Chatterjee_2006_Remote-Sensing-of-Environment

RemoteSensingofEnvironment102(2006)176–

Chatterjee_2006_Remote-Sensing-of-Environment

Chatterjee_2006_Remote-Sensing-of-Environment

185

SubsidenceofKolkata(Calcutta)City,Indiaduringthe1990sasobservedfromspacebyDifferentialSyntheticApertureRadarInterferometry

(D-InSAR)technique

R.S.Chatterjeea, ,BenedicteFruneaub,J.P.Rudantb,P.S.Royc,Pierre-LouisFrisonb,

http://www.wendangwang.comkheraa,V.K.Dadhwala,RanajitSahad

a

IndianInstituteofRemoteSensing(IIRS),NationalRemoteSensing,Agency(NRSA),Dept.ofSpace,Dehradun,Indiab

InstitutFranciliendesGéosciences(IFG),UniversitédeMarne-la-Vallée(UMLV),Marne-la-Vallée,France

c

NationalRemoteSensingAgency(NRSA),Dept.ofSpace,Hyderabad,Indiad

WestBengalStateWaterInvestigationDirectorate,Kolkata(Calcutta),India

Received28August2005;receivedinrevisedform9February2006;accepted10February2006

Abstract

InKolkataCity,Indiapotentiallandsubsidence,duetoover-draftingofgroundwaterunderconfinedcondition,hasbeenreportedbyanumberofpreviousworkersandbythelocalmedia.Thepresenceofathicksurfaceclaylayerwithanaveragethicknessofmorethan40movertheaquifersandlayerraisesquestionsonthepossibilityanddoubtfulnessoflandsubsidenceinKolkataCity.Inthiswork,D-InSARbasedstudyhasbeenundertakentodetectandmeasurelandsubsidencephenomenoninKolkataCity.

FordetectingslowlandsubsidencephenomenoninKolkataCityoccurringprimarilyduetopiezometricfallconsequenttogroundwaterover-drafting,wehavechosentheInSARdatapairsacquiredduringpost-monsoon(t1)–pre-monsoon(t2)periodswhentheloweringofpiezometricheadwasthemaximumandthereforelandsubsidencewouldbemoreprominentthanthatofpre-monsoon(t1)–pre-monsoon(t2)andpost-monsoon(t1)–post-monsoon(t2)periodsofsimilartimeintervals.

Fordetectingslowlandsubsidencephenomenonessentiallyfromlongtemporalbaselinedatapairs(usuallyinyears),temporaldecorrelationandatmosphericartefactshavebeenfoundtoposeseriousdifficulties.Adaptivefilteringofthenoisyinterferogramsfollowedbysummingoftheindependentinterferogramswasperformedincomplexdomaininordertosuppressnoisefromthefringesandhighlightthedeformationfringesoveratmosphericartefactsrespectively.

ResultsindicatethatanareainKolkataCitysurroundedbyMachhuaBazar,CalcuttaUniversityandRajaBazarScienceCollegehadbeenundergoingsubsidenceduringtheobservationperiod,i.e.,1992–1998withanestimatedrateof5to6.5mm/year.©2006ElsevierInc.Allrightsreserved.

Keywords:D-InSAR;ERS;Landsubsidence;Kolkata(Calcutta);Groundwaterover-draft;ESACategory-1project

1.Introduction

Amongvariousaerial-andspace-basedtechniquesavailableto-date,D-InSARappearstobeanefficienttechniqueformeasuringspatiallycontinuouslandsubsidence(Amelungetal.,1999;Carnecetal.,1995;Crosettoetal.,2002;Fruneau&

Correspondingauthor.Tel.:+911352745516;fax:+911352741987/2748041.

E-mailaddresses:rschatterjee@iirs.gov.in,rschatterjee@http://www.wendangwang.com(R.S.Chatterjee).

0034-4257/$-seefrontmatter©2006ElsevierInc.Allrightsreserved.doi:10.1016/j.rse.2006.02.006

Sarti,2000;Strozzietal.,2001;Tesauroetal.,2000;).D-InSARisusedfortwobroadpurposes:(i)identificationoflandsubsidencephenomenoninanarea,and(ii)quantitativeanalysisandmodelingofdeformationphenomenonwithparticularemphasisonprecisionofmeasurements.Inthelattercase,D-InSARtechniqueshouldbeaccompaniedbypreciseGPSmonitoringand/orground-basedlevelling.

KolkataisthesecondlargestcityinIndiaafterMumbaiandperhapstheninthlargestintheworldwithatotalurbanpopulationof13.217million(CensusofIndia,2001)overanarealextentof900km2(Kundu&Nag,1996).Ithasbeenundergoing

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