MONSOONASSEMBLAGES

ELEMENTSOFTHEURBANHYDROLOGYOFSOUTHCHENNAILiteratureReview

Author:MicheleVianelloDate:February2017

ProjectDocumentNumber:OV_Vianello_2017A

MonsoonAssemblagessisaprojectfundedbytheEuropeanResearchCouncil(ERC)undertheEuropeanUnion’sHorizon2020researchandinnovationprogramme.GrantAgreementNo.679873.

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ThisreviewlooksattheliteratureregardingthehydrologyandthebuiltupenvironmentofSouthChennaiaswellasthedifferenttypesofknowledgeshapedaroundthem.Itexaminesacademicpapers,booksandbookchaptersoriginatinginawidevarietyofdisciplines(eg.architecture,socialsciences,geography,hydrology)aswellasnon-academictexts(eg.newspaperarticles,officialadministrativebodywebsites,NGOreports)andmaps(eg.fromofficialagencies,academicpapers).Itparticularlyattemptstounderstandhowthedifferentmonsoonalcycleshavebeenplayingaroleinshapingthehydrologyandthebuiltupenvironmentaswellasthedifferenttypesofknowledgeusedtointerpretthemandactuponthem,orelsehowthesecyclesfailedtobeeffectivelycapturedintheknowledgeproduction.

Addressingthesethemesrequiredtoexamineaverydiverseliterature,attimestacklingveryspecificaspectsoftheissuesathand.AconsistentattempthasbeenmadetocoherentlyextractthosebitsofinformationandbuildanoverallpictureoftheareawhilelayingoutthecontextandidentifyingrelevantissuesfortheMonsoonAssemblagesresearchproject.Inspiteofthis,thisreviewdoesnotclaimtobeacompleteinvestigationontheelementsofthehydrologyofSouthChennai:theobjectivehasbeenratherthatofidentifyingwhichgaps,pertinenttotheMonsoonAssemblageslineofenquiry,willhavetobefilledaswellasscopingthefieldfortheoverallresearch.

ThisliteraturereviewconsidersastudyareainSouthChennairoughlycomprisedbetweentheoverallbendingshapeoftheAdyarRiver,limitingittotheNorthandtheWest,andtheBayofBengaltotheEast.ItssouthernlimitisproposedtobetheKovalambackwaters,aplacemarkingtheseparationbetweentwodifferentmarshywatersystems:theGreatSaltLaketotheSouthandthePallikaranaiMarshtotheNorth.Thislimitsthefieldtoanareastretchingabout35kmsouthofcentralChennaiandencompassingthebulkoftheurbandynamicsconnectedtothedevelopmentoftheITcorridorandtakingplacearoundthePallikaranaiMarsh,whichplaysthekeyhydrologicalrole.TheonlyexceptionisthepartofthereviewanalysingtheliteratureabouttheChembarambakkamlakewhich,althoughsituatedoutsideofthedefinedfield,stillplaysacentralroleinthewaterprovisiontotheareaandultimatelyinfluencesitsdynamics.

Ingeneraltermsthestudyareathisliteraturereviewconsidersismostlycomposedofacategoryofspacesreferredto,bydifferentresearchers(eg.Arabindoo2009;Dahiya2003;Gajendran2016),as“peri-urban”:adefinitionattemptingtocapturetheirrapidlyshiftingphysical,economicandsocialcharacteristics.Thisaddsalayerofcomplexitytotheinterplaybetweencity,waterandknowledgeandcontributestoidentifyingrelevantemergingthemesinthecurrentdevelopmentofthecity.

Inordertobreakdownsuchcomplexity,afteradescriptionofthemaincharacteristicsofthelocalhydrologyandoftheproblemsencounteredingraspingitsmanifoldaspects,thereviewidentifiesandlooksatsixfamiliesofinterconnectedelements:1.theBuckinghamCanal,theOkkiumMaduvuandthelowlyingareasalongthem;2.theerys;3.thetempletanks;4.theChembarambakkamlake;5.theAdyarriver;6.theVeerangalOdaiandotherstormwaterdrains.Thereviewisorganisedinasectionforeachofthemwhichexpoundstheirroleinthehydrology,howeachofthemhashadaninfluenceonthedevelopmentofthebuiltupenvironmentandhowknowledgehasbeenconstructedaroundthem.

ThelocalhydrologyManyoftheofthemostcomprehensivetextsexaminedinthissectionhaveanoriginintheraisinginterestinclimaterelatedurbandisasters,inparticularfloods.Thealleviationandpreventionofthedamagescausedbytheseeventsplayabigroleinthetextsandconnectthemtotheoverarchingthemesof“risk”and“vulnerability”.Theinformationavailableinthesepapersandreportshasbeenconfrontedwithofficialmapsfromrelevantinstitutionsdealingwithwatershedmanagement,such

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astheAgriculturalEngineeringDepartmentofTamilNadu(AED)ortheMinistryofAgricultureoftheGovernmentofIndiaanditsSoilandLandUseSurveyofIndia(SLUSI)inordertobuildamorecompletepictureofwhatisknownabouttheseareas.Asaresult,thedelimitationsofwatershedsasdrawnintheMacro-WatershedAtlasofIndia(MinistryofAgriculture,nodate)havebeenfoundtobeconsistentwiththescientifichydrologicalliterature(eg.Bharadwajetal.,2014;Vanaja&Mudgal,2013)andhavebeenusedasthemaintermofreference.

Accuracyofgeographicalinformationisnotalwaystobetakenforgranted.Forinstance,thedelimitationsofthewaterbasinsoftheChennaiareaproducedbytheWaterResourceOrganisationofthePublicWorksDepartmentoftheGovernmentofTamilNadu(PWD,nodate)showwatershedbordersdifferenttothoseoftheSLUSIatlaswhichappeartobelessscientificallyaccurateandhavebeentakenhereasalessreliabletermofreference.Itisinterestingtonotice,thatthedifferencebetweenthemisverysubstantialsincethetwomapsshowabigdifferencebetweentheshapeofthe“Adyarwatershed”(SLUSIAtlasmap)–excludingalmostallofSouthChennai–andthatofthe“Adyarsub-basin”(PWDmap)–encompassingthePallikaranaiMarshandabigpartSouthChennai.Thesecondmapisshowninthereportonthe2015floods(Narasimhanetal,2016)andisofficiallyproducedandusedbythePWD,oneofthemaingovernmentagenciesdealingwithflood-relatedissues.ThisraisesquestionsandrequiresfurtherinvestigationontheoriginandtypeofknowledgeusedinordertodealwithurbanplanninganddisastermanagementonthepartofTamilNaduStateagenciesandthecityofChennai.

Anyway,duetothelow-lyingcharacterofthelandscape,itislikelythatthedivisionbetweentheAdyarwatershedandtherestofSouthChennaidoesnotnecessarilyimpairrun-offflowingacrosstheirbordersincaseoffloods.Thelowgradientofthelandmightexplainalsowhybothpreviouslymentionedmapsdonotnecessarilyoverlapwiththoseofthecity’sDrainageCatchmentAreasmap(Narasimhanetal,2016afterCMDA),suggestingthatman-madedrainageinfrastructuremayattimesignorethewayinwhichthewaterwouldnaturallyflowdownstream.

Relativeflatnessplaysindeedamajorroleinthespatialcharacterofthecity:Chennailiesatanaverageelevationof6.7meanfromthemeansealevel(Lavanya,2012),andischaracterisedbythepresenceofalluvialsoilandthelocalemergenceofdifferentrockformations-mainlycharnockite,agranite-likestone(Packialakshmietal,2010).ThisnotablymarksthesouthernbankoftheAdyarriverandseparatesitfromthenextwatershed,namedKovalaminthemapsoftheAgriculturalEngineeringDepartmentofTamilNadu(AED,nodate).

TheKovalamwatershed,justlikemostoftherestoftheterritoryofthecity,ischaracterisedbysmallinclinationsandisdividedintothreedifferentsub-watershedsormini-watersheds(Mambakkam,SengaduandKazhanipakkam)(AED,nodate).Outofthesethree,theMambakkamsub-watershedencompassesthebulkofthePallikaranaiMarshandoftheongoingperi-urbandynamicsofchangeinlandusesshapingcontemporarySouthChennai(Packialakshmietal.2010).

TheMambakkamsub-watershedandtheotheronesareinturndividedinmultiplemicro-sheds(MinistryofAgriculture,nodate),lackingatypicaltreeshapedstructureofriverbasedwatersheds.Theabundanceofsubdivisionswithnoimmediatelyapparentmaindrainisconsistentalandscapecharacterisedbyasmallgradientformingvastinterconnectedlowlyingareas,atslightlydifferentheights.Thisconfiguration,seemstopurporttheideathatthegeneralbehaviourofthiswatershedwouldbenaturallycharacterisedbyfillingoflow-lyingareaswithrun-offwaterandtheconsequentwaterlogging,evaporation,infiltrationintothegroundandslowflowintothesea.ThesecharacteristicsareexplainedbythedescriptionofthestretchofcoastbetweentheAdyarandPalarasapalaeo-lagoonorpalaeo-tidal-flatssystem,characterisedbyanongoingandlongtermprocess

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ofgradualformationofsandbarsandfillingofcoastalbrackishandfreshwaterbodieswithsediments(Srinivasaluetal.,2007).Theyearlychangesinbeachcoastalsedimentation,whichinfluencethefunctioningofthistypeofsystems,havebeenassociatedwithseasonalmonsoonalcyclemanifestations(Chauhan1995).

