
of
pie
r and a
butm
ent fo
otings m
ay b
e lim
ited b
y
str
eam
bed c
hara
cte
ristics.
•
Footings s
hould
be inspecte
d p
eriodic
ally
aft
er floods f
or
str
eam
bed e
rosio
n.
Co
nsid
era
tio
ns:
62
Scour
(Pie
rs &
Abutm
ents
)
D.2
In
sta
ll F
low
Defl
ecto
rs
Insta
ll “V
” shaped f
low
defl
ecto
rs o
n o
r im
media
tely
upstr
eam
from
the u
pstr
eam
sections o
f pie
rs a
nd a
butm
ents
to r
educe
flow
velo
citie
s a
nd p
rote
ct fo
otings f
rom
scouring. Insta
ll a
concre
te c
olla
r on low
er
section o
f pie
rs im
media
tely
above the
footing. A
lso e
xte
nd low
er
sections o
f abutm
ents
and the
win
gw
alls, if p
resent. T
his
will assis
t in
deflecting flo
od flo
ws
aw
ay f
rom
the p
iers
and a
butm
ents
, and w
ill e
limin
ate
str
eam
bed s
cour
alo
ng a
nd u
nder
them
.
Eff
ecti
ven
ess:
•
Flo
w d
eflecto
rs a
re v
ery
eff
ective, part
icula
rly f
or flood
flow
s w
ith h
igh v
elo
citie
s.
•
Pie
r colla
rs a
nd a
butm
ent sub-w
alls a
re m
odera
tely
eff
ective.
•
Pie
r colla
rs a
nd e
xte
nded a
butm
ent and w
ingw
alls m
ay
pro
vid
e a
dditio
nal pro
tection fro
m im
pact of
rocks a
nd
debris.
Lim
itati
on
s:
•
Flo
w d
eflecto
rs s
hould
be inspecte
d p
eriodic
ally
after
floods f
or
impact dam
age a
nd f
or
str
eam
bed e
rosio
n.
Co
nsid
era
tio
ns:
Scour
(Pie
rs &
Abutm
ents
) 63
BRIDGES
D.3
In
sta
ll S
em
icir
cu
lar
or
Tri
an
gu
lar
En
dn
oses
Sem
icircula
r or
tria
ngula
r en
dn
oses m
ay b
e insta
lled o
n the
upstr
eam
ends o
f th
e p
iers
to r
edirect flood flo
w v
elo
citie
s. P
ier
endnoses a
re a
pro
tection m
easure
, such a
s s
heet m
eta
l
attached to the p
ier
to r
edirect flow
. E
ndnoses s
hould
als
o b
e
desig
ned to b
oth
pre
vent debris a
ccum
ula
tion a
nd to p
rote
ct
the p
iers
and a
butm
ents
fro
m flo
ating d
ebris im
pact.
Eff
ecti
ven
ess:
•
Modera
tely
eff
ective w
here
flo
od flo
w v
elo
citie
s a
re
rela
tively
hig
h.
•
Less e
ffective w
hen f
lood flo
w v
elo
citie
s a
re r
ela
tively
low
.
Lim
itati
on
s:
•
Pie
rs s
hould
be inspecte
d p
eriodic
ally
after
floods f
or
impact dam
age a
nd f
or
str
eam
bed e
rosio
n.
•
Bridge d
ecks n
eed to b
e h
igh e
nough to p
ass f
loating
debris.
•
Any d
ebris that accum
ula
tes in the b
ridge o
penin
g n
eeds
to b
e r
em
oved d
uring the flo
od o
r im
media
tely
after
the
flood p
eak h
as p
assed.
Co
nsid
era
tio
ns:
64
Debris Im
pact
(Pie
rs &
Abutm
ents
)
E.
Deb
ris Im
pact
(Pie
rs &
Ab
utm
en
ts)
In
tro
du
cti
on
Pro
ble
m:
Dam
age to b
ridge p
iers
and a
butm
ents
resultin
g
from
the im
pact and a
ccum
ula
tion o
f debris.
Mit
igati
on
Ob
jecti
ve:
To p
revent fu
ture
debris d
am
age to
bridge p
iers
and a
butm
ents
by d
irecting d
ebris a
round a
nd
aw
ay f
rom
them
, by p
rovid
ing c
lear
passage o
f debris thro
ugh
the b
ridge o
penin
g, and b
y m
inim
izin
g a
mount of
debris
catc
hin
g o
n the s
tructu
ral ele
ments
of
the b
ridge.
Mit
igati
on m
easu
res t
o p
rote
ct
bri
dg
e p
iers
an
d a
butm
ents
fr
om
flo
od
dam
age c
au
sed
by d
eb
ris im
pact
inclu
de:
1.
Insta
ll D
ebris D
eflecto
rs............................................
p. 65
2.
Insta
ll B
atters
...........................................................p. 66
3.
Repla
ce W
ood P
ile B
ent P
ier
Str
uctu
re W
ith
S
olid
Concre
te C
olu
mn P
ier..................................
p. 67
4.
Constr
uct D
ebris C
atc
hm
ents
..................................
p. 68
5.
Insta
ll S
em
icircula
r or
Triangula
r E
ndnoses
.......S
ee b
elo
w
6.
Constr
uct B
ridge W
ingw
alls
..............................
See b
elo
w
7.
Realign P
iers
and A
butm
ents
............................
See b
elo
w
8.
Repla
ce M
ulti-S
pans W
ith S
ingle
Span B
ridge...S
ee b
elo
w
7.
Realign P
iers
and
Abutm
ents
(p. 52)
5.
Insta
ll E
nd
no
se
s (
p.
63
) 6
. C
on
str
uct
Bri
dg
e W
ing
wa
lls
(p
. 49)
8.
Repla
ce M
ulti-
Spans W
ith
Sin
gle
Span B
ridge (
p. 56)
Debris Im
pact
(Pie
rs &
Abutm
ents
) 65
BRIDGES
E.1
In
sta
ll D
eb
ris D
efl
ecto
rs
Deb
ris d
efl
ecto
rs o
r d
eb
ris f
ins s
hould
be insta
lled o
n the
upstr
eam
ends o
f pie
rs a
nd a
butm
ents
and a
ngle
d s
o a
s to
direct floating d
ebris into
are
as o
f hig
h flo
od flo
w v
elo
citie
s. T
he
debris d
eflecto
rs a
nd fin
s s
hould
be “
V”
shaped a
nd e
xte
nd
upstr
eam
a s
uff
icie
nt dis
tance to o
rient th
e flo
ating d
ebris f
or
easy p
assage thro
ugh the b
ridge. D
ebris d
eflecto
rs o
r fins
should
be d
esig
ned to b
oth
pre
vent debris a
ccum
ula
tion a
nd to
pro
tect th
e p
iers
and a
butm
ents
fro
m flo
ating d
ebris im
pact.
Eff
ecti
ven
ess:
•
Very
eff
ective in a
reas that have s
ignific
ant debris loadin
g
in the u
pstr
eam
dra
inage a
nd flo
od flo
w v
elo
citie
s a
re h
igh.
•
Less e
ffective w
hen f
lood flo
w v
elo
citie
s a
re low
. L
imit
ati
on
s:
•
Bridge d
ecks n
eed to b
e h
igh e
nough to p
ass f
loating
debris.
Co
nsid
era
tio
ns:
66
Debris Im
pact
(Pie
rs &
Abutm
ents
)
E.2
In
sta
ll B
att
ers
Insta
ll b
att
ers
(ste
el pla
tes)
on the u
pstr
eam
ends o
f concre
te
pie
rs w
ith s
em
icircula
r or
“V”
shaped e
nd
no
ses, or
on
win
gw
all e
nds a
nd w
ingw
all/a
butm
ent ju
nctions to p
rote
ct
them
fro
m the im
pact of floating d
ebris.
Eff
ecti
ven
ess:
•
Very
eff
ective in p
rote
cting p
iers
fro
m d
ebris im
pact
dam
age.
Co
nsid
era
tio
ns:
Debris Im
pact
(Pie
rs &
Abutm
ents
) 67
BRIDGES
E.3
R
ep
lace W
oo
d P
ile B
en
t P
ier
Str
uctu
re W
ith
S
olid
Co
ncre
te C
olu
mn
Pie
r
Repla
ce a
pie
r constr
ucte
d w
ith w
ooden p
iling w
ith a
solid
concre
te c
olu
mn p
ier.
T
his
measure
will pre
vent debris f
rom
becom
ing c
aught and a
ccum
ula
ting in the p
ile b
ent pie
r configura
tion, and w
ill p
rote
ct th
e p
ier
from
debris im
pact.
Eff
ecti
ven
ess:
•
Very
eff
ective in a
reas that have s
ignific
ant debris loadin
g
in the u
pstr
eam
dra
inage.
•
Eff
ectiveness incre
ases w
ith d
eb
ris d
efl
ecto
rs o
r d
eb
ris
fin
s, sem
icircula
r or
“V”
shaped e
nd
no
ses, and/o
r b
att
ers
.
Co
nsid
era
tio
ns:
68
Debris Im
pact
(Pie
rs &
Abutm
ents
)
E.4
C
on
str
uct
Deb
ris C
atc
hm
en
ts
Debris c
atc
hm
ent str
uctu
res, such a
s d
eb
ris b
arr
iers
(tr
ash
racks)
or
low
heig
ht dam
s, m
ay b
e c
onstr
ucte
d o
n s
mall
trib
uta
ry s
tream
s u
pstr
eam
fro
m the b
ridge. T
he c
atc
hm
ent
str
uctu
res s
hould
be d
esig
ned to tra
p d
ebris w
hile p
assin
g the
str
eam
flo
w.
If
a d
ebris c
atc
hm
ent
dam
is c
onstr
ucte
d, it m
ust
inclu
de a
n e
merg
ency s
pill
way.
Eff
ecti
ven
ess:
•
Eff
ective w
here
the s
ourc
e o
f debris is f
rom
hig
hly
vegeta
ted d
rain
age a
reas u
pstr
eam
fro
m the b
ridge a
nd
where
there
are
adequate
sto
rage a
reas u
pstr
eam
fro
m the
catc
hm
ent
str
uctu
res.
•
Less e
ffective o
n larg
er
trib
uta
ry s
tream
s.
