375
1 INTRODUCTION
Santos Port, in São Paulo State Coastline (Fig.1),
throughputsapproximately15%ofBrazilianmaritime
cargo,morethan110milliontonsperyearandisthe
most important maritime cargo transfer terminal in
theSouthernHemisphere.Therequirementtoenlarge
and deepen the Santos Port Outer Access Channel
(depth,
width and radius) to receive Post Panamax
Plus and New Panamax, typically vessels of 12,000
TEUs(LOA=398m,B=56.4m,Tfullload=15.0m)
trainingwallscrossingtheOffshore Bar are the best
cost‐benefit solution to avoid huge dredging rates.
Thisconceptwasalready
presentedinthefirstMaster
PlanofSantosPort,proposedinthesixties,anditis
thePhase1 oftheSeawardConceptualPlanningfor
the Offshore Port (Alfredini, Arasaki & Moreira,
2015).
Furthermore,thesealevelriseoccurredinthelast
century (IPCC, 2014) and the increasing rates of
extreme
events of storm surges require different
alternatives concerning sea defenses structures in
Santosbeaches,mainlyinPontadaPraialocation.
AccordingtoAlfredini,Arasaki&Moreira(2015),
the construction of two training walls, with a total
length of 9 km, is an engineering solution for the
reducing Santos Port dredging
rates in the Offshore
Bar. Indeed, this solution would provide a
significantly reducing the maintenance dredging
OPEXcosts,re‐designingthechanneldimensionsina
suitablewayforthelargervessels.
Otherwise,duetothestormsurgeattackinPonta
daPraiaarea(Fig.1),itisalsoimportanttoprovidea
shoreprotectionstructure.
For Port and Municipality Authorities decision
support, the Hydraulic Laboratory of Engineering
Alternative study for the Nautical and Shore Protection
Structures in the Estuary of Santos, Brazil
P.Alfredini,E.Arasaki&J.C.M.Bernardino
UniversityofSaoPaulo,SaoPaulo,Brazil
G.daSilva
HydraulicTechnologicalCenterFoundation,SaoPaulo,Brazil
ABSTRACT: For the enlargement of the nautical dimensions of Santos Port Outer Access Channel (Brazil),
trainingwallscrossingtheOffshoreBarareneeded. Thetrainingwallschoicetoreduce dredgingratesalso
inducestoconsideracouplingplanningbetweennauticalpurposesandshoreprotection
measures,asSantos
Municipalityhaveseriouserosionproblemsnowadaysduetotheurbangrowthinthebackshoreandsealevel
rise. For decision support, the Hydraulic Laboratory of Engineering School of University of Sao Paulo was
commissionedtostudyinacompositemathematicalandscalemodel.Resultsincludechangesin
waveheight
anddirectionand currentspeedanalysisto conditionswithtrainingwallsandsegmentedbreakwaters.The
water renewal was also analyzed to the condition with segmented breakwater and compared to current
situation,basedonhydrodynamicsresultsandconsideringthatthisstructurecanreducewaterqualityinthis
area.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 12
Number 2
June 2018
DOI:10.12716/1001.12.02.19
376
SchoolofUniversityofSaoPaulowascommissioned
to evaluate, in a composite mathematical and scale
model (Fig. 2), the morphological impacts of the
trainingwalls,consideringthenauticalpurposesand
a compatible solution for the shore protection
structures.
Thegoalinthispaperistopresentthefirstresults
of two conceptual projects solution, considering the
nautical purposes as mandatory, but also trying to
find a compatible solution for the shore protection
structures.
2 MATERIALANDMETHODS
2.1 StudyArea
SantosCityislocatedintheSouthernBrazilianlittoral
and constantly faces negative impacts with storm
surge events and
consequent inundation of coastal
areaanderosionduetowaveactionandsealevelrise.
ThemostcriticalareainthisbeachiscalledPontada
Praia,locatedintheeasternendofthisbeach.Itisa
residentialareawhereislocatedtheAvenueSaldanha
da Gama, and is near
the maritime entrance to the
PortofSantos(Fig.1).Atechnicalanalysishasbeen
developedbyAlfredinietal.(2013)whodiscussesthe
possible causes of this event and explains the
situationagainstsealevelrise.
Figure1.Locationmapofstudyareaandobservationpoints
P1,P2,P3andP4(dots).
The data set was obtained with an ADCP gauge
fromSantosPilot(2016),locatedinpointP2(seeFig.
1). Two conceptual projects solutions were studied:
the construction of training walls and a segmented
breakwaterstructure(Fig.3).
2.2 NumericalModellingDescription
Theeffectivenessandefficiencyofthecitedstructures
were analyzed
using numerical modeling. Delft3D
numericalmodel(DELTARES,2014),FlowandWave
modules, was used in the present study with the
application of complete formulations for shallow
water equation finite‐difference calculation, the
hydrostatic hypothesis and the Boussinesq
approximation. The Boussinesqapproximationstates
that,ifdensityvariationsaresmall, the density
may
be assumed constant in all terms except the
gravitationalterm(Broomans,2003).
