Revista de Gesto Costeira Integrada / Journal of Integrated
Coastal Zone Management, 15(4):XXX-XXX (2015)
http://www.aprh.pt/rgci/pdf/rgci-553_Gutierrez.pdf|DOI:
10.5894/rgci553 Long-term morphological evolution of urban pocket
beachesin Montevideo (Uruguay): impacts of coastal interventionsand
links to climate forcing* @, Ofelia Gutirrez @, a; Daniel Panarioa;
Gustavo J. Nagyb; Gustavo Pieiroc; Carlos Montesd ABSTRACT Two
pocket beaches, Ramrez and Pocitos (Montevideo, Uruguay) are
analyzed to assessing their evolution (erosion/accretion)
associated with human interventions and climatic forcings from
1927-2008. A multitemporal study was conducted using GIS, long
series of aerial photos, satellite imagery, survey of historical
background, and statistical analysis. Qualitative indicators of the
stability of the beach area are proposed. The relevance of this
methodology is analyzed on beaches whose fluctuations tend to mask
their long-term evolution. Both beaches remain relatively stable
but fluctuating since 1927, with slight loss of surface, especially
in Ramrez. The influence of the following factors is discussed: i)
human interventions; ii) ENSO events; iii) storm
surges;iv)changesinbeachareaaccordingtotheBruunruleandrisingsealevelinMontevideo.Althoughthefourofthem
appear to have acted in different periods, the evidence is not
conclusive regarding their relative quantitative importance. This
article highlights the importance of using long series of remote
sensing and historical analysis to interpret processes linked to
inertiaofthepastinenvironmentsthathavebeenmodifiedfromlongstanding.Thetrendanalysisofthesetwourbanpocket
beachesallowstoinferthattheirresiliencehasnotbeenaffectedyet,whichwouldallowthemtofacenotextremeclimatic
stressors. For the purpose of better management it is recommended
to: i) conduct continuous monitoring; ii) minimize the
ac-tionsofmechanizedcleaningandsandlossesbyleakageorremoval;iii)implementthereconstructionofnaturalstructures
such as primary dunes; and iv) apply the methodology explained in
this paper in other Montevideo urban beaches to better un-derstand
the climate forcings. Keywords: Remote sensing, sandy beaches,
coastline proxy records, erosion/accretion, omega parameter,
coastal management. @ Corresponding author to whom correspondence
should be addressed. a Universidad de la Repblica, Facultad de
Ciencias,Instituto de Ecologa y Ciencias Ambientales (IECA),
UNCIEP, Montevideo, Uru-guay. e-mails: Gutirrez ; ; Panario ; b
Universidad de la Repblica, Facultad de Ciencias, Instituto de
Ecologa y Ciencias Ambientales (IECA), Grupo de Cambio Ambiental y
GestinCosteroMarina,OceanografayEcologaMarina,Montevideo,Uruguay.e-mail:;
c Universidad de la Repblica, Facultad de Ciencias, Instituto de
Ciencias Geolgicas, Departamento de Evolucin de Cuencas,
Montevideo, Uruguay. e-mail: ; d Universidad Autnoma de Madrid,
Facultad de Ciencias, Departamento de Ecologa, Madrid, Espaa.
e-mail: * Submission: 11 SEP 2014; Peer review: 11 OCT 2014;
Revised: 25 MAY 2015; Accepted: 7 JUN 2015; Available on-line: 8
JUN 2015 This article contains supporting information online at
http://www.aprh.pt/rgci/pdf/rgci-553_Gutierrez_Supporting-Information.pdf
in pressGutirrez et al. (2015)2 RESUMO Evoluo morfolgica de longo
prazodas praias urbanas de bolso de Montevidu (Uruguai): impactos
das intervenes cos-teiras e relaes com as forantes climticas. Duas
praias de bolso, Ramrez e Pocitos (Montevideo, Uruguai) foram
analisados para avaliar a sua evoluo (eroso / acre-o) associado a
intervenes humanas e forantes climticas durante o perodo 1927-2008.
