347
1 INTRODUCTION
ThePortofSantos,officiallyinauguratedonFebruary
2, 1892, located in the municipalities of Santos and
Guarujá,isthelargestportinLatinAmerica.In2022,
thePortofSantoshandledapproximately162million
tons,thehighestvolumeinitshistory.
Located in an estuarine region,
sheltered from
wave action,thePort of Santoswas the target of its
first major dredging of the Access Channel only in
1964,72yearsafteritsinauguration.Atthattime,the
intention was to deepen the average natural depths
(approximately‐10mCD)toestablishachannelwith
adepth
of‐14.8m(CD).Thisdepthwasneverreached
duetoinsufficientdredgingproceduresadopted.The
averagedepthoftheportchannelwasapproximately
‐12.5m(CD).
From 2008, with the improvement in dredging
efficiency, the Access Channel to the Port of Santos
nowhas depthsclosertothetarget
of‐14.8m(CD).In
2010, a second major deepening dredging was
defined,thistimeforthe‐15.0m(CD)depth.OnJuly
10,2017,themaximumoperationaldraftofthePortof
Santoswassetat12.6m,afterdepthslower than14
meterswerefoundinthebar
region.
In a scenario of increasing ship dimensions
worldwide, associated with the role of the Port of
Santosasahubport,itisestimatedthat,soon,itwill
be necessary to implement a new design depth to
servenewvessels.PionandBernardino[3]indicated
thatthereisanincrease
inthemaintenancedredging
volumes required to maintain greater depths in the
accesschannel.Forthemaintenanceofthecondition
presented by the bathymetric survey of 2016, a
maintenancedredgingofapproximately4,325,000m³
Potential Reduction of Dredging Volumes in the Access
Channel to the Port of Santos through the Use of Jetties
L.M.Pion
1
&J.C.deMeloBernardino
2
1
HydraulicTechnologicalCenterFoundation,SaoPaulo,Brazil
2
UniversityofSaoPaulo,SaoPaulo,Brazil
ABSTRACT:SantosisthemostimportantBrazilianport,handlingabout162millionoftonsin2022.In2010,
therewasagreatcapitaldredgingtodeepentheAccessChannelto15mdeep(ChartDatum‐CD).Thisdepth
wasnotachieved,dueto
inefficiencyondredgingprocedures.Previousstudieshaveindicatedthat,inorderto
maintainthebathymetricconditionpresentedbythesurveycarriedoutinMarch2016,anannualdredgingof
approximately4,325,000m³wouldbenecessary.Thisvalueincreasesfordifferentprojectdepths,increasingby
15%,55%,and80%,consideringdraftsof
15,16,and17meters,respectively.Consideringthissituation,this
studyevaluatedthepossibilityofimplementingjetties intheregionofthePortofSantos,usingacalibrated
hydrodynamicandmorphological computationalmodel for thearea ofinterest.Fromthesimulationof two
differentscenariosto representlocal hydrodynamic conditions,
reductionsof approximately 45%, 40%, 35%,
and30%wereestimatedfortheconditionpresentedbythe2016bathymetryandfordraftdepthsof15,16,and
17meters,respectively.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 18
Number 2
June 2024
DOI:10.12716/1001.18.02.11
348
per year would be necessary, increasing to
approximately 5,000,000 m³, 6,700,000 m³ and
7,900,000m³consideringdepthsof15m,16mand17
m,respectively,fortheAccessChanneltothePortof
Santos.
Thus, this paper presents the analysis of the
potentialimplementationofjettiesintheregion
ofthe
Port of Santos to reduce the accumulated volumes
alongtheaccesschannel,basedonhydrodynamicand
sediment transport modelling, considering this
possibility as an alternative to reduce spending on
maintenancedredgingcampaigns.
2 STUDYAREADESCRIPTION
AsdescribedinPion andBernardino[3],theport of
Santosis
situatedonthesoutheasterncoastofBrazil,
asdepictedinFigure1.ThecityofSantosislocated
on Sao Vicente Island, within a highly intricate
estuarinesystemwithover60riveroutfalls.Theport
islocatedonbothsidesoftheestuaryoutlet,asshown
inFigure2.The
accesschanneltotheportisdivided
intofourdifferentareas,illustratedinFigure3.
Figure1. Location of the Port of Santos‐Brazil (Google
Earth).
