DTIC ADA444118: Measuring Taylor Slough Boundary and Internal Flows, Everglades National Park, Florida

17 Pages·3.9 MB·English

by  Defense Technical Information Center

Measuring Taylor Slough Boundary and
Internal Flows, Everglades National Park,
Florida
U.S. Geological Survey Abstract
Open-File Report 01–225
Four intensive data-collection efforts, intended to
representthespectrumofprecipitationeventsandassociated
flowconditions,wereconductedduring1997and1998inthe
TaylorSloughBasin,EvergladesNationalPark.Flowveloc-
itieswere measuredbynewlydeveloped,portable Acoustic
Doppler Velocitymetersalongthree transectsbisectingthe
Taylor SloughBasinfromeasttowest,roughlyperpendicu-
lar tothe centerline axisofthe sloughaswellasa fourth
transectalongthe slough’saxis.These metersprovidedthe
requiredlevelsof accuracyinflow-velocitymeasurements
whileenablingtherapidcollectionofmultipletimeseriesof
flow data atremote sites.Concurrently,flow measurements
were made alongborderingroadculvertsandunder L-31W
andTaylor Sloughbridges.Flowsacrossthe studyarea’s
boundariesprovidednetflow of water intothe systemand
transectmeasurementsprovidedflow data withinthe basin.
Collecteddata are available throughthe WorldWide Web
(http://sofia.usgs.gov/projects/flow_velocity/). The high-
water andlow-water eventscorrespondedwiththe highest
andlowestflow velocities,respectively.The July1998data
hadlower thanexpectedflow velocitiesand,insome cases,
strongwindsreversedflow direction.
By Gina M. Tillis
1
Report Documentation Page Form Approved
OMB No. 0704-0188
Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and
maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information,
including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington
VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it

does not display a currently valid OMB control number.
1. REPORT DATE 2. REPORT TYPE 3. DATES COVERED
2001 N/A -
4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER
Measuring Taylor Slough Boundary and Internal Flows, Everglades
5b. GRANT NUMBER
National Park, Florida
5c. PROGRAM ELEMENT NUMBER
6. AUTHOR(S) 5d. PROJECT NUMBER
5e. TASK NUMBER
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
U.S. Department of the Interior 1849 C Street, NW Washington, DC REPORT NUMBER
20240
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)
11. SPONSOR/MONITOR’S REPORT
NUMBER(S)
12. DISTRIBUTION/AVAILABILITY STATEMENT
Approved for public release, distribution unlimited
13. SUPPLEMENTARY NOTES
The original document contains color images.
14. ABSTRACT
15. SUBJECT TERMS
16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER 19a. NAME OF
ABSTRACT OF PAGES RESPONSIBLE PERSON

a. REPORT b. ABSTRACT c. THIS PAGE SAR 16
unclassified unclassified unclassified
Standard Form 298 (Rev. 8-98)
Prescribed by ANSI Std Z39-18
INTRODUCTION
Overthelastcentury,manhasextensivelyalteredthehydrologic
systemofsouthern Florida by constructinga system ofcanalsand
leveesforthe purposesofdrainingthewetlands,providingwater
supply,andcontrollingfloods.Althoughtheseeffortsmadesouthern
Floridamoresuitableforurbanizationandagriculture,theycreated
another set of problems, which included lowering of ground- and
surface-waterlevelscausedbyover-drainage,frequentdry-seasonfires
indrought-strickenwetlands,andsaltwaterintrusionincoastalareas.
