'l he Narth
aaralilu Celrrdrhe^ lla/xrle I i, 2A06,
fr. l. t 9
1
Mapping Flood Extent Using a Simple DEM-Inundation Model
Tao Zhengt and Yong Vhngl
Central trfi chigan Univcrsih,l
l:,asr Catolina Universi6l
A gtid bascd one-dimensional digitai eler. ation modcl (DE\I) -inundation model has
been dcvclopcd as a tool for flood extent mapping on floodplains. l hc validitv anrl ac_
curacv of the rrodel hale been assessed through compadson of modclcd rcsulrs rvrrh
those dcrir.ed ftorr the widely used standard and complcx 1 D Hvdrologic Enginecring
Centct Rir.cr,\nalvsis Svstem (HEC RnS) modei and vcrification against the Septcm_
bcr 1999 tlood on the lo*er'Iar Rirei floodplain, Notth Catoiina. 1hc two models are
comparable in accuracv. lfith its simple implementation and ease of parametcrization,
the DEll-inundatioo model is a potential altetnatir-e to the FIEC-RIS model.
Inffoduction
Floods ate onc ofthe most significant natutal
hazards, costing lir.es, serious d^magc to ptopert\,,
and di._uprions ro..c al and rconomic ccrrvrties. l'he abilitv to map the flood cxtent accurately and timelv can pror.ide ctitical infotma-
tion fot immediate flood relief acrir.ities, and
and post flood mitigation effotrs (\{i1eti
1999, Colby et al. 2000, Yang and Tsai 2000,
AI-Sabhan et a1.2003). To this end, hydraulic
models har-e been developcd and used for map
pre
ping flood extenr (Hydtaulic Fingineeing Center
1997, Cotreia et al. 1998,,\ckerman er xl. 2000,
Chang ct aI.2000, l)obson and Li 2000, -\l
Sabhan ct al.2003, Hunrer ct aI.2005, Bates et
al.2006). Over the vears, both trvo and one
dimensional hvdraulic models hale been dcr-el
oped. The 2 D models include rhose that emplov sophisticated full finite,elcmcnt approaches
or that t^he grid-based apptoachcs. For instance,
Galland et al. (1991) der.elopcd a 2
D finitc
element numerical model, thc TELEXIT\C-2D.
Nicholas and Nlitchell (2003) also der-cloped a
finitc-element 2-D model that solves the depthavcraged shallou. *'ater foim of rhe \aviet Stokcs
equations. The 2-D modcls are genetallv capable of achieving high mapping accuracl-, cspcciallv fot hldraulic processes at fioe spatial
tcsoluiion, b,-:r the1. tequire digical elevarion
modeis (DEi\{s) of high rcsolution and accu
tacl', as v'eil as othcr geophvsical model inputs.
Thev all atc computatioflailv intensir'e. To ar.oid
the dtawbacks of the finite element models, Batcs
and Dc Roo (2000) der-elopcd a tastet bascd
model, thc I-ISFLOOD,FP, rvhich takes a stora€le
cell approach to simulate flood hydtologic aod
hl'dtaulic process. Thc LISFI-OOD FP has been
subsequentlt improred and 1'alidated for the
Januatv 199 5 flooding on the Rir-et N{cuse, the
Nethetlands (Hunter et al. 2005, Bates et al.
2006).
Unlike 2 D modeis, 1-D hydraulic models
are r,vpicallv chatacterized bv a serics of ciosssections of channcl and floodplain topogtapht.
\ralidation resrs ha\.e tepotred that 1-D mod
els, such as the Hl.dtaulic Engineeting Center
Rir-et r\nalvsis System (HEC R.\S), atc capable
uf -caching hrgh nccurdc\ rn foocl cxLcr-,napping
(Flortitt and Bates 2002). Inlcstigations
have
bccn also conducted on ho!"'the accuracv of
the model can be affected b). \'arious factots,
:ucl_ as mr.h -esolutior. topoglnpnic rcfresen
tation, and spatial resolr.rtion (Horritt and IJates
Horritr et al.2006).
In shorr, rhc existing 1 D an<l 2,D modcls
can map a flood extent accurafell., buf thcr- are
Jif[icu]r 'o bu parancrerrzeJ. \m,,nq L,illcr-.
2001,
TL?
the cstimatiol of Manning's coefficient of ftiction
as input to the modcls, which is also rcferled
to
as N{anning's
z (Chov 1959), is highly un-
certain and unreliable. For instance, laboratorv
cxperiments har.e reported higher r.alues fot
\Ianning's r thao those recommended in the
rvell-established tables by \l T. Chorv in 1959
(\\rilson and Hottitt 2002). ..\lthough different
\.alucs halc been recommended (Acrement and
Schneider 1989) and cxtersive studies have been
conducted to derive the coefficients (Werncr
et al. 2005, Wilson et al. 2006), thcte is still no
Pfo\ren wav to estimate the r \\'ith a high levcl
of confidence and accuracy. Additionalll', the
implementation of the existiflg models tequitcs
advanced ler.els of hydtologic and hydtaulic
knowledge and expertise, rvhich is often lacking among prospective users, therefore hindcring
the use of the models. Thus, thete are clear
needs
for a hvdrar.rLic model that is simplc in
DENI-inundatioo modeL accounts for these factors in the."vater sutface height interpolation.
In summary, the objectives of rhis paper are
to detail the deleiopment of a DEN{ inuoda
tion model, to compare the model wirh rhe FILC
RAS model to assess thcir accutac,v in flood
extent mapping, and to validate rhe DEM in
undation model against a real flood event.
Methodogy: HEC-RAS Model
To meet thc needs for flood extent map
ping, thc Hvdraulic Engineeting Centcr (HEC)
of the
US Armv Cotps of Engineers dcveloped
a scrics of GlS-based hydraulic models, from
the Atc/FlEC2 to HEC RAS (Hi'dtologic En
gineeting Center 1997, I{taus 2000, Acketman
ct al. 2000, USACE 2007). HEC RAS is one
of the most popular 1 D hvdraulic models.
Compalcd rvith its ptedecessors, HEC-RAS
Xar. C,7.:ar G
locaooos
s:e- d
and rou?:-::e:; o
bett-eec:ie--rp
Iength re:e:: :o d
cross sec--:o::- r
o\'eibark- ::.:iE (
quired- Tc' e:;dc
uses eoe:z; lo$
\{anoioe'. z rrlrr
b) cotltrac:os ri
eraluate i:.2::sioo
vert loss coe:-dci
to s'eir s55e- F
and enrralca rnd
lic inputs =clu&
informaior- rod
clude kaor:: srr
depth. no:=rJ &
Methodologr:
can providc ioitial aod pteliminarl' analysis, and
comes vith some majot improvements. It facilitates the usc of digital datasets such as DEN.{
and TIN (ttiangular irre€tular netwoik) (Correia
et al. 1998, Dobson and Li 2000, Yang and Tsai
2000), and featurcs an enhanced gtaphical uscr
the result cao help the complex model fot in
depth study.
To meet the necds for simpie flood-extent
mapping models, \Vang et al. (2002) dcveloped
a model that maps flood extent by lincarl,v inrcrpo alng rhe :urFace ua cr hcighr of a rirer
between cwo reighborirg g..rugirg clarion5 Lsiog the heights measuted ar the srations. In this
intetface that simplifies the flood extent modeling ptocesses.
The HEC-RAS model is designed to perfotm 1-D hydraulic caLculation for a fulL net
work of natural or constructed \,'atet channelsIn the model, surface profiies of a stead,v florv
in rvhich changcs in flos' depth and r.elocity
occur graduallv ovet a considerable length of
of
article, an imptoved r-etsion of Wang et al. (2002)!
modeL is developed. The nervly developed model
is a 1 D DENI inundation model that features
thtcc majot improvemeots. Fitst, Wang et al.