AccordingtoChatzirodou&Karunarathna(2014),
Delft3D is a finite difference code that solves the
Navier‐Stokes equations under the Boussinesq and
shallowwaterassumptions,in2Dor3Ddimensions.
For a 3D flow simulation, the system of
equations
thenreads:
dU dV
S
tx y
(1)
2
0
11
xx x V
UUUU u
UV fV PFM
txyh h
(2)
2
0
11
yy y V
VVVV
UV fU PFM
txyh h
(3)
where f is the Coriolis parameter; U and V are the
horizontal velocities in x and y directions;ωis the
verticalvelocityinrelationtoσcoordinates;F
x,Fyare
the horizontal Reynold’s stresses; ν
V is the vertical
eddy viscosity; P
x, Py are the horizontal pressure
termsapproximatedby the Boussinesq assumptions;
M
x, My are external forces added as source or sink
terms in the momentum equations (2), (3); ρ
0 is the
reference density; S represents the contributions per
unitareaduetothedischargeorwithdrawalofwater,
evaporationandprecipitation;ζisthewaterlevel;dis
thewaterdepthinrelationtoareferencelevelandhis
thetotalwaterdepth(h =ζ+d).
Delft3D‐
Flow module grid includes São Vicente
Estuary,SantosEstuaryandBertiogaWaterway,with
59096elements.Thegridresolutioninthestudyarea
has15x15manditwasusedonelayerinthevertical
direction.
Basedonwaterlevelandwatercurrentfielddata
(Santos Pilots, 2016) was possible to calibrate
and
validate the mathematical model. Boundary
conditions, as wave height and direction, wind
velocityanddirection were obtainedwiththeaid of
theWAVEWATCHIII
®
modeldevelopedbyNational
Oceanic and Atmospheric Administration, National
WeatherService,NationalCentersforEnvironmental
PredictionandMarineModelingandAnalysisBranch
(NOAA/NWS/NCEP/MMAB,2016).
Data analysis was based on the variation due to
the presence of the structures in wave significant
height and direction and current intensity and
direction. The
period simulated started on June 17
th
,2012 and finishedon July 15
th
,2012. Itincludes the
stormeventofJune20
th
,whichgeneratedwaveswith
significanthigherthan2,5minpoint P1 (Fig1).The
scenariossimulatedweredefinedas:
S1‐No Structure: current situation, without any
structure;
S2‐Trainingwalls: futuresituationin long‐term,
withnauticalpurposes;
377
S3 – Segmented breakwater: future situation in
short‐termwithcoastaldefensespurposes.
The scenario 3 includes an analysis of water
renewal. This analysis was included because this
structure can affect water circulation and
consequentlyleadstopoorwaterqualityinthisarea,
therefore,aconstanttracerhasbeen
includedtoS3.
2.3 ScaleModel
The Spectral Wave Simulator for Port and Coastal
Studiesisconstructedinawavebasinreproducingin
fixedbed,aportionofSantosBayandPontadaPraia
Beach. It is a facility of Hydraulic Laboratory of
PolytechnicSchool,UniversityofSãoPaulo.
This
facility(Fig.2),withdimensionsof37mx17
mx1.5m,hasawaterreservoircapacityof650m
3
,10
independent piston wave generators with 1KW for
500 mm piston translation. Irregular short‐crested
spectral waves can be reproduced with individual
wave period above 0.6 s (f = 1.66 Hz) and wave
heightsbetween8and250mm.
Figure2. General viewof the SpectralWave Simulator for
Port and Coastal Studies of Hydraulic Laboratory of
PolytechnicSchool,UniversityofSãoPaulo.
3 RESULTSANDDISCUSSION
3.1 EffectsonWaveandCurrent
Simulation results showed thatboth structures were
effective with the purpose of protecting Ponta da
Praia Beach from higher wave height. Figure 4
presents the significant wave height in the storm
surgeevent(July20
th
,2012at15h:00).
Comparing Figure 4 (A and B) it is possible to
verifythedifferencesbetweenwavesignificantheight
withoutandwithtrainingwalls,whereasFigure4(A,
C and D) shows the effect of the segmented
breakwater in comparison to current situation.
Indeed,itispossibletoobserve
thediffractioneffect
in breakwater gaps, illustrating the effect on wave
directionandheight.
Although wave incident direction is parallel to
training walls alignment, wave height was reduced.
Figure 5 shows the entrance area of training walls,
where is verified the influence of the structure in
reducingthewaveheight
anddirection.
Figure3.Schematiclocationoftheproposedtrainingwalls
andsegmentedbreakwater.
Figure4. Significant wave height (m) during the storm
surgeeventon July20
th
,2012 at15h:00,for threedifferent
scenarios:A–S1‐Currentsituation;B–S2–Trainingwalls;
C–S3‐Segmentedbreakwater;D–ZoomS3.
Figure5. Wave peak direction to S1 (blackvector) and S2
(whitevector).
Figure6showscurrentintensityanddirectionfor
the time of maximum flood and ebb velocities in
springtideconditionsforscenariosS2andS3.