Inhistoricaltimes,humaninterventionhasalteredthedevelopmentofthisspontaneousprocessandtheMambakkamsubwatershedlow-lyingareashavenowaconstantpresenceofsalt-waterandadirectconnectiontotheseathroughtheAdyarestuaryandtheKovalamCreek.ThisseemstohavehappenedinconnectionwiththeconstructionoftheBuckinghamCanalincolonialtimes,themorerecentworksconcerningtheOkkiumMaduvuwaterbody(whichwillbediscussedinaspecificsection),aswellastheeffortstokeeptheKovalamCreekoutlettotheseaopen,opposingthetendenciesofcoastalsedimentation(Patnaik&Srihari,2004).

Humanmodificationofthelandscape,inordertoharvestrainwaterandcontrolrun-off,isadefiningcharacteristicoftheareaandofthewiderregion,atstatelevelandbeyond.Asaresult,thelocalhydrologyiscomposedofrecurringelementswhichareoftentheresultofaseriesofintricateactionsimposingman-madestructuresonnaturalfeatures;particularlyinthecaseoftheerysystem(whichwillbediscussedinaspecificsection).Thedefiningaspectsoftheseprocessesaremoreclearlytraceableinnon-urbanisedcontextsandforthisreason,muchinformationabouttheoriginalfunctioningandbehaviourofsomeoftheelementsofthehydrologycanbeunderstoodlookingatliteraturerelatingtoruralsettings(eg.Mukundan,2005;Mosse1997).Ontheotherhand,thewayinwhichtheseelementshavechangedandhavebeentakingnewroleswhenincorporatedintourbansettingsisarelativelynewprocessinSouthChennai,andhasbeenanalysedlookingatcurrentacademicproduction(eg.onchangesinlanduses)andatnewspaperarticlesreportingonsocialprocessesandphysicalchangesinvolvingelementsofthehydrology.

Eachoftheelements,orfamiliesofelements,arepresentedanddiscussedonebyoneintheremainderofthereview,unpackingrelevantaspectsrelatingtothethreecategoriesofhydrology,builtupenvironmentandknowledgeproduction.

TheBuckinghamCanalandtheOkkiumMaduvuThewayinwhichtheKovalamwatershedhydrology,andtheMambakkamsub-watershedhydrologywithinit,actaccordingtomerelocalconditionsoftopographyandgeologyinwaysthatprecedehumanpresenceandintervention,hasbeenmodifiedovertimebythesuperimpositionofseveralman-madestructures.Fromtheperspectiveoftheoverallstudyarea,oneofthemainfeatureswhichbroughtradicalhydrologicalmodificationshasbeentheconstructionofthecanalknowntodaybythenameofBuckingham.Thecanal,whoseconstructionstartedin1806,wasmeantasanavigationwaterwaytomovegoodsalongthecoast,andparticularlysalt.Itsconstructionwasmarkedbyacomplexengineeringandeconomichistory:thecanalwasbuiltindifferentmomentsalongdifferentsectionsandcalleddifferentnamesasaresultofalongandfragmentedprocessofconstruction(Russell,1898).Ingeneralterms,thecanalhasbeenlaidoutparalleltothecoaststretchingabout800km,usingnaturaldepressionsandconnectingexistingoutletstotheseaandestuariesthroughthelow-lyingareasandwetlandscharacterisingthispartofthecoast(Janakarajanetal,2007).

Inthestudyarea,itsdesignintegratedmany“localstreams,backwaters,artificialandnaturalriverchannels”andmeasuredanaveragewidthof25metres(Seenivasan,2016).Furthermore,itenvisagedarathercomplexsetofdevicesmeanttocontrolthelevelofthewatersfeedingit,comingfromtheAdyarestuaryandtheKovalamCreek,aswellassidebundsmeanttoseparateitfromtherun-offwateroftheKovalamwatershedandfromtheflood-prone,low-lyingareasitstretched

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across.Bytheendofthe19thcentury(Russell,1898),withinthestudyarea,thecanalhadtwosystemsoflocksthatcontrolledtheinflowandoutflowofwaterattheoutletstothesea,whosetracesarestillvisibletoday(Narasimhanetal,2016).Othermechanismsofwatercontrolwerealsopresent:three“flushescapes”andone“dropinlet”(Russell,1898).Althoughthereisnoreferencetothesedevicesinmorerecentliterature,theywerelikelytobeusedinordertoletexcesswaterflowoutofthecanalwhenneeded,ortopartiallydrainthecanalfordesiltingandmaintenance.Nevertheless,newspaperarticlesrefertothedesiltingofthecanalasbeingcarriedouttodayusingmechanicaldredges(TheHinduChennaieditorialstaff,2011),hintingatthefactthatthosedevicesarenotinuseorhavealsofallenintodisrepair,alongwiththelocks.

Alltheseengineeringfeaturesoriginallymadethecanalasaltwaterone(Appasamy&Lundqvist,1993;Murali,1994)duetotheperviousconnectionwiththeAdyarestuaryandtheKovalamCreek,andtothecontroldevicesseparatingitfromthehydrologyoftheKovalamwatershed.Butdespitetheseseparations,onceintroduced,thewatersoftheBuckinghamCanalstartedplayinganincreasinglyrelevantroleinthehydrologicalsystem.Forinstance,theBuckinghamCanalwasdugbetween10to12metresbelowtheaveragegroundlevel,atadepthwherethegroundcanbearpotablewater,whileapproximatelybelowthatlevelthewaterbecomesbrackish(Ganesan,2008).Thepositioningofthecanalparalleltothecoastandatthatdepth,surelyinteractedwiththegroundwaterhydrologyofthecoastallow-lyingareas.

Butthecanalhadalsoothereffectsonthevasterhydrology.InthenorthernpartoftheMambakkamsub-watershed,forinstance,run-offiscollectedinthePallikaranaiMarshand,throughthewaterbodyknownastheOkkiumMaduvu,wouldflowintothelow-lyingareaswheretheBuckinghamCanalwasbuilt.Thesearedescribedasnaturallypronetoflooding,namelyintheareaofSemmencherri(Jothilakshmy&Malar,2010),andhistoricalmaps(SurveyOfficeofMadras,1905)donotshowclearorpermanentoutletsconnectingthemdirectlytotheocean,hintingatthevariablenatureoftheselow-lyingareasandconfirmingtheshiftingcharacterofthelandscapeofthistraitofcoast,inlinewiththenatureofapalaeo-lagoonorapalaeo-tidalflatssystem.Theconstructionofcanalbundscuttingacrossthem,lednecessarilytoanalterationoftheircrucialroleinthehydrologyandalteredtheircapacitytoaccommodaterun-off.Theconsequencesofthesealterationsbecameincreasinglyevidentasthecanalfellindisrepair,itswatercontroldevicesandbundsbecamenon-functionalorwerealtered,andthewaterwaybecameanintegralelementoftheKovalamwatershedhydrology.

Particularly,astheBuckinghamCanalstoppedbeingusedfornavigationin1954(Gupta&Nair,2011),itincreasinglystartedplayingamajorroleasadrainageinfrastructure(Seenivasan,2016),arolethatextendedtothatofa“floodbuffer”(Roumeauetal.,2015)andwasobservedinconnectionwithaseriesoffloodsthathitthecityintheyears1943,1976,1985,1996,1998,2005,2010(Gupta&Nair,2011),andmorerecentlyin2015(Narasimhanetal.,2016).Thisnewroleledtonewchallenges,suchas,forinstance,thepresenceoflargeramountsofsiltinitsbed(Krishnakumarietal.,2016),,notforeseeninntisoriginaldesign.Highlevelofpollution,whichmaketheBuckinghamCanalalongwiththeCooumriverthe“widelyrecognised”mostpollutedwaterwaysinthecity(Gupta&Nair,2011),alongwithobservationsofanaerobicwatersandofthepresenceofsewage,featuredinthe2015FloodAssessmentReport(Narasimhanetal.,2016),indicatethattheBuckinghamCanaliscurrentlyusednotjustasadrain,butaspartoftheseweragesystem,too(Steinbruch&Hörmann,2015).

Althoughnoofficialmapsofthedrainagesystemappeartobeavailable,cityofficialshavedeclaredthatamajorproducerofwaterdischargesuchasthePerungudiSewageTreatmentPlantdischargesintotheBuckinghamCanal(Roumeauetal.,2015)confirmingthecrucialroleofthiswaterwayinthe

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currentcitydrainagesystem.Thisinformation,though,shouldbequestioned,asothersourcesreportthenon-functionalityofthetreatmentplantandreportthatitmightbedischargingdirectlyintothePallikaranaiMarshratherthanintheBuckinghamCanal(Patnaik&Srihari,2004).Steinbruch&Hörmann(2015)attachfurtherimportancetotheconstructionofthatsewagetreatmentplantin2006:theyattributetoitacrucialroleindischargingacontinuousflowofwaterintothePallikaranaiMarshconvertingitsnorthernpartintoaperennialshallowwaterbodyfeedingthealreadyperennialwaterbodyOkkiumMaduvu.Theintroductionofthisinflowofwater,inconnectionwiththediggingofapermanentconnectionbetweentheOkkiumMaduvuandtheBuckinghamCanal(whichwillbediscussedlater)have,accordingtotheseauthors,switchedthe“surfaceflow”fromaSouth-NorthtoaNorth-SouthdirectioninanarearoughlyoverlappingwiththeMambakkamsub-watershed(Steinbruch&Hörmann,2015).