(2002)'s rnodcl did not identifv the central channel
of the tivet; this model does. Second, Wang et
channel arc solved bv using a 1-D energ'' equation
parametetization and implementation. Such a
simple model, if capable of teaching compa-
of the complex modei, can serve
as an altetnative. In addition, a simple model
tabLe accutacy
water surface height at different florv condi-
and cnergt'head loss equation (Hvdraulic Engineering Center 1997). The steady fLow's
rvatet surface profiles are computed from dorvn
stream to upstream at cross sections for a given
dischalge fate at upstream and \r.atet sutface
height value at downstream. In the soh.ing of
the vater sutfacc profile along a dvet channeL,
HEC R-\S requites geomettic and hydraulic input
parameters. The geometric parametets include
the river system schcmatics, cross section profile, reach length, energv loss coefficient, and
stteam junction information. The schematic
patametets dcfinc how river reaches are con-
tions, weie not modeled (\Vang et al.2002). This
ncctcd. Ctoss sectioo profiles ate tequited at
al. (2002) represented distance betrveen gauging stations with a sttaight line, whereas this
model traces the distance aLong the central
channel line betrveen tlvo ncighboriog gauging
stations. l,astlv. the changes in elevation of a
tivcr channel and banks along a tivet, s'hich
are
important geometdc factois affectrng
a tir'-et's
DEM-inundd
Compr-ec
the
sd
l-D DE\I-ran
6cial g-ater ieizhr s
a stream gi cc
the DE\f to ie:erm
non flooded a:er;
suf€menrs are aFril
the disrance bersq
c.st
fl!
attificial \zre: @
tions mar be
tlveen s laEioas
in four majo: :;eF
ceotetline,
deireri:
the centerline-
esi
centellrne's s rt:aa! r
cented.ine. arci iod
herght grid ior difr
eate the
cenieiic (
a) Or-eriar co-I
motelv ser.ed
the strean i€c
trr'e cenrerii:re
:
positionei ap
the leli ard :!!
b)
Ideodi- &e
i
The
Narth Carolina
Geoparher
Iocations rvhete changes in discharge, slope, shape,
and roughness occur along the rivei channel
between the up- and dowo stleam. The reach
length tefers to the measured distance betrveefl
cross sections. Thc reach icngths fot the left
overbank, right overbank, and chanoel are requited. To er-aluate energy losses, HEC-RAS
uses enetgy loss coefficients inciuding a)
N{anning's z value fot ftiction loss (Chow 1959),
b) conttaction and expansion coefficients to
evaluate tiansitioo loss, and c) btidge and culvert loss coefficients to evaluate losses related
to weii shape, pier configuration, pressure flow,
arrd enttance and exit conditions. The hvdtaulic trptr's include flo,.r regine. pcaL discharge
infoimatiorr, and boundaty conditions that include known watet surface eler.ation, ctitical
depth, normal depth, and ratiflg curve.
J
of the tentative centetline, and use it as the
center for seatching the pixel witl.r lowest eleva
tion r-alue within a certain tadius. Out expedend
ment indicated that a radius of 300 m is suffi
cient for most cases, rvhich is equivalent of 10
plxels on 30 x 30 m USGS DENL This pixel
*ith
the lorvest elevation is then the actual location of the delineated centedine. N{ove one pirel
do$'ristream aloflg the tentative centetline, and
perfotm the similar searching until the dorvnstream cnd of the tentative centedine is rcached.
Thus a lowest-elevation plxel is identiEed fot
each cottesponding pixei od the ceoterline.
c) N{anually draw a new centerlifle by tracing
through all the pixels with tle Lowest-elevation
values from the upstream to downsffeam ends.
d)
Veri!' the centedinc
created in
tle
step 3
with
dre DENI, aerial
Methodology: One Dimensional
DEM-inundation Model
Compared with the complex HEC-R-\S model,
the 1-D DE}I-inundation model calculates an arti
6cial water heighr surface using sutface water height
of a stream and compates the artiEcial sutface with
the DEM to determine watet/noo-watet ot flooded/
non flooded ateas. The sutface \vater height measutements ate available at gaugng statioos. Because
the distancc between two neighboring gauging sta
tions may be quite latgc, sutface water heights between stations must be interpolated to create tl1e
attificial watet height sutface. This is accomplished
in fout major steps, tie delioeation of the stream
centetline, derivation of surface water herght aloog
of the reach of the
ceotetlinet surface watet herght forlocations off dre
centedne, and finaliy creation of the surface vater
height grid for different flow conditions. To delineate the centefline of a dvet section, we
a) Or,.erlay coJocated aetial photogtaphs ot temotely sensed images or.et the DEN{ coveting
the sfteam section in question. Then, a tentathe centedine, estimation
trve centedine is drawn in such a wav that it is
positioned approximately equidistant between
tle left and right banks.
b)
Identif
the first DEM pixel on the upstream
photognphs ot satellite irnages.
If needcd, iepear steps a), b), and c) until a sat
isfactory tesult is achieved. A satisfactoty
centetline should be continuous with each pirel
positiooed at the lowestpointof its cottespond1ng cross secuofi.
T1picall1., dre delineated centedine is a curr.ed line
compo.ed oI rhe deepesr pirels along a rir cr sucarr.
Second, the water suface heght at each Location or pirel along the centetline is calculated. An
assumption used for this calculation is that vrater
sudace height decreases from upstream to dorvnstream and that the decrease depends on the changes
of location and elevation long *re centedile. Figure
1 illusttates the calculation. Let I be the upstream
end and B the downsfteam end where the channelt
clerations (E,, and E) on rir.er's centedire and surface water height (H, and H) ate knorvn. kt Xbe
a location between A and B. At X, elevation (E_) is
deril.ed from DElvl and watct surface herght (H*) is
computed using
If M LD=o andEx+Dr=o
I
E^D, r-L,-l
lu.=u. -ut.E\+D\
M AD
It"
IfM.AD+0 orE,+D,+0
ll
,
(1,
'l he
rr,here
H,
= rr,atcr surfacc hcight at Lrcation,,1,
AFI = *ater surface herghr diffetence benvccn
gaugrng stauons
I
and
13,
AE = clcvation dift-ctcncc betNeen:'1 end
-\l)
Lli.rrncc ber.eerr L.na B al,'n$ fl'L
.-rrin
centefltne,
F/,:
rvatct slLrface height at poinr X,
E., = stream channcli clcvation at location X, end
/). - distance bet*,een ,-1 and X along thc strean
centeilifle.
ln gcncral, onc should select k>cations.1and B *here
gaugng -stati1115 etc locatcd. Thr,rs, H, and H,, as
rvell as E , and
L-,,
atc knor," n.
't hird, with \\'xter surfacc heighrs at cach pircl
alon!! the ceotedine c^lculatcd, one is read! to com
putc \r^tci hcights at pixcls off the celtetLine. With
lhc,..LrmlEnn rha
is lclel, calculation of
,,r
,
r
'e
r
'
u
r l ,r
r
centerlioc pi\cl accordiog to r1.re assumpdon of
lerel ',. r c' r_'1, ( r, -u-(1]'n (Lojj-rccLronr.
c) Rcpcat the proccss for al1 oft- ceotedine
oirrl. \orc: \{ lrogrrm r.l. \n cn o!c
B,
, rr ,, I ro.. 'cc:or'
: '
jlan t,;-
Crr.ss S:
con.rplish this stcp.)
Lasd1, oncc all of the surfacc rvarcr hcights arc
T--_
calculatcd, both on centetlinc and ofl--cerrter]ire, a
suifecc \\?tcrhcl+t lai'er (a grid) is cteatecl \.ith same
spatial (esolution as undcrhing DEtrl. It shouid be
pointecl out drat if the size of thc scarch radius iot
thc ncetes! on ccntcrline pirel to oftline pi\el is dif
ficult to determinc, scarching the entite studv erca
H.
e: r , a'r. 1r,,,.'.cr.r.bc\(f\ Lime
consuming. 'l hete are othel mcdrods ar ailablc fot
c,,.rld Lr
rr r-rcrr.
nr
a-
<.
intetpolating rvatcr surfacc heighr based orr kno\rn
\\'atcr surfxce height at nearcst points. lor cxamplc,
Ltscd the inlersc distance s'ciglrtccl
iotc4roLatioo.