TaylorSlough(fig.1),historicallyamajorcontributoroffreshwater
toFloridaBay,lieswithinthesoutheasternpartofEvergladesNational
Park(ENP).Theduration,timing,andextentofwetlandinundationof
TaylorSlough’sinterconnectedwetlandsandfreshwaterflowsthrough
FloridaBaycreeksareacriticalcomponentoftheEvergladesecosys-
tem.Sincethemid-1960’s,numerouscontrolstructuresontheL-31W
andC-111canalshavemanipulatedTaylorSloughwaterlevels,resulting
inalteredtiminganddistributionofflowsintoTaylorSlough.Hydro-
logicregimealterationspromotedhypersalineconditionsinFlorida
Bay,alteredplantandanimalcommunities,decreasedpopulations
ofwadingbirdandanimalspecies,andreducedhabitat.Anthropogenic
encroachmenthasplacedtheCapeSableseasidesparrow,American
crocodile,andFloridapantherontheendangeredspecieslist,andhas
had many other detrimental effects on the ecosystem. To better
managethesystem,inflowandcirculationpatternsfortheTaylor
SloughBasinarebeinganalyzedsothatthenaturaltiminganddistrib-
ution offlowstothe basincan assist water-resourcemanagersin
theoverallEvergladesrestorationeffort(McPhersonandothers,1999).
TheU.S.GeologicalSurvey(USGS),incooperationwiththe
Americanalligator EvergladesNationalPark,beganastudyin1997tocollecthydrologic
dataintheTaylorSloughBasin.Thestudywasaccomplishedaspartof
theSouthFloridaEcosystem Program,a collaborativeeffortbythe
USGS,variousotherFederal, State, andlocalagenciesand Indian
tribes,toprovideearthscienceinformationneededtoresolveland-use
andwaterissuesinsouthernFlorida.Ongoingeffortsareunderwayby
theUSGSandENPtocollectadditionalhydrologicdatainthepark.
Purpose and Scope
Thepurposeofthisreportistodescribethemethodologyusedin
collectingandassimilatingflowdataintheTaylorSloughBasinandto
referencetheresultantdataarchiveavailableontheWorldWideWeb
(http://sofia.usgs.gov/projects/flow_velocity/).Datawerecollectedat
boundaryandinternalsitestohelpcalibrateandverifyahydrodynamic
modeloftheinterconnectedwetlandandtidalecosystemandtoprovide
baselinedataforevaluatingprocessessuchasevapotranspiration,flow
resistanceeffectsofvegetation,andground-water/surface-waterinter-
actions.Thiseffortwasoneofthreeconcurrentstudiescollectingflow
data acrossthestudyarea’sboundaries. Flow datathroughFlorida
Bay’s tidalcreeksand along theC-111 canaloverbankand outflow
areasareavailableathttp://sofia.usgs.gov/projects/freshwtr_flow/#data
andhttp://sofia.usgs.gov/projects/coupling_mdls,respectively(Patino,
undated;Schaffranek,undated).
2
Thisreportdescribesdata-collectionmethods,illustratesone
oftheavailabledataformats,identifiesgeometricpropertiesofthe
internaltransects,anddiscussesseasonalvariabilityinsurface-flow
velocitymagnitudeanddirectionthroughtheTaylorSloughBasin.
Datacollectionwasconductedduringfourintensivecollectionefforts
(July1997,September1997,November1997,andJuly1998)and
coveredawidespectrumofprecipitationeventsandassociatedflow
conditions.Seasonalvariabilityinsurfaceflowwithinthebasinas
Figure1. LocationofTaylorSlough
studyarea,southFlorida. wellasnetflowofwaterintothesystemisdocumented.