Para tal, desenvolveu-se estudo multitemporal utilizando GIS, uma
srie longade fotos areas, imagens de satlite, exame dos
antecedentes histricos, e an-lise estatstica. So propostos
indicadores qualitativos da estabilidade da praia. A relevncia da
metodologia utilizada
ana-lisadaempraiascujasvariaestendemamascararasuaevoluoalongoprazo.Ambasaspraiaspermaneceram,desde
1927,relativamenteestveis,emboracomvariaeseligeiraperdadesuperfcie,especialmenteapraiadeRamirez.Neste
artigo discutida a influncia dos seguintes fatores: i) intervenes
humanas; ii) eventos de El Nio; iii) temporais; iv) mu-danas na
praia de acordo com a regra Bruun e elevao do nvel do mar, em
Montevidu. Embora os quatro fatores referi-dos tenham atuado em
diferentes perodos, as evidncias no so conclusivas quanto sua
importncia quantitativa relativa. O artigo destaca a importncia da
utilizao de sries longas de sensoriamento remoto e da anlise
histrica na interpretao dos processos ligados inrcia do passado em
ambientes que foram modificados desde h muito. A anlise de
tendncias des-tas duas praias urbanas de bolso permite inferir que
a sua resistncia ainda no foi afetada, o que lhes permitiria
enfrentar os
estressoresclimticosextremos.Comoobjetivodeconseguirumamelhorgesto,recomenda-se:i)realizarmonitoramento
contnuo; ii) minimizar as aes de limpeza mecanizada e as perdas de
areiapor vazamento ou remoo; iii) implementar a
reconstruodeestruturasnaturais,comodunasprimrias;eiv)aplicarametodologiaapresentadanesteartigonoutras
praias urbanas de Montevidu para compreender melhor as forantes
climticas. Palavras-chave: sensoriamento remoto, praias de areia,
indicadores da linha de costa, eroso / acreo, parmetros omega,
gesto costeira. 1. Introduction Beach erosion is a serious
world-wide problem;
accord-ingtoBird(1985),atleast70%ofsandybeachesare
recessional.Fromthe1990s,thisfindinghasdrivento the achievement of
long-term studies, in some countries taking advantage of the
existence of high-resolution
im-ages(fromcirca1930)andcartographicprecisionsur-veys(sincethelatenineteenthcentury).Therelation-shipbetweentrendsandnaturalorinducedeventshas
allowedtounderstandtheprocessesinvolvedineach
case,anddevelopbaselinescenarios(i.e.,Diasetal., 2000; Ferreira et
al., 2006; Dolch, 2010; Baptista et al.,
2011;Klemas,2011;Pilkeyetal.,2011;Satoetal., 2011; Almeida, 2012;
Freitas & Dias, 2012; Echevarra et al., 2013; Ribeiro et al.,
2013; Splinter et al., 2013).Achieving integrated coastal
management of beaches is
aglobalaspirationbecauseoftheirvulnerability,eco-logicalandheritagevalue,andthemountingpressure
ontheecosystemdrivenbythesteadyincreaseinthe
populationsettledincoastalareasoverthepastfew decades (Brown &
McLachlan,
2002).Modificationofcoastalecosystemsandincreasedpres-suresontheresourcesthatsustaintheirstructureand
function,shouldbeseenasaglobalproblem,asthese
ecosystemsareoffundamentalimportance,providing
variousgoodsandservicesthatdirectlycontributeto
socio-economicdevelopmentdefinedbytheMillen-nium Ecosystem
Assessment (2005) as the direct or in-direct benefits that humans
obtain from ecosystems. Abstract and captions tranlation to
Portuguese on behalf of the Editorial Board
Thus,healthyandfunctionalbeachesprovidevarious
ecosystemservices,whichcanbegroupedintothree
mainfunctions:provisioning,regulatingandcultural.
However,theseecosystemshavebeenmodifiedand
adaptedbydirectorindirecthumaninterventions, which ultimately
affect the system's capabilities to pro-vide these services and
therefore support social
welfare.Inthisarticle,theconceptofecosystemservicesisthe
frameworkofourresearchandhypotheses.Therefore, the focus is on the
surface of the beach and not only in the behavior of the coastline.