VV
\\'ernet (2001)
t-
the sufacc *'ater height at en
off-centerLine pisel is boiled dorvn ro tinding thc on-
ccnretline pirel to s'hich thc off-ccnterline pirel
shates a senrc ctl)ss section- This is achicycd bv ftnd-
ing thc on-ccntctlinc pircl r,, ith shortest straight lioc
distancc to dre off centctlinc pixcl in qucstion.'l here
arc four steps inroivcd in tl,is proccdurc:
a) ldcntifi all the oo centc inc pi\cls th^t
^rc
*'ithir-r a specrtied radius of the off centcrlinc
pL\c1_
b)
Calcuiate the strejght Lire distance bc'nvecn
the off-ceotedifle pixel and each on-ccntcrlinc
pixcl using rhe cquation:
D=
(\ \r, + (r ,.r)1, ,
-
r
\
Q)
of pirel
(-,:,.. and.l are x and l coordinates of pirel 1). I
= 1, 2, 3, ..., n and feptesents the series of oncentetline pixcls that lie s'ithln thc scarch fll
wheie
afld-1' are
and t- coordioetcs
dius (Ftgure 2). The x an<ly cootclinates ate tcla
tivc to thc origro located at the iorvcr lcft cornet
the studl arca as co\-efed bv the Dlill, assuming thc DEII u-sed is of a squarc or rectan
gular shape.
. Ir..:r\ rl .,,n renre-l crn\c L Lr.,rhai
of
the shottcst straight lir-ic distance to the ot|
cefltetlire Pi\el.
d \.irqr -l c.urface r,are- [eiqhr ',' rJrr ',ft
Methodology: Modeling Flood Extents by Using DEM-inundation and
HEC-RAS Models
In dre delincation oF the flood e\rent, the 1-D
DE\I inundatioo mrdci supcrimposcs thc calculated
surf^ce \\,atet height lar.cr or-cr thc DEII lar,er. llecxusc both la\ers
grids wirh the samc spatial rcso
^re
lutron, the lalues oi surfacc \\.ater he+lht and llround
clc\-ation at cxch pi\el are knorvn. To delincate rva
ter/non-rlater (regulat tlot) or fl oodcd/non-floodcd
(tl'"'d i"rv rrr.r.. o'te rtecd. ,, h. rc rl ^ .cr, "t r
str:eam\ surtacc \vzter hcights (a regular oie end a
flood o[e).'Ihus, nvo surtxccs of the warcr herghrs
arc calculatcd. .\t e locarion X,lct lJ,._,,,,. b c thc regu
lar herght and / /,-,.- bc the floodcd hcighr on thc
t\vo surfaccs, rcspecti|eh,- Thcn,
' if a locationt clcr.ation (on rhe DE\I data)is
S H.,,.,,,,,, t1-ren the location is classiticd as regulat sttcam area,
. if its clcr-atiou is > 1 i,.,._,. and :l H,.,, thcn
".
thc Iocatior-r is a tloodcd atca, or'
' if the elcr arion is > 1 1.,,,"., thcn the Location
is non floodcd or dn--
The Ill:,C R.\S modcl sirulatioo with re!!u
lar and I'loocl rivel surfece height sill also classif,r'
-:::-'
r. ::-.
Figure 2.
and 1)
atc
o.
calc-r:::
>
Cross Section,zl
Waier Strface
lrc ss Sectron -tr
Bottom
H
"l
1
Cros s Section
I
D
lo_
l"x
Datum
IF
A-D
Figure 1' Illustration of thc inrerpolation of water surface height,
H.
at a gi'en location
X on the stteam
centcrline.
A location alvay
ft'om the centerline
of a stretm
Pq
Figure 2. Interpolation of rvater surface herght fot an off ccntetrine location, c Fire poirts. p. p- p. 2
and P-, on the central channel ate shown as an exampre. nistances between c and aLr point"
on i" .n^n*t
arc calculated, so that the point(s) on the centetLine haring the shortest distance to Cwill
be idcntified.
Z/ten.! t
each pixel
lithin
llooclecl, ol
rhc stud\ area as rcgulat srrcam,
dn (non f-kroclcd).
accufacv assessment of flood extents
derived by both models
inundatio[ crtcnts from bodr
moclels, first rve summanzc dcscnptir c statisdcs
l3 Scptcmber 1999 agair-rst reo-roteh seosecl clarx
inr mclrsurelnents obraincd at sc\crai sitcs.
'lhc clrte ancl si.c sclccdon lrc bxsed o[ a\-aihb]c
ancillar\ datascts deteilccl rn the ncrt sccdolr. ljlror
m.i ni e! .rr( 1r.. Irnqr .rr, \ r'r(.-i rpp rre .., ( r. rc.
on
.r,td in
Methodology: Comparison and
'1b compare the
of
thc rcgulxr strcem area. fhoded arca, and non-
Methodology: Study Area and
Datasets
'l'he snrch erca is on thc lorver floodplain of
lloodcd atca. Ncsr, spetial comparison anallsis of
thc e\tcflts at thc same ilos conditioo is cardc'd out
t() quantif| the amount of agrccment bcn\,ccn thc
nro moclels on a pirei bv plrel basis. If l pirel is
classit-rcd as samc catcgotv (tcgulat sttcam, lloodcd,
or nor-r'i1c.,oclcd arca) br thc nlo modcls, thcre is an
rlgl'ccmcnt; othc^\,isc, thcre is a disagreemeflt.
'I hc s atcL/nrn rvetct or floodcd/non-floodcd
boundeties deLineeted bl thc l)l-lll-inuncletlotr ancl
FIII(I R.\S moclels can clifier so to understand thc
r ariatiot of rhc boLrndarics sratisricallr', rvc ,,rscc1 thc
marchcdl)xir / tcst of thc bor-rndancs on borh sidcs
of thc rilcr channci. Irigurc 3 shous nvo scts of
bo,,Lnclatics, onc ccnterlifle, and dne chrnnel ctoss
sections. fl he centerlinc is dcpicted as straighr iitc
t,,r' rrnl.i. r'
- Vlnl
\, y1'",'r'rn" cfu.:-.u, Lur. n (
rhc Tar/PamLi.co Rilcr (drair.regc area - l5l limr),
(latoline. 1r cr)rers per of Pitt (iounn'on rhc
\orth
rr-est and
Berutirrt CountL on thc east (FigrLtc'1).
'fhc Tar Rircr flots into Pirr from thc north\\'csf
rnd c\its t() Rcaufi)rt ft) rhc casr. .\ficr passing thc
bridgc
of Flighr,ar
lrr.rr.-e
11, it is callccl thc
lil
ico lUr er
r" lit'i
Grccm ille aod thc othcr at \\hshiogton (Figulc -l).
Crccnr ilLc is thc Iergcst cin io Pitr (i)unh'. antl \\'rLshir-rgtoo is thc llrgest ciB in Beaufort Coultr'. 'l here
xfc ahrcc nlej()r rcasons for choosing this perticular
ireight and daih meao discharqe;afld ofl going ilood
lcscarch in this erea has rcsultccl in se|cral in-housc
gco-spatjal and rcmotc scnsing datascts ((loib\' ct 41.
ccntcillnc (c.9., lriglrrc 3).
rLtc
.100
lrinallv, to laLiciatc thc I D Dl-i\l inundation
mocle1 as rvell ',ls HF,C-R.\S modc1, rve elaluated
rnodclcd llood c\tenfs aa a rccord lrrgir flood llov
3.