EXPLANATION
EVERGLADESNATIONALPARK TAYLORSLOUGH
URBANAREA BUILT-UPAREASAND
AGRICULTURALLAND
F
ROCKYGLADES L
O
AIRBOATTRAIL RI
CANAL S-174 CONTROLSTRUCTUREANDNUMBER DA
TRANSECTS
T1 T4
T2 Centerline
T3
(cid:12)(cid:5)(cid:3)(cid:8)(cid:1)(cid:6)(cid:4)(cid:5)(cid:11) (cid:12)(cid:5)(cid:3)(cid:7)(cid:8)(cid:6) (cid:12)(cid:5)(cid:3)(cid:4)(cid:13)(cid:6)(cid:4)(cid:5)(cid:11) (cid:12)(cid:5)(cid:3)(cid:4)(cid:5)(cid:6)
(cid:1)(cid:8)(cid:3)(cid:4)(cid:5)(cid:6) 27 1
S-174
C-113
Homestead
Pa-hay-okee Frog
C
Overlook Pond -1
TaylorSlough 11
9336 Bridge S-332
S-175 S-178
d RoyalPalm
oa Road S-177
R L C
(cid:1)(cid:8)(cid:3)(cid:1)(cid:1)(cid:6)(cid:4)(cid:5)(cid:11) nPark RoRSyataanltigPoeanrlm -31W -111E
ai
M L-31W
M gh Bridge
u
OD Slo
NA or S-18C
RODE Mahogany Tayl C-111 1
E
Hammock
S-197
(cid:1)(cid:8)(cid:3)(cid:10)(cid:8)(cid:6)
NineMile
Pond JoeBay
PicnicArea
WestLake
Florida Bay
BasefromU.S.GeologicalSurveydigitaldata,1972 0 5MILES
AlbersEqual-AreaConicprojection,DatumNAD1983
StandardParallels(cid:1)(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)and(cid:7)(cid:8)(cid:3)(cid:4)(cid:5)(cid:6)(cid:9)centralmeridian(cid:1)(cid:4)(cid:3)(cid:5)(cid:5)(cid:6) 0 5KILOMETERS
3
Previous Studies
TheEvergladeshydrologiccyclehasintriguedresearchersand
environmentalistsfordecades.AmongnumerousstudiesintheTaylor
Slough Basin,the following areexamplesthathaveanalyzed the
relationbetweenrainfall,waterlevels,andoutflowstoFloridaBay
(MeyerandHull,1969;VanLent,1993;VanLentandothers,1993;
Tsihrintzisandothers,1996;Balesandothers,1997).However,inter-
nalflowsweredifficulttoquantifyduringtheaforementionedstudies
asaresultofinstrumentationlimitationsandadverseenvironmental
Figure2. AerialviewofTaylorSlough. conditions.
Area Description
TaylorSlough,withheadwatersintheRockyGladesareaof
westernDadeCounty,providesoneoftwomajorfreshwaterpath-
waysintoeasternEvergladesNationalPark(fig.2).Inthisbasin,
surfacewaterandgroundwaterflowsouthwardforabout20miles
(mi)beforemergingintoFloridaBayviaanumberofsmallcreeks
andchannels.Thesloughcoversmorethan158squaremiles(mi2)
andextendsabout21mifromitsupstreamendnorthofFrogPond
tothecoastalmangrovesalongcentralFloridaBay(fig.1).TheMain
ParkRoadpartiallyencirclesthestudyareatothenorthandwest;
theC-111canalistheeasternmostboundary,andFloridaBayisthe
southernmostboundary(fig.1).Thenorthernportionoftheslough
isfreshwatermarshdominatedbyrushandcypressheads;saltwater
influenceisapparentbythetransitiontosawgrassandmangroves
onthesouthernpartoftheslough.
Precipitation
Figure3. Monthlyrainfalland30-year PrecipitationdatafromtheNationalOceanicandAtmospheric
normalmonthlyrainfallfortheNational
AdministrationstationattheRoyalPalm VisitorCenter,located
OceanicandAtmosphericAdministration
withinthebasin,wasutilizedinthisstudy(fig.3).Thebimodalwet
stationattheRoyalPalmVisitorCenter,
EvergladesNationalPark,Florida. season,whichischaracteristicofsouthFlorida,hasintenserainfall
25
30-YEARNORMALPRECIPITATION
TOTALMONTHLYPRECIPITATION
S
E 20
H
C
N
I
N 15
I
N,
O
TI
A 10
T
PI
CI
E
PR 5 Data
o
N
0
F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D
1996 1997 1998
4
Table1. Timetableofdata-collectiontrips
[Darkshadingrepresentsthedatesofdatacollection]
1997 1998
7/29 7/30 7/31 9/22 9/23 9/24 9/25 9/26 11/17 11/18 11/19 11/20 7/20 7/21 7/22 7/23
Transect1
Transect2
Transect3
Transect4
Centerlineofslough
C-111outflowarea
L-31W
TaylorSloughbridge
Parkroadculverts
C-111culverts
duringJune,followedbyaperiodofminorprecipitationeventsuntil
theonsetofgreaterrainfallinlateAugustorearlySeptember(Van
Lent,1993;McPhersonandHalley,1996).The1997calendaryear
wasaparticularlywetyear,mostlikelytheresultofElNiñoinflu-
encedweatherpatterns.Juneprecipitationpeakedat20.90inches
(in.),morethantwicetheaverageof9.64in.(NationalOceanicand
AtmosphericAdministration,1996-98).
