Springer Geography Aznarul Islam · Pravat Kumar Shit · Dilip Kumar Datta · M. Shahidul Islam · Suvendu Roy · Sandipan Ghosh · Balai Chandra Das   Editors Floods in the Ganga– Brahmaputra– Meghna Delta Springer Geography AdvisoryEditors Mitja Brilly, Faculty of Civil and Geodetic Engineering, University of Ljubljana, Ljubljana,Slovenia RichardA.Davis,DepartmentofGeology,SchoolofGeosciences,Universityof SouthFlorida,Tampa,FL,USA NancyHoalst-Pullen,DepartmentofGeographyandAnthropology,KennesawState University,Kennesaw,GA,USA MichaelLeitner,DepartmentofGeographyandAnthropology,LouisianaState University,BatonRouge,LA,USA MarkW.Patterson,DepartmentofGeographyandAnthropology,KennesawState University,Kennesaw,GA,USA MártonVeress,DepartmentofPhysicalGeography,UniversityofWestHungary, Szombathely,Hungary TheSpringerGeographyseriesseekstopublishabroadportfolioofscientificbooks, aimingatresearchers,students,andeveryoneinterestedingeographicalresearch. The series includes peer-reviewed monographs, edited volumes, textbooks, and conference proceedings. It covers the major topics in geography and geographical sciencesincluding,butnotlimitedto;EconomicGeography,LandscapeandUrban Planning,UrbanGeography,PhysicalGeographyandEnvironmentalGeography. SpringerGeography—nowindexedinScopus * * * (cid:129) Aznarul Islam Pravat Kumar Shit (cid:129) Dilip Kumar Datta M. Shahidul Islam (cid:129) Suvendu Roy Sandipan Ghosh Balai Chandra Das Editors Floods in the – – Ganga Brahmaputra Meghna Delta Editors AznarulIslam PravatKumarShit DepartmentofGeography Post-GraduateDepartmentofGeography AliahUniversity RajaN.L.KhanWomen'sCollege(Autonomous) Kolkata,India Midnapore,WestBengal,India DilipKumarDatta M.ShahidulIslam EnvironmentalScienceDiscipline DepartmentofGeographyandEnvironment KhulnaUniversity UniversityofDhaka Khulna,Bangladesh Dhaka,Bangladesh SuvenduRoy SandipanGhosh DepartmentofGeography DepartmentofGeography KalipadaGhoshTaraiMahavidyalaya ChandrapurCollege Darjeeling,WestBengal,India PurbaBardhaman,India BalaiChandraDas DepartmentofGeography KrishnagarGovernmentCollege Krishnanagar,India ISSN2194-315X ISSN2194-3168 (electronic) SpringerGeography ISBN978-3-031-21085-3 ISBN978-3-031-21086-0 (eBook) https://doi.org/10.1007/978-3-031-21086-0 ©TheEditor(s)(ifapplicable)andTheAuthor(s),underexclusivelicensetoSpringerNatureSwitzerland AG2023 Thisworkissubjecttocopyright.AllrightsaresolelyandexclusivelylicensedbythePublisher,whether thewholeorpartofthematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseof illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similarordissimilarmethodologynowknownorhereafterdeveloped. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublication doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant protectivelawsandregulationsandthereforefreeforgeneraluse. The publisher, the authors, and the editorsare safeto assume that the adviceand informationin this bookarebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernortheauthorsor theeditorsgiveawarranty,expressedorimplied,withrespecttothematerialcontainedhereinorforany errorsoromissionsthatmayhavebeenmade.Thepublisherremainsneutralwithregardtojurisdictional claimsinpublishedmapsandinstitutionalaffiliations. ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland Foreword The famous American geographer, Gilbert F. White (1911–2006), observed that, while floods may well be “acts of God,” flood damages result from “acts of man.” The rivers that ultimately feed to the great Ganga-Brahmaputra-Meghna (GBM) delta are indeed part of the natural world, and that world has traditionally been viewed as a sacred creation, held in reverence through religions practiced by the inhabitantsoftheriverbasins.However,withitsveryhighpopulationdensity(about 200 persons per square kilometer) plus the infrastructure associated with perhaps 150milliontotal inhabitants,thisregionisobviously atveryhighvulnerabilityfor immenseflooddamages. The rivers that drain to the GBM delta derive their flow from five different modern nations. The Ganga has tributaries that drain the Himalaya Mountains of India and Nepal, extending into parts of Tibet (China). Brahmaputra tributaries extend from India to Bhutan, and the main course traverses the Himalaya Range through the Tsangpo Gorge, draining much of southern Tibet (China), where the mainstem is known as the Yarlung Tsangpo. Along with the Meghna, these rivers convergeinBangladeshandbreakintothedistributarycomponentsofthedelta.Of these,thePadmaandHooghlyareespeciallynoteworthy,lyingnearthemegacities of Kolkata and Dhaka, with respective populations of about 15 million and nearly 23million. ThispresentbookdealsthefloodsandtheassociatedhazardsposedtotheGBM delta, the world’s largest, covering an area of more than 100,000 km2. Deltas develop where rivers come to rest as they enter bodies of standing water, in this casetheBayofBengaloftheIndianOcean.Deltasoccurwhererivergradientsareat their lowest, and their entrained sediments get deposited in channel bars (alluvial islands),orwhentheriversleavetheirbanksandspillintoadjacentlandthatisbuilt up by the sediment accumulations of successive inundations. Given that these low-lying lands are naturally inundated, they are really portions of their associated rivers. Thus,humanhabitationofsuchlandsisliterally“intheriver,”eventhough theflood-pronelandisnotcontinuouslyinundated. v vi Foreword TheGBMriversareladenwithsedimentderivedfromtheintenseerosionofthe world’s greatest mountain range, the Himalaya. This circumstance is the result of special geological history. About 35 million years ago, the northward-migrating subcontinental plate of peninsular India collided with the southern margin of the Asiancontinentalplate.ThecompressionzoneofthiscollisioncreatedtheTibetan Plateau and the great Himalayan Mountain Range. Sediments derived from these mountains filled a trough that was created to the south of collision zone, and the modernGangesRiverflowseastwardalongtheaxisofthistrough.Thecombination of very high mountains with south Asian Monsoon, bringing extremely heavy seasonalprecipitation, producestheimmensely highrates oferosion, water runoff, andsedimentyieldsthatcharacterizethisregion. Though it is fed by some of the world’s greatest rivers, the GBM becomes a tidallydominateddeltaatitsmouth.Thelowertidalreachesoftheriversareathigh riskfromtheoccasionaltropicalcyclonesandfromprogressiveimpactofrisingsea level.The greatcycloneofNovember 1970wasoneoftheworld’sworstdisasters for the loss of life, resulting in over a half million deaths. Progressively rising sea level associated with global warming is exacerbating the hazard for future tropical cyclones. The tidally dominated lower reaches of the delta are spread across an east-west distanceofabout300km,withthenationofBangladeshtotheeastandtheIndian state of West Bengal to the west. The coastal margins of the delta comprise the world’s largest mangrove forest. Unfortunately, the progressive destruction of this forest is limiting its positive role in moderating the impacts of tropical cyclones, furtherexacerbationtheirpotentialhazard. The many flood-related problems described in this book contrast with the great reverencefor theregion’s rivers. Itcanbe hopedthat the religious traditionof that reverence can inspire the kind of stewardship that will both mitigate the flooding hazardandproduceasustainablerelationshipbetweentheriversandthehumansthat inhabitthem. VictorR.Baker RegentsProfessorofHydrology andAtmosphericSciences TheUniversityofArizona Tucson,AZ,USA Preface