FurthermodificationswerebroughttothecanalwhenvaststretchesofitspathwereearmarkedforthedevelopmentoftheChennaiMRTSsystem,anurbanelevatedrailwaysystemconceivedinthe1970s(MadrasAreaTransportationStudyUnit1973)andimplementedstartingfrom1990s(Seenivasan,2016).InthenorthernpartofthestudyareatheMRTSlineissuperimposedtothecanal,withhugeconcretepillarsbuiltinitsbed:achoicemadeduetothepublicownershipofthecanal,whichcircumventedtheacquisitionofprivatelandsfortheimplementationoftheproject.Asaresult,intheaffectedareastheBuckinghamCanalhavebeenreducedinwidthfromanoriginalaverage25metres,to10metres,particularlywhereMRTStrainstationshavebeenbuilt(Stephen,2016).Notonly,then,theBuckinghamCanalwasnotmeanttoserveasawaterdrainoreventuallyasasewer,butsubsequentplanningdecisionsconnectedwiththeMRTSprojectbroughtintoplay“legalencroachments”whichhindereditsroleasafloodbuffer,too(Jameson&Baud,2015).

Inspiteoftheactiveinterestonthepartofacademics,activistsandcityofficialinthecanal,itsactualcurrentroleinthehydrologydoesnotseemtobefullyunderstood,bothbecauseofalackofdataandpropermonitoring(Narasimhanetal.,2016)andbecauseofthefragmentaryfashioninwhichthecanalislookedat,analysedandincludedintodecision-makingprocessesbythejudiciary,differentstateagenciesandlocaladministrativebodies.TheMadrasHighCourtpronunciationinthecaseExnoravsTheGovernmentofTamilNadu(2006),forinstance,representsacrucialmomentinwhichthedemandonthepartofanNGOforamorecomprehensiveunderstandingofthehydrologyandtheecologyoftheareainordertoinformeffectiveandcoherentplanning,wasoverruledbycircumstantialconsiderationsonthelargerpublicinterestoftheMRTSproject,aswellasbyanarrowinterpretationofthelegaldefinitionof“natural”waterbodies,insteadofconsideringthecomplexrelationshipbetweenthecity,thehydrologyantheroleofman-madeinfrastructure(Seenivasan,2016).

ButthemostimportantmodificationoftheBuckinghamCanalwhichhadlargescaleconsequencesonthehydrologyatlarge,involvingthePallikaranaiMarshandespeciallythepermanentwaterbodyknownasOkkiumMaduvu,isratherrecentandeventhoughithaspreviouslybeenmentionedinrelationwiththeconstructionofthePerungudiSewageTreatmentPlant(Steinbruch&Hörmann,2015)needsfurtherclarifications.

TheOkkiumMaduvuistheonlypermanentwaterbodywhichisnotanery(seerelatedsection)withinthestudyareaandisalreadymarkedintheSurveyMapof1905(SurveyOfficeofMadras,1905).Itscurvedanddendriticshapeisconsistentwiththatofacreekdischargingexcesswaterfromthemarshandallowingtidalflowsinit,arolesupportedbythedescriptionofitscyclical–respiratory–functioningmadebyCoelhoandRaman,whodescribeitwiththemetaphorofan“aorta”or“pulmonaryvein”(Coelho&Raman,2013).

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TheinterestintheOkkiumMaduvustartedmakinganappearanceintheearly2000s,whenaseriesofmassiveinterventionswereinitiatedonit.TheTamilNaduSlumClearanceBoard,inaccordancewiththeCorporationofChennai,decidedtotransformavaststretchofit,alongwithasubstantialchunkofwetlandsalongitscourse,intowhatwasmeanttobecomeoneofthebiggestslumresettlementcoloniesinIndia:KannagiNagar.Theentireoperationhappenedbyreclaimingthewetlandswithlandfills,alteringtheshapeoftheOkkiumMaduvumaincourseanddeepeningit,andfinallydirectlyconnectingitwiththeBuckinghamCanalbybreachingitsbunds.AllthesemeasuresweremeanttopossiblyguaranteethesafetyofKannagiNagarincaseoffloods,compensatingforthelossofwetlandsitwasbuiltupon,whileprovidingamoreefficientdrainagetothewiderarea(HousingandLandRightsNetwork,2014).Coelho&Raman(2013)reportthattheveryOkkiumMaduvuhadcompletelybeentransformedinsuchway,andpermanentlyconnectedtotheBuckinghamCanalbytheearly2000s.

Shortlyafter,andinconnectionwiththoseinterventionsontheOkkiumMaduvu,the13.5kmlongtraitoftheBuckinghamCanalcomprisedbetweentheOkkiumMaduvuitselfandtheKovalamCreekgotwidened.ThewideningwastheresultofengineeringworksfinancedundertheJawaharlalNehruUrbanRenewalMission(JNNURM)andcarriedoutaround2014(Lakshmi,2016)whichenlargedthesectionofthecanaltoupto100minordertoencompassthewetlandspresentonitstwosidesandturnthemintopartsofthecanal.TheenlargementwasconductedbybreachingregularlythebundsoftheBuckinghamCanalanddeepeningthewetlandsalongit.Althoughsomeofthesebreachesmighthavecomeintoexistenceduetoalackofmaintenance,thisprojectconductedunderJNNURMwasthefirstinterventionshowinganactivewilltodoawaywiththeseparationofthecanalfromtherestofthehydrology,andturntheconnectionsbetweenthePallikaranaiMarsh,theOkkiumMaduvu,thecoastallow-lyingareasandtheBuckinghamcanalintoasinglewaterwayasperviousandpermanentaspossible.AlltheseworkswerecarriedoutwiththepurposeofmitigatingfloodriskTheHinduChennaieditorialstaff,2010),inconnectionwiththeworksatKannagiNagarandweremeanttobefurtherprogressedbydiggingoutapermanentconnectionbetweentheOkkiumMaduvuandtheocean,whichwasneverrealised.Theimprovedefficiencyinpreventingormitigatingfloodsofthecurrentconfigurationremainstobeassessed.

Theappearanceoflandfillsemergehasoneofthemajorelementsbothshapingthebuiltupenvironmentandmodifyingthehydrology.Threemajorlandfills(thetwomainphasesoftheKannagiNagarresettlementcolonyandtheso-calledSecretariatColony),havebeendescribedindetailinCoelho&Raman(2013),butmanymorearelikelytobepresentevenifnotcoveredintheliterature.

ItisalsoimportanttonoticetheroleattributedtotheBuckinghamasastormwaterdraininsemi-officialdocuments,hintingatitsroleinthedevelopmentofthephysicalformofthecity:inapaperpresentedinaseminarorganisedbytheCorporationofChennai,theBuckinghamCanalissaidtodrain29%ofthecity’sstormwater(inSeenivasan,2016).Ifthismustbeinterpreted,asitislikely,thatactualstormwaterpipedconnectionshavebeenlaidoutlinkingtheroadsidedrainstothecanal,itislikelythatthepresenceofthecanalhassignificantlydriventhespatialpatternsofdevelopmentofthecity,providingaready-madeinfrastructure.

Atleasttwothemesregardinghowknowledgehasbeenproducedandusedinordertocapturethecomplexmonsoonalhydrologyinthestudyareaandactonit.ThefirstthemeisthedifferencebetweentheconstructionoftheBuckinghamCanalononehand-takingadvantageofthepalaeo-lagoonconfigurationoftheareaandcontrollingitsinterferenceswiththewatershedbehaviour;andtheenlargementoftheBuckinghamCanalontheotherhand-anactiveattempttomodifythefunctioningofthehydrologyinordertocarryoutlandreclamationforpurposesofpublicinterest

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(eg.implementinganefficientdrainagesystem).Thesecondthemeisthefragmentationofknowledgeintopiecemeal,sectorialapproachesappliedinplanningdecision-makingandimplementationprocesses,correspondingtoafragmentaryandpartialknowledgeheldbytheinstitutionsactingontheBuckinghamCanalandtheOkkiumMaduvuthemselves.ThisemergedintheprocessofconstructionoftheKannagiNagarslumresettlementcolony,initiatedaroundtheyear2000bytheTamilNaduSlumClearanceBoard,notinaccordancewiththeurbanplanortoacity-widehydrologicalmapandfinancedbyasetofdiverse,circumstantial,non-coordinatedprogrammes,suchastheJNNURMandtheEmergencyTsunamiReconstructionProject(ETRP)(HousingandLandRightsNetwork,2014).TheseservedemergencypurposesandsupportedtheclearanceoftheBuckinghamCanal,ratherthanlongtermobjectivesandvisions.Inthisframework,theknowledgeproducedbyNGOs,activists,academics,playsavitalroleinordertoovercomethefragmentationandunderstandhowoldandnewmajormodificationstothelocalhydrologyhavebeenstackedontoeachother,resultinginwholenewconfigurationsthatbearmajorconsequences.Thistypeofknowledgeisproducedinseveralways:inresearchesreconstructingthetortuousdevelopmentofbigurbantransformations(Coeho&Raman,2013),orcity-widedevelopmenttrends(Gajendran,2016);instudiesanalysingthespatialandsocialresultsoflocalisedchangesinthesocialandphysicalfabricofthecity(eg.Arabindoo,2011),butalsoinfieldworkstudiescollectingprimarydatawiththeurbanpoor(Jothilakshmy&Malar,2010;HousingandLandRightsNetwork,2014;Gajendran,2015).Particularlythesepopulations,reasonablymoreexposedtofloodriskortothedailyinteractionsbetweenwaterandthecityintheirmostvisiblemanifestations,seemtobevaluableinformantsinordertounderstandthehowdifferentmonsoonalcyclesshapethebuiltupenvironmentandclashwithit,underthecurrentmodesofdevelopment.