Lim
itati
on
s:
•
Any d
ebris that accum
ula
tes u
pstr
eam
fro
m the c
atc
hm
ent
str
uctu
res n
eeds to b
e r
em
oved d
uring the flo
od o
r
imm
edia
tely
after
the flo
od p
eak h
as p
assed.
Co
nsid
era
tio
ns:
Build
ings
69
BUILDINGS BUILDINGS
BU
ILD
ING
S
Dam
age to b
uild
ings f
rom
flo
odin
g is c
aused b
y thre
e facto
rs:
satu
ration, velo
city, and h
ydro
sta
tic f
orc
es. A
ll re
trofits
of
buildin
g s
tructu
res m
ust allo
w the a
ccom
modation o
f
hydro
sta
tic f
orc
es.
Actions taken d
uring r
esto
ration c
an h
elp
build
ings to r
esis
t
flota
tion, collapse, and late
ral m
ovem
ent during a
flo
od e
vent.
The u
se o
f seala
nts
to r
educe s
eepage, in
sta
llation o
f pum
ps
and/o
r check v
alv
es t
o r
educe inte
rior
wate
r le
vels
, and the
ele
vation o
f buildin
g c
om
ponents
can a
ll pro
tect build
ings a
nd
their c
onte
nts
to v
ary
ing d
egre
es.
Assessin
g t
he C
au
ses o
f B
uild
ing
Dam
ag
e
Wate
r satu
ration d
am
age c
an inclu
de:
•
Inundation o
f build
ings a
nd their c
onte
nts
, or
•
Slo
pe f
ailu
res a
nd insta
bili
ty.
Dam
age fro
m h
igh v
elo
city flo
ws m
ight in
clu
de:
•
Destr
uction o
f build
ings a
nd o
ther
str
uctu
res;
•
Ero
sio
n/s
couring o
f em
bankm
ents
, slo
pes, le
vees, and
foundations; or
70
Build
ings
•
Dra
inage f
acili
ty d
am
age (
i.e., d
islo
dged o
r m
oved
culv
ert
s).
Dam
age d
ue to h
ydro
sta
tic forc
es m
ight in
clu
de:
•
Destr
uction o
f build
ings, fo
undations, and o
ther
str
uctu
res,
or
•
Soil
ero
sio
n a
nd/o
r subsoil m
ovem
ent.
In a
dditio
n to d
irect dam
age, colla
tera
l dam
age m
ight in
clu
de:
•
Conta
min
ation o
f w
ells
and o
ther
facili
ties inundate
d b
y
sew
age, hazard
ous m
ate
rials
, and o
ther
conta
min
ants
in
the flo
odw
ate
r;
•
Debris f
rom
dam
aged h
om
es, vegeta
tion, orp
haned d
rum
s,
etc
., c
ausin
g d
ebris d
am
s o
r exacerb
ating v
elo
city d
am
age
as p
roje
ctile
s im
pact str
uctu
res; or
•
Silt
ation o
f ditches, ro
adw
ays, dra
inage f
acili
ties, etc
.
This
section d
iscusses m
itig
ation m
easure
s for
com
mon flo
od d
am
ages to b
uild
ings, w
hic
h a
re
caused b
y:
A
. In
undation
.................................p
. 71
B.
Hig
h V
elo
city F
low
s....................
p. 77
Inundation
71
BUILDINGS
A.
In
un
dati
on
Intr
od
ucti
on
Pro
ble
m:
Dam
age to b
uild
ings, equip
ment, a
nd o
ther
com
ponents
are
most com
monly
caused b
y f
loodw
ate
r
inundation. F
loodw
ate
r in
undate
s the b
uild
ing, satu
rating the
buildin
g m
ate
rials
and its
conte
nts
. T
he flo
odw
ate
r is
usually
conta
min
ate
d b
y a
num
ber
of
substa
nces, such a
s s
ew
age a
nd
oth
er
hazard
ous m
ate
rials
.
Mit
igati
on
Ob
jecti
ve:
The m
ost eff
ective m
itig
ation is f
ully
pro
tecting the b
uild
ing f
acili
ty fro
m flo
odw
ate
rs, such a
s
thro
ugh r
elo
cating o
r ele
vating the b
uild
ing.
Mit
igati
on m
easu
res t
o p
rote
ct
buildin
gs f
rom
flo
od
dam
ag
e c
au
sed
by f
loo
dw
ate
r in
un
dati
on
in
clu
de:
1.
Relo
cate
Build
ing
...........................................p. 72
2.
Ele
vate
Build
ing
.............................................p. 73
3.
Wet Flo
od-P
roof B
uild
ing................................
p. 74
4.
Dry
Flo
od-P
roof B
uild
ing
................................
p. 75
5.
Insta
ll B
ackflow
Devic
es o
n S
ew
er
Dra
ins.......p. 76
72
Inundation
A.1
R
elo
cate
Bu
ild
ing
Relo
cate
the e
ntire
build
ing o
ut of
the a
rea s
ubje
ct to
flo
odin
g
and to a
safe
are
a, outs
ide the 1
00-y
ear
floodpla
in o
r a 5
00-
year
floodpla
in if
a c
ritical fa
cili
ty.
Eff
ecti
ven
ess:
•
The m
ost eff
ective m
itig
ation p
ossib
le, as the s
tructu
re w
ill
no longer
be s
ubje
ct to
flo
odin
g.
Lim
itati
on
s:
•
Appro
priate
receiv
ing s
ite m
ust be o
bta
ined.
Co
nsid
era
tio
ns:
Inundation
73
BUILDINGS
A.2
E
levate
Bu
ild
ing
Ele
vate
the b
uild
ing f
acili
ty o
n fill
or
a s
tructu
re a
bove the
desig
n f
lood e
levation o
r above the 1
00-y
ear
flood. B
uild
ings
can b
e e
levate
d o
n p
erim
ete
r w
alls, pie
rs, pile
s, or
fill.
If w
alls
are
used to e
levate
, th
ey m
ust be v
ente
d to a
ccom
modate
hydro
sta
tic f
orc
es.
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Are
a u
nder
the b
uild
ing (
if b
uilt
on p
iers
) m
ay b
e u
sed for
sto
rage, park
ing, or
access.
Lim
itati
on
s:
•
Build
ing a
ccess w
ill be im
peded d
uring flo
od e
vents
.
•
Fill
should
be c
om
pacte
d a
nd p
rote
cte
d fro
m e
rosio
n.
•
May r
equire a
dditio
nal m
itig
ation c
onsid
era
tions f
or
are
as
of
heavy d
ebris loadin
g.
Co
nsid
era
tio
ns:
74
Inundation
A.3
W
et
Flo
od
-Pro
of
Bu
ild
ing
Allo
w f
loodw
ate
r to
inundate
sele
cte
d p
ort
ions o
f th
e f
acili
ty in
are
as that are
not vuln
era
ble
to d
am
age f
rom
flo
odw
ate
r
satu
ration b
y u
sin
g w
ate
r-re
sis
tant constr
uction m
eth
ods,
desig
nin
g o
penin
gs f
or
flood w
ate
r passage, and e
levati
ng
vuln
era
ble
syste
ms, such a
s e
lectr
ical equip
ment
above the
desig
n f
lood e
levation. D
esig
n s
hould
inclu
de the c
onstr
uction
of
openin
gs to e
qualiz
e h
ydro
sta
tic p
ressure
, and c
onstr
uction
of
the w
alls to r
esis
t hydro
sta
tic p
ressure
.
Eff
ecti
ven
ess:
•
Very
Eff
ective.
Lim
itati
on
s:
•
Port
ions o
f buildin
g v
uln
era
ble
to flo
odw
ate
r w
ill be
inaccessib
le d
uring flo
od e
vent.
•
Not pra
ctical in
are
as o
f hig
h v
elo
city o
r debris im
pact.
•
Advance w
arn
ing n
eeded s
o that sto
red m
ate
rials
can b
e
rem
oved.
Co
nsid
era
tio
ns:
Inundation
75
BUILDINGS
A.4
D
ry F
loo
d-P
roo
f B
uild
ing
Seal th
e b
uild
ing s
o that floodw
ate
r does n
ot ente
r.
Com
ponents
of
dry
flo
od p
roofing m
ay inclu
de: 1
) C
onstr
ucting
exte
rior floodw
alls; 2
) C
onstr
ucting a
n im
perm
eable
berm
aro
und the f
acili
ty; and/o
r 3
) S
ealin
g the b
uild
ing w
ith w
ate
r-pro
of
mate
rial.
The b
uoyancy o
f th
e b
uild
ing m
ust be c
onsid
ere
d. H
ydro
sta
tic
and h
ydro
dynam
ic f
orc
es m
ust be taken into
account.
Eff
ecti
ven
ess:
•
Very
eff
ective in p
reventing d
am
age to b
uild
ing c
onte
nts
.
•
Berm
s a
nd flo
odw
alls c
an b
e inte
gra
ted into
landscapin
g.
Lim
itati
on
s:
•
May n
ot be p
ractical in
are
as o
f hig
h v
elo
city flo
ws o
r
heavy d
ebris loadin
g.
•
May r
equire a
ccess g
ate
s b
e m
ain
tain
ed a
nd c
losed p
rior
to flo
odw
ate
rs r
eachin
g s
tructu
re.
•
Site s
hould
be d
esig
ned to r
esis
t th
e f
orc
es o
f floodw
ate
rs
and a
ccom
modate
on-s
ite d
rain
age n
eeds.
•
Slo
pes e
xposed to m
odera
te o
r hig
h v
elo
city flo
ws s
hould
be a
rmore
d.
Co
nsid
era
tio
ns:
76
Inundation
A.5
In
sta
ll B
ackfl
ow
Devic
es o
n S
ew
er
Dra
ins
Insta
ll backflow
devic
es, in
clu
din
g o
ne-w
ay a
nd o
rdin
ary
valv
es,
on s
ew
er
lines a
nd f
loor
dra
ins. T
hese d
evic
es p
revent
sew
age a
nd/o
r sto
rmw
ate
r fr
om
bein
g f
orc
ed b
ack into
the
facili
ty.
E
ffecti
ven
ess:
•
Very
eff
ective, part
icula
rly for
buildin
gs o
uts
ide o
f th
e
floodpla
in.