.-u.l\ .rrc.r. f^,'J rr:,. .J Lr 1,.. r p c. ,r''r,.
'r"l'i,.,- l',rrn. . rr,l h'.r'i,,rr- ',ctr_ rrr\ "r
r, rrrlr ir
'1 , .qrl' ,,r,r: )r'1\'' r'' (- .Lll'l
,ll 'l. lrl ,r t.lr t'r. crl L rL r'1c. ir, irn("1t5 li,r \..t(' : rra,, r'
m apatt ir rhis snrclr'. -\long each cross
scction. t\\o infcrccpt1on pornts Nith rhc boundarics
rrc obtaincd; thc distaflccs bcnr,ecn the nvo poiots
and thc ccnrcrLinc arc calcularccl. (lncc Lhc clisrancc
nrcilsLrl('1r_lcnts frrr all closs scctions afe conrputccl,
thcfc afc f,vo scts of distrncc'lllcasLrrcilclrrs: ()rrc
liom thc l) I,l\l inLLndation modcl and thr: othcr tr-on
thc FIEC-R \S moCc1. 'l hc null hlpothesis (H,) for
ftc / tcst is that thcrc is no diffcrcncc benr-cen thc
distenccs from the nro moclels (i.c.. thc bor-rndarics
etc stadsdcalh idcnocai), and thc altcrnatir-e l-upoth
csis i[l ) is tlut a significanr differcnce erists bc
t\\'ccn rhc t\!o moclcls. \ sigriiicant 1cr cl o f tI=(1.(15
is cltosen to test rr hedrer I /,, should bc rcjcctcd. Similatlt', disrance measurcrncnts and /-tcst \as bc cx1'
ried oua for thc b()urrderies on rhe ofher side of thc
roughh
Figure
2l.X)1.).
\\rang d
aL. 20U2.
\\ana 2001, \\ang
a0c1
Zhcng
2(Xl5).
llasccl on thc sfxrc\\i(lc lend use arrd land cor-cr
1ar
cr crcatcd by thc
\otth
(lalrLina (lcntcr tirr (lco-
llrxphc Iflfotnudon and .\nali sis. thcrc arc tlficcn
land usc and land co\ cl tlpes rr itlifl the snrdl arei
$
st an-rps
cultilatctl arcas tcrc clomirrant land ctx'ct npcs
ang 200.1). l3ottr>mland lblcsts/har-dr,,ood
ancl
the stuclr-etea). 1'hc botton-rland bt
oi clecicluous and
\oodr r cgctation tlllcr thafl 3 m, \'hcre croNn den
sin is ar lcasr 25" u. -frLpclo (,\. allahrf and c\T)rcss
(Cr4r.rvr') atc rhc major spccics. l he cultir atccl lands
(about l3{"o
oi
ests/iratds'rrrd sr,,amps dre areas
occupied b\' croPs of cortorrr corn, tol)acco,
^r-cas
and sorbc^ns. L-r additron, thcrc arc dcrclopcd ar
ees, rvhich count firr abour 30 o of thc studt atea and
a,:c meioh' concentratccl in tirc r icinitr of thc ciries
Figutc 1. i
::.
Ttu Xar/h Cnnlitu Ceo!tublto.
Brrundades deli\red fiom HEC-RAS mrrdel
I
'-<
CenterLine
--+-
--J/
I
Fltrodsd
5.t
="<\--l>\=__
/ ,/
--j/
fri)ln l)Fl\t
rlunorltlon mrrdel
Figure 3. Lllpothetical boundarics
der.ir.ed from the FIlic-R-\S an<l Dl.]rI in'ndarjon models. Ninc
cross-sections erc plottcd at c\'coh, distributcd intet\ a1s.
Figure 4. Landsat I E'tlIi dara of ba'd 8 on 23 Septen.rbcr 1999 (path/ro*, 1.+/35). The studv
oudi.ed b' the dotted lines cor-crs thc l ar/Pamlico Rir.er floodplain, North car.lina
arca
of
Green\-ille end \\rashington (\\irng 200.1). Thc
statc$'idc land u-se a[d land cover date tre uscd to
estima!c fhc trlanningi z coefficient of roughncss at
each cross section elong thc nr cr channei, u-hich is
onc of the most importaot ioput paramctcrs to dte
HEC R\S model.
Tirc sr,rrfacc \\'ater heighr and dischargc data
collccted at thc gaugrng stations of (]teenlrlle and
Washington are gilen in lhble 1. Thc Dl-lll-inunda
tion model onlr uscs tlte \\,atei sutfacc hcight,
rvhcrcas HF,C-R.\S model requites borh heiglrt and
dischargc akrng s'ith othcl pre\.iouslv discussed in
puts. Tn,"rndation extents are modclcd at n\''o rcprc
sentad\-e tloodinE florv conditions:
a flood-srr+ie flo\r
on 28 ltbrual 2003 and a record hgh flood florv
on 23 Scptember 1999. Ihe florv condition on 28
Julv 1999 is used as the tegular florv (because of thc
ar ailabilin'of Landset I-TN{+ data). l hus, con-rpari
-sons oi thc nodcled results undct drc trvo disdnct
flood florv sinrations as tefcrcnccd to the regular flow
condition cao be petformed.
Dlitrl data tbr drc studr arca werc obtxined
tr<rm rhc USGS Nanonal l-lelation Datasct. Thc
l)ll\l has a 30 m br. 30 m horizontal spatiel resolu-
tion ancl a rertical eccutacv of
!1m
(USGS
\l-D
Thc tcttain rvithin the studv area is flet $ifh x
minimurn clctetion of (J.0 n-r, a mcdian of 3.5 m. a
r'r.r\''1 urr of 2).i rr. ,r tr.rrr ot 'l - rn, ..nd r . rn
datd dcviation of 4.{l m- Thus, anl silyrificant in
crcasc of ri\'cr'.s surfacc vater height could inund^tc
a Largc arcr- .\lso, it shoulcl be ioted dlat the south
sidc of thc'lat Rilet has considcraLrl)- morc relief
than fhc north sidc. Conccir_abh', thc eccuracl ol
2007).
l)EXI
has a signiticant impact on floocl mapping and
thc arailabilin
oi hghct
accutacv l)1,,\l u'illimprole
floodpiailr modeling asscssmcnt. C)fl thc othcr hancl,
because D!,\I accutacl should similarh irnpact both
models, thc NED Dlr\l is consiclerecl as a telson
ablc choicc fot con-rparing dre trvo models undcr the
same set of conditionsRemoreh' scnscd imagett arcl aerial phorog
taphvrrere used to idcndfv floodecl a11cloon {loodcd
arcas to aid the lalidation of inundatir;rr cxrcrrrs rcsultiag tiom thc nvo n-rodels. Thesc datasets include
Landsat I F,'l trIi clata accpired on 2l3Juh-1999 and
23 Septembet 1999, and obiiquc acrial photographs
takcn orr 23 September 1999. lhcsc datascrs, con
bincd s'idr fu.'rZ obseh'ations mxde in Ocrobct 1999,
Tab-e
rvete used to idcnriil tveiry fl\-e lloodcd sites,
twentr-n\-c reguler nr-cr sitcs, and t\vent\-6\.e oooflooded sites. Thus. the accuraci'oi dre modclcd
tlood cxtcnrs at the record high flood flo*'can bc
e\ aluated at thc sc\_cnt\ -tir_c sitcs. The erees coteted
bl thc sitcs aocl br catcgorics arc: Legular flrer atca
of ,+.61 kmr, floodcd area of -1..11 kmr, and non
floodcd arca of 5.32 lim:, for a rotal oi 1-1.36 kmr or
9.101, ofthe entire studv atca. Sincc rhclc is no othcr
temorelv senscd at in .ti/ ddt^scts on 28 lrcbruair
2003, no lcriflcation of the modeled resuifs were
pertoimcd. lt should bc notcd that d.re USGS Digi
tal Otthophoto QrLartet (I)OQQs) accpitecl io 1998
1
l)atc
Disch:::: :
\\hrer::;:--
s'ctc uscd to aid the initiaL idcntihcation of thc srcam
((n(rlinr/'rthcl)l \l
rnd irrJr,r.t ca cgorc. r,'sites \\,hete gtound acccss rs impossiblc. Iiinalh, aLI
digital datascts used for tJris studv hale bceo rc projccted into ttrc U nircrsal Tran sr ctse \{etcator (tr 1 \ D
coordinatc srstem using thc \\bdd'Geodctic Sl'srcm
19{3-1
Rcgula::
Flood s:-'---;:l
(\\GS8.1) models iot the sphcroid and datunr.