Despite the interest in beach conservation, management
successeshavebeenfew,andsincethe1980swide-spreaderosionofbeaches(Bird,1985)hasincreased
duetoLandUseChange(civilconstruction,realestate
pressure,aggregateextraction),orsimplybygradual
depletionofcirculatingsand.Thesechangesareen-hancedbytheeffectsofclimatechangesuchasrising
sealevels,andincreasedfrequencyandintensityof storms (Nordstrom,
2004).Causesofsuccessivefailuresaremultiple,buttwocan
behighlighted:firstlythelackofknowledgeofthe
long-termdynamicsofeachparticularbeach(Carter, 1988) and secondly,
the multiplicity of jurisdictions and
interestsactinginthiscomplexsystem.InUruguayin
particular,duringthetwentiethcentury,humaninter-ventionshavechangedthecoastalmorphologyanddy-namics,whileinparallelthebeachesbegantoshow
erosionandretreatofthecoastlinewasobserved (Panario & Gutirrez,
2006).According to Dias et al. (2012) in order to adopt
correc-tivemeasuresandaneffectivecoastalzonemanage-ment,itisessentialtounderstandthecurrentsituation.
in pressRevista de Gesto Costeira Integrada / Journal of Integrated
Coastal Zone Management, 15(4):###-### (2015) 3 This analysis
focuses on two beaches, Ramrez and
Po-citosatMontevideo,thecapitalcityofUruguayand
hometoamillionandahalfinhabitants.Bothbeaches have economic
importance as areas for recreation, tour-ism, culture, and as
iconic symbols. The intensity of use
inbothbeachesledtoalossoftheirnaturalstructure,
leavingonlysandsurfacesborderedbyawaterfront
promenade,calledRamblaCostanera"orsimplyLa Rambla, which is the
most popular ride in the city.
Becauseoftheirimportance,thesebeacheshavebeen certified for
bathing, according to ISO 14001 standards
bythemunicipalgovernmentofMontevideo(IdeM).
Thesestandardsrequiretheimplementationofacon-tinuousimprovementprocess.Therefore,aretrospec-tiveanalysiswasperformedinorderto:i)depictthe
historicalevolution;ii)projecttrendsoferosion-accretion,takingadvantageoftheexistenceofalarge
numberofremotesensingimages;andiii)establish management
recommendations. The trends and drivers of the historical evolution
of the beaches are analyzed from the extensive series of verti-cal
aerial photographs since 1927, old maps, chronicles
ofphysicalandclimaticdatabasesovertimeusingsta-tisticalindicatorsandvariousindicatorsofchangesin
thecoastline.Sotherelevanceofthemethodoflong
multi-temporalanalysis(1927-2008)istestedon
beacheswhosefluctuationstendtomasklong-term trends. 2. Study area
and characterization 2.1. The Beaches
RamrezandPocitosaretwourbanpocketbeacheslo-cated opposite each
other, on a headland. They are
ori-entedNNE-SSW,theformertotheeastsideandthe latter to the west
side of the bow (Figure 1). This coast is a microtidal environment
(amplitude less than 50 cm,
Verocaietal.,2015),wave-dominated(significant waveheight[Hs]:0.54
m;waveperiod[T]5.66 s)and
locatedinthemiddleregion(brackishwaters)ofthe Ro de la Plata river
estuary.Ramrezisadissipativebeachwithaconvexprofile
boundedbytwoheadlands(Figure2a),agentleslope (1.9) that accentuates
to the north end with a maximum
of2.7degreesbetween0.5and1.5mwaterlevelamsl (meters above mean sea
level reference = 0.91 m), with wetanddrysectors10-15and65
mwiderespectively, measuredinitsmiddlesection,withacoastlineof 500
m.Asaparticularfeature,Ramrezexposesmore than100
mofadditionalbeachduringebb,composed of sediments enriched with
dense minerals. Pocitosisalsoboundedbytwoheadlands(Trouville and
Kibn). It is a sandy beach convex toward the berm
(Figure2b),withagentleslope(1.8),whichisaccen-tuatedtothenorthend(2.6betweenwaterlevels0.5
and1.5 m),concomitantwithitsnorthwardevolution
fromadissipativebeachintoanintermediateone.This
beachhasawetareaof10to15 mwidthatitsmiddle zone and a dry width of
65 m. The coastline is 1,427 m length. Both beaches are bounded by
the wall of the wa-terfront,whichissemicircularinRamrez,andboth
lacktheprimarydune.ThesedimentsofPocitosand
Ramrezbeachesoriginatefromdifferentsources:es-tuarinesandsandgravels,subrecentautochthonousal-luvium,erosionofthecrystallinebasementdebrisand
bioclasticmaterial(shells).Thesesedimentsarepar-tially
re-transported by runoff, human action in mecha-nized maintenance,
and wind action with sand losses to the mainland (roads). 2.2.