Lim
itati
on
s:
•
One-w
ay v
alv
es m
ay b
ecom
e b
locked b
y d
ebris a
nd f
ail
to
clo
se.
•
Gate
valv
es r
equire that th
e v
alv
e b
e m
anually
clo
sed p
rior
to inundation.
Co
nsid
era
tio
ns:
Hig
h V
elo
city F
low
s
77
BUILDINGS
B.
Hig
h V
elo
cit
y F
low
s
Intr
od
ucti
on
Pro
ble
m:
Hig
h v
elo
city flo
ws c
an s
cour
the s
oil fro
m u
nder
and a
round f
ootings, th
reate
n the b
uild
ing’s
str
uctu
ral in
tegrity
,
and e
ven k
nock b
uild
ings o
ff o
f th
eir f
oundations.
Mit
igati
on
Ob
jecti
ve:
Pro
tect build
ing facili
ties f
rom
dam
age
due to e
rosio
n c
aused b
y h
igh v
elo
city flo
od flo
ws.
Mit
igati
on m
easu
res t
o p
rote
ct
buildin
gs f
rom
flo
od
dam
ag
e c
au
sed
by h
igh v
elo
cit
y f
low
s in
clu
de:
1.
Constr
uct P
iling o
r N
ew
Spre
ad F
ooting..........
p. 78
2.
Repla
ce F
ooting M
ate
rials
..............................
p. 79
78
Hig
h V
elo
city F
low
s
B.1
C
on
str
uct
Pilin
g o
r N
ew
Sp
read
Fo
oti
ng
Build
ing f
oundations c
an b
e u
nderm
ined d
ue to h
igh v
elo
city
flow
s that scour
aw
ay the s
oils s
upport
ing the f
oundation. B
y
constr
ucting a
pili
ng o
r new
spre
ad f
ooting, th
e f
oundation is
support
ed, th
ere
by p
reventing f
ailu
re in s
ubsequent floodin
g.
Eff
ecti
ven
ess:
•
Very
eff
ective.
Lim
itati
on
s:
•
Spre
ad f
ootings s
hould
not be u
sed in a
coasta
l environm
ent.
•
Are
a m
ay b
e inaccessib
le to p
ile d
rivin
g e
quip
ment.
•
Pile
drivin
g m
ay c
ause d
am
age to a
dja
cent fa
cili
ties.
Co
nsid
era
tio
ns:
Hig
h V
elo
city F
low
s
79
BUILDINGS
B.2
R
ep
lace F
oo
tin
g M
ate
rials
To b
etter
secure
footings a
nd the s
urr
oundin
g m
ate
rial, r
epla
ce
lost fo
oting m
ate
rial of
soil
or
gra
vel w
ith c
oncre
te o
r gro
ute
d
gra
nula
r fill.
S
oil
consolidation a
nd s
ettlin
g c
aused b
y
inundation, or
ero
sio
n o
f th
e s
oil
due to flo
w p
ast th
e f
ooting,
can o
ften u
nderm
ine the s
oil
beneath
the footing, w
hic
h c
reate
s
a s
pace b
etw
een the b
ottom
of
the f
ooting a
nd the top o
f th
e
soil b
eneath
the footing.
Eff
ecti
ven
ess:
•
Very
eff
ective.
Lim
itati
on
s:
•
May n
ot
be e
ffective if fu
ture
ero
sio
n c
annot be c
ontr
olle
d,
or,
if
in the c
ase o
f in
undation, soil
consolidation is n
ot
com
ple
te.
80
Utilit
ies
UT
ILIT
IES
U
tilit
ies w
hic
h a
re f
requently d
am
aged in flo
od e
vents
inclu
de
ele
ctr
ical pow
er,
wate
r, s
ew
er
and g
as d
istr
ibution, colle
ction
and tra
nsm
issio
n s
yste
ms (
i.e., d
istr
ibution lin
es),
as w
ell
as
housin
g f
or
utilit
y o
pera
tions o
r com
ponents
(ele
ctr
ical
substa
tions).
F
lood d
am
age to these u
tilit
ies is c
aused b
y h
igh
velo
city flo
ws that cause s
oil e
rosio
n, as w
ell a
s c
onsolid
ation
and s
ettling o
f soils
or
slides. T
he m
ost appro
priate
mitig
ation
measure
is d
ependent upon the type o
f flood d
am
age incurr
ed
by e
ach u
tilit
y s
yste
m.
This
section d
iscusses m
itig
ation m
easure
s to
pro
tect various u
tilit
ies fro
m c
om
mon flo
od
dam
ages that are
caused b
y:
A. H
igh V
elo
city F
low
s................................p. 81
B. S
oil
Settle
ment.
......................................p. 85
Hig
h V
elo
city F
low
s
81
UTILITIES
A.
Hig
h V
elo
cit
y F
low
s
Intr
od
ucti
on
Pro
ble
m:
Hig
h v
elo
city flo
ws c
an s
cour
and e
rode s
oils, w
hic
h
underm
ine a
utilit
y’s
support
.
Mit
igati
on
Ob
jecti
ve:
Pro
tect th
e u
tilit
y f
acili
ty fro
m h
igh
velo
city flo
ws that can e
rode s
oils a
way f
rom
the u
tilit
y, le
avin
g
it v
uln
era
ble
to flo
od d
am
age.
Mit
igati
on m
easu
res t
o p
rote
ct
utiliti
es f
rom
flo
od
d
am
ag
e c
au
sed
by h
igh v
elo
cit
y f
low
s in
clu
de:
1.
Relo
cate
Utilit
y........................................
p. 82
2.
Ele
vate
Utilit
y .........................................p
. 83
3.
Encase the U
tilit
y.....................................p
. 84
82
Hig
h V
elo
city F
low
s
A.1
R
elo
cate
Uti
lity
Relo
cate
the u
tilit
y to a
safe
location a
way f
rom
the h
azard
.
Als
o c
onsid
er
bury
ing the u
tilit
y.
Eff
ecti
ven
ess:
•
Very
eff
ective.
Lim
itati
on
s:
•
New
location s
hould
be f
ree o
f oth
er
hazard
s, such a
s
exposure
to h
igh w
inds a
nd u
nsta
ble
slo
pes.
Co
nsid
era
tio
ns:
Hig
h V
elo
city F
low
s
83
UTILITIES
A.2
E
levate
Uti
lity
Ele
vate
and/o
r seal vuln
era
ble
com
ponents
of
the u
tilit
y
syste
m, in
clu
din
g e
lectr
ical com
ponents
and a
ccess p
oin
ts,
above the d
esig
n flo
od e
levation.
Eff
ecti
ven
ess:
•
Very
eff
ective in p
reventing flo
odw
ate
rs f
rom
ente
ring the
syste
ms,
such a
s:
ele
ctr
ical contr
ol panels
, tr
ansfo
rmers
and s
witches, and u
tilit
y a
ccess p
oin
ts.
Lim
itati
on
s:
•
May r
equire s
hutd
ow
n o
f th
e f
acili
ty.
•
May inhib
it m
ain
tenance a
ccess.
•
May n
ot be feasib
le in a
reas o
f deep flo
odin
g o
r in
urb
aniz
ed a
reas.
Co
nsid
era
tio
ns:
84
Hig
h V
elo
city F
low
s
A.3
E
ncase t
he U
tility
Encase u
tilit
y lin
es, such a
s e
lectr
ical, c
om
munic
ation, gas a
nd
wate
r tr
ansm
issio
n a
nd d
istr
ibution lin
es in c
oncre
te a
nd/o
r
conduit to p
rote
ct th
em
fro
m the d
am
agin
g e
ffects
of
floodw
ate
rs, in
clu
din
g s
couring.
Eff
ecti
ven
ess:
•
Very
eff
ective.
Lim
itati
on
s:
•
May n
ot be feasib
le in a
reas w
ith fin
e s
oils s
ubje
ct to
hig
h
velo
city flo
ws, or
where
exte
nsiv
e e
rosio
n is c
om
mon.
•
Main
tenance a
ccess m
ay b
e s
ignific
antly r
estr
icte
d.
•
Utilit
y lin
es c
ould
be v
uln
era
ble
to e
art
hquakes, slides, or
oth
er
eart
h m
ovem
ent events
.
Co
nsid
era
tio
ns:
Soil
Sett
lem
ent
85
UTILITIES
B.
So
il S
ett
lem
en
t In
tro
du
cti
on
Pro
ble
m:
Consolidation a
nd s
ettle
ment of
soils
that dam
age a
utilit
y f
acili
ty d
uring a
flo
od e
vent.
Mit
igati
on
Ob
jecti
ve:
Pro
tect th
e u
tilit
y f
rom
soil
settle
ment,
inclu
din
g s
lides, fr
om
futu
re d
am
age.
Mit
igati
on m
easu
res t
o p
rote
ct
utiliti
es f
rom
flo
od
d
am
ag
e c
au
sed
by s
oil s
ett
lem
ent
inclu
de:
1.
Lin
e D
am
aged P
ipes
...................................p
. 86
2.
Bury
the U
tilit
y.............................................p
. 87
86
Soil
Sett
lem
ent
B.1
L
ine D
am
ag
ed
Pip
es
Pro
vid
e a
lin
ing
insid
e d
am
aged s
torm
and s
anitary
sew
er
lines to p
revent in
filtra
tion a
nd/o
r exfiltra
tion a
nd a
ssocia
ted
ero
sio
n a
nd s
ettle
ment. Lin
ing w
ill a
lso p
revent in
cre
ased
flow
s d
ue to infiltra
tion o
f excessiv
e g
roundw
ate
r th
at could
overw
helm
tre
atm
ent pla
nts
or
oth
er fa
cili
ties d
uring p
eriods o
f
wet w
eath
er.
S
evera
l linin
g techniq
ues a
re a
vailable
. T
he
most com
mon techniq
ues a
re s
lip lin
ing a
nd invers
ion lin
ing.
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Will
pre
vent in
filtra
tion/e
xfiltra
tion o
f floodw
ate
rs.
Lim
itati
on
s:
•
Lin
ing m
ay n
ot be u
sefu
l if s
yste
m c
om
ponents
are
too f
ar
out
of
alignm
ent.