llc c. rci
Results and Discussion
Tt'o la-i'crs consisring of \\:ater and iofl
\\:ater
catcsorics co1€ring the cntife stud! arca \\'efe fttst
crcarcd nr thc rcgular dr-er f1os. condition (lable 1)
using DFitr{-inuodation and LlliC-R\S modcls, rc
floodcd r:.- -1r
and or_crl:..::-:
mal)S rcP:aira .jRirrt s-a: :: . :l
c.... In tl r jgu'r. .hr $1rrr.rfc..
shot'n in black and non watcr atca in rvhite. lhc
'l(.o\(1.
Fid,n
main chaoflel oi rhc 'far Rilcr is clearlv dclincatcd,
and nvo ffibularies (Chicod and Tiantcrs clccks,Irig
ulc 5b) arc idenrified. \'isual examinetioo of thc
mocleled tcsuits indicatcs that drc n'arcl ar-cas rlav
bc sin-rilar. Hcxvelet, in thc upstream secti{)n rherc is
mote atca classihcd as rvatet bv rhc FIIIC ]L\S modcl
than bv thc DEtrI inundarjon model {Figure 5). .\t
the regulat flor'', s'atcr areas ate 1 1.85 Lm3 and 1(r.95
Ln', according tcr thc DIrIl-inuodarlor model dfld
HFIC-R.\S model, re-<pcctir eh' (l'able 2).
Four additional lavers \\ ere modeled for \\'eter
and nofl-$ater categolics iof thc flood-stagc flo\'
and recotd high flood f1os.conditions using the nvcr
modcls. Thc \\:atet aLeas on ell thcsc tbur ialcrs in
clude the regulat tivcr suriacc atea (e.g., Figute 5).
:.
\\,hich sh.,i .:
tccord lig:r :.
.":
In drcsc ilE:::.t.t..L .t.- -- :
-:
i
in rvhirc.
:i
:.:
(lrigurc 6.. :::r:r
.:
\t
tl: e
rh.r.orTr'-.--north oi ria :: ::
lief on drc :: ::
contdbudc-a : ,--:
iltundation ::_--,:: :
occlrf\\-ithl.:l_. -:
p.rr .h". ' r"
oofl tloodcc ri,::
i
rr,r
.\ rnnt. -: -.
Table 1. Rivet data measured at the Greeflyille aod \I'ashington gauging statrons.
Darc
28/07 / 1999
28 /
02/2003
Dischatge (mr,/s)
.r.39
/
N.\
302.99
Water height (m)
0.37
/
0.27
3.30
Table
2. \{odeled
Recotd-high
flow
311.19
0.31
1816.26
,1.96
/
/
2152.08
1.60
extents of regular rivet, flooded, and non-flooded atcas (lirn:) at three flow conditions.
Regular
Flo oded
Non- floodcd
HE(]-R.\S
DIr\{ inundation
11.85
16.95
11.85
xxx
+
1,10.02
HEC-R-\S
16.9 5
DEtrI inundation
11.i15
FII,C-R-\S
16.95
lJ
Flood stage
/
/
23/09/1999
tl i\l-
1flU
n
w'hich should be cxcluded in otder
to map the
flooded area. This cxclusion is donc through tecoding
and ovedaving opetations. Thus four inundation
maps reptcsenting thc flood extents s,hen the Tat
R-ir'-er rvas at a flood stage florv (Frgure 6) and at a
recotd-high flood florv fgure 7) rvere generared.
In tlese f,gures, rhe regular river areas aie sho$rn in
black, the flooded arca in gray and flon flooded atca
rn rvirite.
At the flood-stage flou, on 28 Februatv 2003
(Tigurc 6), there ate latge flooded arcas surrounding
the tegular tir.et atea, and r-trote flooded areas to the
north of rhc riYet thao to the south. l'he io\r€i rclief on the nordl badli than south bank is a factot
contibuting to this difference. Comparison of both
rnundation maps indicates that morc disagreements
occur within the upperhalf
of
the snrcl,v arca
lnorur-
\'-est) than at the lo$'er half (sou*reast). fhcrc are
non-flooded islands (surtounded br' flooded area).
Fot cxample, thete is an island in the middle of the
56.10
45.61
7 7.80
74.35
89.02
4.35
61.31
65.67
9
flooded arca on rhe inuodation map dedr.cd from
the DFl\I-inundation model figure 6a), aod an island of much larget size exists at thc cortesponding
location on the flood map detivcd ftom the Hll,CR.\S model (lrigure 6b). Bodr islands ate identified
using black attou's in thc ftgutcs.
Frgure 7 shorvs thc modeled inundation ex
tents at a rccord high flood florv condition. Thc cx,
te11ts are risually similar The aerial digrral photo_
gtaphs acquted on 23 Septcmber 1999 and ground
truth collccted in October 1999 indicate that thc
majoritv of flooding occutred on the north side of
tl-re rivet, rvl, ere thc eler-ation is much los,-et thao the
cotresponding part on the south side. The sLighrly
higher eler-ation on the south bank is onc major factor to its smaller floodcd area as compated to the
notth side. Trvo noticeablc disagtcements of thc
e\tents
as pointed bI t\\,o paifs of black arto$,s are
obserl.ed: onc occuts neat the notthvest cotncL and
tie other ncar the castctnmost location. In addition,
Zt '., l' ll t.
DElr,'tl-Inundatlon
Tlte
\o,; a;- :r:
N,Ioc1€1
(a
IIEC-RAS h4i:de1
(tr
Figure 5. Regular rir cr atea
modcl
(irr blacl<) and
ar.rd
b)
non rvaaet atea (in rvhite) dclivcd ftom a) DIi\I inundation
at a repplar flo*, on 28Juh'1999.
HllC-R\S model
Figure 6, h:=c-:
a flood stage:i::
iloocei
Figure 6. Inundarion ertenrs deri'cd from a) the DEr{ inundation model
a
ancl b) rhe HLC-R\S model at
flood stage florv on 28 Febtuarr' 2003. 'l he rcgular dr.cr- area is in blacli, floodcd arca in qra\.. ancl non
flooded area i. rvhite. Unflooded islaods cxist, as pointecl b1. biacli arro* :. .,, .rn-pler.
12
Zheng
d'
lvn,g
The l',axlt
Ca,':s (
in compatison sr
ir f
flooded area
sffeam sectroa
si
islands ate noq- d
eas are anribured
ard discha4r rol
pated to 28 Feb,rr
marizes the a:ra r
tion exrenr rup- -l
stage ro recor&b
flom
crease
56-10
undation moddi
modei).
r
The ganel
eled inundaooo r
quanrified -&e dq
pixel basrs, The
r
by the nro oodel
km: or
9t1.5'
'
o
140.34 km: or 89.
j
Cfable 3,. Tail€
disagreemelr. br
The res:Its,
from the srream r
or flooded noGd
of
the
inunc;io
July 1999. .'and.l
boundaries :r'e li
and 1.6ji aod O
tir-elr: The : rz.Lr
null hrpotheses a
vatef/norr F4tct
DENl-inunciaoo r
tisticallr ditr'er€c-
fot
ahc
ilood
.4r
dr
are all gteater
conclude riat
de
on thc nor,h rod
same.