Issues and Background a. Ramrez Beach
MapsbytheBritishNavy(years1849and1883)and
theFrenchNavy(1867)indicatethatRamrezwas wider and extended to the
NW about 800 meters (about
twiceaslongasby2008),andseawardabout200me-ters(twicethewidthremaininginitscurrentlocation)
(Figure3).ThesurveyoftheIdeM(25/07/2007man-zanas.dwg,file)includedcadastralreferencesthatare
now located under water on this beach.Ramrez beach was probably
used as one of the primary sources of sand for construction of Old
Montevideo and laterthesurroundingneighborhoods,aswassubse-quently
Pocitos, once the expansion of the city reached
itsvicinity.Inparticular,intheearly1960s,according
toMTOP/PNUD/UNESCO(1979)Ramrezwasused
asasourceofsandtomakeanattempttonourishment of Pocitos beaches.
Ramrez suffered significant erosion before 1927,
leav-ingasurfaceenrichedwithsandyheavyminerals,
whichexplainstheslopeofthebeach.Anarealocated
totheNWwascoveredbytheconstructionofthe
southernwaterfrontpromenade,andthefillmaterial
wassanddredgedfromtheoffshorevicinities,which
reducedthestockofnearshoresedimentavailablein this area.
Inphotographicrecordsof1927and1929,aretreatof 200 meters had
already occurred. The chart of the
Mili-taryGeographicService(publishedin1929)basedon
surveysconductedin1920,recordedthisshorelinere-treat with a
configuration similar to the present. In turn, the image of 1927
presumably reflects the effect of
ex-tremestormsurgesthatoccurredin1923and1924,a feature clearly
documented in the existing iconography. The storm surge of July
1923 was the strongest ever
re-cordedsincethebeginningofmeasurementsin1898 (Verocai et al.,
2015) with a water level of 3.39 m amsl
andanestimatedreturnperiodof821years
(MTOP/PNUD/UNESCO,1979).Thestormsurgeof in pressGutirrez et al.
(2015)4 Figure 1 - Location of the urban pocket beaches Ramrez and
Pocitos, metropolitan area of Montevideo, Uruguay. Figura 1
Localizao das praias urbanas de bolso, Ramrez and Pocitos, na area
metropolitana de Montevideo, Uruguay. in pressRevista de Gesto
Costeira Integrada / Journal of Integrated Coastal Zone Management,
15(4):###-### (2015) 5 Figure 2 - Digital elevation models of (a)
Ramrez and (b) Pocitos beaches. Contour interval is 20 cm. Figura 2
Modelos digitais do terreno das praias de (a) Ramrez e (b) de
Pocitos. Equidistncia: 20 cm. Figure 3 - a) Current location of the
coastline of Montevideo overlapped over the old map of Montevideo
(Royal Navy, 1849). The current urban blocks (turquoise), the
waterfront (La Rambla, in blue), the coastline according to WDL-RM
at 1927 (green) and 2008 (red). The location of some urban blocks
is on the beach. b) The same composition, but with the
superpo-sition of the April 2008 image. Note in this case, the
location of urban blocks under water. Figura 3 a) Localizao actual
do litoral de Montevidu sobreposto a um antigo mapa de Montevidu
(Royal Navy, 1849).
Osatuaisblocosurbanos(turquesa),abeira-mar("LaRambla",emazul),olitoraldeacordocomWDL-RMem1927
(verde)eem2008(vermelho).Alocalizaodealgunsblocosurbanossitua-senapraia.b)Amesmacomposio,mas
com a sobreposio da imagem de Abril de 2008. Neste caso, alguns
blocos urbanos situam-se debaixo de gua. in pressGutirrez et al.