Figure2.PortofSantosArea(GoogleEarth)
Theclimateoftheregioncanbeclassifiedintotwo
distinct seasons. The rainy season typically occurs
betweenspringandsummer(fromOctobertoMarch),
whenaround70% of theannual rainfalltakes place.
ThedryseasonoccursbetweenAprilandSeptember
and is generally referred to as winter. During this
period, high significant wave heights are observed
duetotheoccurrenceofcoldfrontsgeneratedinthe
oceanicarea, known asstormsurges,which are less
frequentinthesummerperiod.
Figure3. SchemeoftheAccess Channel oftheSantosPort
(GoogleEarth)
The tide in the region is semidiurnal, with
amplitudesrangingfrom0.27mduringneaptidesto
1.23mduringspringtides.However,meteorological
effectscanincreasethewaterlevelupto1.83m.The
maximum flow speed is around 1 m/s near the
estuaryoutlet,butitdoesnotexceed
0.5m/sinmost
ofSantosBay.
The bottom sediment in Area I is predominantly
sand(70%).The sandfractiondecreases towardsthe
interioroftheestuary.InAreaII,thesandfractionis
around50%,whereasinAreaIIIitisaround40%.In
Area IV, the innermost area,
the bottom sediment is
mainlyfinesediment(siltandclay).
Forareasthatarenotaffectedbywaveaction(II,
III,andIV),sedimentdepositionismainlyassociated
withtheseasonalityofrainfallduetothehigherriver
flow and total sediment transport load. Hence,
sediment deposition inthese areasis
expected to be
moreintenseduringthesummerperiod.
Incontrast,Area Iisexposedtowave actionand
located in an area characterized by low current
speeds.Thesedimentdepositionpatterninthisareais
primarilyinfluencedbythewaveclimate.Generally,
during the winter period, when waves are
higher,
sediment deposition is more intense in Area I. In
periods characterized by higher waves, sediment
tendstoberemovedfromthebeachesanddeposited
inthechannelarea.
3 DATABASEANDMODEL
During this study, the model presented in Pion and
Bernardino[3]wasused.Thismodelwas developed
in
the Delft3D® platform [2], widely used for the
representation of coastal and estuarine processes in
studiesofthistype.Themodelwascalibratedbased
ondataofcurrents,tidallevel,andwavesmeasured
in the region of the Santos estuary and bay, in
additiontodataofsuspendedsedimentconcentration
used to calibrate the sediment transport model. For
boundary conditions,the global models WaveWatch
III (waves), NCEP/CSFR (wind and sea level
elevation),andTPXO(tidalconstants)wereused.
349
More details about the equations used and the
calibration of the tool can be obtained in Pion and
Bernardino [3]. Figures 4 and 5 illustrate the
computational grids of wave, current, and sediment
transportusedduringthestudy.
Figure4.WavegridofthecomputationalmodelofthePort
ofSantos
Figure5. Flow and sediment transport grid of the
computationalmodelofthePortofSantos.
4 DESCRIPTIONOFTHEJETTIES
To assess the potential reduction of accumulated
volumes in the Santos Port Access Channel, a
configuration of jetties was designed both in the
SantosBayregionandinsidetheestuary,asshownin
Figure6.
Figure6. Scheme ofthedesignofthejettiesfor the Santos
BayandEstuary.
The jetties located in the bay are based on the
recommendationofastudycarriedoutbyReis[4]at
theBrazilianNationalInstituteofWaterwayResearch
(INPH).Thesestructuresservetoconfinethestream,
increase velocities, and prevent sediment
accumulationattheinlet.Additionally,theirlocation
protectstheChannelArea
I(seeFigure3)fromlittoral
transport, whichis the main mechanism responsible
for sediment deposition in this region. Lastly, their
position was defined to ensure safe navigation
trajectories for vessels. According to Reis [4], a
reduction of up to approximately 50% in sediment
accumulationinChannelAreaIof
theAccessChannel
wasexpected,aimingtomaintainadepthof‐14.8m
(CD).
Inthepresentstudy,thejettieswereextendedby
250minrelationtotheoriginaldesignproposedby
Reis[4],astheideawastoevaluatetheuseofjettiesto
allowthemaintenanceofdeeper
levelsinthechannel
(‐15,‐16,and‐17m‐CD).
Theinternaljettiesweredesignedtoacceleratethe
flow in the wider areas, so that the flow presents
higher competence of transport, reducing the
accumulationofmaterialintheseareas.