TheerysLongbeforeurbanisationrevolutionisedthelandscape,theageoldadaptationtomonsoonalcyclesledhumanpopulationsintheareatomanipulateitinordertoharvesttheseasonallyandcyclicallyavailablerainwateranduseitfordifferentpurposes-withthebulkofitbeingemployedforirrigation.Thisprocesshasresultedinacarefully,collectivelydesignedlandscapeofrainwaterandriverrun-offharvestingreservoirs,whosemanagementhasnumerousdeepcultural,symbolicandsocialimplications(Mosse,1997;Ludden,1979):theerys.

Erys(alternativelyspelledyeris,erisoraeris,oralsocalledtanksorlakesinEnglish)areartificialwaterbodies,builttakingadvantageofnaturaldepressions.Theyworkwiththenaturalgradientoftheland,withonesideopenandshallowinordertocollectrun-offandtheotheronerelativelydeepandsurroundedbyabund.Thebundisnormallypiercedbysluiceswhichdistributewatertoothererysandirrigatethelandscapethroughanetworkofgravity-fedirrigationchannels(Jameson&Baud,2016).Whentheycollectanddistributewaterfromadiversioninariver(calledanicut)erysarecalledsystemerys.When,despitebeinginterconnectedamongthemselves,theyrelyonrainwatercatchmentareastobefilled,theyareclassifiedasnon-systemerys,whicharealesscommonoccurrence(Mukundan,2000).

Eryshavehistoricallyplayedamajorroleinirrigationandhave,uptoquiterecently,supplied1/3ofthewaterneededforagriculture“inareaswithrelativelylow-rainfall,suchasmostpartsofKarnataka,AndhraandTamilNadu”makingthemadefiningcharacteristicofthewholeregion,(Mukundan,2000)andoriginatingseveralplacenames(Sudhakar2016).Theyhavebeenorganisedbasedonpreciseempiricalknowledgeoftheland,asthedevicesneededtocontrolthemarearticulatedacrossvaststretchesofterritory.Mostnotablythoseare:sluices,placedatdifferentlevelstoirrigatefieldslyingatdifferentheights;weirs,meanttocontroloverflows;percolationponds,meanttomanageexcesswater,supportirrigation,collectsilt;andthealreadymentioned

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irrigationcanals(Mukundan,2000).Manyoftheseelementsarestillpartiallyvisibletodayintheurbanlandscape.

Duetotheirneedtobefedbyrun-offwateranddistributeittocultivableland,eryswerelaidoutwheretheeffortofbuildingandmaintainingonewouldpayoff.Forthisreason,withinthestudyarea,theyarefoundatareasonabledistancefromtheshoreline,soastoallowthepresenceofasizeablecommandarea.LackingtheMambakkamsub-watershedthepresenceofariver,theerysinthestudyareaareofthenon-systemtype,makingtheverylocalgeologicalconditions(thealreadymentionedpresenceofcharnockiterockandalluvialsoils)andmorerecentlythedegreeofurbanisation,crucialinunderstandingtheirhydrologicalfunctioningandcurrentconditions.Astheseerysgotprogressivelyincorporatedintourbanisedareas,theyincreasinglysawchangesinthesocialcontexttheirmanagementwasbasedon,andinthelandusesoftheirayacuts,butalsointheirshapeandsize(eg.Saravanam&Vennila,2015).

Thedecreaseintheuseoftheerysforagriculturalpurposes,though,isnotnecessarilyadirectconsequenceofurbanisation,andhasbeendebatedinruralcontexts(Vaidyanathan,1992)aspossiblybeinglinkedtosubsequentshocksandchangesinsocialandeconomicconditionsaswellasinadministrativeset-upsoveraverylongperiodoftime(Mosse,1999);orasbeenattributedtotheirlowereconomicprofitabilitycomparedtootherformsofirrigation,namelywells(Sakurai&Palanisami,2001).Thedecreaseintheirrigationusesoferysisofcoursenaturallyledtothatofnon-irrigationusesoferys(eg.thecollectionofsilttouseasfertiliser),worseningtheirstateofmaintenanceandperformanceincollectingandretainingwater.Thesenon-irrigationusesaccordingtoPalaniswamietal.(2011)areinprinciplestillcapableofgeneratingenoughrevenueastopayfortheexpensesofoperatingandmanagingthem,somethingthatmighthaveinterestingimplicationsinurbansettings,too.

Erys’pastuses,eveniftoavastextentorganisedthemorphologyoftheterritory,havedramaticallydecreasedinthestudyareaandthesewaterbodiesaretodayintheprocessofacquiringnewrolesinChennai’shydrology.Thiscomeswithshiftsintheknowledgebuiltaroundthem.Erysaretoday,infact,oftenmadetheobjectofactivistactionsandacademicstudieswhichaimatfindingnewhydrologicalandsocialrolesforthem,consonantwiththeirurbansetting.Theseenquiriesvaryconsiderablyinscope:theyinvestigatetheerys’possiblecontributiontoaneffectivefloodmanagementstrategyandadvocatefortheirintegrationinthecitystormwaterdrainagesystem(Jameson&Baud,2016);theyanalysetheinteractionbetweenayacuts’hydrologyandnewlandusesorencroachmentsandbuildexperimentalcasestudiesaroundtheintroductionoflocalsupply-chainsofpotablegroundwater(Saravanam&Vennila,2015);theylookattheirdecreaseinsizeasaconcauseofworseningfloodhazard(Suriya&Mudgal,2012);ortheyhighlightthespecificbreakwiththepastandtheabruptlossoflocalknowledgeconnectedwiththeirmanagementbroughtinbyurbanisationintheterritoryinandaroundChennai(Arabindoo,2011).

Someoftheurbanerysappearrecurrentlyintheinthelocalnews,inconnectionwiththeirperceivedlackofmaintenance,excessofsilt,pollution,presenceofencroachmentsetc.(eg.fortheVelacherylake,Oppili&Lakshmi,2013).Inveryfewcases,whereurbanisationislesspervasive,itispossibletofindreferenceofthechannelsconnectingthemandtracethem.TheRajBhavanchannelconnectingtheerysoftheGuindyparkandtheVelacherylake,forexample,isreferredtoasoneofthosewhichhavebeenmanagedwithaviewtopreventdumpingofgarbageandinvirtueofitsjurisdictionundertheWaterResourceOrganisationofthePublicWorksDepartment(Lopez,2014).Thisexemplifieshow,whenerychannelsareindeedmaintained,theyareincludedinpoliciesthatdonotnecessarilyconsiderthemaspartofacomprehensivesystem,acrossbureaucraticandmanagementboundaries.

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Erys,besidesbeingelementsinthelocalhydrology,relyorusedtorelyoncomplexinstitutionalset-upsmanagingwateravitalresourceforthecommunity,whichrequiredacomplexunderstandingofclimate,hydrologicalandtopographicalconditionsand,inshort,requiredtheproductionofhighlyspecialisedknowledgeheldandproducedlocally(Arizaetal.,2007;Mosse,1997,1999;Ludden1979;Vaidyanathan,1992).Communitieshaveconstantlymadeestimatesofthewateravailableintheerybasedontheirbestknowledgeofmonsoonalcycles.Suchestimateswereusedtomakesurethatthemostefficientuseofavailablewaterwouldbeensuredandthatwatercouldeventuallylastforaperiodofoneyearormore.“Folkknowledge”isreferredtoinMukundan(2000)asabletopredictrainfallquantitiesreasonablyinadvancedependingontheobservationof–unspecified–naturalphenomena,preparingfarmersforshortageinrainfalls.Traditionalcropsystemsusedintheayacutswerefinelytunedtomonsooncycles,too,andcontrarilytofarmingsystembasedontheGreenRevolutionparadigm,madecarefuluseoftheavailablewater,making“optimaladjustments”toitsavailability(Mukundan,2000).

Thisrefinementoftheknowledgesystembuiltarounderys,though,hasbeensignificantlyputinacriticalperspectivebyMosse(1997;1999),whopointedattheinfluenceofadministrativebodiesrestructuringitinordertoservewideradministrativeandcontrolpurposes.Preciselocalknowledgeoftheirrigationandwateravailabilitypatterns,aswelloftheconditionsofandqualityofthesoil,althoughvariedanddwindledovertimeduetoacomplexseriesofreasons,translatedintoratherpreciseclassificationoflandusesmatchedbyinstitutionalset-upsatalocalandsupra-locallevel,whichalsowentthroughprocessesofcrisisandrestructuring(Mosse1997;1999).Notably,thecomplexlanduseclassificationinherenttoeryirrigationsystemswaseventuallysimplifiedundertheBritishrevenuesystem(Mosse,1997),givingrisetothelandusecategoryof“wasteland”whichendedupencompassingseveralpreviouslyexistingmorespecificcategoriesconnectedwithpatternofirrigation,andfloodingandtothemonsoonalcycles(Basu,2008;Singh,2013;Vencatesan,2006;Yanagisawa,2008).Thissimplificationislikelytohavehadprofoundimpactsoncontemporarypatternsandmodesofurbanisationontopofformerayacuts,asimpliedinsomesources(eg.Saravanam&Vennila,2015).Theseimpactsare,forinstance,connectedtotheoftenpublicownershipattributedtowastelandsbythemodernIndianlegalsystem,andthescarcelegalrecognitionattributedtocustomaryrightswhichcommunitiesoftenenjoyedoverthem(Vencatesan,2006).