(2015)6 January1924reachedawaterlevelof2.19mamsl (MTOP/PNUD/UNESCO,
1979; modified from the
da-tabaseoftheDirectorateofOceanography,Meteorol-ogy and
Hydrography of the Navy-SOHMA). The 1923 storm had winds of over
150 km/hour. This storm
dev-astatedthesouthcoastofthecity,whichwasreported
bythepress:"Allthe(South)Ramblahasdisappeared
aswellastheresortsofRamrezandPocitos"(ElPas Newspaper the day after
the storm surge). Thecartographicdocumentationhiatusbetween1886 and
1920 has not allowed generating a reconstruction of the rhythms of
intense erosion process verified over that period, or specifying
their causes. Theexistenceofadunefieldisreflectedinoldplace
names(e.g.,RoadtotheDunes:CaminoalosMda-nos).Therecirculationofthissanddunefieldorigi-nated
from the mouths of the two creeks that existed on
thisbeach.Thisrecirculationwasstoppedearly(late
nineteenthcentury),whenthewaterfrontpromenade La Rambla was built,
encircling the arc of the beach.
ThisfirstlayoutofthewaterfrontatRamrezbeach,
confinedthebeachtoawellconstrainedarc.Suchin-tervention modified
the beach, dividing what was
origi-nallyafunctionalunit,consistingofanarcofbeach with the
presence of a small tombolo near his its south-ern end.
Subsequently, the northwest beach portion was
filled,withthepromenade(publicwalk),whichwas built gaining land to
sea.Thearcofbeachontheoutsidedidnotencompassthe
shapeaswastheoriginalnaturalsetting,becausethe new beach had a
greater curvature. Since then the storm waves concentrate at both
ends. b. Pocitos Beach
ThegeomorphologicalchangesdocumentedinPocitos beach have also been
dramatic. Near the mid-nineteenth
centurythereweredunesupto10metershigh,anda
beachprismseveralmetershigherthanthecurrent
situation(Ros,1923;Garca-Moyano,1969;Barrios-Pintos,1971).Theseduneswereremovedalongwith
beachsand,tobeusedforconstruction(Ros,1923;
Garca-Moyano,1969).Thisactivityseverelyaffected the amount for the
beach sediment budget, to the extent
thatthefoundationsofhouseswereseenduringanex-tremelowwatereventintheearlytwentiethcentury
(Ros, 1923). Atthebeginningofthetwentiethcentury,threecreeks flowed
into this beach, but when the southern stretch of
thewaterfrontwasbuiltin1912,thecreekswereen-casedanddiverted.Thisoriginalwaterfrontprotruded
intoasectionofbeachanddivideditintotwosections (See Supporting
Information SI.1c). At that time a large
building(HoteldelosPocitos)wasbuiltonthe beach, but was demolished
in 1935, after being affected
bytheextremestormsurgein1923.The1927photo
showsonlythePocitoscreek(SeeSI.1b),whichin
1945(SeeSI.1a)hadalsobeenencasedandwidened,
cuttingtherecirculationofsanddunefieldsthroughits
mouth.By1950,thelayoutofLaRamblawasrecti-fiedtoitspresentform,andthesurfaceofdrybeach
located in the NE sector was artificially extended.Prior to the
construction of La Rambla, the beach was wider, from 40 to about 80
meters (based on an accurate
surveyconductedforthe"SanitationProjectofthePo-citos Creek Basin",
Garca, 1908). Also in that time, the
prismofthebeachwasapproximatelytwometers
higherthanpresent(Figure4),whereastheprismnow fluctuatesaround60
cmthickabovealayerofre-workedPleistocenesands.Bythetimeofthephoto-graphic
record of 1927, it had already occurred a wide-spread retreat of
the coastline (See Supporting Informa-tion SI.2).
Despitetheimportanceofbeachesinthesocialimagi-nary for Uruguay,
there is only one systematic study of
beaches(MTOP/PNUD/UNESCO,1979),whichin-cludesareferencetoPocitosandtherecommendation
forarefillofsand,andanarticlefromSaizar(1997) which predicts its
evolution using the Bruuns Rule. 3. Materials and methods
Amulti-temporalanalysiswasundertaken,usingre-mote sensing from
1927-2008, GIS techniques and
his-toricalinformation.Atotalof23and21aerialphoto-graphicsurveys(1927-2008)wereanalyzedfor
RamrezandPocitosrespectively(Table1),obtained from the archives of
the IdeM, the National Directorate
oftheEnvironment(DINAMA),theMilitaryGeo-graphicService(SGM),andGoogleEarthsatelliteim-ages.