•
May n
ot be feasib
le f
or
sm
all
dia
mete
r pip
es.
Co
nsid
era
tio
ns:
Soil
Sett
lem
ent
87
UTILITIES
B.2
B
ury
th
e U
tility
Pla
ce a
bove g
round u
tilit
ies, such a
s tra
nsm
issio
n a
nd
dis
trib
ution lin
es f
or
ele
ctr
icity a
nd c
om
munic
ation lin
es,
underg
round to a
void
dam
age f
rom
flo
odw
ate
rs, debris, and
from
soil
settle
ment.
Eff
ecti
ven
ess:
•
Very
eff
ective.
Lim
itati
on
s:
•
Main
tenance a
ccess m
ay b
e r
estr
icte
d.
•
Buried u
tilit
y lin
es c
ould
be v
uln
era
ble
to e
art
hquakes,
slides, or
oth
er
eart
h m
ovem
ent events
.
Co
nsid
era
tio
ns:
88
Irrigation F
acili
ties
IRR
IGA
TIO
N F
AC
ILIT
IES
T
ypic
ally
, irrigation s
yste
ms a
re m
ade u
p o
f severa
l
com
ponents
, in
clu
din
g: inta
ke, conveyance,
and d
istr
ibution
syste
ms. D
ue to the n
atu
re a
nd g
enera
l lo
cation o
f th
ese
facili
ties, all
may b
e a
t risk to d
am
age fro
m flo
odin
g. Irr
igation
facili
ties a
re m
ost vuln
era
ble
to h
igh v
elo
city flo
ws.
This
section d
iscusses m
itig
ation m
easure
s for
com
mon flo
od d
am
ages to irr
igation facili
ties, w
hic
h
are
caused b
y:
A. H
igh V
elo
city F
low
s................................p. 89
Hig
h V
elo
city F
low
s
89
IRRIGATION FACILITIES
A.
Hig
h V
elo
cit
y F
low
s
Intr
od
ucti
on
Pro
ble
m:
Hig
h v
elo
city flo
ws im
pact an irr
igation f
acili
ty
causin
g e
rosio
n that either
underm
ines s
upport
or
directly
dam
ages the f
acili
ty.
Mit
igati
on
Ob
jecti
ve:
To p
revent dam
age b
y r
educin
g h
igh
velo
city flo
ws that w
ill re
duce e
rosio
n.
Mit
igati
on m
easu
res f
or
com
mo
n f
loo
d d
am
ag
es t
o
irri
gati
on
facilit
ies c
au
sed b
y h
igh
velo
cit
y f
loo
d
flo
ws inclu
de:
1.
Insta
ll an Invert
ed S
iphon
...............................p. 90
2.
Lin
e E
art
hen C
anals
......................................p. 91
3.
Pla
ce R
ipra
p .
........................................
See b
elo
w4.
Insta
ll F
low
Div
ert
ers
.............................
See b
elo
w
3.
Pla
ce R
ipra
p (
p. 13)
4.
In
sta
ll F
low
Div
ert
ers
(p
. 4
4)
90
Hig
h V
elo
city F
low
s
A.1
In
sta
ll a
n In
vert
ed
Sip
ho
n
Constr
uct an invert
ed s
iphon to tra
nsport
irr
igation w
ate
r under
a s
tream
or
canal in
ord
er
to p
revent floodw
ate
rs a
nd d
ebris
from
dam
agin
g the a
t-gra
de flu
me o
r culv
ert
cro
ssin
g.
Eff
ecti
ven
ess:
•
Very
eff
ective in p
reventing d
ebris im
pact dam
age a
nd
floodw
ate
r causin
g o
verf
ill to irr
igation facili
ties.
Lim
itati
on
s:
•
Depth
of
str
eam
and g
eolo
gy m
ay p
reclu
de this
option.
Co
nsid
era
tio
ns:
Hig
h V
elo
city F
low
s
91
IRRIGATION FACILITIES
A.2
L
ine E
art
hen
Can
als
Aft
er
repairin
g e
rosio
n-d
am
aged irr
igation e
art
hen c
anals
, apply
cem
ent concre
te to the c
anal w
alls
. L
inin
g is
accom
plis
hed b
y p
um
pin
g a
nd s
pra
yin
g the m
ixtu
re o
ver
rein
forc
ing w
ire in a
reas that are
exposed to h
ighly
ero
siv
e
flow
s. (
Shotc
rete
and G
unite a
re e
xam
ple
s).
T
he c
oncre
te
and r
ein
forc
ing w
ire s
hould
be a
pplie
d f
rom
concre
te s
tructu
re
to c
oncre
te s
tructu
re, or
from
an u
pstr
eam
cut-
off
wall
insta
lled
to p
revent flow
s f
rom
scouring u
nder
the u
pstr
eam
edge o
f th
e
insta
llation.
Eff
ecti
ven
ess:
•
Very
eff
ective.
•
Lin
ing lim
its s
cour
dam
age to c
anal w
alls.
•
Lin
ing a
lso lim
its c
anal w
ate
r lo
ss f
rom
perc
ola
tion thro
ugh
canal soils.
Lim
itati
on
s:
•
Aquifers
or
wetlands m
ay b
e im
pacte
d d
ue to loss o
f
gro
undw
ate
r perc
ola
tion.
Co
nsid
era
tio
ns:
92
Mis
cella
neous F
acili
ties
MIS
CE
LL
AN
EO
US
FA
CIL
ITIE
S
There
are
a n
um
ber
of m
iscella
neous f
acili
ties, such a
s f
ences,
buoyant fixtu
res, and b
oat ra
mps, w
hic
h s
usta
in flo
od d
am
age
due to inundation o
r ero
sio
n c
aused f
rom
hig
h v
elo
city flo
od
flow
s. T
his
section w
ill d
iscuss m
itig
ation m
easure
s d
esig
ned
to p
rote
ct th
ese m
iscella
neous f
acili
ties d
uring flo
od e
vents
that
will re
duce o
r pre
vent fu
ture
dam
age.
This
section d
iscusses m
itig
ation m
easure
s for
com
mon flo
od d
am
ages to b
y v
arious facilities,
whic
h a
re c
aused b
y:
A.
Inundation
............................................p. 93
B.
Hig
h V
elo
city F
low
s...........................p. 96
Inundation
93
MISCELLANEOUS FACILITIES
A.
In
un
dati
on
Intr
od
ucti
on
Pro
ble
m:
Dam
age to m
iscella
neous f
acili
ties, such a
s f
ences
and b
uoyant fixtu
res a
re c
om
monly
caused b
y flo
odw
ate
r
inundation. In a
dditio
n to s
atu
ration d
am
age, th
e f
acili
ty c
an b
e
dam
aged o
r destr
oyed b
y d
ebris that is
carr
ied thro
ugh the
floodw
ate
rs.
Mit
igati
on
Ob
jecti
ve:
To p
rote
ct m
iscella
neous f
acili
ties f
rom
dam
age d
ue to flo
odw
ate
r in
undation.
M
itig
ati
on m
easu
res t
o p
rote
ct
vari
ou
s f
acilit
ies
from
flo
od
dam
age c
au
sed
by f
loo
dw
ate
r in
un
dati
on in
clu
de:
1.
Str
ength
en F
encin
g....................................
p. 94
2.
Anchor
and T
ie-D
ow
n B
uoyant F
acili
ties
.....p. 95
94
Inundation
A.1
S
tren
gth
en
Fen
cin
g
Str
ength
en f
ences d
am
aged b
y low
to m
odera
te v
elo
city flo
ws
by: 1
) U
sin
g h
eavie
r gauge m
ate
rials
; 2)
Addin
g b
ack b
racin
g
to the lin
e p
osts
; and/o
r 3
) In
sta
lling inte
rmedia
te lin
e p
osts
.
Eff
ecti
ven
ess:
•
Fence s
trength
enin
g is g
enera
lly e
ffective in a
reas that are
flooded b
y low
velo
city flo
ws w
ith m
inim
al debris loadin
g.
•
Additio
nal m
easure
s, such a
s p
rovid
ing s
acrificia
l fe
nce
sections to a
llow
flo
odw
ate
rs to p
ass, m
ay b
e r
equired to
incre
ase the e
ffectiveness d
uring tim
es o
f m
odera
te flo
w.
Lim
itati
on
s:
•
Fence s
trength
enin
g h
as lim
ited e
ffectiveness in a
reas o
f
modera
te to h
eavy v
elo
city a
nd d
ebris loadin
g.
•
Fence s
trength
enin
g c
ould
, in
som
e e
xtr
em
e c
ases, cause
a d
am
min
g e
ffect, r
ais
ing u
pstr
eam
wate
r le
vels
.
Co
nsid
era
tio
ns:
Inundation
95
MISCELLANEOUS FACILITIES
A.2
A
nch
or
& T
ie-D
ow
n B
uo
yan
t F
acilit
ies
Pro
vid
e a
nchors
and tie
-dow
ns f
or
fuel ta
nks a
nd o
ther
buoyant
facili
ties, such a
s m
obile
off
ices, sto
rage b
uildin
gs, and
pla
ygro
und e
quip
ment to
keep them
fro
m b
ein
g w
ashed a
way
during flo
od e
vents
. E
ffecti
ven
ess:
•
Anchors
and tie
-dow
ns a
re v
ery
eff
ective in k
eepin
g s
mall,
buoyant fa
cili
ties f
rom
bein
g w
ashed a
way.
•
Als
o p
revents
obje
ct fr
om
becom
ing a
debris p
roje
ctile
or
a
sourc
e o
f conta
min
ation.
Lim
itati
on
s:
•
May n
ot
be e
ffective in a
reas o
f m
odera
te to h
igh v
elo
city
flow
s w
ith m
odera
te to h
eavy d
ebris loadin
g. In these
insta
nces, re
locati
on
, ele
vati
on
, o
r oth
er
mitig
ation
altern
atives s
hould
be c
onsid
ere
d.
96
Hig
h V
elo
city F
low
s
B.
Hig
h V
elo
cit
y F
low
s
Intr
od
ucti
on
Pro
ble
m:
Dam
age to m
iscella
neous f
acili
ties, such a
s f
ences
and b
oat ra
mps, can b
e d
ue to h
igh v
elo
city flo
ws that ero
de
support
ing m
ate
rials
, or
carr
y d
ebris that im
pacts
and then
dam
ages the f
acili
ty.