Theperceptionofthemanifoldfunctionsoftheerysandtheknowledgeproductionbuiltaroundthemarestilltodayobjectofspecificstudiesaimedatunderstandingerys’roleincontemporaryruralcommunitiesinTamilNadu(Arizaetal.,2011;Kumarasamy,2015),asthesehavebeenconstantlyreproducing,challengingandrenegotiatingsocialandinstitutionalarrangementsaroundthesewaterbodies(Mosse,1997).Thedeclineoftheerysisthusacomplexphenomenonthatisdifficulttopindown,andraisesinterest,discussionsandnewformsofmobilisationsandeffortstorethinktheirroleincontemporaryurbansettings.

NewtypesofactivismarehavinganinfluenceinthewayerysarereappearinginthepublicdiscourseinChennai,inwaysthatcanbeascribedtothedeploymentofwhatArabindoohascalledhydro-politics(Arabindoo,2011).Inthecaseoftheerys,hydro-politicsmanifestthemselvesinconflictsandactionsaroundtheuseofthesewaterbodiesinthecity.Groupsofcitizens,oftenofanupper-middleclassextraction,lobby,protestandpromotecommunityactions,topushanagendaforthe“environmental”recuperationoftheerys,inconnectionwithfloodmitigation,groundwaterrechargeandespeciallytheprovisionofpleasantpublicandleisurespaces.Theseactionsaremeanttopromoteastrongerlegalandadministrativeframeworktocontrolpollution,encroachment(illegallandfillsorinformalsettlements)andoftenattracttheattentionofthelocalmedia(Srikanth,

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2015;Kanthimathi,2016).Nevertheless,thesemobilisationsseemtovoiceonlypartialaspirationsandconcernsinChennai,failingtotakeintoconsiderationthewiderpicture,bothintermsofthesocialandeconomiccontextinwhicherysareplaced(crucialforarealreinstatementofmeaningfulcommunitymanagement)andintermsoftheirnewroleintheurbanhydrology.ThesituationisrenderedevenmorecomplexbytheoftencontradictoryandfragmentaryapproachesofTamilNadustateagencies,whichononesidearemeanttooverseeandpromotethemaintenanceofmanyurbanerys,andontheotherhavebeenpromotingtheconstructionoflandfillsthatalteredthemandreducedtheirsize,withnocomprehensiveplanbalancingouttheeffectsofthelostwatercollectingcapacity(Packialakshmietal.,2010).

ThetempletanksTempletanksaregenerallysquare,artificialwaterbodiesfoundintheproximityofatempleandoftenclusteredwithitinasinglespatialensemble.Theyaresurroundedbystonestepsonallsidesleadingtothewater,andvarybetween2,000to30,000sqminsurface(Ganesan,2008).Eventhoughitisnotclearwhethertempletanksalwaysplayedacoherentroleinthenetworkoftheirrigationsystem,earlymapsofcolonialMadras(theformernameofChennai),showbothtempletankslinkedtosecondaryderivationsoftheirrigationsystemoriginatingfromerys,andtempletanksindependentfromthatsystem(Ravenshaw,1824).BothpossibilitiesareconsistentwiththedescriptionoftempletankrestorationsmadebyGanesan(2008)asfacingproblemsbothintermsofclearanceoftheircatchmentareas,andintermsofmaintenanceofthechannelsfeedingthem.

Fromtheperspectiveofthehydrologicalsystem,theseobjectsplayedmultiplerolesaccordingtotheirconfiguration:eitherasrain-waterharvestingdevicesfortheimmediatelyadjoiningareas,oraselementscontributingtomanagingexcessirrigationwatercomingfromtheerys,withthevariousderivativefunctionsofthismainone,suchassiltcollection.Thesefunctionsareinlinewiththosedescribedforpercolationponds(Mukundan2000)andfindconfirmationintheroleattributedtothesewaterbodiesinrechargingsurroundingwaterwells(Ganesan,2008;Arabindoo,2011;Ramesh,2013;Vivek,2016)andactingasfloodcontroldeviceswhilecruciallycomplementingtheecologicalsystemoftheerysinruralTamilNadu(Arizaetal.,2007).

Thetempletanks’connectionwithgroundwaterandwatertablelevelsismultiple:theyinteractwithgroundwater,notjustbymeansoflettingrainwaterpercolatefromthetanksintotheground,butalsobyprovidinganescapeforexcessgroundwatersoakingthesoil,adaptivelyrespondingtodifferentmonsoonalconditions.Atleastonewellisalwayspresentinthefloorofeachtempletank,afactthatseemstoindicatethatalsothesurfacingofgroundwater,indeterminateconditions,playsanimportantroleinactuallyfillingthesewaterbodies,consideringthatpiezometriclevelsincentralChennaiaftermonsoonalrainscanbe1to2metresbelowgroundlevel(Ganesan,2008).Forthisreason,thedesiltingoftempletankshasbeencentralinmaintainingtheirefficiencyinthepast.Ontheotherhand,Arabindoo(2011)proposesthatthepresenceofwells,atleastinsomeoccasions,istheresultofrecentdiggingandnewtempletankrestorationinitiatives,alteringpreviousmodesofinteractionbetweentheseelementsandgroundwater.Ineithercase-infiltrationandpercolationfromthetempletanksteppedwallsorwatersurfacingfromfloorwells-desilting,cleaningandmaintenanceplayedamajorroleintheeffectivefunctioningandfillingoftempletanksandthetasksrelatingtothoseactivitieswereencompassedinthecommunitylifeandreligiousritestakingplacearoundtempletanks(Ganesan,2008).

Ingeneral,templetankstraditionallyplayedavitalroleintheactivitiesofTamilNaducommunities,andwereconnectedtovitalculturalaspectsofeverydaylifeandtotheperceptionoftimecycles,suchasinthecaseofthetownofKancheepuramwhereseventanksare,stilltoday,associatedwiththesevendaysoftheweek(Ganesan,2008).Althoughtheirroleistodaynotascentralasitusedto

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be,theystillplayasignificantroleinthesocialandculturallifeofcommunities.Forinstance,whenreligiousfestivalsareorganised,templetanksarethesettingsofceremonies,festivals,rituals,socialgatheringsetc.(Ganesan,2008;Arabindoo,2011).

WhiletheirroleintheHinduistreligiousworshipwouldrequirealiteraturereviewofitsown,severalsourcesrefertotempletanksasbeingtheobjectoftheproductionoflocalknowledge,relevantforboththephysicalshapingofcityaswellasforthepoliticaldevelopmentofitselites.Forinstance,Washbrook(1973)writingabouttheperiodbetween1880and1930,mentions“templescommittees”asoneoftheplaceswhereMadraselites,pushedoutoftheofficialadministrativedecision-makingprocessesasthecitygrew,wereabletofindnewspacesofpoliticalorganisation-attimesthroughshadowypracticesoflobbying-andtryandinfluenceurbanpolicies,thereincludedthoseregardingwater.

Today,temples,andespeciallytempletanksarestillatthecentreofpoliticalmobilisation.Middleclassactivistsmobiliseandlobbyfortheirrestoration,insimilarwaysastheydofortheerys,bothbecausetheyareseekingtofindalternativemeanstosecurelocalwatersupplythroughgroundwaterrecharge,andtomaterialisetheirpoliticalaspirationsbybeautifyingurbanspace:thehydro-politicsinvesttempletanks,too.Muchofwhathasbeensaidabouterysistoasignificantextentvalidfortempletanks,too,andactuallyArabindoo(2011)hasfocussedheraccountofthelocalaspectsofhydro-politicspreciselyontherestorationofatempletank,theperceivedrolethatsuchanendeavourwouldhaveonwatersecurityforthelocalcommunity,anditsactualeffects.

Restorationsoftempletanksweredrivenbothbyconcernsabouttheirroleinthehydrologicalequilibriumofgroundwaterlevelsandbyconcernsabouttheirpoorstateofmaintenanceandtheycontributedtoproduceandreproduceaspecifictechnicalknowledgeonthematerialcultureembeddedintempletankconstructionandmaintenance(Ganesan,2008),andpossiblytopartiallyreinventit.

Templeandtempletankshaveastructuringroleindefiningthebuiltupform,typologyandconcatenationofspaceinTamilvillages,havinginmostcaseacentralpositioninthesettlement(Ganesan,2008)andareportedlyacentralroleintheorganisationofTamilcities(Singer,1971).DuetotheestablishmentofChennaionalandwhichhasalonghistoryofhumansettlements,templesmostlikelyplayedaroleinshapingthegrowthofthePortugueseandBritishsettlements.Indicationsoftempletanksandstreetsirradiatingfromthemandstructuringtheirsurroundingsarevisibleinmapsfromtheand19thcenturies(eg.Ravenshaw,1824).ThisoverlapbetweenthepasttracesofruralsettlementinfluencingtheshapeofthecityareconsistentwiththeaccountsthatdescribeChennaiasa“ruralmetropolis”wellintothe1970s(Vasanthakumaranetal.,2012).Work-in-progressacademicliterature(Srirangam&Forsyth,2012)seemstosupportthisidea,byproposingataxonomyoftheurbanmorphologiesoftempleclusters,lookingattherelativepositionsoftempleprecincts,templetanksandstreets.Thesecompositionsofurbanmaterialsseemtohaveadirectinfluencenotjustonhowneighbourhoodsarespatiallyorganised,butalsoonhowsocialactivitiestakeplaceinthestreets,andparticularlyonhowcommerceispresentincertainplacesandnotothers.Ontheotherhand,despitetheirroleinstructuringitsform,urbanisationseemstohaveanadverseeffectonthehydrologicalroleoftempletanksanditsblamedforthelossoftempletanks’capacityintermsofcatchingandmaintainingwater(Ganesan,2008).

