Rainfall Triggered Landslide Hazard Zonation in Cox’s Bazaar and Teknaf Municipalities as well as Introducing Community-based Early Warning System for Landslide Hazard Management Report on Landslide Inventory & Land-use Mapping, DEM Preparation, Precipitation Threshold Value & Establishment of Early Warning Devices ComprehensiveDisasterManagementProgrammeII(CDMPII) MinistryofFoodandDisasterManagement(MoFDM) DisasterManagementandReliefDivision(DMRD) GovernmentofthePeoplesRepublicofBangladesh RainfallTriggeredLandslideHazardZonationinCox’sBazar&TeknafMunicipalitiesas well as Introducing Communitybased Early Warning System for Landslide Hazard Management Revised Report on Landslide Inventory and Land-use Mapping, DEM Preparation, Precipitation Threshold Value & Establishment of Early Warning Devices TableofContents Chapter1: LandslideInventoryMapping,LanduseMapping&DEMPreparation..................................................5 Executivesummary................................................................................................................................................5 1. LandslideInventoryMapping...............................................................................................................9 1.1. Introduction...............................................................................................................................................9 1.2. StatementoftheProblemandDescriptionoftheStudyArea........................................................10 1.2.1. GeneralLandslideHistoryofBangladesh.........................................................................................10 1.2.2. LandslideProbleminCox’sBazarandTeknafMunicipality.........................................................12 1.2.3. RegionalPhysiography..........................................................................................................................16 1.2.4. PhysiographicFeaturesofCox’sBazarTownandSurroundings.................................................18 1.2.4.1. Landuse&Topography.........................................................................................................................18 1.2.4.2. DrainageandWaterSupply.................................................................................................................23 1.2.4.3. VegetationandCulture.........................................................................................................................23 1.2.5. PhysiographicFeaturesofTeknafTownandSurroundings..........................................................23 1.2.5.1. Landuse&Topography.........................................................................................................................23 1.2.5.2. DrainageandWaterSupply.................................................................................................................27 1.2.5.3. Climate.....................................................................................................................................................27 1.2.6. TectonicSettingoftheArea..................................................................................................................27 1.2.7. RegionalGeology...................................................................................................................................29 1.2.8. GeologyofCox’sBazarTownandSurroundings............................................................................29 1.2.8.1. GeologicalStructure...............................................................................................................................29 1.2.8.2. Stratigraphy.............................................................................................................................................29 1.2.9. GeologyofTeknafTownandSurroundings.....................................................................................31 1.2.9.1. GeologicalStructure...............................................................................................................................31 1.2.9.2. Stratigraphy.............................................................................................................................................32 1.2.10. PhysicalsettingandHumanInterventionsintheMunicipalities..................................................34 1.3. CollectionofLandslideInformationfordevelopingtheLandslideInventory...........................35 1.3.1. Overviewoftechniquesused...............................................................................................................35 1.3.1.1. DocumentReviewandFieldInvestigation........................................................................................35 1.3.1.2. Meetingwithlocalgovernmentandotherstakeholders.................................................................37 1.4. ExplanationonclassificationoffuturerisklevelsusedinInventoryoflandslides...................37 1.5. LandslideInventorydevelopedthroughfieldmapping.................................................................38 CDMP 1 datEx-ADPC Rainfall Triggered Landslide Hazard Zonation in Cox’s Bazaar and Teknaf Municipalities as well as Introducing Community-based Early Warning System for Landslide Hazard Management Report on Landslide Inventory & Land-use Mapping, DEM Preparation, Precipitation Threshold Value & Establishment of Early Warning Devices Chapter2 PrecipitationThresholdValue..........................................................................................................................88 ExecutiveSummary..............................................................................................................................................89 2. PrecipitationThresholdValue..............................................................................................................92 2.1. Introduction.............................................................................................................................................92 2.2. GeneralApproachforestablishmentofRainfallThresholdsofLandslides................................93 2.3. LiteraturereviewontheExistingThresholdDefinitions................................................................94 2.3.1. ImpactofRainFallonSlopeInstability..............................................................................................94 2.3.2. UnderstandingthetriggersforEstablishmentofRainfallThresholdvalues..............................94 2.3.3. Rainfallandclimatevariablesusedintheliteratureforthedefinitionofrainfallthresholds..95 2.4. SuggestionsontheApplicableThresholdDefinitionsforCox’sBazaarandTeknaf...............101 2.5. ConcludingRemarks............................................................................................................................106 Chapter3 EstablishmentofEarlyWarningDevices.....................................................................................................109 Executivesummary............................................................................................................................................110 3. Establishmentofearlywarningdevices...........................................................................................111 3.1. Introduction...........................................................................................................................................111 3.2. ProjectObjectives..................................................................................................................................111 3.3. ProcessofCommunitybasedLandslideEarlyWarningSystem.................................................112 3.4. NextStep................................................................................................................................................124 4. References.............................................................................................................................................128 AnnexA Descriptiononthelandslideeventscollectedfromnewspaper&othersources AnnexB ListoftheinventoryonlandslideeventsinTeknafandCox’sBazar CDMP 2 datEx-ADPC Rainfall Triggered Landslide Hazard Zonation in Cox’s Bazaar and Teknaf Municipalities as well as Introducing Community-based Early Warning System for Landslide Hazard Management Report on Landslide Inventory & Land-use Mapping, DEM Preparation, Precipitation Threshold Value & Establishment of Early Warning Devices ListofTables: Table1:ChronologyofmajorlandslidesinBangladesh................................................................................10 Table2:ListofMajorLandslideEventsinCox’sBazarMunicipality.........................................................13 Table3:ListofMajorLandslideEventsinTeknafMunicipality..................................................................15 Table4:LandformCharacteristicsoftheCoxsBazarCoastalPlain(Alamet.al.,1999).........................31 Table5:ListofRainfallInducedLandslidesinBangladesh..........................................................................35 Table6:AnExampleofdescriptorsforriskzoningusingpropertylosscriteria......................................37 Table7:Rainfallandclimatevariablesusedintheliteratureforthedefinitionofrainfallthresholdsfor theinitiationoflandslides.................................................................................................................95 Table8:LandslideInventory(LandslideCatalogue)usedindefiningtheThresholdlimits..................98