Thu-. a:
Figure 7, Ioundation extents derived from
a) DENrt-inundation model and b)
tecotd-high flood flow on 23 Septembet 1999.
FIEC lL,\S model at
a
rlr
models hare co,q
The frndrngs ?f,e rt
inundation aodd
put to the i':el e
flood erceor,. at d
'l/t( \atth Coi)/lnd
Geou..dret.
io cornparison tith Fisurc 6, there is mucl.r grcatet
iloodcd area in |igute 7, cspecrallv rvithio thc upsltcam sccdon rvhete fhc maioflt\ of non-floocled
islands are nos' flooded. Thc incteascd flooded areas ate attributcd to thc highcr \\.atei surfacc lerel
and dischargc volumc on 23 Seprembcr 1999 compared to 28 |cbtuarr' 2003 (fablc 1). 'thble 2 sum
marizcs the arca oi cach catcgorv on cach inundahon extent map. -\s thc dr-cr changcs tiom its flood
sfegc to record high flood florvs, iloodcd ereas increasc fton.r 56.10 to 77.80 kmr(>ascd on DljtrI inundation modcl) and -{5.61 ro 7-1.35 Lrnr (HE(l,R\S
model).
'L
he spatial colr-rpatison alxlvsis of thc mod
clcd inundador-r maps at thc samc tlos' condition
cu:n:lcJ
.
drc
J,cn, 'r .tr'c.m.n ,,n.r pir..l,r'
c...:t.d.,s - rr :,rnrrc.,rcqu"1(...
bl the nvo modcls is 150.18r km (oi a rotal arca of
157 km) or 95.1'li, on 28 Jul.r' 1999 naps, 1.12.08
lim'or 90.59/o on rhc 28 f-ebrual 2003 maps, and
r<lbasr.. I I c..r'er
kmr or 89..10i, on 23 Scptcmbcr 1999 maps
3).
thblc i also detalls rhc a€yccmcnrs and
fl'ablc
drsagtccments bv rhe cafcgories.
'l he rcsults oi thc / tcsts on the mean distance
ftom drc stream cefltcdinc to thc rvatcr/non satet
ot flooded/non tlooclccl bour-rclaries on both banks
of thc inundation maps arc shotn in 'l able.1. On 28
Jolr' 1999, I andp r-alues for thc \\-arer/noo-wxrei
bounclancs atc 1.573 and 0.122 lot the notrh banli
ancl 1.63i and 0.109 iot rhe soutl, banli, rcspec
tl\'ch. 1he I ralucs at borh banks suggest that rhc
r-rull hrlorl,cscs arc nof rcjecrecl, indicarirg rhat the
\\1lrrr' .lor rr,. rr lrnurJ fl(.r r(.u :.1! t.uri th(.
DI-\l-ir-runclation and HIiC R-\S models are ior sre
1.10.34
ustlcallt dtittircnt. Bccause rhcf r.alucs of the I tests
fot thc flood srige flo\v and rccord-l.righ flood flosale all gtcatcr than or cqual to 0.103 (fable:l), rvc
conclude that rhc flooded/non floodcd boundanes
oo the nofth and south banks are statistrcalfi.rhe
saffrc,
t
hr"rs
tir,
the l)FiNl-inundaoon and HFIC,R-\S
moclcls hare comparabLc resulfs in this srudr area.
Thc finclings atc lcrl cncour^gjeg. Ne\r, thc DEII
iltundation moclcl and thc FIIIC R \S modcl rvcr.c
puf to the hnal tcst. lhe accutac\.of rhc modeled
tloocl crrcr-rts at the sercntr-fi\.e sclcctcd sites werc
Lj
r.alidated against the ancillal- datasets collcctcd dut
ing ar-rd aftet thc 1999 llood, as dcscribed in the prcrous sections.'l he rcsults indicatecl thar bod.r rnod
els tcachcd high accuracv (Iable 5). Based on thc
DEII inundation modcl, the producer's accuracics
ate betrvcen 88.31'o and 99.3r.i, en<l uscr's accuracies
93.1u'o and f.i.6'1i,.'t hc or-etaLl accuraq' is 9-5.1oi,.
r
:tjl rl l rh .r(\ rr.ic e. ,rr, .lso ror.l 1ql
thc Fll-(l-R.\S modcl (l rbic
$1 1..in,,
-5).
Conclusion
,\ hldraulic 1D Dl:r.Il inr,rndation modcl,
rvhich is simpler lhan rhe srandarcl complc\ l,D
HEC-lL\S trodcl, has bccn clerelopcd. Comprrcd
with thc HE(l R\S modcl, rhe Dliil-inuoclarion
modcl requires t1\\,c1 tnpur parametets thatare reacliL|
alailable. Thc DF,trl inrLndation modcl is also casicr
to implcmcnr than rhc HLC R-\S modei. l.utthcr.n_orc.cu np..ri.,,n.L(n\rc.l t1 r-rJ. i.,ncrrcn. lr,,m
the models and accuracl elaluatioo tbr a iloo<l cr ent
on thc floodplain of thc'lar/Pamlico Rir.er, Nonh
(iarolina hale sho\\'n that fhc results fron drc nlo
moclcls arc r crv similer and bodr tcachcd or.ctali ac
clLracl greater than 93'r',,.'1hus, the DIIII inundation model can bc an efitctir.c alternatir-e to d1e morc
cotrplcr FII-C-R\S model.
Refote concluding, t e \r)uld likc ro mcfldon
drrce tecent dcrclopmcnts: the crcatio[ of the DIIII
fot thc statc oi \orth (iatoLina, implemcntation of
lnote fl\_cl Eaugl'1g staUons bt' thc USGS, and ar-ai1
abiJln of rcal-time gaugc data. ,\li of rhcsc dc\alop
mcnts posrti\-ch impacr r|c appJicarior of rhc DFI\tinunclation modcl. -\itet thc 1999 tlood in easrcrn
North (iarolina, thc srafc of North Carolina initi
atcd a starewidc flood mappingprogram (\iC Fitxrd
plain i\lapping Progtam 2007). Onc of rhc producrs
dorvnloedablc for free from thc progtan is the starc
s'ide Lieht cletection and rangrng Q,ID,\R) dcrir-ed
DIllI. 'l he DI-trI is oi 15 r 15 m (5iJ s 50 ft.) rcscr
iuoon, and ITas a r_ertical accuracr.of apporir-ratch'
0.2 n-r. One distinct fearulc oF the nc*, LID:\R dcrn'ed Dlrll. as colrrpared rvith othet DtIIs (e.g.,
\.-LD D1-110, is rhat the LID-\R deriled DEtrI has
been hlclro corrcctcd, i.e.! allthe channcls of stteams
l4
Zhpr,
!"
Table 3. Spatial compadson of the inundation extent maps detir,ed ftom both modeLs at fiiee flow
The arca is in Lm'?, and the petcentage within the [l is computed out of the tota] studr.area.
(a) A regular flow
(07
ly
Lt
Tbe
llartl Ctn:z; (
stages.
Table {,
\f:
I
/28/1999)
HEC
DEI,I-inundation model
Non-u'atet atea
Water
R-AS model
Nnn-s7,tPr erc,
\Y/"i.'
\\iter rm-
139.17 [88.7o;]
s.es [3.8%]
0.8.1 [0.svo]
11.01 17.0%l
On nor,!
On so:&
h
h
(a) A flood-stagc flow (02/28/2003)
HtC
Non-flooded atea
R \S moJel
1.07
Flooded atea
87.94 [56.0%]
1 .02 [4.sv"]
Rcgular rir.er atea
0.04 [0.0%]
0.i10
Flooied oc
[0.7%]
43.L3
p1.s9rl
ls.l%l
On nord.