To better understand the long-term morphological
changes,mapsofthenineteenthandearlytwentieth
centurieswerealsoincluded,whichhaveacceptable accuracy.
Theseriesofaerialphotographswasscannedat1200
dpi,andtheGoogleEarthimagesweredownloadedin
thebestpossibleresolution.ArcGIS10wasusedfor
georeferencing,whichwascarriedoutusingadetailed mapping of the wall
of the waterfront surrounding both
beachesmadebytheDepartmentofGeomaticsofthe
IdeM.Thismapwasmadebyorthorectificationand
checkpointsfromdifferentialGPSwithsub-meterrela-tive accuracy,
allowing to minimize errors between im-ages. An accuracy of one
pixels is assumed for the
im-aginggeoreferencingprocess.TheUTM(Universal Transverse Mercator)
Zone 21S projection and WGS84 datum was
used.Shorelinesweredigitizedonscreenusingaconstant scale of 1:3000
to standardize the procedure, according to Ciavola et al. (2003),
Gutirrez & Panario (2005) and Armaroli et al. (2006). The
landward limit of the beach in pressRevista de Gesto Costeira
Integrada / Journal of Integrated Coastal Zone Management,
15(4):###-### (2015) 7
Figure4-Contoursdigitizedevery1meter(madein1906fortheSanitationProjectofthePocitoscreekBasin;Garca,
1908) superimposed on an image of 2007. The red line is the
location of the current waterfront and the turquoise line shows
theprevioushightidehighwaterlevel(PHTH-WL).Notetheincreasedheightandwidthofthebeachshorelinein1906
compared to 2007 (Source: Image-2007, IdeM). Figura 4 Linhas de
nvel digitalizadas a cada metro (feito em 1906 para o "Projeto de
Saneamento da Bacia do riacho Poci-tos"; Garca, 1908) sobreposta a
uma imagem de 2007. A linha vermelha corresponde localizao do cais
atual e a linha
turquesatraduzonvelmximodamarcheia(PHTH-WL).deressaltaragrandealturaelarguradapraiaem1906
comparativamente de 2007 (Fonte: Imagem-2007, IdeM). in
pressGutirrez et al. (2015)8 Table 1 -List of imagery. Image
availability is highlighted in green. Tabela 1 - Lista de imagens.
A disponibilidade das imagens est realada a verde.
Date*SourceOriginal scaleRamrezPocitos 1927, March
16DINAMA1/8.0001929, March 21SGM1/7.5001939IdeM1/5.000 1942,
November 25DINAMA1/7.300 1945, JanuaryIdeM1/10.000 1949DINAMA?
1954, May 14IdeM1/15.000 1954, May 17IdeM1/30.000 1961, December
13IdeM1/15.000 1961, December 21IdeM1/15.000 1965, October
26IdeM1/10.000 1966, January 26SGM1/20.000 1970, July 21IdeM1/7.500
1970, August 21IdeM1/7.300 y 1/10.000 1970, December 07IdeM1/10.000
1971, May 01IdeM1/10.000 1975, January 29IdeM1/10.000 1979, March
29IdeM1/10.000 1983, February 12IdeM1/12.000 1985,
DecemberIdeM1/10.000 1991, MayIdeM1/5.000 1996, JuneIdeM1/40.000
2000, September 22Google Earth2001 August 09Google Earth2002,
September 21Google Earth2003, October 23IdeM1/10.000 2004, May
28Google Earth2005, November 27Google Earth2006, September 6Google
Earth2006, September 24Google Earth2007, September 29IdeM1/10.000
2007, December 8Google Earth2008, April 30Google Earth Totals of
available imagery for each beach:2321 * Detailed dates of the
images are not always available. Abbreviations:IdeM: municipal
government of Montevideo;DINAMA: National Directorate of the
Environment;SGM: Military Geographic Service. in pressRevista de
Gesto Costeira Integrada / Journal of Integrated Coastal Zone
Management, 15(4):###-### (2015) 9
wasdefinedasthewallofLaRambla,asithashis-toricallyfunctionedasthelimitoftheactivelittoral
zone,definedhereastheareawheresedimentex-changes between the beach
and the nearshore occur.
