GeographyofVenice

　　ThebuildingsofVeniceareconstructedoncloselyspacedwoodpiles,whichwereimportedfromthemainland.(Underwater,intheabsenceofoxygen,wooddoesnotdecay.Itispetrifiedasaresultoftheconstantflowofmineral-richwateraroundandthroughit,sothatitbecomesastone-likestructure.)Thepilespenetrateasofterlayerofsandandmuduntiltheyreachthemuchharderlayerofcompressedclay.Woodforpileswascutinthemostwesternpartoftoday'sSlovenia,resultinginthebarrenlandinaregiontodaycalledKras,andintworegionsofCroatia,LikaandGorskikotar(resultinginthebarrenslopesofVelebit).Mostofthesepilesarestillintactaftercenturiesofsubmersion.Thefoundationsrestonthepiles,andbuildingsofbrickorstonesitabovethesefootings.ThebuildingsareoftenthreatenedbyfloodtidespushinginfromtheAdriaticbetweenautumnandearlyspring.

　　Sixhundredyearsago,Venetiansprotectedthemselvesfromland-basedattacksbydivertingallthemajorriversflowingintothelagoonandthuspreventingsedimentfromfillingtheareaaroundthecity.Thiscreatedanever-deeperlagoonenvironment.

　　Duringthe20thcentury,whenmanyartesianwellsweresunkintotheperipheryofthelagoontodrawwaterforlocalindustry,Venicebegantosubside.Itwasrealizedthatextractionoftheaquiferwasthecause.Thissinkingprocesshasslowedmarkedlysinceartesianwellswerebannedinthe1960s.However,thecityisstillthreatenedbymorefrequentlow-levelfloods(so-calledAcquaalta,"highwater")thatcreeptoaheightofseveralcentimetersoveritsquays,regularlyfollowingcertaintides.Inmanyoldhousestheformerstaircasesusedbypeopletounloadgoodsarenowflooded,renderingtheformergroundflooruninhabitable.ManyVenetianshaveresortedtomovinguptotheupperfloorsandcontinuingwiththeirlives.

　　Somerecentstudieshavesuggestedthatthecityisnolongersinking,[12][13]butthisisnotyetcertain;therefore,astateofalerthasnotbeenrevoked.InMay2003theItalianPrimeMinisterSilvioBerlusconiinauguratedtheMOSEproject(ModuloSperimentaleElettromeccanico),anexperimentalmodelforevaluatingtheperformanceofinflatablegates;theideaistolayaseriesof79inflatablepontoonsacrosstheseabedatthethreeentrancestothelagoon.Whentidesarepredictedtoriseabove110centimetres,thepontoonswillbefilledwithairandblocktheincomingwaterfromtheAdriaticsea.Thisengineeringworkisduetobecompletedby2011.

　　SomeexpertssaythatthebestwaytoprotectVeniceistophysicallylifttheCitytoagreaterheightabovesealevel,bypumpingwaterintothesoilunderneaththecity.[14]Thisway,somehope,itcouldriseabovesealevels,protectingitforhundredsofyears,andeventuallytheMOSEprojectmaynotbenecessary(itwill,controversially,alterthetidalpatternsinthelagoon,damagingsomewildlife).Afurtherpointaboutthe"lifting"systemwouldbethatitwouldbepermanent;theMOSEProjectis,byitsverynature,atemporarysystem:itisexpectedtoprotectVeniceforonly100years.

　　In1604,todefraythecostoffloodreliefVeniceintroducedwhatcouldbeconsideredthefirstexampleofwhatbecameelsewherea'stamptax'.Whentherevenuefellshortofexpectationsin1608Veniceintroducedpaperwiththesuperscription'AQ'andimprintedinstructionswhichwastobeusedfor'letterstoo