Finally,theveryarchitecturaldesignoftanksreflectstheusesofthewaterheldinthetank,suchastherecurrentpresenceofalandingeverytensteps(Ganesan,2008),whichmighthavebeenusedtomorecomfortablyaccesstheresourceaswellasprovidingstrengthtotheoverallstructure.These

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usesmighthaveplayedacentralroleinstructuringsocialactivitiesinthecityasitwasgrowingandshiftingfromruralusestourbanones.

TheChembarambakkamlakeTheChembarambakkamlakedoesfallwithinthestudyarea,buthasbeenincludedamongtheelementsstudiedinthisliteraturereviewduetoitsroleininthepipedwatersupplytovastpartsofSouthChennai,whichendupbeingdrainedbytheKovalamwatershed.Nevertheless,excesswaterdischargefromthiswaterbodycannotbeconsideredtohaveplayedaroleinthe2015floodsinthestudyarea(Narasimhanetal.,2016),despitetheconnectiondrawnbysomeofthemedia(eg.TheHindueditorialstaff,2016).

ChembarambakkamisoneofthelargeeryswhicharefoundinthewesternpartofChennaiurbanarea.Thisseriesofbiggererysislocatedinanareaparalleltothecoastbetween12and30kmfromtheshoreline,andcomprisePoondi,Puzhal,Cholavaramlakesamongothers.MostofthemarehavespecificecologiccharacteristicandarelistedasEcologicalHeritageSites(Sudhakar,2016).Theirunusualdimensionscouldbeexplainedwithspecificgeologicalcharacteristicsofthelandscapewherethesewaterbodiessit.ThePuzhallake,forinstance,sitsonalocalisedformationoflateriteandbauxite,partofalargerpresenceoflateriticformationsintheeasterncoastofTamilNadu(Achyuthan,1996),fromwhichitprobablytakesitsEnglishnameofRedHillslake.TheChembarambakkamlake,instead,occupiestheeasternmostareaofanextensiveformationofplutonicrocks(Suriya,2014).Itispossiblethatthisspecificity,besidesthelocaltopographicconditions,havehadaninfluenceintheviabilityofconstructingaconsiderablybiggereryspecificallyinthisarea,whichinthecaseofChembarambakkampotentiallyirrigateanayacutof5,452ha(Sivaraman,2005).

Chennai,asunurbansettlement,isnotaloneinitspairingwithlargeerys.ItisinterestingtonoticethatotherurbansettlementsinthenortherncoastalareaofTamilNadushareasimilarrelationshipwithcomparablebodiesofwater,likelysecuringwaterprovisionorlargescaleagriculturalproduction:PuducherryislocateddownstreamoftheOsudulake,whileChidambaramislocateddownstreamoftheVeeranamlake.Andindeed,largeerysinthecaseofChennaihaveplayedafundamentalroleintheurbanisationofcity:Puzhallakewasincludedintheurbanwatersupplysystemin1870(Janakarajan,2009),whileotherwaterbodiesfollowedsuitoveralongerperiodoftimeandplaytodayavitalroleinsupplyingwatertothecity(Krishnakumarietal.2016).TheChembarambakkamlakewasacquiredbyMetrowater(theTamilNaduagencyforwatersupplyandservicesinChennai)forthispurposeafterurbanlandusestookoveritsayacut,makingitsuseforagriculturalpurposesinefficient.Thisprocesshappenedgraduallyandwascompletedbytheyear2000(Srinivasan,2015)whenitbecameofficiallyincorporatedintothewatersupplysourcesofthecity(Coelho&KumarReddy,2004).

Inordertorespondtothenewdemandofwaterforurbanuses,Chembarambakkamhadtoundergodifferentalterationsandhadtohaveitswholefunctioningredesignedsoastoartificiallykeepitswaterlevelsasconstantaspossibleandguaranteeareliablesupplyofwater.TheTeluguGangainfrastructuralproject,firstapprovedin1977andcompletedaroundthemid-1990s(Sampathkumar,2005)wasmeanttoenhancesuppliesbydivertingtowardsthecity,andpartiallyintotheChembarambakkamlake,partsofthewateroftheKrishnariverinAndhraPradesh.TheprojectwasconceivedinordertoincludemostoftheabovementionedlargeerysWestofcentralChennai,withthepurposeofbothstoringwateranddistributingittothedifferentareasofthecity.ItfirstreachedPoondilake,andfromtheredistributedwatertoPuzhallake,first,andtoChembarambakkamlakeafterwards.Inordertofulfilthisnewroleasacityreservoir,thephysicalinfrastructureoftheChembarambakkamwasmodifiedsoastoincreaseitscapacity:itsfullreservoirlevelswerebrought

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upbytwofeet(Sampathkumar,2005)byrestructuringthebundofthelakesothatitcouldcontainupto103.2millioncubicmetresofwater(Coelho&KumarReddy,2004).Thismodificationintheregimeofwaterintake,drawntoChennaifromveryfaraway,hasledtofundamentalchangesinthepreviousfunctioningofthelake,forinstancebringingmodificationstothecyclesofexpansionandcontractionofthevolumeofwaterpreviouslyexclusivelytunedtolocalmanifestationsofthemonsoonalcycles.Inthecourseofthesealterations,specificphysicaldeviceswereaddedtothelake,suchasaweirandcanalmeanttocontrolitsexcesswateranddischargingintotheAdyar,upstreamoftheairport,possiblymodifyingapre-existingweirorotherelementsofthebundinthe1990s,inordertomanagebiggerquantityofwaters(Lakshmi,2015).

AconsistentamountofthewatercomingfromChembarambakkamlakeisdistributedtohouseholdsplacedwithinthelimitsoftheKovalamwatershedasshownintheofficialmapofthecity’swaterpipedinfrastructureanddistribution(Metrowater,nodate).Althoughnoreliableandcompleteinformationisavailableonthepathsthiswatertakesonceisflushedawayordischargedfromthehouseholds,differentsourcesreferthat,atleastpartially,itmightendupindifferentwaterbodieswithintheKovalamwatershed,suchastheBuckinghamCanal,thePallikaranaimarsh(Steinbruch&Hörmann,2015)ortheVelacherryery,wheresewageandwaterdischargeshavebeenobserved(Manikandan,2012).

TheChembarambakkamlakecannotbesaidtohavehadadirectinfluenceontheshapeofthebuiltupenvironmentwithinthestudyarea,butcertainlyitwasbothinfluencedbyandhadaninfluenceonsomeoftherecenttrendsconnectedtotheurbangrowthofChennai.WhileurbanlandusesontheChembarambakkamayacutarementionedasoneofthereasonforitsacquisitionbythestate-ownedwatersupplycompanyMetrowater(Srinivasan,2015),itispossiblethatthegreaturbandevelopmentexperiencedinthenorthernareasoftheKovalamwatershedreceivedpropulsion,startingintheearly1990s,inconnectionwiththeinfrastructuralworksontheChembarambakkamlake.Theseopenedtheprospectofareliablepipedwatersupplyinthesouthernpartofthecity,whichwaseventuallybroughtaboutwiththeconstructionofdifferentwaterdistributionstations,suchastheVelacheryone,commissionedin1994(Pratheeba,2011).

ModificationsofboththeChembarambakkamlakeandthelandusesonitsayacut,aswelltheshiftingobjectivesbehinditsmanagementexplainhowovertimethetypesofknowledgeusedtoharness,controlanduseitswatersgraduallyshiftedfromthosediscussedforerys,toothersconcernedwithconstantwatersupplytothecityandfloodhazardmitigation.TheseshiftisdiscussedbyArabindoo(2017)inrelationtofloodsandcanbetracedbacktoasfarasthe1970s,whendecisionsregardingthewateratChembarambakkamstartedtobetakenaccordingtodifferentcriteriafromthosewhichthetankwasoriginallymeanttoobeyto.Engineeringknowledgeconceivedforthemanagementofwatersupplyreservoirs,meanttoretainwaterasmuchaspossiblearenowappliedtoanery:aphysicalinfrastructurebuiltforcyclicalretentionandirrigationfollowingmonsoonalclimaticconditions.

TheAdyarriverTheAdyarriverhasreceivedagreatdealofattentionintheliterature,inconnectionwiththebehaviourandevolutionoflandusesonitswatershed(Ramesh,2013;Janakarajanetal.,2007;Vanaja&Mudgal,2013)anditsrelationwithurbanisationprocesses(Suriya&Mudgal,2012;Bharadwajetal.,2014),and,asoneofthemainwaterwaysinthecity,itwasalsoacentralobjectofanalysisintheassessmentof2015floods(Narasimhanetal.,2016).