It should be noted thatthe structures adopted in
thisdocumentareonlyareferenceforevaluatingthe
potentialreductionofdredgingvolumesusingjetties.
Noalternativeoroptimizationstudiesoftheadopted
layoutwerecarriedout.Itislikelythat,dependingon
the desired depth, it will be necessary to extendthe
structuresinthebaytodeeperregions.
Thechoiceof
internal structures, in turn, was based only on
hydraulicaspectsandexistingterminalsandmustbe
furtherevaluatedinaccordancewiththepremisesof
portexpansionandotherimpactsintheregion.
5 SIMULATIONS
TheEstuaryandSantosBayregionischaracterizedby
twodistincthydrologicalperiods,
dryandrainy.The
dry period, from April to September, is responsible
for approximately 30% of the average annual
precipitationin theregion. Thus, as thecontribution
of fluvial sediment has a direct relationship with
precipitation, the rainy period, from October to
March, represents most of the fluvial sediment
contributionto
thenavigablewaterwaysoftheSantos
Port.
On the other hand, the dryperiod comprises the
winter,whencoldfrontsaregeneratedintheoceanic
region, causing swells and the incidence of more
intense waves in the Bay region, being the main
conditioningfactorforsedimenttransportinAreaI
of
theSantosPortAccessChannel(Inlet–seeFigure3).
Thus,torepresentthetwocharacteristicperiodsof
the region, two distinct scenarios were simulated:
SummerandWinter.Thesimulationswere monthly,
aiming to characterize a dry and a rainy period.
Directionalwavehistogramsfortheaveragesummer
conditions and
for the selected month are shown in
Figures7and8,respectively.Likewise,Figures9and
10 show the directional wave histograms for the
averagewinterconditionsandfortheselectedmonth.
350
Regardingtheriverflow,averageflowvalues(winter
period) and maximum flows (summer period)
availableintheEnvironmentalImpactAssessmentof
thedeepeningdredgingwereused.
Figure7. Directional wave histograms for the average
summer conditions (data series from 1979 to 2016) in the
SantosBay.
Figure8. Directional wave histograms for the month
selected(January,1982)torepresent summerconditionsin
theSantosBay.
Figure9. Directional wave histograms for the average
winter conditions (data series from 1979 to 2016) in the
SantosBay.
Figure10. Directional wave histograms for the month
selected(May,2013)torepresentsummerconditionsinthe
SantosBay.
Thewinterandsummerconditionsweresimulated
for each of the channel reference scenarios
(bathymetry of March/2016, 15, 16, and 17 meters),
consideringimplementationofthejetties.
6 RESULTSANDDISCUSSION
6.1 Hydrosedimentologicaleffectsresultingfromthe
implementationofjetties
Figure 11 to Figure 17 present the comparison
between the scenarios
with and without the jetties
described in chapter 5, regarding wave incidence,
current fields, and sediment erosion and deposition
patterns in the areas where the jetties were
implementedinthecomputationalmodel.
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Figure11. Wave field comparison between conditions:
without jetties and with jetties–Area Iofthe SantosPort
Channel.
Flood
Figure12. Comparison of the flood tide current fields
between the conditions: without jetties and with jetties –
AreaIoftheSantosPortChannel.
Figure13. Comparison of the ebb tide current fields
between the conditions: without jetties and with jetties –
AreaIoftheSantosPortChannel.
Flood
Figure14. Comparison of the flood tide current fields
between the conditions: without jetties and with jetties –
AreasIIIandIVoftheSantosPortChannel.
352
Figure15. Comparison of the ebb tide current fields
between the conditions: without jetties and with jetties –
AreasIIIandIVoftheSantosPortChannel.
Figure16.Comparisonofthesedimenterosion(coldcolors)
and deposition (warm colors) between the conditions:
without jetties and with jetties–Area Iofthe SantosPort
Channel.
Figure17.Comparisonofthesedimenterosion(coldcolors)
and deposition (warm colors) between the conditions:
without jetties and with jetties – Areas III and IV of the
SantosPortChannel.
The simulation results indicate that the
implementation of the jetties in the Santos Bay
reduces wave intensity in the Area I of the Access
Channel, sheltering it from littoral transport.
Additionally, the implementation of these structures
acceleratesthecurrentsinthisregion.Together,these
effects cause a significant reduction in sediment
deposition in Area I, especially in the curved reach.