DATA COLLECTION
Fourintensivedata-collectiontripsintotheTaylorSloughBasin
wereconductedduringJuly,September,andNovember1997,and
July1998(table1).Thesetripscoincidedwithprecipitationevents
thatwouldproducesufficientwaterlevelsforairboataccess(fig.4),
andcoveredawidespectrumofwaterlevelsandflowconditionswith
whichtoconductanalyses.Datacollectedinthisstudyhavebeen
usedtocalibrateandverifyahydrodynamicmodeloftheintercon-
nectedwetlandandtidalecosystemandtoprovidebaselinedatafor
evaluatingprocessessuchasevapotranspiration,flowresistance
effectsofvegetation,andgroundwater/surface-waterinteractions.
(Harvey,1996;JenterandSchaffranek,1996;Schaffranek,1996;
LeeandCarter,1997;Swain,1999).
Equipment
Thedata-collectioneffortcoveredawidevarietyoftasksand
requiredvarioustypesofequipment.Atsiteswheretheuseofacoustic
instrumentswasimpractical,vertical-axiscurrentmeterswereusedto
Figure4. AirboataccesstoTaylorSlough.
measurewatervelocity.Vertical-axiscurrentmetersoperatebasedon
theproportionalitybetweenthevelocityofthewaterandtheresulting
angularvelocityofthemeter’srotor.Thenumberofrevolutionsthe
rotorcompletesduringameasuredintervaloftimeisdirectlyrelated
tothewatervelocityatthatpoint.Additionally,multiplyingthewater
velocitybythecrosssectionalareaofthestreamproducesanestimate
ofdischarge.
5
Acousticinstruments,calledAcousticDopplerVelocity-meters
(ADVs)andAcousticDopplerCurrentProfilers(ADCPs),usethe
Dopplershiftprinciplebytransmittingsoundatafixedfrequencyand
recordingthefrequency-shiftedechoesreturningfromparticlesinthe
Figure5. SignalpatternsofanAcoustic
DopplerVelocitymeterandAcoustic water(SimpsonandOltman,1993;Gordon,1996;SonTek,1996).
DopplerCurrentProfiler.
Bymeasuringacoustictraveltime(fig.5),theseinstrumentsareoften
capableofdetectingthedistancetoasolidboundary,suchasachannel
bottom.Thecompass-equippedADVrecordsthevelocityinthree
directionalcomponents:X,Y,andZ,whicharetranslatedintomag-
neticeast,magneticnorth,andup.Thewading-rod-mountedADV
isapointvelocitymetercapableofmeasuringvelocitiesaslowas
0.0033feetpersecond(ft/s)indepthsasshallowas0.33foot(ft).
ADV
AcousticDoppler
Velocitymeter
ADCP
AcousticDoppler
CurentProfiler
Compass
Customized
wadingrod
6
Thesamplevolumecentroidisapproximately0.16ftfromtheprobe
tip.Thevessel-mountedADCPmeasuresvelocitythroughoutthe
water-columnandcomputestotaldischargeastheboatmovesacross
thecrosssection.TheADCPaccuratelymeasuresflowsasslowas
0.4ft/sindepthsasshallowas3.3ft(USGS,1997;RDInstruments,
undated).
Customizedwading-rodsweredesignedforADVvelocity-profile
measurements.A top-setting rodwasusedbecauseofthe conve-
niencein settingthe meter atthe properdepth. The top-setting
wading-rodhasa1/2-inchhexagonalmainrodformeasuringdepth
andanadapted3/8-inchdiameterroundrodforsettingtheposition
oftheADV,accountingforthesamplevolumeoffsetfromtheprobe
tip.Typically,awading-rodbasemeasures31/4in.indiameter.The
speciallydesignedwading-rodbasediameteris1ft.Thelargerbase
distributesthe rodandmeterweightover agreaterareaandmini-
mizes compaction ofthesoftlitterlayeron theslough bottom.