On so::fr
0.00 [0.070]
s.94 [3.87C
11.01 [7.0%]
have been
h
h
l:r:uel
aod po-in:
been temor ei io
l,vsts,
(a) A record-high flood flow
(09
/23 /1999)
HEC-lL\S model
Non-flooded
area
13.0%1
62.67 p9.9ah)
4.64
1.3412..84^l
Regular river area
0.00 [0.0%]
67.09
1.21
sreaal
&
flrgule 8a, are bar
(Figure 8b . S-rce
sufes su{face elesll
Flooded area
Non-flooded arca
l.looded area
ample,
and or-erpassc
112.7y"1
0 10.0%l
6.37 l1.1y"l
10.8%1
10.58 16.7%l
sfr
instead oi tha: oi
dto correcrioq i r
nuiq of rzter ic s
surfaces befleeir (
hydro-correcdocof a steam 'cecoo
r
this simpliEes fre
undation modei r
lina).
The
DE\t-n
used oo a sre3:E
s
The Narth Camlina Ceorrarher) I/olane
|
4, 2006, pp.
I
j-
28
15
Table 4. N{atched-pairs l tests on the $'ater/''on-water or flooded/non-flooded bouodaties derived
ftom DEM-inundation and HEC-R-\S models at thtee flow conditions.
(a)
A regular flow condtnon p7 /28/ 1,999)
Watef /riori-water boundary
On notth bank
On south bank
@)
At tle
1.573
12.20k
1..633
10.9%
flood-stage and record-high flood conditions.
flow
(02/28/2003)
r
p
The flood stage
Flooded/non-flooded
On north bank
On south bant
boundary
The record high flood flow
(09
t
/23/1ee9)
p
1.620
11.1"/,'
1.612
10.3"k
1..490
14.30k
1.648
1.0.6%
have been manually and cleatly delineated by analysts, and portioris of bddges arrd ovetpasses have
been removed from *re DENI (Frgure 8). For ex
tions where prefetably no major inflow from tribu
taries erists. With rhe inflow (ftom the ttibutaries
into the main steam) the sutface watet height at the
ample, stteams cleady depicted by the LIDAR DEM
(Figure 8a) ate barely noticeable in the NED DEM
(figute 8b). Since the airbome LIDAR sensor measutes surface elevation, surface elevations of btidges
dowostream gauging starion will be aqmented. Thus,
and or.erpasses will appear on the uncorrected DENI
instead of that of dre undedying surfaces. The hydro cotrection is necessary to ensute the florv continuity of watef ifl stieams uoder bridges and oo toad
surfaces beneatl overpasses. Thus, because of the
hydto-cottection, the delineatioo of the centet the
of a steam becomes easy or may already be done;
*ris simpJifies tlre implementation of fie DEN{-in
undation model (within the srare of Nortl CaroIna)
The DENI-inundation modelis designed to be
used on a ctream .ecrion berween rwo gauglng sfa-
the inflow can affect the model output. Although
this may limit the applicabiliq' of the model, the er,rcr
increasing numbcr of gaugrag stations in the United
of a ptoblem. Fot example,
atea, thrce additional gauging stations
States is making this less
in the study
(between the Gteenville and Sfashington stations)
har.e been recently added (LISGS
NXriS 2007). The
surface water heights measured at the new Chicod
Cteek and Ttanters Creek stations (e.g, Figures 4
and 5) will help address the influeoce of the tribu
taty inflows (to the Tat River) and estimation of the
sufface water heights at the meeting poilts of the
Tat River/Chicod Creek and Tat River/Ttantets
Cteek. The new gauging station (SR1565) near
Grimesland at Tar Rivef flot only divides the stream
ro
Zhenlr d-7 Wa
!
The North
Cz-,is
t
Table 5. Error matrix and classiFcation accuracy derir'-ed from bo*r modeis at sitcs of tegular water,
flooded, and non-flooded areas. The date is 23 Seprembct 1999. The atea is in kmr.
(a) DENI inundarion model
Reference data
Model
o.otqwt
l.koded
area
Non-/looded
Flooded area
1.17
0.31
Nan llooded ared
Rega/ar water area
0.24
0.00
4.98
Tatal
1.41
area
Repalar uatet
area
0.24
0.08
0.03
ProCucer! acctracr :o ,,
Total
4.72
+.31
5.30
4.34
4
6i
1416
rccJraclo
,r
L ser.q
Flooded area
88.3
94.6
Non-flooded area
93.9
93.6
Regulal rvatet area
99.3
93.1
Overall Accuracy 95.17o
Figure 8- Sll
comP2rE
(b) HEC RAS N{odeL
segment betsreed
Model
F-/ooded
output
area
arca
4.22
Floaded
Non,fl.aaded
area
trt
tlvo segmeolr-
Refetence data
BJgklar water
dtea Tltal
0.23
0.18
4"63
Nonflooded area
0.19
5.04
0.06
5.29
Rega/ar water area
0.00
1.44
4.41
0.05
5.32
1.39
7bt.
4.63
t4.36
dent
measurem
tictmore. dre
of nearlr
L9
18.[f,8
more lil<elr 6ar d
two statiofls. Fro
herght meaolu
one can use the
s
extent scenrlos tt
Producet's
Flooded area
91.1
95.7
Non-flooded area
Regular vater alea
95.2
94.7
98.9
94.8
Overall Accuracy
1
tty The h{tr deai
the
DE}I-inuodai
ing the need. tor
situations br 6e d
agencies at ditt-erer
situations $ here d
9
3.19ro
logrc/ hr-draulic hc
implement dre
R'\S,
u
TELE\L\C-
Figure 8.
Strean-rs or centerlines are cleady delineated in the hydro-corrected
LIDAR DEX{ (a)
compared to the USGS DEN.I (b). The DIIN{s cor.et ateas near (east ot)
Greenr_ille. NC.
scgment betwcen Gteeor.ille and Washington into
two segments, but also providcs another indepefl_
dent measutement of the sutface rvater height. Furthcrmore, the USGS cutrendv maintains a network
of nearlr. 18,000 gaugng stations across the country. The high densirr of gaugillg stations has made it
more likelv that thete is no major tributary between
two starioos. Finallv. using feal-time surface water
heighr reasuremerrs ar.alal_r c ar gruging .rauq-,t.,
ooe can usc the model to simulate a range of flood_
cxtefll scenaflos 1n an e1rcnt of a flood. Thereforc,
tie DEN{-inundation model wi11be capable of meet
ing t-hc needs for quick imolemerradon in wgenr
situations by the flood management and mitigation
diffetent gor:€inmeflt levelsJ especially in
situations rvhere thete is a lach of suf{icient hydroagencies at
logic/hldrauli, knorr ledg< and ti-ru,rd,esource\ ro
irnplemeot tJre mote complex modeis (e.g, HEC_
RAS, TELENL{C 2D, and LISFLOOD },p).
as
Refetences
Ackerman, C, T., Evans, T. A., and Brunnei, G.
W., 2000. HEC GeolL,\S: Linking GIS to hv
dtaulic analysis using ARC,/INFO and HECIL{S. In: N{aidment, D., Djokie, D.
@ds.), H-1
drokgi and H-1dua/i. Madeli g Srlj)part uith Gea
Infomatitt Sylnnt. ESRI press, New york.
Acrement,Jr., G., and Schneider, V, 19g9. Guide
graplic
for selecting tr{anning,s roughness coefhcients
for narural channel and floodplains. LlSG.l1.eth
ica/ Rqon W.\'P2ii9.
Al-Sabhan, W., Mulligan, M., and Blackburn, G.
A., 2003. A real-rime hv&ologrc modei for flood
prcdiction using GIS ar'd r\eW\l' Conpaten,
Enirannent, and IJ tb.ta SJnenr.2j,9-32.