Differentproxyrecordswereexploredasindicatorsof
coastline(Boak&Turner,2005)inordertointerpret
theresponsesofthesystem,i.e.,i)theprevioushigh
tidehighwaterlevel-PHTH-WL(Boak&Turner,
2005;Mooreetal.,2006)and,ii)inordertoevaluate the consistency of
the results, the wet/dry line or run-up
maxima-WDL-RM(Boak&Turner,2005;Dolanet
al.,1978,1980;Overtonetal.,1999).Forthestudied beaches, and in
agreement with Boak & Turner (2005),
bothlinesareclearlydistinguishablefromtheother.
ThePHTH-WLisidentifiedbythemarksleftbythe
tide(i.e.plantdebris),andWDL-RMcanbedistin-guished by the wet-dry
sand contrast.
Duetothesmallsizeofthebeachesandthemulti-temporalevolutionoftheaccretionandretreatofthe
coastline,abeachpolygon(area)wasdrawnaspro-posedbyGutirrez&Panario(2005)whichisdefined
byeachcoastlineproxyineachoftheimagesandthe
correspondinglandwardlimit.Thisprocedureallows
reducinguncertainty,sincethesurfaceisequivalentto
infinitetransects(methodcommonlyusedforthese studies), and
ultimately, the beach area is the parameter of greatest
socio-economic, ecological and management interest. It was
calculated the percentage difference between the
largest/smallestareaforRamrezandPocitosbeaches from 1927 to 2008
and their current areas.
Anartifactcalled"landwardlimitsofthebeachin
1927"(L27)wasusedinPocitosbeach,wherethe landward limit of the
beach was defined on the basis of
itsconfigurationin1927,inordertoknowthetrend,
regardlessofpublicworksthatexpandedtheirarea
(creekdiversionandre-alignmentofthecoast).Asec-ondartifactcalled"landwardlimitsofthebeachin
2008"(L08)wasused,wherethelandwardlimitisthe current (2008) spatial
configuration.Theanalysisincludedthelong-termfluctuationsofthe
beacharea,especiallythereductions,whichwere evaluated against
freshwater and sea levels increases in
theRodelaPlatariverestuaryproducedbythegreat
floodsoftheriversParanandUruguay(combinedor
separated),thetime-seriesofseverestormsurges,and the occurrence of
El Nio Southern Oscillation (ENSO) El Nio and La Nia anomalies.
Data for sea-level and storm surges at Montevideo (brackish waters)
and river flow at the middle Ro de la Plata river estuary are
pro-videdforthestudiedperiod(1928-2008)bytheUru-guayanServiciodeOceanografa,HidrografayMete-orologadelaArmada(SOHMA)andtheArgentinean
InstitutoNacionaldelAguayelAmbiente(INA)re-spectively.
Mineralogicalanalysisofthesubaerialandsubacuatic
sedimentsofRamrezandPocitosbeacheswascon-ducted. For Ramirez beach
the Deans dimensionless parameter ! (Hb / wf . T) was calculated
where Hb is the signifi-cant wave height, wf is the sediment fall
velocity and T isthewaveperiod,appliedasproposedbyWright& Short
(1984). A simple regression statistical analysis is performed
us-ingR-CRANstatistical(RCoreTeam,2013)software
tocalculatethemodelparametersofsandsurfaceevo-lution.Theassumptionofnormalityandrandomness
waspreviouslyevaluated(SeeSupportingInformation SI.I and SI.II).
The Anderson-Darling test for normality
wasconductedonthesurfacesvalueseriesandarun test was applied with
PAST 1.96 (Hammer et al., 2001). The run test analysis is a
non-parametric test for values
obtainedintimesequencetoanalyzerandomnessof events. The data set
was transformed by subtracting the
average,toobtainpositiveandnegativenumbers.This
testwasusedbecausethedataarenotcontinuousby
nature,sincetheflightswerenotplannedforthesys-tematicsurveyofthemorphologicalevolutionof
beachesandthatdespitetheirstatisticalsignificance, the small
magnitude of the changes could introduce un-certainty about the
randomness of trends. 4. Results and discussion 4.1. Evolution of
Ramrez beach To analyze Ramrez beach, the start date was set at the
date of the first image available (1927), when the arc of beach was
similar to the current one.
Usingafirstseriesof16images(1927-2007),theevo-lutionofthecoastlineaccordingtoPHTH-WLand
WDL-RMindicatorsshowedaweaksignificanttrend oflossofsurface(p