378
3.2 WaterRenewalontheBeach
Consideringthatthehydrodynamicsoftheareawill
changeaspresented onitem3.1,thereisanotherissue
tobeconsidered,thewaterrenewalonthebeacharea.
This aspect was analyzed to the condition with
segmentedbreakwaterbasedontheresultsobtained
from
current intensity(Fig.6 A and C), fromwhere
was observed lower currents to the condition with
breakwater in comparison to the condition with
trainingwalls.
Figure6.Currentintensity(m.s‐1)anddirectionforScenario
2:A‐flood;B–ebb. ScenarioC–flood;D–ebb.
In order to analyze this aspect, a constant tracer
source was included on the hydrodynamic
simulation.Thesourcehasaconstantconcentrationof
10kg.m
‐3
anditsoutputsarelocatedat5pointsonthe
lee of the breakwater segments. After one week of
constantdispersion of traceronthebeach,resultsof
itsconcentrationwereanalyzed.
From Figure 7 it is observed that the tracer
concentration increases in the situation with the
segmented breakwater,
as expected. Besides, it was
observedavariationontracerconcentrationalongthe
beach.Thehighestconcentrationislocatedonthelee
of the spur breakwater, reaching values near the 10
kg.m
‐3
,whereasthelowestconcentrationislocatedat
the last breakwater, with concentrations near 0.1
kg.m
‐3
.
Figure7.Tracerconcentrationnexttothecoastline(kg.m
‐3
)
anddirectionforScenario1:A,andScenario2:B.
3.3 TimeSeriesforWavesHeight
Figure8presentstime‐seriesfromJune17th,2012and
finishedonJuly15th,2012forwaveheightinP4.The
significant reduction in wave height shows the
effectiveness of the segmented breakwater (S3) in
protectPontadaPraiaBeach.
3.4 StormSurgeEventRegistered
inAugust21st,2016
InFigure9ispresentedthelocationmapshowingthe
curveoftheOffshoreBarChannel.
TheSantosPilotsADCPgauge,locatedintheP2
(Fig.1),recordssealevelandsignificantwaveheight
(Figs. 10 and 11), according to Santos Pilots (2016).
The Meteorological Station
of Santos Pilots
anemometerrecordsthewindintensity(Fig.12)and
direction(Figs.9and13).
Confirming that the environmental premises
considered in this study are adequate as extreme
eventsfordesignpurposes,inthisitemisdescribeda
recentstormsurgewithatleast10yearsofrecurrence
period.
Figure8.SignificantwaveheightinP4toS1(continuousline),S2(dashedline)andS3(dottedline).
379
Figure11.SignificantwaveheightinP2duringthestormsurgeofAugust21
th
,2016.
In August 21
st
, 2016, an extreme event was
recorded in the ADCP (Figs. 10 and 11) and in the
Meteorological Station (Figs. 12 and 13). The storm
surgewasinducedbywindblowingmorethan12h
from SW fetch (Fig. 13), with maximum velocities
from20to58knots(Fig.12),rising
morethan1mthe
predicted astronomic sea level in Santos Bay and
inducingseawavesupto4.25m(seeFig.11).
Figure9. Location map with wind direction during the
stormsurgeofAugust21
st
,2016.
Figure10.MeasuredsealevelinP2duringthestormsurge
of August 21
st
, 2016: maximum height (astronomical high
water); minimum height (Chart Datum); predicted level
(dotted);measuredlevel(continuousline).
3.5 ScaleModelResultsfortheSegmentedBreakwater
The tests in the scale model of scenario S3, with a
stormsurgesimilartothesimulatedinthenumerical
model, is showed in Figure 14. It is possible to
observe the similarity of the diffraction pattern
comparingwithFigure4D.
Figure12.WindintensityduringthestormsurgeofAugust
21
st
,2016.
Figure13.Graphicofwinddirectionduringthestormsurge
ofAugust21
st
,2016
380
Figure14. Zenithal picture of the diffraction pattern with
thesegmentedbreakwaterinthescalemodel.
4 CONCLUSIONS
Thispapershowedthe studies thathavebeenmade
in Hydraulic Laboratory of Engineering School of
UniversityofSaoPaulo,withthegoaltoanalyzethe
best solution for Santos Bay nautical and shoreline
protectionissues.
Two structures were simulated at this area,
showing alternatives to improve the navigation
demands and also the shoreline protection with
classicalstructures,liketrainingwallsandsegmented
breakwater.
Model simulations with segmented breakwater
showed the effectiveness in reducing wave height
morethan50%inPontadaPraiaBeach,whichmeans
waveenergyreductionof75%inastormsurgeevent.
The presence of
the segmented breakwater has
affectedthecapacityofwaterrenovationatthebeach
area,suggestingthatthisisanissuetobeconsidered
ifthisalternativeisapplied.
For the training walls model simulations, the
current velocities in the Access Channel increased,
showing the real possibility to reduce the dredging
rates
here.Moreover,results obtained also indicated
that the structures reduce wave height in Ponta da
Praia Beach, which would enhance the protection
againstshoreerosioninthiscriticalarea.
Therefore,bothstructuresshowedtobeefficientin
protectPontadaPraiaBeachagainstwaveerosion.
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