Asanadditionalpositiveeffect,itisnoteworthythat
theimplementationofthesestructuresreduceswave
intensityinthePontadaPraia region,thusitcanbe
evaluatedasanintegratedsolutionforcoastaldefense
inthefuture.
Intheinternal
region,particularlyinAreaIV,the
introduction of jetties causes an increase in current
intensity, leading to a reduction in sediment
depositioninthisarea.Infact,somelocationswithin
this area show a reversal in sediment movement
pattern after the implementation of the structures,
exhibitingerosivetendencies.
6.2 Estimationof
accumulatedvolume
Accordingtothehydrodynamiceffectscausedbythe
implementation of jetties in the Santos Bay and
Estuary, as presented in the section 6.1, these
interventionsshouldresultinareductionofsediment
accumulation and, consequently, a decrease in the
needfordredgingintheAccessChannel.
Figure 18
shows a comparison between the
estimates of sediment deposition volume for the
March/2016 bathymetry condition, considering the
situations with and without the structures, for each
areaoftheAccessChanneltothePortofSantos.
353
3.252.000
1.644.000
438.000
216.000
954.000
1.836.000
786.000
726.000
48.000
276.000
0 500.000 1.000.000 1.500.000 2.000.000 2.500.000 3.000.000 3.500.000
Total
Area I
Area II
Area III
Area IV
ANNUAL SEDIMENT DEPOSITION - NO STRUCTURES X WITH
JETTIES - AREAS
With jetties No jetties
Figure18. Comparis on of the annual sediment deposition
between the conditions: with jetties (orange color) and
without jetties (blue color), considering the March/2016
bathymetry as the initial condition for simulation. This
comparisonisconsideringtotalarea of Santos PortAccess
Channelandeacharea(I,II,IIIandIV)separately.
Theimplementationofthejettiesreducessediment
depositionby52%,78%,and71%inAreasI,III,and
IV,respectively.Thereisanincreaseofapproximately
65% in the accumulated volume in Area II. This
increase occurs because some of the material that
would be deposited in Areas III and IV
considering
the situation without jetties, tend to accumulate in
Area II region, due to the changes in the local
characteristicsofcurrentsaftertheimplementationof
the jetties. However, the introduction of jetties may
result in a reduction of approximately 45% in the
overall estimated dredging volume for the access
channel,consideringthecurrentbathymetry.
Figure19showsacomparisonbetweentheoverall
estimatesofdepositedvolumeforthecurrentscenario
and with the implementation of jetties in the Santos
BayandEstuary,consideringthedifferentevaluated
draftsfortheSantosPortAccessChannel.
3.252.000
3.804.000
5.022.000
5.904.000
1.836.000
2.280.000
3.318.000
4.242.000
0 1.000.000 2.000.000 3.000.000 4.000.000 5.000.000 6.000.000 7.000.000
March/2016
15
16
17
ANNUAL SEDIMENT DEPOSITION - NO STRUCTURES X WITH
JETTIES - DESIGN DEPHTS
With jetties No jetties
Figure19. Comparis on of the annual sediment deposition
between the conditions: with jetties (orange color) and
without jetties (blue color), considering the volume
deposited in the total area of the Santos Port Access
Channel.Thiscomparisonisconsideringdifferentdepthsas
initial conditions for simulation (March/2016 bathymetry
anddesigndepthsof
15m,16mand17m).
Theimplementationofjettiesresultsinareduction
of40%,35%,and30%fordraftsatlevelsof‐15m,‐16
m, and‐17m (CD),respectively, when compared to
the situation without the jetties. The efficiency
decreaseswhenthechanneldeepensisexpectedsince
the greater the distortion imposed on
the
environment, the greater the difficulty of
maintenance. It is worth noting that the proposed
structures were based on the 2016 bathymetry and,
depending on the draft, should undergo changes to
optimize their spatial configuration, such as the
extensionofthejettiesintheSantosBay.
According to Alfredini [1],
the ratio between the
volume dredged in the dredgerʹs tank and the
corresponding in situ volume is 1.33 for the Access
Channel to the Port of Santos. Thus, Table 1 below
presents the final values of estimated maintenance
dredging volumes for each evaluated depth
throughout the study, considering the
implementation
ofthejetties.
Table1.Annualsedimentdepositionanddredging
predictionforeachdesigndepth,consideringthe
implementationofthejetties.
