Beaches:•  Depositionallandform•  Extendsfromthehighesthightidetothelowestlowtide.•  Veryimportanttemporarystoreincoastalsystem.•  Accretion:sedimentreturningtothevisibleportionofabeach•  Beachaccretionwilltakeplaceduringaprolongedperiodofconstructivewaves,driven

bystorms100’sofmilesaway.•  Destructivewaves,resultinginlocalisedstormsmayexcavate(dig/remove)thebeach

removingalotofsedimentandcouldexposewave-cutplatforms.

ChesilBeach,DorsetUKHighenergy,shinglecoastline

BrightonBeach,SussexUKPebblebeach 1

Swash-alignedBeaches:•  Forminlowenergyenvironmentse.g.

bays•  Wavesarriveparalleltotheshore•  Couldbesandorshingledependingon

natureofsedimentandpowerofwaves•  Highenergywavestransportsandbut

depositcoarsershingle•  Lowenergywavesdepositsandor

mud.

Drift-alignedBeaches:•  Formwhenwavesapproachthecoast

atanangle.•  Longshoredriftmovessedimentalong

thebeach,oftenformingaspitwhichisasedimentstoreorsink.

•  Sedimentmaybegradedonthedrift-alignedbeach.Finershingleparticlesarecarriedfurtherbylongshoredriftandbecomeincreasinglyroundedastheymove.

Beachesaredescribedasswash-alignedordrift-alignedwhichrelatestotheirorientationrelativetotheprevailingwindandwavedirection.

2

Beachforms:•  Beachesarepartofabiggerdepositionareaextendingoffshore.•  Characteristicsofbeachesare:berms,cusps,runnels.•  Bermsareridgesthatdeveloponthebeachparalleltothewater,showingtheaverage

hightidemark,resultingfromdeposition.•  Bermsrepresentdifferenttidallevels.•  Stormbermsshowthehighestpointonabeach.•  Bermsaremadefromsandorpebbles.

BrightonBeachUK,(abovecentre,andright)hasalotofBerms.Whathappenedinthispicture?

Above=sandyberm

3

Cusps=semi-circulardepressionsformedbyacollectionofwavesreachingthesamepoint.Thesideschanneltheincomingswashandproducesastrongerbackwashwhichdragsmaterialdownthebeachfromthecentreofthecusp.

Runnels(ripples)=thespreadingoutofwavesenergyacrossawideareaofbeachcreatingridgesandinterveningdepressions.Theyarecommononshallow,sandybeaches.

4

Spits:•  Longnarrowfeature•  Madeofsandorshingle•  Extendsfromlandintothesea,

orpartwayacrossanestuary.•  Formondrift-alignedbeaches•  Formedbylongshoredrift

continuingwhenthecoastlinechangesdirectione.g.becauseofariverestuary.Sedimentbuildsupacrosstheestuarymouthandaspitwillform.Theflowoftheriverwillstopthespitfromextendingacrosstheentiremouth.

•  Arecurvedtipiswhentheendofthespitcurvesaroundbecausewaverefractioncariesmaterialroundintothemoreshelteredwaterbehindthespit. 5

Tombolo:•  Isabeachorridgeofsandandshinglethathasbeenformedbetweenasmall

islandandthemainland.•  Depositionoccurswherewavesloseenergyandthetombolobeginstobuildup.•  Tombolo’smaybecoveredathightide.E.g.stNinian’sintheShetlandIslands

6

Offshorebars:•  Alsoknownassandbars•  Submergedorpartlyexposedridgesofsandorcoarsesediment•  Createdbywavesoffshorefromthecoast.•  Destructivewaveserodesandfromthebeachwiththeirstrongbackwashanddepositit

offshore•  Offshorebarsactasbothsedimentsinksandpotentiallysedimentinputstores.•  Theycanabsorbwaveenergytherebyreducingtheimpactsofwavesonthecoastline.

7

BarrierBeaches:•  Alsocalledbar/barrierbar.•  Whereabeachorspitextendsacrossabaytojointwoheadlands.•  E.g.StartBayDevon,whichis9kmlongandisformedfromroundedshingledeposits

(mostlyofflintandquartzgravel)•  CantrapwaterbehindandcreatealagoonsuchasSlaptonLey.•  BarrierbeachesandbarsonthesouthcoastofEnglandarebelievedtohavebeen

depositedfollowingrisingsealevelsafterthelastglacialperiod.SedimentdepositedbymeltwaterinwhatisnowtheEnglishChannelwasbulldozedonshoretoformthepresent-daybarrierbeachorbar.