TheAdyarriverisoneofthetwomainfreshwaterwaysthatrunthroughcentralChennaiand,muchlikethesimilarCooumrivertotheNorth,isalimentedbytherun-offof“tanksandsmalllakes”

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upstream(Murali,1994).ItscourseissubstantiallydefinedbythepresenceofCharnockiterockformationsonitsSouthbankwhich,alongwiththesmallgradient,contributetodefineitslowercourse.TheAdyarhasitssourceinagroupoferysintheKancheepuramdistrict,andcatchessurplusfromabout450morealongitspath(Gupta&Nair,2011;Narasimhanetal.,2016).EventhoughtheChembarambakkamlakewouldnotnaturallybelongtotheAdyarwatershedaccordingtoofficialdata(SLUSI,nodate),thepresenceofaweirandofacanalforthecontrolexcesswatermakeasubstantialamountofitswatersdischargeintotheAdyarriver,somuchsothatthelakeisnowconsideredoneofitsmainsourcesofwater,andhydrologicalstudiesincludeitinitswatershed(Bharadwajetal.,2014).TheChembarambakkamlakeiscreditedformakingthepresenceof–slowly–flowingwaterintheAdyarriverconstant,aphenomenonthatwasalreadydescribedinthemid-1990s(Murali,1994)anditsroleinthefloodsoftheAdyarwatershedisuniversallyrecognised(Arabindoo2017;Narasimhanetal.,2016)

TheAdyarmostlypassesthroughalluvialsoil,presumablycarryinginitscurrent,especiallyduringmonsoonalrains,substantialamountsofsediment,afactthatseemstobesupportedbythereferencestotheAdyarestuaryasamutablelandscape,characterisedbytheformationofsandbarsattheopeningtowardsthesea.Thesesandbarsarereportedasacauseofconcern(Suriya&Mudgal,2012)andinneedofconstantbreachinginordertokeepwatersfreelyflowingfromtheriverintotheocean(egHemalathai2011).TheestuarinenatureoftheAdyar’soutlettotheseaisconfirmedbythechangingshorelinenoticeableinrelativelyrecenthistoricalmaps,wheretherivermouthismarkedonekilometrenorthofitscurrentposition(Johnstonatal.,1894;Bartholomew&Bartholomew,1893),stillcharacterisedbysandbarsandislandsformingintheproximityofitsmouth.Furthersourcesrefertothereintroductionofmangroves,aspartofecologicalrestorationeffortsofsomeofitsmeanders–namelytheonearoundQuibbleIsland–whichmayinferthepastpresenceofthistypeofecosysteminitsestuary(TheHindueditorialstaff2013).

Thewaysinwhichrestorationoreco-restorationprojectsarecarriedout,andtheirimplicationsinthepoliticalarenaofChennai,istheobjectofseverescrutinyonthepartofresearchers(eg.Coelho&Raman,2010,2013;Arabindoo,2011).Beautificationschemes,eitherpastorupcomingareacommitmentofstateagenciesthroughtheconstitutionofanadhocbody:theChennaiRiverRestorationTrust,establishedin2010bytheTamilNaduGovernment.Thisbodyhasapowertodesignandinterveneontheriversandwaterwayswithinaspecificmandate,whichdoesnotnecessarilyentailacomprehensiveunderstandingofthewidereconomic,socialorevenhydrologicaldynamicsoftheurbanterritory(Adaikalam,2010),orcoordinationwithotherbodies.TheTamilNaduSlumClearanceBoardortheTamilNaduHousingBoard,forinstance,havebeenusingdrainagechannels,wetlandsandriverbanksaslocationforslumresettlementsandlow-incomehousingprovision(eg.HousingandLandRightsNetwork,2014).Similarly,theproposalfornewarterialroadinfrastructurebytheTamilNaduRoadDevelopmentCorporationchosetheAdyarriverbankstoproposeanewmajorroadinfrastructure,innocoordinationwithotherprogrammesorplanninginitiativesconcerningtheriver(Coelho&Raman,2010).Thefragmentaryapproachwithwhichplanningisconceivedandinfrastructuralprojectsarecarriedouthindersacomprehensiveunderstandingoftheriver’sbehaviouranditsroleinthehydrologyofthecity.

Asaresult,urbanpoorandinformalsettlements,duetotheirphysicalpresenceontheveryriverbanks,areoftenblamedforencroachingitandmakingfloodseffectsmoresevere,whilewidercausesareneglected.Slumsarethenbrutallytargetedwithevictionsanddemolitions(Coelho&Raman,2010),whileformalplanningallowsdevelopmentsfeaturinglandfillsandhighriseapartmentsblockswhichhavesimilar,ifnotmoredubious,impactsonfloodhazard(Coelho&Raman,2013).Thedebateabouthowtomitigateandcombatfloods,andtheemergencydiscourse

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builtaroundthem,seemtohavealteredthewaytheriversareconceptualisedanddiscussed,eveninhydrologicalterms.These,tendoftentobeseenas“macrodrainages”andtobeperceivedasentitiestobemanagedinordertoevacuateexcesswaterincaseoffloods,ratherthancomplexurbanwatersystems(Jameson&Baud,2016)whosebehaviourisconnectedwithmonsoonalcycles.Buttheapproachtousingknowledgetoactonurbanriversseemstobeendlesslycontradictoryandsectorial.Whenwaterscarcity,forinstance,hasbeentheobjectofpolicies,checkdamshavebeenbuiltontheAdyarinordertorechargethewatertable.WhilethismoveissupportedbystudiesaboutitseffectivityinthewiderareaofChennaihydrological,considerationsonitsappropriatenessareapparentlylimitedtogroundwaterbehaviour(Renganayaki&Elango,2013),overseeingpossibledetrimentaleffectsonurbanfloodsorinteractionswithurbanimpermeablesurfaces.

Fragmentaryandincompleteapproaches,arepossiblytheresultofverycompartmentalised,bureaucraticmanagementofplanning,onthepartoftheStateofTamilNaduanditsagencies.Agendasseemstolookattheissuesatstakefromsingular,narrowperspectives,ratherthaninacomprehensiveway.Thisisaccompaniedbyalackofinvestmentinreliabledatacollection,necessarytobuildacompletepicture:the2015Chennaifloodsassessmentreport(Narasimhanetal.,2016),forinstance,referstothelackofreliablegaugingstationsalongtheAdyar,andthereforetothelackofreliabledatasetsregardingtheevolutionofthefloods.Ontopofthis,thecityhasevolvedontheriverdevelopingcomplexandinteractingspatialandsocialpatterns.ThebanksoftheAdyarhavebeenforalongtime,wellintothe60s,aprimelocationforhigh-endresidentialdevelopmentsandrepresentativebuildings(Murali,1994).Longstandinghighland-valuesandthepresenceofhighendrealestatelocationsareprobablytobeputinconnectionwiththetendencyonthepartofthecolonialelitetooccupytheareaaroundtheAdyarwithgardensandmansionssincetheearly19th(Basu,1993)andstilltoday,representative,symbolicbuildingsandhistoricalmansions,suchastheChettinadHouse,theMadrasClubortheAdyarVilla,canbefoundonthebanksoftheAdyar,eventhoughothertypesofdevelopmenthaveappearedovertime,makingtodayamuchmoremixedurbanenvironment.

ThebanksoftheAdyarwerealsousedforthepurposesoftrade.AccordingtoMurali(1994)parcelsofgovernmentlandwereconcededinleasetomerchants,whousedtheriverasawaterwaytotransportthemupuntilthemid-20thcentury.ConcomitantlywithvasterprocessesofurbanisationinvestingChennaifromthe50sonwards,vacantspacesalongriverbanksandotherwaterbodiesandbeachesbecamethelocationswhereinformalsettlementswouldgrow.ReferencestotheirpresencealongtheBuckinghamcanal,theAdyarriverandmultipledrainagecanalsarerecurrent(Seenivasan,2016;Lavanya2012;Gupta&Nair,2011).Morespecifically,theriverbanksareoneoftheplaceswherethisphenomenonhasbeenmorethoroughlyobservedanddiscussedinthepress,duetoitsperceivedresponsibilityintheencroachmentoftheriverandinitsroleinworseningtheeffectsof2015floodsorhinderingpreparedness(eg.TheHinduChennaieditorialstaff2013b;Coelho,2016;Philipi,2015;Sashwath,2015).

TheVeerangalOdaiandotherstormwaterdrainsFinally,thisliteraturereviewtacklesthesmallestelementscomposingthelocalhydrology:stormwaterdrains(PublicWorksDepartment,StateofTamilNadu2016).Thisdefinition,forthepurposeofthisenquiryandwithinthestudyarea,referstosurfacechannelswhichfunctionasdrainsinthenorthernpartoftheKovalamwatershed,andhaveanorigininpreviouslyexistingeithernaturaldrainsandstreamsorexcesswaterchannelsderivingfromtheerysystem.Inthestudyarea,inparticular,therearetwomainones,theVeerangalOdaiandtheVelacherydrain,andtheyplayamajorroleindrainingwaterfromthenorthernpartoftheMambakkamsub-watershed(Narasimhanetal.,2016).

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Inparticular,theVeerangalOdaipresenceintheliteratureandcoverageinthepress,isherediscussedasrepresentativeofthecomplexissuesthatinvestedstormwaterdrainsintheprocessofurbanisationandcausedlocalscalemodificationswithmajorimplicationsfortheoverallhydrologyofthestudyarea.Theseissuesregarditsphysicaldesign,itsmanagementanditspropertystatus.