________________________________________________
Design AnnualSediment AnnualDredging
Depth Deposition(m³) Volumes(m³)
________________________________________________
March/16 1,836,0002,441,880
15m 2,280,0003,032,400
16m 3,318,0004,412,940
17m 4,242,0005,641,860
________________________________________________
7 CONCLUSIONS
Themaintenanceofdredgedchanneldepthsisoneof
the most costly and important activities for the
development of port activities. As the environment
tends to return to its natural state of equilibrium,
periodic maintenance dredging is necessary to
maintain the required clearance for nautical spaces
andensure
safenavigationofvessels.
If the desired clearance depth is significantly
greaterthanthenaturaldepthsoftheaccesschannel,
the necessary frequencyof interventionsto maintain
the levels can be so high that the maintenance
dredging becomes unfeasible due to operational or
financial reasons. In this case, structures, such as
jetties,arepresentedasapossibilityforachievingthe
desired clearance, as they increase the local flowʹs
competence to transport sediments, creating a
tendencyfordepthsdeeperthanthenatural.
The present study, based on results of numerical
sediment transport modelling, evaluated the annual
estimateofvolumesdepositedin
theAccessChannel
to the Port of Santos, consideringthebathymetry of
March2016andclearancesatlevels‐15m,‐16m,and‐
17m(CD).Theseclearanceswereevaluatedtosupport
future studies for decision‐making, considering a
scenarioofdemandfortheoperationoflargervessels
attheterminals.
Considering the implementation
of jetties, there
was a reduction of up to approximately 45% in the
accumulated volume in the access channel area,
considering the bathymetric survey carried out in
March 2016. In the most adverse condition, using a
clearanceof17mdepth,theimplementationofjetties
caused a reduction of approximately
30% in the
accumulated volume compared to the situation
withouttheimplementationofthesestructures.
It should be noted that, for this study, only one
spatialconfigurationofjettiesfortheregionwasused,
based on past studies, with the aim of defining a
potentialreductionindredgingvolumesinthe
areaof
interest through the implementation of these
structures. From the definition of the desired
354
clearance depth, different spatial configurations of
jettiesshouldbeevaluated.
It is important to highlight that the simulations
carried out to obtain the estimates consider an
averagescenarioofflowcharacteristicsintheAccess
Channel to the Port of Santos region. This is a
complex region, subject to different environmental
conditions,suchaswavesandriverflows,whichvary
significantlyaccordingtothelocalclimatebehaviour
pattern. Thus, the volumes deposited in the channel
should show variability according to the flow
characteristicspresentedintheregion.Inaddition,the
implementation of new clearances should be
evaluatedfromageotechnicaland
structuralpointof
view, in order to verify the stability of the new
channel geometry and the need for structural
reinforcementsattheterminals.
Finally,itisessentialtopointoutthelimitationsof
themodellingperformed.Sedimenttransportmodels
haveequations that,when wellcalibrated, can show
significant deviations from
variations found in the
field,duetothedifficultiesoffullyrepresentingthis
phenomenon through mathematical equations. In
addition,thelackofinformationaboutthechronology
of dredging procedures, carried out between
bathymetricsurveys,limitsthemorphologicalmodel
calibration procedure, further increasing
uncertainties, as the removal of material from the
bottom modifies the sediment balance and depths
measured in the field. However, it should be noted
that despite the limitations mentioned, the study of
sedimenttransportusingcomputationalmodelling,as
developedinthisreport,iscurrentlythemostsuitable
approachforaddressingthestudiedproblem.
REFERENCES
[1]Alfredini, P. “Evaluation of the evolution rates of the
bottomoftheaccesschanneltothePortofSantosinthe
period from 1997 to 2003” (in Portuguese). Technical
Report,2004.
[2]DELTARES. “Delft 3D‐FLOW‐ Simulation of multi‐
dimensional hydrodynamic flows and transport
phenomena, including sediments”. User Manual. 712p.
Delft,2014.
[3]Pion, L.M., Bernardino, J.C.M. “Dredging Volumes
Prediction for the Access Channel of Santos Port
Considering Different Design Depths”. TransNav, the
International Journal on Marine Navigation and Safety
ofSeaTransportation,Vol.12,No.3,2018.
[4]Reis, L.F.B. “Study on a movable‐bed physical scale
modelof
theSantosPort”(inPortuguese).1stCycleof
CoastalEngineeringLectures.RiodeJaneiro,1978.