Afewyearsback,whentravellingfloodedBengal,agraduatestudentfromAhmed Draia University said, ‘You have too many water resources to manage, but we die from dehydration’. He uttered the serious truth of the Earth’s extreme contrast of climate.Rather,extremecontrastofall–thesoil,thewater,theair,thelifeandthe living.InIndia,betterallovertheworld,thethreatofwaterscarcityisincreasingday by day. It is reported that even the Bengal basin will come under the threat of permanentdroughtinnearfuture.TheloweringofgroundwaterlevelintheBengal basinisringingthealarm.Dischargesofriversarediminishingrapidly.Somerivers havedriedoutandgotlost.Manylakesandswampshaveceasedtoexist. Yet our fellows get killed under flood water! Our cattle and poultry get washed away.Eachyear,eitherhereorthere,floodstollourlands,ourproperties.We,from theGanga-Brahmaputra-Meghnadelta,sufferthepainsoffloods.Itgoesbeyondour capacityforutilizationandmanagement.Theflooderasesalldifferencesinterrain. Evenbarriersofinternationalbordercrossingsdisappearunderfloodwaterandmake the landscape uniform. People of different nations feel the pain and suffering of floodsthesameway.Regardingfloods,IndiaandBangladeshhavefellowfeelings. Moreover,duringtheCovid-19situation,webecameaccustomedtoonlinecommu- nicationtocomecloser. In2020,whentheCovid-19pandemiclockeddowntheentireworld,DrAznarul Islam took the initiative to introduce ourselves to each other, and eventually, we cameclosertothinkingonasinglepointwithmulti-dimensions–theflood.Wefelt theurgetoworkandinvitedarticleson‘FloodsintheGanga-Brahmaputra-Meghna Delta’ and did pile huge responses from worldwide contributors, which offered us the opportunity to be selective. We are very much thankful to our authors who contributedtothisvolume.Theirthought-provokingcontributionsmadethisvolume knowledgeable. We are also equally thankful to our compadre authors, whose articles do not appear as chapters in this volume but who made us feel blessed withtheirarticlesrichinnoesis. vii viii Preface WearegratefultoDrGuidoZosimo-Landolfo,EditorialDirector/AssetManager of Springer Nature Switzerland AG, for signing the agreement on this project and providing the opportunity of using their prestigious pages for manuscripts of our eminentauthors. We hope, the outcomes of this volume will flood the thoughts of scholars, faculties,plannersandstakeholdersreturningustheaptworth. Kolkata,WestBengal,India AznarulIslam Midnapore,WestBengal,India PravatKumarShit Khulna,Bangladesh DilipKumarDatta Dhaka,Bangladesh M.ShahidulIslam Darjeeling,WestBengal,India SuvenduRoy PurbaBardhaman,WestBengal,India SandipanGhosh Krishnanagar,WestBengal,India BalaiChandraDas Contents 1 FloodsofGanga-Brahmaputra-Meghna DeltainContext. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 SandipanGhosh,SuvenduRoy,AznarulIslam,PravatKumarShit, DilipK.Datta,M.ShahidulIslam,andBalaiChandraDas 2 FloodInundationModellinginData-SparseFlatlands: ChallengesandProspects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 JoySanyal 3 NatureofFloodandChannelSedimentationintheTorsaRiver: AHydro-GeomorphicStudy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 UjwalDeepSaha,MdJuberAlam,SomaBhattacharya, andArijitMajumder 4 FloodRiskAssessmentofHimalayanFoothillRivers: AStudyofJaldhakaRiver,India. . . . . . . . . . . . . . . . . . . . . . . . . . 63 AdrijaRaha,SurajGupta,andMeryBiswas 5 FloodDynamics,RiverErosion,andVulnerability intheCatchmentofDharlaandDudhkumarRivers inBangladesh. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 MdRejaurRahman,SabbirAhmedSweet, andA.H.M.HedayutulIslam 6 AssessingHumanControlonPlanformModification overFloods:AStudyofLowerMahananda–Balason RiverSystem,India. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 SumanMitra,MehebubMondal,KhusbuKhatoon,SusmitaOraon, andLakpaTamang ix