•  Laterlongshoredrifthasaddedmorematerialandreworkedthesediment.•  Thisisagoodillustrationofenergyflowsanditalsodemonstratestheimportanceof

timeintheformationofpresent-daylandforms.•  Wecannotalwaysassumethatlandformsaretheresultsolelyofprocessesoperating

atthepresenttime.

8

BarrierIslands:•  Whereabeachbecomesseparatedfromthemainlanditisreferredtoasabarrier

island.•  Barrierislandsvaryinscaleandform.•  Theyareusuallysandorshinglefeatures•  Commoninareaswithlowtidalrangesandwheretheoffshorecoastlineisgently

sloping.•  Large-scalebarrierislandscanbefoundalongthecoastoftheNetherlands,andin

NorthAmericaalongtheSouthTexascoast.

9

Sanddunes:•  Sandybeachesmaybebackedbysanddunes.E.g.StudlandinDorset.•  Sandhasbeenblownoffthebeachbyanonshorewind.•  Anoffshoresandbarisanidealsourceofsandforasanddune.•  Prerequisitesforsanddunestoform:

q  Largequantitiesofavailablesand,washedonshorebyconstructivewaves.q  Largetidalrangecreatinglargeexposureofsandthatcandryoutatlow

tideq  Dominantonshorewindsthatwillblowdriedsandtothebackofthebeach

•  Dunesdevelopwheresandisinitiallytrappedbydebristowardsthebackofthebeach.

•  Vegetationhelpstostabilisethesandandgraduallydunesdevelop.

10

Bolonia,Andalucia,SouthSpain

11

Sanddunevegetationsuccession:•  Thefirstcolonisingspeciesarecalledpioneer

species•  Pioneerspecieshaveadaptationstohelpthem

survivethehostileconditions.•  Searocketandcouchgrassareplantswhichareable

tocopewithverydry,saltyandexposedconditions.•  Embryodunesarethefirstdunestodevelop•  Foredunesareoncethesanddunebecomesbigger,

andisyellowincolourbutovertimedarkentogreyduetodecayingplansaddinghumus.Marramgrassisfoundinthiszoneandisadaptedwithlongtaprootstoseekwater.Therootshelpbindthesandandaddstabilitytothedune.

•  Depressionsbetweendunescandevelopintoduneslackswherethereismoredampconditionsbecausethewatertableisclosetoitoratthesurface.

•  Thefinalcommunitywillbeadjustedtotheclimaticconditionsoftheareaandisknownastheclimaticclimaxcommunity.

12

Estuarinemudflats:²  Riverestuariesareimportantsedimentstores(sinks)wherehugequantitiesofriver

sedimentisdepositedinwaterclosetotheedgesoftheriverawayfromthefastertidalcurrentsthatscourthechannels.

²  Risingtidescreateabuffertotheriverflow,slowingvelocityandleadingtoconsiderabledeposition.

²  Mostofthesedimentthataccumulateshereismud,duetothelowvelocities,andovertime,expansivemudflatscanformthatthendevelopintosaltmarshes.

13

Saltmarshes:q  Saltmarshesareareasofflat,siltysedimentsthataccumulatearound

estuariesorlagoons.q  Theydevelopinthreetypesofenvironment:

q  Shelteredareaswheredepositionoccurs(e.g.leeofaspit)q  Wheresaltandfreshwatermeet(e.g.estuaries)q  Wheretherearenostrongtidesorcurrentstopreventsediment

depositionandaccumulation.q  TheyarecoveredathightideandcommonaroundtheBritishcoast.

14

Saltmarshvegetationsuccession:q  Theydevelopovertimewithvegetationsuccession.q  Tostartmudisdepositedclosetothehightidelinedroppingoutofthewaterby

aprocessknownasflocculation.Flocculationiswhentinyparticlesofclay/mudsticktogethertoeventuallyhavethecombinedmasstosinktotheseabed.

q  Eelgrassandcordgrassstarttocolonisethetransitionzonebetweenhightideandlowtide.Theseplantscantolerateinundationbysaltwaterandtheyalsohelptrapinthemuddeposits.

q  Oncethemudlevelrisesabovethehightidemarkalowersaltmarshdevelopsawiderrangeofplantsthatnolongerneedtobewelladaptedtosaltyconditions.

q  Soilconditionsimproveandvegetationsuccessioncontinuestoformameadow.q  Eventuallyshrubsandtreeswillcolonisetheareaasthesuccessionreachesits

climaticclimax.