Thebaseplaterestsonthelitterlayer,andthedepthofwateris
readonthegraduatedmainrod.
Figure6. TypicalAcousticDopplerVelocity
metermountedonaspeciallydesigned Water-quality meters(collocated withall velocityprofiles)
wadingrod. collecteddataatmiddepthandmeasuredthetemperature,specific
conductance,salinity,dissolvedoxygen,andpH.Measuredtemperature
andsalinityvalueswereusedincomputationofwatervelocitybecause
bothparametersaffectthespeedofsoundinwater.Allwater-quality
meterswerecalibratedatthebeginningofeachday.
GlobalPositioningSystem(GPS)instrumentationestablished
horizontalsampling locations inNorthAmerican Datum of1983
(NAD83)coordinates.Fieldnotesincludedthelatitudeandlongitude
coordinates,GPSdrift,anddescriptionofdistinctivefeatures,(nearby
staffgagesandcypressheads).Thesecoordinateswereconvertedto
UniversalTransverseMercator(UTM)coordinates(NAD83,Zone17)
forreportingandmodelinputpurposes.
Afterpositioningthe ADV foravelocity measurement with
minimumdisturbancetothesurroundingvegetationandflowfield,the
hydrographerretreatedfromtheprobeandthepresumedflowpath
(fig.6).About2minuteswasallowedforthesampleareatoreturnto
equilibrium beforestarting avelocitymeasurement.Measurement
burstslasted120seconds,ata10hertzsamplingrate,andproduced
time-seriesmeasurementsof1200pointsattheappropriatedepthsin
thewatercolumn.
Description of MeasurementSite Network
Thedata-collectionnetworkwasestablishedforthepurposeof
quantifyingboundaryandinternalflowsfortheTaylorSloughBasin
alongfiveinternaltransectsinthebasinandthroughculvertsacross
theMainParkRoad.Theinternaltransectsdatawereusedtodeter-
minesurface-flowmagnitudeanddirectionthroughthebasin.The
MainParkRoadprovideda“natural”boundarytothestudyarea.
7
Inflowsacrossthisboundaryweremeasuredconcurrentlywiththe
internaltransects,utilizingvertical-axiscurrentmetersandADCPs.
TwoconcurrentSouthFloridaEcosystemprojects,theFloridaBay
andCanalWetlandFlow/TransportInteractionprojects,provided
tidalcreekflowandC-111canaloverbankandoutflowdataalongthe
southernandeasternboundariesofthestudyarea(Patino,undated;
Schaffranek,undated).
Measurementsiteswererestrictedtoareasalongestablished
airboattrails(fig.1).Initially,internalflowsweremeasuredacross
threetransectlines(T1,T2,andT3)bisectingtheTaylorSlough
Basinfromeasttowestaswellasatransectalongthecenterline
axisoftheslough.InNovember1997,afourthtransect(T4)was
addedtothedata-collectioneffort,connectingtransectsT2and
T3alonganorth-southairboattrail.Three-dimensionalvelocity
measurementswereconductedatthetransectsitesutilizingADVs,
which provided therequiredlevelsofaccuracyaswell asrapid
collection of multiple time series of flow data at these remote
sites.Waterdepth,water-qualityparameters,litter-layerthickness,
weatherconditions,sitedescription,sitelocation,bottomconditions,
andvegetativecoverwererecordedconcurrentlywithADVmea-
surements.Individualvelocitysamplingsiteswerechosentoberepre-
sentativeofthevegetationtypeanddensityaswellaswaterdepthin
thesurroundingarea.
Forwaterdepthslessthanafoot,thevelocitymeasuredat60
percentofthedepthfromthewatersurfacewasusedasthemean
velocity in theverticalwatercolumn.Thethree-pointmethod
(multiplemeasurementsat20,60,and80percentofthedepthfrom
thewatersurface)wereusedwhenwaterdepthswere1ftorgreater.