Mit
igati
on
Ob
jecti
ve:
To p
rote
ct m
iscella
neous f
acili
ties f
rom
futu
re d
am
age d
ue to h
igh v
elo
city flo
ws.
Mit
igati
on m
easu
res t
o p
rote
ct
vari
ou
s f
acilit
ies s
uch
as b
oat
ram
ps f
rom
flo
od d
am
ag
e c
au
sed b
y h
igh
velo
cit
y f
low
s inclu
de:
1.
Insta
ll S
acrificia
l F
ence S
ections
.....................p
. 97
2.
Repla
ce B
oat R
am
p M
ate
rial W
ith C
oncre
te....
p. 98
3.
Constr
uct a J
etty to P
rote
ct B
oat R
am
p...........p
. 99
Hig
h V
elo
city F
low
s
97
MISCELLANEOUS FACILITIES
B.1
In
sta
ll S
acri
ficia
l F
en
ce S
ecti
on
s
Insta
ll sacrificia
l (b
reak-a
way)
fence s
ections in b
oundary
or
oth
er
fences (
i.e. fe
nce s
ections d
esig
ned to f
ail
at
str
ate
gic
locations)
to a
llow
flo
odw
ate
rs to p
ass, re
lievin
g p
ressure
on
adja
cent fe
nce s
ections, pre
venting m
ajo
r dam
age to the
fence.
Sacrificia
l sections s
hould
be d
esig
ned s
o that th
e f
aile
d
sections d
o n
ot becom
e loose in the flo
odw
ate
rs a
nd c
reate
additio
nal debris o
r cause c
ollate
ral dam
age.
Eff
ecti
ven
ess:
•
Allo
ws the p
assage o
f hig
h v
elo
city flo
ws a
s w
ell a
s d
ebris
in r
estr
icte
d d
rain
ages.
Lim
itati
on
s:
•
Sacrificia
l fe
nce s
ections m
ay r
equire r
epairs a
fter
flood
events
.
•
May n
ot
be e
ffective in p
reventing d
am
age in s
ituations
where
flo
odw
ate
r velo
citie
s c
over
a larg
er
are
a than w
ithin
the tra
ditio
nal flood c
hannel.
Co
nsid
era
tio
ns:
98
Hig
h V
elo
city F
low
s
B.2
R
ep
lace B
oat
Ram
p M
ate
rial W
ith
Co
ncre
te
When b
oat ra
mps a
re d
am
aged b
y e
rosio
n, re
pla
ce the e
roded
gra
vel boat ra
mp o
r th
e f
oundation m
ate
rial ero
ded f
rom
under
a c
oncre
te b
oat ra
mp w
ith c
oncre
te.
Eff
ecti
ven
ess:
•
Repla
cem
ent of
ero
ded m
ate
rial w
ith c
oncre
te m
ay b
e v
ery
eff
ective in a
reas o
f in
frequent, m
inor
ero
sio
n d
am
age.
•
Oth
er
measure
s, such a
s r
ipra
p o
r oth
er
slo
pe p
rote
ction
techniq
ues a
pplied to the d
ow
nstr
eam
sid
e o
f th
e r
am
p,
may incre
ase the e
ffectiveness o
f th
is m
itig
ation
altern
ative.
Lim
itati
on
s:
•
May n
ot
be e
ffective in s
ituations w
here
the b
oat ra
mp is
frequently inundate
d a
nd d
am
aged b
y h
igh v
elo
city flo
ws.
•
Relo
cation o
f th
e r
am
p, if p
ossib
le, or
oth
er
altern
atives
such a
s c
onstr
uction o
f a jetty to p
rote
ct th
e r
am
p s
hould
be c
onsid
ere
d in these insta
nces.
Co
nsid
era
tio
ns:
Hig
h V
elo
city F
low
s
99
MISCELLANEOUS FACILITIES
B.3
C
on
str
uct
a J
ett
y t
o P
rote
ct
Bo
at
Ram
p
Constr
uct a jetty u
pstr
eam
fro
m the b
oat ra
mp to p
rote
ct it fro
m
hig
h v
elo
city flo
ws.
Eff
ecti
ven
ess:
•
Constr
uction o
f a jetty u
pstr
eam
fro
m the b
oat ra
mp m
ay
be v
ery
eff
ective in a
reas o
f m
odera
te to h
igh v
elo
city
flow
s.
•
Oth
er
measure
s, such a
s r
ipra
p o
r oth
er
slo
pe p
rote
ction
techniq
ues, applied to the d
ow
nstr
eam
sid
e o
f th
e r
am
p
may incre
ase the e
ffectiveness o
f th
is m
itig
ation
altern
ative.
Lim
itati
on
s:
•
Consid
er
relo
cati
ng
the r
am
p to the s
lackw
ate
r bay.
Co
nsid
era
tio
ns:
Appendix
A
i
APPENDICES
AP
PE
ND
IX A
R
EG
UL
AT
ION
S A
ND
CO
NS
IDE
RA
TIO
NS
This
Appendix
briefly d
iscusses s
ignific
ant re
gula
tions a
nd
issues that should
be c
onsid
ere
d w
hen d
evelo
pin
g o
ne o
f th
e
pro
jects
identified in this
handbook. T
o s
tream
line the u
se o
f
the H
andbook, th
ese c
autions a
re r
epre
sente
d b
y s
ym
bols
.
The m
ost applic
able
sym
bols
accom
pany e
ach m
itig
ation
measure
in the H
andbook. It is
sole
ly the p
roje
ct pro
ponent’s
responsib
ility
to e
nsure
that all
applic
able
codes a
nd s
tandard
s
are
met, r
egard
less if
they a
re identified in this
Handbook.
N
ati
on
al E
nvir
on
men
tal P
olicy A
ct
(NE
PA
)
All
federa
l agencie
s m
ust consid
er
the e
ffects
of
federa
lly-f
unded p
roje
cts
upon the e
nvironm
ent as
required b
y N
EP
A. A
ctions identified b
y this
sym
bol
may h
ave a
n im
pact on the e
nvironm
ent and m
ay
require f
urt
her
investigation to d
ete
rmin
e the e
xte
nt of
any im
pacts
. E
nd
an
gere
d S
pecie
s A
ct
(ES
A)
The E
SA
pro
tects
anim
als
and p
lants
that are
federa
lly
liste
d a
s thre
ate
ned o
r endangere
d (
as w
ell a
s their
habitat)
. A
ctions identified b
y this
sym
bol m
ay h
ave a
n
aff
ect on e
ndangere
d s
pecie
s o
r th
eir h
abitat.
Consultation a
nd a
ppro
val by the N
ational M
arine
Fis
heries S
erv
ice a
nd/o
r th
e U
.S. F
ish a
nd W
ildlif
e
Serv
ice m
ay b
e n
ecessary
when e
ither
agency h
as
jurisdic
tion.
Nati
on
al H
isto
ric P
reserv
ati
on
Act
(NH
PA
)
NH
PA
str
ives to p
rote
ct our
nation’s
herita
ge, and
requires the r
evie
w o
f any p
roje
ct th
at aff
ects
a
str
uctu
re 5
0 y
ears
or
old
er
that m
ay b
e o
n (
or
elig
ible
for)
the F
edera
l R
egis
ter
of
His
toric P
laces, or
that
aff
ects
a s
ite w
hic
h m
ay c
onta
in a
rtifacts
of
arc
haeolo
gic
al or
cultura
l sig
nific
ance. F
or
any a
ction
identified b
y this
sym
bol, F
EM
A m
ay n
eed to c
onsult
with the S
tate
or
Tribal H
isto
ric P
reserv
ation O
ffic
e to
dete
rmin
e w
heth
er
any a
dditio
nal action o
r m
itig
ation is
necessary
.
ii
Appendix
A
Cle
an
Wate
r A
ct
(CW
A)
The U
.S.
Arm
y C
orp
s o
f E
ngin
eers
(C
orp
s)
is
responsib
le f
or
ensuring that pro
jects
in ‘th
e w
ate
rs o
f
the U
nited S
tate
s’ do n
ot advers
ely
aff
ect such w
ate
rs.
Actions identified b
y this
sym
bol m
ay r
equire a
perm
it
by the C
orp
s.
Flo
od
pla
in / W
etl
an
ds
Actions identified b
y this
sym
bol are
subje
ct to
Executive O
rder
11988 o
n F
loodpla
in M
anagem
ent
and/o
r E
xecutive O
rder
11990 o
n W
etlands. T
he
Executive O
rders
on F
loodpla
ins a
nd W
etlands a
re
inte
nded to e
nsure
that fe
dera
lly-f
unded p
roje
cts
avoid
long a
nd s
hort
term
im
pacts
associa
ted w
ith the
modific
ation o
f floodpla
ins o
r w
etlands.
Rig
ht
of
Way C
on
str
ain
ts
Mitig
ation m
easure
s identified b
y this
sym
bol m
ay b
e
limited b
y r
equired r
ight of
way w
idth
s, cle
ar
zone
constr
ain
ts, and/o
r geom
etr
y o
f em
bankm
ent
constr
ain
ts.
Do
wn
str
eam
or
Up
str
eam
Eff
ects
Actions identified b
y this
sym
bol in
dic
ate
that th
e a
ction
may im
pact dow
nstr
eam
flo
w v
olu
mes o
r m
ay c
reate
backw
ate
r eff
ects
upstr
eam
of
the m
easure
.
Co
st
The c
ost of
actions identified b
y this
sym
bol m
ay b
e
pro
hib
itiv
ely
expensiv
e.
Main
ten
an
ce
Actions identified b
y this
sym
bol m
ay r
equire s
ignific
ant
and/o
r continuous m
ain
tenance.
En
gin
eer
Actions identified b
y this
sym
bol re
quire that an
engin
eer
be c
onsulted o
r hired to d
evelo
p a
nd/o
r appro
ve the r
etr
ofit.
Appendix
B
iii
APPENDICES
AP
PE
ND
IX B
G
LO
SS
AR
Y &
IN
DE
X O
F F
LO
OD
DA
MA
GE
KE
YW
OR
DS
[Keyw
ord
s a
re u
nderlin
ed]
Arm
ori
ng
.