Bates, P. D., and De Roo, A. p. J., 2000. A simple
raster based modcl for flood inundation simu_
lattor. .loarna/ o.f Hldro/agy,236, pp. 5l_17 .
Bates, P. D., Wilson, M. D., Hordtt, M. S., 2006.
.y'.
floodplain inundation dynamics ob_
scr\-ed using airborne synthetic apeihrre radar
Reacl-r scale
Zhcn.g
imagcrr: l)ata analvsis aod modeling. /azrzzl
[
|
fi nkgl,
af'
328 (1 -2): 306-318
Chang, T. J., Hsu, M-H., Teng, W-H., and
Huang, C-J., 2000. -\
(lIS
disributcd
t'etcrshcd modcl tbr simulanog flooding and
assisted
tnur,rlatiotr. .larrnal of tc .lmeictt V'aterRetoutut
.,7!!aid/irt. 3 6(5): 9r5 988.
Chow, V T.,1959, Orlen (banw/ I lldnulit.\IcGrawILIL Book Companr, Ncrv \brk.
Colbn J. D., Mulcahy,
K,
and Wang,
Y,
2000.
lodeling floocling extcnt from Hurricane Fiold
h tlre coastal plains of North C,atdtra. Enitr
ronlrrn/dl I Ididrd!.2: 157-
1611.
Correia, F. N., Rego, F. C., Saraiva, M. D., and
Ramos,I.,1998. CoupLing GIS rvirh hldtologLc
and lrldtaulic flood n-rodeling. V'dler Ra;our*t
llanagentn/. 12: 229 219.
Dobson, R., and Li, X., 2000. il hc accuracv ard
cfltcicncl of CIS-based floodplain detetmioa
tions. In: \Iaidment, D., Djokic, D. (L.ds.), lJ1rlralogtt and Illdna/i t\Iodling.f gfoi tuilL Gea
gtphi tnlirnatian Jj'tla,,z.r l.)Sl{l Prcss, Ncrv\.orL.
Galland,J. C., Goutal, N., Hervouet, J . M.,1991.
'i FlLEltrl.\C-a ncu, numcdcal-modcl for soh'ing
shxlk)\ \\.efct eg.r tlons. .,1ird te! in ll'aler I\t
razr,n. 1.1 (3): 13ii i.lli.
Horitt, M.
S., and Bates, P. D., 2001. Effccts of
spatirl rcsolution on a iasrer based model of
flood flors. Jarrn al al lJldrolagl. 253, pp. 239 -249.
Horritt, M, S,, and Bates, P. D., 2002. Evaluarion
of 1D aod 2D numcricel tnodels fot ptedicting
nlcr flood inr,rndation. H y/ro laELu / P 'aallrt. 268
(1,:l): 87-99
Horritt, M.
\O\'
S., Bates, P. D., and
Mattinson, M.
J., 2006. I,iffects of mcsh tcsolr,rtion en<l topo
graphic rcprcscntation io 2I) finite |olumc
models oi shallow \\'afet flit'ral t1o*-. .launal ol
t lydn log. 329 (.1 -2): 306 311.
Hunter, N. M., Bates,
P.
D., Horritr, M. S,, De
Roo, P. J., and Werner, M. G. F., 2005. Utilin'
looJ r"f Ctffcrcrrr .r..r.. r1e. t'- c.,Ll'-r'rnq
undatioo models s'ithin a (]LUE liames.ork.
I lydnkgy and Eartl Jjrnn Sienn.9 (1):172-130.
Hydraulic Engineering Center, 1997. I IE(. P-/LJ'
Riler .1nahri.r ,ten: Hlrurli Relirenu llanta/.
Hlclraulic Enginccring (ienter, Dar-is, C,\.
V
att.2
The
Kraus, R., 2000. Floodplain determinrrion using
--\rcYicrv CIS and FILC-R \S.ln: trlaidment, D.,
D (I:ds.), lfinln$t atd H-lduttli Nodelin! J ffarl witL Cuograpl:it Inlilrndti)n .1.)ltenr.
ESRJ Ptess, Nerv \blk.
Mileti, D. 5.,1999. Dltat/,::r: $ dcsign: d rctrlcvenl
r.tl nutunt I ha:.a r* h the L- nttel S tu tr.t.
John Hcnr\
Djoloe.
1)ress,
\\iashilgton D.C.
NC Floodplain Mapping Program, http://
*:ncfl oodmaps.cotl. I-ast acccssed: Dcccm
ber 2001.
Nicholas, A.P., and Mitchell, C.A., 2003. Nun.reri
r,,'s
cJ 'lmLrrrno" oiu.erL,tr'. 1'1 '6s q:. 1ep6
3-"phi,,'11. (umfl( \ flaodnl3 - rn\'rr"rIn(n,
Hylrologttal Pro,v.r.,er. 1l (:l): 72i-l+0.
.
USACE, http:/ /*.sthec-usace.atmt.mil/sofnvate/
hcc tas/. 1,asr \ccessed: Decembet 2i)0f.
USGS NED, http://ncd.uses.gor-/. Last acccsscd:
Decetnbet 2001.
USGS NWIS, http://\\.aterdata.usgs.gor./nc/nrvis.
l-ast accesscd: Dcccmbet 20lll.
Wang, Y., Colby, J., and Mulcahl', K., 2002. -\r.r
efftcietrt n-rethod fot mapping flood exteit in a
coastal tloodplain b\' intcgtaflng Lendsat '1trl
,rnd Dl-l\t drt^. I tendlil dl .la tr// .l Renate
S e ni tg. 23 (18) 3681 3696.
Wang, Y., 2004. Using l,andsat 7 t ll dara acq,,rited
dals aftcl a throd e|cnt to delinearc thc maxi
rnnm flood on a coastal floodplain. l landhzl1Ltl
.larrna/ al Reno/c Stn.ting.25(5) 959 9
Wang.
Y
t"1.
and Zheng. -t., f,![$. t-,,np. rr*
,r ' 'i
<ligital clcr ation models and undetstanding
.hririrnp..'. r'n
1 2002.
C;
Ll
coastal floodplain
of
(\,(rnr?ll .L4'r.
oi Notth Carolina. laanrl
c ionJ
Hd prdt 1I iau, 6(.1). 34-4A.
Werner, M. G. F., 2001. Impact of gnd sizc in GIS
besed floocl cxtenf mappine using r 1-D {1orv
nodel. Phy.tit.t ani CLutit/ry' al t/tt Earlh Part B
Hlln/o3y
Orat
and .1tnn.tphere.26, pp. 51 ,. -522.
Wernei M. G. F., Hunter, N. M., Bates, P D.,
2005. ldentitrabilin of drstriburcd floodplain
toughness \.alues in llood extert estinraooa.Jrl1/-
,.t q [[ ,.0,. 11.] I t:1.11 tWilson, C., and Ho(ritt, M., 2002. Ileasuring thc
florv rcsistance of submerged gtass. I lldtoiogiLa/
l)lz.r.rra. 16, 2589 259f1.
Xorii
C
;' ':
Wilson, C.
{'. \
and Bare=,
"C)pc::::-.:of sub:-r:--rtlratr,;.:,':;:-,
Yang, C., ani T
GIS br.r::l
pLain
Al lla
r
:e
--:
"::': 56-,5- -.
r
Wilson, C. A., M. E., Stoesser, T., Bates, p. D.,
and Batemann Pinzen, A., 2006. Ciosute ro
"Opcn channel flos, thtough diffitcnt forms
of submergcd flexibl e rcgetaioi' . loarnul al' I 11,
drarll Eu,ginuing ASCE. 132 (7):750-150.
Yang, C., and Tsai, C., 2000. Der.elopmcnt of a
GIS-bascd flood infotmation si,stem for flood
plarn modcling and datnage calcultiot.
Joarnal
aJ
theAm idn ll'ahr
567 517.
RatawLet
lroiaiot.36
e.):