Windinfluence,non-uniformbottom,vegetativeresistancetoflow,
variableflowarea,andshallowwaterdepthsaddedtothecomplexity
ofthevelocityprofile.Therefore,thethreeobservationswereaver-
agedarithmeticallytodeterminethemean water-columnvelocity
(Rantzandothers,1982).Onoccasion,morepointsweremeasuredin
thewatercolumnandthedepth-weightedmeanoftheobservations
wasusedasthemeanwater-columnvelocity.
Flowthrough128culvertsacrosstheMainParkRoadfromthe
ENPentrancetoNineMilePond,fig.1,wasmeasuredusingvertical-
axisPygmycurrentmeters.ThePygmycurrentmeterswereusedfor
waterdepthsof0.3to2.5ftandvertical-axisPriceAAcurrentmeters
wereusedfordepthsof2.5ftandgreater(Rantzandothers,1982).
FlowunderTaylorSloughandL-31Wbridgeswasmeasuredwith
vertical-axisPriceAAcurrentmeters.Additionally,anADCPmea-
suredflowlossesfromtheL-31Wcanal,betweenstructureS175and
itsterminus(about3.5misouthofS175)whereallflowbecomes
sheetflowthroughthewetlands.
8
Geometric Properties of Transects
Thedata-collectioneffortintendedtohavetransectsperpendicular
to theslough axis.However,tominimizeenvironmentaldamage,
measurementswereconfinedtolocationsalongestablishedairboat
trails(fig.1).Thesetrailsfollowtheslough’snaturallandscapefea-
turesandarenotalwaysperpendiculartothesloughaxis.TransectT1
isfairlystraightwiththeexceptionofadetouraroundcypressheads
neartheslough’scenter.TransectT2isthemostnoncollineartran-
sect,owingtonumeroustreeislandsandfirebreaks.TransectT3’s
bowedshaperesultsfromthenaturalmeanderofcreeksthroughthe
densemangroveforestnearthecenterlineoftheslough.However,the
mangrovesgivewaytoopenwaterandsparsesawgrassonthewestern
andeasternsectionsofthetransect.TransectT4followsawinding
airboattrailsouthfromtransectT2totransectT3.
Data Analysis
ADVdatawerepostprocessedutilizingsoftwarefromtheequip-
mentmanufacturer.Postprocessedfilesincludethecontrolfile(input
informationrequiredtooperate theADV equipment), velocity
(componentsinthemagneticeast,magneticnorth,andupdirections),
correlation(dataqualityforeachofthethreeacousticreceivers),and
signal-to-noiseratio(signalstrengthforeachofthethreeacoustic
receivers).
Anautomatedspreadsheetincorporatedpost-processedfilesfor
furtherprocessingtodeterminetheaverageeast-westandnorth-south
velocitycomponentsateachmeasurementdepth.Thevelocitycompo-
nentswereadjustedtoaccountfordeclination,thedifferencebetween
truenorthandmagneticnorth.Thesedatawereusedtocalculatethe
time-averagedvelocitymagnitudeanddirectionateachmeasurement
depthaswellasthemeanwater-columnvelocity,withrespecttotrue
north,foreachmeasurementsite.
Adatabasewasdevelopedtofacilitateinformationanddata
transferofallcollecteddatatoSouthFloridaEcosystemProgram
researchers.Thedatabasecontainsallfieldnotedataaswellaspro-
cessedvelocitydata.Thedata-base“key,”auniqueidentifierforeach
data-baserecord,isbasedonthesitelocationanddateofmeasure-
ment.Forexample,W01T20997representsthemeasurementatsite
W01ontransectT2inSeptember1997.Sitelocationsareavailable
inbothNAD83latitudeandlongitudecoordinatesaswellasUTM
coordinates.Anoutputdataformatthatemulatestheactualfield
notesisshowninfigure7.Thedatabaseandspreadsheetscanbe
accessedathttp://sofia.usgs.gov/projects/flow_velocity/ontheWorld
WideWeb.
Asaquality-assuranceprocedure,spotcheckswereconductedas
wellascompleteduplicationofthedataanalysisprocessforrandom
sites. Utilizinga spreadsheettemplateminimized datainput and
processingerror.Additionally,examinationofthecontrolfile,filtered
datasummaries,profilecomputations,histograms,andgraphshelped
detectdataerrors.
9