TheVeerangalOdaiappearsinsatelliteimagery,aslateastheearly2000s(DigitalGlobe,2002),asafreelymeanderingwaterwaydischargingwaterfromtheAdambakkameryandsurroundingareasintothePallikaranaiMarshandischaracterisedbysuchasmallgradient,thatitsnatureis,insometraits,thatofalow-lyingwetlandintegraltothePallikaranaiMarshwidersystem.By2016,itscoursehadbeenregimentedandrectifiedandpartiallybuiltover(Stephen,2016),transformingitintotwoconcretestormwaterdrainsalonganurbaninfrastructuralcorridorcomposedofaraillineandamajorsixlanethoroughfare.ThesouthernmostsectionoftheInnerRingRoadinfrastructure–partofthemaininfrastructuralstrategiesmeanttomeetthegrowthneedsofthecityinrecentyears(Sekar&Kanchanamala2011)–pairedwithanextensionoftheMRTS,hadbeenbuiltontopofitstartingfrom2008(TheHindueditorialstaff2008).

Asaconsequence,theVeerangalOdaiwasreducedinwidthfromabout150metresin2000tolessthan10,today(DigitalGlobe,2000;2016).Thisreduction,whichmadethewetlandsalongitscoursedisappearandforceditbetweenconcretewalls,dramaticallyaltereditsspeed,capacityandinteractionwiththegeologicallayers,andcausedithaveanimportantroleinthe2015floodsinthestudyarea,alongwithVelacherydrainwhichwasinvestedbysimilar,althoughlesser,processes(Narasimhan,etal.,2016).

ThereasonsbehindtheplanningchoicesregardingtheVeerangalOdaiaresimilartothosementionedforbuildingtheMRTSontopoflongstretchesoftheBuckinghamCanal:freespaceandthepossibilityofcircumventingprivatelandacquisitionforinfrastructuralprojects.Infact,waterbodies,theiradjoiningareasaswellasareassubjecttoflooding,betheyconnectedtoerys,channels,orpartofwetlandsandmarshlands,asanticipatedbeforearemostlyclassifiedaswastelandsorporomboke(outoftherevenuesystem)inTamilNadu(Vencatesan,2006).Thismeansthattheyareoftencharacterisedbypoorlyrecognisedcommunitycustomaryrightsofuse,byanofficialstatusaspublicpropertyorunderpublictrustprotection,andbylanduseseasilysubjecttochangeforreasonsofgeneralinterestandsubjecttoacquisitionthroughEminentDomain(Singh,2013).

ThecomingtogetherofthesespatialandlegalaspectsmadetheVeerangalOdaiahydrologicalelementendingupdictatingthespatialdevelopmentofthecity:itgotcompletelyoverwrittenbyinfrastructuralprojectsdrivenbyadhocpoliciesandplanningdecisions.Aroundit,complexissueswereembodiedinspatiallyveryclearmanifestationsmakingitanexemplarycase,ofprocessespresentalreadyelsewhere,andsimilarforinstancetothosedescribedfortheBuckinghamCanalandtheAdyarRiverinprevioussections

Alongwithalterationswhichchangeditshydrologicalfunctioningatthescaleofthecity,otherlocalisedprocessesinvestedtheusesofthisdrain,aswellasthewaysinwhichitislookedatandconceived.TheVeerangalOdaiislistedasamacrostormwaterdraininofficialdesignations(CMDA,2010)servinganadjoining,increasinglyimpermeable,residentialareas,asreportedinthepress(TheHindueditorialstaff2002).Allegationsofitsillegalusefordischarginggreyandwastewatersarereferredinconnectionwiththeactivismoflocalgroupsprotestingpollution,poorstateofmaintenanceormisuseofpublicfundsmeanttomaintainorimprovethedrain(TheHindueditorialstaff2003;TheHindueditorialstaff2016b).TheVeerangalOdaiisalsoinvolvedinanothersocialandpoliticalprocess:thepoliticalpatronageoflocalleadersininformallydecidingandapprovingillegal

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usesofthewaterways,thereincludedtheconstructionofpermanentstructuresontopofit(TheHindueditorialstaff,2002).Thesetypeofdynamicspossiblysuperimposeontheknowledgeofthelocalhydrologyafurtherlayer:thatofthegeographyofpoliticalcorruptionandallegianceswhichinfluencethewaythehydrologyislocallyinterpretedandengagedwith.Atalargerscalethisshouldbetakenintoconsiderationwhilefurtherinvestigatingotherwaterbodies,too.

Sectorialengineeringknowledge,compartmentalisedinfrastructuralprojectsandthelackofanurbanplanningframeworktocoordinatethem,mighthavehad,asintheothercaseshighlighted,asevereinfluenceonitshydrologicalrole,superimposingdifferenttypesofcontradictingknowledge,inspiredbydifferentobjectives.TheVeerangalOdaiissuchaclearcaseofthisoccurrencethatisoneofthefewwaterbodiesthathavedirectlybeenobjectofpolicyorientedstudiesmeanttoreviseprivate-publicpartnershipininfrastructureconstruction,aswellreformingparticipationpolicies(Santha,2010).Itscurrentstateisalsomentionedasaclearexamplewhichshouldmakepolicy-makersreconsidertheclassificationoffloodsinChennaire-categorisingthemfromnaturaltoman-madedisasters(Stephen,2016).

ConclusionThisliteraturereviewhasattemptedtodisentanglesomeoftheprocessesinvestingthebuiltupenvironmentandthehydrologyofcontemporarySouthChennai.Itdidsobyfocussingonthesingleelementsthatcomposethecomplexlocalhydrology,whichistheresultofalongstandingandcomplexsuperimpositionofman-madestructuresandtheactionofmeteorologicalandgeologicalelements.Init,precisebordersbetweenhumanandmore-than-humanagencyare,attimes,difficulttopindownanddiscrepanciesandgapsintheinformationavailableontheseelements,especiallyasthebasisfortheconstructionof“official”knowledge,havebeenpointed,offeringinsightsforfurtherresearch.

Theroleofmonsoonalcycles,withtheirdifferenttemporaldimensions,hasbeenbroughtintothepictureinordertounderstandhowtheyinfluenceseveralprocesses:thegeologicalformationofthecoastallandscapeanditsevolution,themodificationsofthelandscapeinordertoretainrainwater,therecurrenceofclimaterelatedurbandisastersofwhichtheyareaconcause.Alltheseprocessesareinturnentangledwiththepoliticaldynamicsofpowerresponsibleforthepoliciesshapingthecity.

Knowledgeshapedaroundtheseelementshasbeenaccountedforfromacriticalperspectiveinordertoavoidsimplifiedviewsonlonglosttraditionalunderstandingofmonsoonalcyclesand“nature”.Butthefragmentaryandpartialapproachwithwhichhydrologicalelementsareunderstood,interpretedanddealtwithintheplanningofthecityareequallyoutlined.

Havingasanobjectivetheidentificationofgapsinwhatiscurrentlyresearched,thisliteraturereviewhasaimedatgivingdirectionsonhowtofosternew,relevantknowledgeontheseissues,particularlypointingathowknowledgeproductionandinterventiononthehydrologymightbenefitfromcomprehensive,integratedunderstandingoftheissuesatstake,betterintegratinglocallyheldknowledgeandcriticalacademicproductioninordertoinspiredesigndrivenproposals.

Someoverarchingresearchquestionsarehereformulated,andarticulatedinfurthersub-questions:

Towhatextent,andinwhichways,arethekeyactorsintheadministrationofthestateofTamilNaduandofthecityofChennaimakingdecisionsoninfrastructureandplanning,failingtotakeintoconsiderationmonsoonalcyclesascomplex,multi-scalarphenomena?Towhichextentaretheymissinginformationregardingthelocalinteractionbetweenhydrology,urbanformsandlocallyheldknowledge,whichcouldhelpthemmakeinformeddecisions?

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-Whoarethepersonstakingthesedecisions,andwhatistheirunderstandingofthemonsoonalcycles?Aretheseconsideredoraretheysubstitutedbymorereductivemodelsbasedonfewvariables,suchasexcessofrainanddroughtdisconnectedfromoneanother?Isthisgapintheknowledgeobservableindesignandgraphicoutputderivingfromthedecisionmakingprocess(plans,planningpermits,thematicplans,etc.)?

Isitpossibletobridgethecurrentgapsinknowledgeaboutthemonsooncycles,emergingfromtheliteraturereview,byintegrating‘officiallyheld’,institutionalknowledgewithknowledgeheldlocallyandproducedaroundlocalinteractionsbetweenhydrology,climateandurbanforms?

-Whichactorsandcommunitieshavealocal,day-to-dayunderstandingofthelocalhydrologyanditsinterplaywithmonsoonalcycles,inwhichwaydotheyproducedknowledgethatcanbeused?Canthispossiblyinformdesigns?Whichoftheseactorsproduceknowledgethathasnotalreadybeentappedintoandthatisrelevant?

-Inwhichwaysisdesignabletotakedifferenttypesofknowledgeproducedaroundthemonsoonalcyclesinthecities,andusethemasinstrumentsinordertospeculativelyreshapehowurbanandhydrologicalelementsareconceptualisedinrelationtothemonsooncycles?

Inwhichwaysaredesignexplorationscapableofputtingforwardscenariosinordertore-tuneelementsofthecityandthehydrologytothemonsoonalcycles?Howcanthesebetested?Howcandesignexplorationsbeusedtoextractnewknowledgeinordertomediate,integrateandenhancetheonescurrentlyheldandused?

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