Pla
cin
g m
ate
rials
, such a
s r
ipra
p, to
pro
tect an
em
bankm
ent or
a s
tream
bank.
Backw
ate
r.
The r
ise in a
str
eam
’s w
ate
r surf
ace e
levation
caused b
y a
n o
bstr
uction o
r constr
iction to the flo
w, such a
s b
y
a d
am
, bridge, culv
ert
, or
a tem
pora
ry o
bstr
uction.
Ban
k.
The late
ral boundaries o
f a s
tream
confinin
g a
ll flow
levels
that do n
ot rise a
bove them
and flo
w o
ut onto
the
floodpla
in. T
he b
ank o
n the left
sid
e o
f a c
hannel lo
okin
g
dow
nstr
eam
is the left
bank.
Ban
k p
rote
cti
on
. R
ock, concre
te,
asphalt, vegeta
tion, or
oth
er
arm
or
pro
tecting a
bank o
f a s
tream
fro
m e
rosio
n. Inclu
des
devic
es u
sed to d
eflect th
e f
orc
es o
f ero
sio
n a
way f
rom
the
bank. S
ee E
mb
an
km
en
t S
lop
e P
rote
cti
on
.
Barb
s. S
ee F
low
div
ert
ers
.
Base f
loo
d e
levati
on
. S
ee D
esig
n f
loo
d e
levati
on
.
Batt
ers
. S
teel pla
tes a
ttached to the u
pstr
eam
faces o
f bridge
pie
rs to p
rote
ct th
em
fro
m d
am
age d
ue to the im
pact of floating
debris. p
p. 66 a
nd 6
7.
Berm
s. E
art
h-f
illed s
tructu
res p
laced o
n a
flo
odpla
in to d
ivert
flood flo
ws, m
ost com
monly
into
bridge o
r culv
ert
openin
gs.
The e
art
h fill
should
be e
rosio
n-r
esis
tant and the b
erm
s s
hould
be c
overe
d w
ith e
rosio
n-r
esis
tant vegeta
tion. B
erm
s s
hould
be
locate
d to e
nsure
no s
ignific
ant in
cre
ase in w
ate
r surf
ace
ele
vations. p
p. 43 a
nd 7
5.
Bevel
rin
g, E
ntr
an
ce. A
round c
olla
r pla
ced o
n a
culv
ert
entr
ance to d
ivert
the flo
w into
the c
ulv
ert
. T
he c
olla
r is
bevele
d fro
m its
oute
r surf
ace inw
ard
to the c
ulv
ert
entr
ance.
iv
Appendix
B
Bio
-en
gin
eeri
ng
. U
se o
f pla
nt m
ate
rials
to s
tabili
ze h
ill s
lopes
or
str
eam
banks. It often involv
es f
ascin
e a
nd b
undle
s in
conju
nction w
ith o
ther
‘hard
’ str
uctu
res s
uch a
s logs, ro
ot w
ads,
rock toes, or
wooden c
rib s
tructu
res.
Bio
-filtr
ati
on
. T
he a
ero
bic
and a
naero
bic
pro
cesses u
sed to
bre
ak d
ow
n w
aste
s, as is typic
ally
im
ple
mente
d a
t a w
aste
wate
r or
sew
age tre
atm
ent pla
nt.
Bu
cket
ou
tlet.
A
concre
te o
r ro
ck s
tructu
re p
laced a
t a c
ulv
ert
outlet to
dis
sip
ate
the e
nerg
y o
f th
e flo
w a
s it exits the c
ulv
ert
.
The s
tructu
re is c
urv
ed u
pw
ard
to thro
w the w
ate
r je
t
dow
nstr
eam
. C
ap
acit
y. T
he e
ffective c
arr
yin
g a
bili
ty o
f a d
rain
age s
tructu
re.
Catc
h b
asin
. A
str
uctu
re that
colle
cts
wate
r.
Ch
eck d
am
s. A
sm
all
rock o
r concre
te s
tructu
re g
enera
lly
pla
ced late
rally
acro
ss s
teep d
itches f
or
the p
urp
ose o
f
reducin
g the v
elo
city in the d
itch. p
p. 4 a
nd 7
. C
riti
cal fa
cilit
y.
C
ritical fa
cili
ties p
rovid
e e
ssential serv
ices to
a c
om
munity, lik
e a
fire s
tation, hospital, o
r nurs
ing h
om
e.
When r
elo
cate
d o
r re
constr
ucte
d, th
e c
ritical fa
cili
ty m
ust not
be locate
d w
ithin
the 5
00-y
ear
floodpla
in. T
he d
istinction o
f
these f
acili
ties is that even a
sm
all
flood c
an h
ave life-
thre
ate
nin
g r
isks, such a
s d
ue to a
ccess a
nd/o
r opera
tions
issues. S
ee a
lso 4
4 C
FR
Chapte
r 9.4
for
a lis
t of
critical
actions.
Cu
lvert
. A
clo
sed c
onduit, oth
er
than a
bridge, w
hic
h a
llow
s
wate
r to
pass thro
ugh a
roadw
ay p
rism
.
Cu
lvert
, A
dd
itio
nal. In
tended to m
itig
ate
culv
ert
mis
alig
nm
ent. A
dditio
nal culv
ert
s a
re d
esig
ned to s
tand a
lone.
Indiv
idual desig
n c
apacitie
s a
re d
ete
rmin
ed b
ased o
n the
am
ount of
anticip
ate
d flo
w thro
ugh s
epara
te s
tream
channels
that have m
igra
ted (
or
are
expecte
d to m
igra
te)
aw
ay f
rom
the
main
str
eam
. p
p. 6 a
nd 4
1.
Cu
lvert
en
tran
ce b
ott
om
s, P
avin
g. p
p. 22, 25, and 3
5-3
6.
Appendix
B
v
APPENDICES
Cu
lvert
en
tran
ce, R
ou
nd
ing
. p
p. 22, 25, and 3
7.
Cu
lvert
en
tran
ce, S
hap
e. p
p. 35 a
nd 3
6.
Cu
lvert
s, M
ult
iple
. Inte
nded to m
itig
ate
insuff
icie
nt capacity.
Multip
le c
ulv
ert
s a
re d
esig
ned a
s p
art
of
the m
ain
str
eam
culv
ert
syste
m. T
hey a
re locate
d a
t th
e m
ain
str
eam
culv
ert
site a
nd s
hould
be a
t diffe
rent ele
vations in the e
mbankm
ent.
(i.e
., S
epara
ted b
y 0
.1 tim
es the d
iam
ete
r of
the c
ulv
ert.)
Cu
toff
wall. A
wall
at th
e e
nd o
f a d
rain
age s
tructu
re, th
e top
of
whic
h is a
n inte
gra
l part
of th
e d
rain
age s
tructu
re. T
his
wall
is u
sually b
uried a
nd its
function is to p
revent underm
inin
g o
f
the d
rain
age s
tructu
re if
the n
atu
ral m
ate
rial at th
e o
utlet of
the
str
uctu
re is e
roded b
y the w
ate
r dis
charg
ing fro
m the e
nd o
f th
e
str
uctu
re. C
uto
ff w
alls
are
som
etim
es u
sed a
t th
e u
pstr
eam
end o
f a s
tructu
re w
hen there
is a
possib
ility
of
ero
sio
n. p
p. 35
and 3
6
Deb
ris b
arr
ier
(tra
sh
rack).
A
deflecto
r pla
ced a
t th
e e
ntr
ance
of
a c
ulv
ert
upstr
eam
, w
hic
h tends to d
eflect heavy flo
ating
debris o
r bould
ers
aw
ay f
rom
the c
ulv
ert
entr
ance d
uring h
igh
velo
city flo
w. p
p. 21-2
3, 30, 35-3
7, 39, 41-4
5, and 6
8.
Deb
ris b
asin
. A
ny a
rea u
pstr
eam
fro
m a
dra
inage s
tructu
re
utiliz
ed f
or
the p
urp
ose o
f re
tain
ing d
ebris in o
rder
to p
revent
clo
ggin
g o
f dra
inage s
tructu
res d
ow
nstr
eam
. D
eb
ris c
rib
. O
pen c
rib-t
ype s
tructu
re p
laced v
ert
ically
over
the
culv
ert
inle
t in
log-c
abin
fashio
n to p
revent in
flow
of
coars
e
bedlo
ad a
nd lig
ht floating d
ebris.
Deb
ris d
efl
ecto
r. S
tructu
re p
laced a
t th
e c
ulv
ert
inle
t to
deflect th
e m
ajo
r port
ion o
f th
e d
ebris a
way f
rom
the c
ulv
ert
entr
ance. T
hey a
re n
orm
ally
“V
” shaped in p
lane w
ith the a
pex
upstr
eam
. p
p. 30, 49-5
2, 56-5
8, 61, 65, and 6
7.
Deb
ris f
ins. W
alls
built
in the s
tream
channel upstr
eam
of
the
culv
ert
. T
heir p
urp
ose is to a
lign d
ebris, such a
s logs, w
ith the
axis
of
the c
ulv
ert
so that th
e d
ebris w
ill p
ass thro
ugh the
culv
ert
barr
el w
ithout clo
ggin
g the inle
t. T
hey a
re s
om
etim
es
used o
n the b
ridge p
iers
to d
eflect drift. p
p. 30, 66, and 6
7.
vi
Appendix
B
Desig
n f
loo
d e
levati
on
. U
nle
ss the c
om
munity h
as
desig
nate
d a
hig
her
ele
vation, th
e 1
00-y
ear
floodpla
in for
bridges, buildin
gs a
nd o
ther
import
ant fa
cili
ties, th
e 5
00-y
ear
floodpla
in f
or
critical fa
cili
ties, and the m
axim
um
flo
od that
frequently o
ccurs
for
all
oth
er
facili
ties.
Dete
nti
on
sto
rag
e. S
urf
ace w
ate
r m
ovin
g o
ver
the land is in
dete
ntion s
tora
ge. S
urf
ace w
ate
r allo
wed to tem
pora
rily
accum
ula
te in p
onds, basin
s, re
serv
oirs, or
oth
er
types o
f
hold
ing f
acili
ty, and w
hic
h is u
ltim
ate
ly r
etu
rned to a
wate
rcours
e o
r oth
er
dra
inage s
yste
m a
s r
unoff
is in d
ete
ntion
sto
rage.
Dra
wd
ow
n. A
low
ering o
f th
e s
urf
ace w
ate
r ele
vation o
f a
str
eam
as it
appro
aches a
nd f
low
s thro
ugh a
bridge o
r culv
ert
.
It is a
measure
of
the d
iffe
rence o
f th
e w
ate
r surf
ace e
levation
upstr
eam
fro
m the b
ridge o
r culv
ert
and a
short
dis
tance
dow
nstr
eam
fro
m their e
nra
nces.
Ed
die
s. C
urr
ents
of
wate
r m
ovin
g in c
ircula
r (w
hirlp
ool)
pattern
s c
ontr
ary
to the m
ain
direction o
f flood flo
ws. T
he
eddie
s m
ay m
ove late
rally
to the d
ow
nstr
eam
direction o
f flow
or
at various a
ngle
s u
pstr
eam
and d
ow
nstr
eam
. E
levate
. p
p. 54, 55, 73, 74, 83, and 9
5.
Em
ban
km
en
t slo
pe p
rote
cti
on
. p
p. 4, 9,
15, 21-2
4, 30, 32,
35-3
7, 39, 41-4
5, 49-5
2, and 5
6-5
8.
Em
erg
en
cy s
pillw
ay. A
constr
ucte
d c
hannel at a d
am
or
oth
er
str
uctu
re d
esig
ned to p
ass f
lood flo
ws that exceed the
desig
n c
apacity o
f th
e flo
w thro
ugh s
tructu
res.
En
dn
oses. T
riangula
r or
curv
ed s
tructu
res a
dded to the
upstr
eam
sid
e o
f pie
rs to d
eflect floating d
ebris a
nd h
igh
str
eam
velo
citie
s. p
p. 63, 66, and 6
7.
En
dw
all (
treatm
en
t/d
esig
n).
A
wall
at th
e e
nd o
f a d
rain
age
str
uctu
re d
esig
ned to p
revent ero
sio
n o
f th
e e
mbankm
ent at its
entr
ance o
r outlet.
pp. 21, 22, 35-3
7, and 4
1-4
5.
Appendix
B
vii
APPENDICES
En
erg
y d
issip
ate
r. A
rock o
r concre
te s
tructu
re d
esig
ned to
reduce the v
elo
city o
f th
e flo
w e
xitin
g a
culv
ert
to p
revent
ero
sio
n o
f th
e s
tream
bed a
nd b
anks.
pp. 10, 21-2
3, 30, 37-3
9,
and 4
1-4
5.
En
tran
ce &
ou
tlet
treatm
en
ts/d
esig
n. p
p. 23-2
4, 30, 32, and
58.
Fla
red
ou
tlets
/en
d s
ecti
on
s. M
anufa
ctu
red e
nd s
ections f
or
culv
ert
entr
ances a
nd o
utlets
. T
he e
nd s
ections e
xpand in
wid
th o
utw
ard
fro
m the c
ulv
ert
end, are
bevele
d to m
atc
h the
em
bankm
ent slo
pe, and h
ave r
ounded c
orn
ers
at th
eir o
ute
r
ends. p
p. 22, 25, and 3
7.
Flo
od
wate
rs. S
tream
flo
ws that have r
isen a
bove the s
tream
bank, and flo
w o
r sta
nd o
ver
adjo
inin
g lands.
Flo
od
walls. W
alls
constr
ucte
d o
f w
ate
r-re
sis
tant m
ate
rial
aro
und the p
erim
ete
r of
a f
acili
ty a
nd e
xte
ndin
g a
bove the
desig
n f
lood e
levation to k
eep flo
odw
ate
rs a
way f
rom
the
facili
ty.
Flo
w d
efl
ecto
rs. T
riangula
r or
circula
r str
uctu
res insta
lled o
n
or
imm
edia
tely
upstr
eam
fro
m the f
ootings o
f bridge p
iers
to
deflect th
e flo
w there
by r
educin
g the flo
w v
elo
citie
s a
nd
pre
venting s
cour
of
the p
ier fo
otings. p
p. 61 a
nd 6
2.
Flo
w d
ivert
ers
. R
ock s
tructu
res p
laced in a
str
eam
to d
ivert
the flo
w a
way f
rom
em
bankm
ents
. U
sually d
esig
ned to e
xte
nd
a s
hort
dis
tance into
the s
tream
, flow
div
ert
ers
or
barb
s a
re
hig
her
at th
e e
dge o
f th
e e
mbankm
ent, a
nd a
re tie
d into
the
bank to p
rote
ct fr
om
ero
sio
n a
t th
eir e
nds.
Flo
w f
ull. T
he flo
w c
onditio
n o
f a c
ulv
ert
when a
ll o
f its c
ross-
sectional are
a is c
arr
yin
g flo
w. In g
enera
l, a
culv
ert
will
flo
w f
ull
when its
outlet is
subm
erg
ed (
wate
r surf
ace is a
bove the tope
of
the c
ulv
ert
outlet)
or
the d
epth
of
wate
r above the top o
f its
entr
ance is 1
.5 tim
es its
dia
mete
r.
Flo
w p
art
ially f
ull. A
flo
w c
onditio
n o
f a c
ulv
ert
when a
ll of
its
cro
ss-s
ectional are
a is n
ot carr
yin
g flo
w. In g
enera
l, a
culv
ert
w
ill flow
part
ially
full
when the w
ate
r depth
is a
bove (
or belo
w)
viii
Appendix
B
the top o
f its e
ntr
ance a
nd the w
ate
r depth
is b
elo
w the top o
f
its o
utlet.
Gab
ion
s. W
ire b
askets
fill
ed w
ith r
ock a
nd p
laced a
long
em
bankm
ents
to p
revent ero
sio
n.
Gra
ded
str
eam
. A
conditio
n w
hen a
str
eam
’s b
ed is n
either
aggra
din
g (
sedim
ent and/o
r gra
vel depositio
n is r
ais
ing the
bed)
nor
degra
din
g (
sedim
ent and/o
r gra
vel ero
sio
n is low
ering
the b
ed).
T
he s
tream
is c
onsid
ere
d to b
e in e
quili
brium
. H
ead
cu
ttin
g. A
conditio
n w
hen a
str
eam
’s b
ed is
pro
gre
ssiv
ely
ero
din
g (
low
ering)
in the u
pstr
eam
direction.
‘Hig
h h
ead
’ co
nd
itio
ns. O
nce a
culv
ert
is flo
win
g f
ull,
an
incre
ase in the w
ate
r surf
ace e
levation u
pstr
eam
fro
m the
culv
ert
has a
rela
tively
sm
all
eff
ect
on the incre
ase o
f flow
thro
ugh the c
ulv
ert
. T
he flo
w thro
ugh the c
ulv
ert
is then
described a
s b
ein
g u
nder
“hig
h h
ead c
onditio
ns.”
H
igh
wate
r m
ark
s. L
ines f
ound o
n tre
es a
nd s
tructu
res
mark
ing the h
ighest ele
vation (
peak)
of
the w
ate
r surf
ace f
or
a
flood e
vent, c
reate
d b
y f
oam
, seed, or
oth
er
debris.
Hig
h w
ate
r o
verf
low
cro
ssin
g. A
depre
ssio
n in a
road p
rism
desig
ned to c
arr
y flo
od flo
ws f
rom
overb
ank a
reas. p
p. 21, 23,
and 2
8.
Hyd
rod
yn
am
ic f
orc
es. F
orc
es im
posed o
n s
tructu
res b
y
floodw
ate
rs d
ue to im
pacts
of m
ovin
g w
ate
r on the u
pstr
eam
sid
e o
f th
e s
tructu
re, dra
g a
long its
sid
es, and e
ddie
s o
r
negative p
ressure
s o
n its
dow
nstr
eam
sid
e.
Hyd
rosta
tic p
ressu
re. T
he p
ressure
exert
ed in a
ll directions
by a
giv
en p
oin
t in
a b
ody o
f w
ate
r, u
sually c
aused b
y the
weig
ht of
wate
r overlyin
g it.
Inte
rmit
ten
t d
rain
ag
es. S
tream
s that do n
ot flow
continuously
. L
inin
g. P
rote
ctive c
over
of
the p
erim
ete
r of
a c
hannel or
the
insid
e o
f a p
ipe. p
p. 4, 5, 86, and 9
1.
Appendix
B
ix
APPENDICES
Lo
w w
ate
r cro
ssin
g. A
depre
ssio
n in a
road p
rism
desig
ned
to c
arr
y flo
od flo
ws f
rom
an inte
rmitte
nt dra
inage. p
p. 23, 27,
and 2
8.
Mean
der.
In
connection w
ith s
tream
s, a w
indin
g c
hannel
usually in a
n e
rodib
le, allu
via
l valle
y. A
revers
e o
r S
-shaped
curv
e o
r series o
f curv
es f
orm
ed b
y e
rosio
n o
f th
e c
oncave
bank, especia
lly a
t th
e d
ow
nstr
eam
end, shoals
and b
ank
ero
sio
ns. M
eandering is a
sta
ge in the m
igra
tory
movem
ent of
the c
hannel, a
s a
whole
, dow
n the v
alle
y.
Overb
an
k. T
he p
ort
ion o
f th
e b
ank w
here
the flo
odw
ate
rs f
low
above the h
isto
rical confines o
f th
e b
ank.
Perm
eab
ilit
y. T
he a
bili
ty o
f a m
ate
rial (g
enera
lly a
n e
art
h
mate
rial) to tra
nsm
it w
ate
r th
rough its
pore
s w
hen s
ubje
cte
d to
a p
ressure
or
a d
iffe
rence in h
ead.
Realig
n p
iers
& a
bu
tmen
ts. p
p. 52, 56, and 5
7.
Relief
cu
lvert
.
Insta
lled to m
itig
ate
debris p
luggin
g o
f culv
ert
s
and b
ridges. R
elie
f culv
ert
s m
ay b
e insta
lled a
t th
e c
ulv
ert
site
at a h
igher
ele
vation o
r at som
e d
ista
nce fro
m b
ridge o
penin
gs.
Relief
op
en
ing
. T
his
openin
g c
an b
e a
culv
ert
or
bridge, or
multip
le c
ulv
ert
s; norm
ally
locate
d a
t natu
ral sid
e c
hannels
. p
p.
56-5
8.
Rep
lace m
ult
i-sp
an
bri
dg
e w
ith
sin
gle
sp
an
. p
p. 56 a
nd 6
1.
Relo
cate
. p
p. 52, 72, 82, 95, and 9
9.
Revetm
en
t. B
ank p
rote
ction to p
revent ero
sio
n.
Rin
g c
om
pre
ssio
n. F
lattenin
g o
f a c
ircula
r culv
ert
resultin
g
from
beveling its
end to m
atc
h the a
ngle
of
the e
mbankm
ent.
Fla
nges m
ay b
e r
equired to s
tiff
en the b
evele
d s
ection o
f th
e
culv
ert
. R
ipari
an
. R
iparian a
reas o
ccur
next to
the b
anks o
f str
eam
s,
lakes, and w
etlands, and inclu
de b
oth
the a
rea d
om
inate
d b
y
continuous h
igh m
ois
ture
conte
nt and the a
dja
cent upla
nd
vegeta
tion that exert
s a
n influence o
n it.
x
Appendix
B
Rip
rap
. R
ock p
laced o
n e
mbankm
ent slo
pes to p
revent
ero
sio
n. p
p. 13, 16, 98, and 9
9.
Ro
ad
way p
rism
. T
he r
oad e
mbankm
ent, s
hould
er,
and
surf
ace.
Ro
un
ded
in
let.
T
he e
dges o
f a c
ulv
ert
entr
ance that are
rounded f
or
sm
ooth
tra
nsitio
n, w
hic
h r
educes turb
ule
nce a
nd
incre
ases c
apacity.
Sco
ur.
T
he r
esult o
f an e
rosiv
e a
ction o
f flow
ing w
ate
r,
prim
arily
in s
tream
s, excavating a
nd c
arr
yin
g a
way m
ate
rial
from
the b
ed a
nd b
anks. W
earing a
way b
y a
bra
siv
e a
ction.
Sed
imen
t. R
oad, gra
vel, o
r cobble
s that origin
ate
fro
m
weath
ering o
f ro
cks a
nd is tra
nsport
ed b
y, suspended in, or
deposited b
y w
ate
r.
Sp
ur
dik
es. E
mbankm
ents
that are
desig
ned to d
irect flood
flow
s into
a b
ridge o
penin
g.
Su
bcri
tical fl
ow
(tr
an
qu
il a
nd
str
eam
ing
).
Low
velo
city
str
eam
flo
w. T
he flo
w a
ppears
to f
low
in tubes w
ith u
niform
velo
city.
Su
bm
erg
ed
. C
overe
d w
ith w
ate
r. H
ere
used a
s s
urf
ace w
ate
r
ele
vations a
bove the top o
f culv
ert
entr
ances a
nd o
utlets
. S
up
erc
riti
cal
flo
w (
rap
id a
nd
tu
rbu
len
t). H
igh v
elo
city
str
eam
flo
w. T
he flo
w a
ppears
to b
e s
hooting w
ith v
ary
ing
velo
city.
Win
gw
alls (
treatm
en
t/d
esig
n).
C
oncre
te w
alls c
onstr
ucte
d a
t
culv
ert
and b
ridge e
ntr
ances a
nd o
utlets
to d
irect flow
s into
their o
penin
gs. W
ingw
alls m
ay b
e c
onstr
ucte
d a
t angle
s u
p to
60 d
egre
es f
rom
the c
ulv
ert
and b
ridge o
penin
gs. p
p. 21, 22,
25, 30, 35-3
7, 41-4
5, 49, 51, 52, 56-5
8, 62, and 6
6.
Appendix
C
xi
APPENDICES
AP
PE
ND
IX C
A
CR
ON
YM
S
CF
R
Code o
f F
edera
l R
egula
tions
CW
A
Cle
an W
ate
r A
ct
EO
E
xecutive O
rders
ES
A
Endangere
d S
pecie
s A
ct
FE
MA
F
edera
l E
merg
ency M
anagem
ent A
gency
HA
ZM
IT
Hazard
Mitig
ation
HM
GP
H
azard
Mitig
ation G
rant P
rogra
m
MIT
M
itig
ation
NE
PA
N
ational E
nvironm
enta
l P
olic
y A
ct
NF
IP
National F
lood Insura
nce P
rogra
m
NH
PA
N
ational H
isto
ric P
reserv
ation A
ct
PA
P
ublic
Assis
tance
PL
Public
Law
PL 9
3-2
88
Robert
T. S
taff
ord
Dis
aste
r R
elief
and
Em
erg
ency A
ssis
tance A
ct
US
AC
E
US
Arm
y C
orp
s o
f E
ngin
eers
xii
Appendix
D
AP
PE
ND
IX D
R
EF
ER
EN
CE
S
C
om
puta
tion o
f P
eak D
ischarg
e a
t C
ontr
actions, by
Kin
dsvate
r, C
.E.; C
art
er,
R.W
.; a
nd T
racy, H
.J. U
S G
eolo
gic
al
Surv
ey C
ircula
r #284. P
ublis
hed b
y U
S G
eolo
gic
al S
urv
ey,
Washin
gto
n, D
C (
1953).
Com
puta
tion o
f P
eak D
ischarg
e a
t C
ulv
ert
s, by C
art
er,
R.W
. U
S G
eolo
gic
al S
urv
ey C
ircula
r #376. P
ublis
hed b
y U
S
Geolo
gic
al S
urv
ey, W
ashin
gto
n, D
C (
1957).
Desig
n G
uid
elin
es for
Flo
od D
am
age R
eduction.
Pre
pare
d b
y A
IA R
esearc
h C
orp
., W
ashin
gto
n, D
.C., f
or
the
Federa
l E
merg
ency M
anagem
ent A
gency.
FE
MA
Public
ation
No. 15, D
ecem
ber
1981.
F
loodpro
ofing N
on-R
esid
ential S
tructu
res. P
repare
d
by B
ooker
Associa
tes f
or
the F
edera
l E
merg
ency M
anagem
ent
Agency. F
EM
A P
ublic
ation N
o. 102, M
ay 1
986.
H
andbook o
f S
teel D
rain
age a
nd H
ighw
ay
Constr
uction P
roducts
, S
econd E
ditio
n. P
ublished b
y
Am
erican Iro
n &
Ste
el In
stitu
te, W
ashin
gto
n, D
C (
1971).
Hom
eow
ner’s G
uid
e to R
etr
ofittin
g: S
ix W
ays to
Pro
tect Y
our
House F
rom
Flo
odin
g. F
EM
A P
ublic
ation N
o.
312, June 1
998. P
ublished b
y F
EM
A, W
ashin
gto
n, D
C (
1998).
Pro
tecting B
uild
ing U
tilit
ies F
rom
Flo
od D
am
age:
Princip
les &
Pra
ctices for
the D
esig
n &
Constr
uction o
f F
lood
Resis
tant B
uild
ing U
tilit
y S
yste
ms. F
EM
A P
ublic
ation N
o. 348,
Novem
ber
1999. P
ublis
hed b
y F
EM
A, Jessup, M
D (
1999).
Public
Assis
tance G
uid
e. F
EM
A P
ublic
ation N
o. 322,
Octo
ber
1999. S
uperc
edes F
EM
A 2
86, is
sued in S
epte
mber
1996. P
ublis
hed b
y R
esponse a
nd R
ecovery
Directo
rate
,
FE
MA
, W
ashin
gto
n, D
C (
1999).
“Sto
rmw
ate
r M
anagem
ent P
ractices in T
ennessee.”
Sto
rmw
ate
r M
anagem
ent fo
r P
ublic
Off
icia
ls a
nd P
lanners
:
Develo
pm
ent
of
an E
ducational M
anual and W
ork
shop P
roje
ct,
Contr
act A
gre
em
ent N
o. 48226. P
ublis
hed b
y the U
niv
ers
ity o
f T
ennessee C
ivil
& E
nvironm
enta
l E
ngin
eering D
epart
ment and
the T
ennessee W
ate
r R
esourc
es R
esearc
h C
ente
r (D
ecem
ber
1997).
In
tern
et: http://w
ww
.engr.
utk
.edu/r
esearc
h/w
ate
r.
W
ate
r-R
esourc
es E
ngin
eering, by L
insle
y,
R.K
. &
Fra
nzin
i, J
.B. P
ublis
hed b
y M
cG
raw
-Hill
Series in S
anitary
Scie
nce a
nd W
ate
r R
esourc
es E
ngin
eering, N
ew
York
(1964).
Appendix
E
xiii
APPENDICES
AP
PE
ND
IX E
C
ON
TR
IBU
TO
R L
IST
Jean C
haney, T
eam
Leader
– P
ublic
Assis
tance
Lois
Lopez –
Public
Assis
tance
Angela
Aubuchon –
Public
Assis
tance
Toni A
ubuchon –
Public
Assis
tance
Dennis
Burt
on –
Public
Assis
tance
Sta
n C
hun –
Public
Assis
tance
Ron H
orm
ann –
Public
Assis
tance
Tom
More
llo –
Public
Assis
tance
JoA
nn O
ram
– P
ublic
Assis
tance
Susan S
late
– P
ublic
Assis
tance
R
ichal S
mith –
Public
Assis
tance
Phil
Carp
ente
r – H
azard
Mitig
ation
Bru
ce K
nip
e –
Hazard
Mitig
ation
Terr
y S
canla
nd –
Hazard
Mitig
ation
Mark
Eberlein
– R
egio
nal E
nvironm
enta
l O
ffic
er
Doak M
ahlik
– E
xte
rnal A
ffairs
E
ric P
eeble
s –
Outr
each
Dayna B
aile
y –
Technic
al A
ssis
tance C
ontr
acto
r
Jay C
oncepcio
n –
Technic
al A
ssis
tance C
ontr
acto
r
Anahid
Kristina T
okes –
Technic
al A
ssis
tance C
ontr
acto
r
A
ppendix
E
