STRENGTH OF PEAT DYKES EVALUATED BY REMOTE SENSING GEBIEDSDEKKENDE DIJKSTERKTE BEPALING MET REMOTE SENSING PROGRAM FLOOD CONTROL 2015

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1 PILOTPROJECT:RSDYK2008 STRENGTHOFPEATDYKESEVALUATED BYREMOTESENSING GEBIEDSDEKKENDEDIJKSTERKTE BEPALINGMETREMOTESENSING PROGRAMFLOODCONTROL DECEMBER2008 HackHRGK 1,VanderMeijdeM 1,VanderSchrierJS 3,AwajuJH 1,RupkeJ 6, BarrittS 1,Van'THofJ 4,MaccabianiJ 2,MareschS 1,CaleroDP 4,Reymer A 4,SchweckendiekT 2,StoopJ 7,WilbrinckH 1,ZomerW 5 1 InternationalInstituteforGeo InformationScienceandEarthObservation(ITC),Enschede, TheNetherlands 2 Deltares,Delft,TheNetherlands 3 RoyalHaskoning,Nijmegen,TheNetherlands 4 TNOScience&Industry,Delft,TheNetherlands 5 StichtingIJkdijk,Groningen,TheNetherlands 6 GemeenteReeuwijk,Reeuwijk,TheNetherlands 7 HoogheemraadschapvanRijnland,Leiden,TheNetherlands

2 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page2of20

3 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page3of20 SUMMARY InthecontextoftheFloodControl2015projectthispilotprojectRSDYK2008isdonetoestablishthe possible correlations between terrestrial remote sensing techniques, geological information of the surroundingsubsurface,geophysicaldetailsofadykeandthequalityofpeatdykes.thepilotproject wasdoneatthreesitesinreeuwijk,thenetherlands. Spatial and temporal variations in the radiation temperatures measured by remote sensing have beenestablishedatallsites.thesethermalresponsesofthedykesaremainlyrelatedtotheseasonal variationandtothedistributioninthemoisturecontentofthetopsoil.thethermalimagesacquired during the dry period (August) show a positive relationship with the images of October and a negativerelationwiththeimagesofdecember.themulti temporalnearinfraredimagesofthesame sitesdonotshowanyobviousrelationship. The subsurface geology and stratigraphic profile have been obtained from interpolated pseudo sections of the 2 D and 3D electrical imaging surveys and from boreholes and Dutch Penetration testing(cpt).thelateralandverticalvariationsaswellastheheterogeneityofthedykematerialis very obvious and a clear relation between resistivity imaging and boreholes and CPT testing is established. Soilmoistureisoneofthemostimportantparameteraffectingsurfacestabilityinsoilstructures.This isbecauseinpeatsoil,theeffectivestressesandshearstrengtharedirectlyrelatedtowatercontent, and even pre failure deformations are largely controlled by the moisture content. Since the distributionofwatercontentandtotalunitweightvary inbothverticalandhorizontallayerinthe peatunitsinthedykes. The problems as kwel and possibly subsidence in the problem dyke site Tempeldijk South are identified by nearly all investigation methods, however, it is often only by knowing from another investigationmethodthattheproblemcouldbepinpointed. Mainconclusionsofthispilotprojectare: The comparison of the reference site (Tempeldijk North) with Tempeldijk South (a known problem location)showsthatinallsurfaceandsubsurfaceinvestigationsthetempeldijk South surfaceandsubsurfacestructurearemoreirregularwhichareduetoorindicate problems such as kwel andsubsidence. ThethermalinfraredimagesofTempeldijk Southshowedalayeredstructurewhichisreflecting thesubsurfacestructureofthedyke.thelayeredstructurewasdetectiblelikelybecauseexcess waterwaspresentinsomeofthelayers. Visual images showed differences in vegetation cover at locations where excess water is likely present. Thegammaraysurveyshowsapatternthatislikelyrelatedtotherealsubsurfacestructure. The data from the Algemeen Hoogtebestand Nederland may show patterns indicating deficienciesinadyke. Recommendations Thermalinfraredincombinationwithnearinfraredimagingandinparticularhyperspectralimaging should be able to accurately locate problem areas in dykes. The near infrared or hyper spectral imagingwilllikelybeasupportingtooltobeusedtocompensatethethermalinfraredinterpretation forvegetation,andenvironmentandclimatechanges.thehyper spectralmethodcouldnotbefully evaluated but is possibly a better means for investigation than near infrared. A combination with Lidar data would probably be adventurous, even the data of the Algemeen Hoogtebestand Nederlandmayalreadygivesufficientaccuratedatafordykeinvestigations.Itisrecommendedthat theideasdevelopedinthispilotprojectarefullyworkedoutandinvestigatedindetailtodevelopa

4 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page4of20 methodologythatwillbeabletodetectdykedeficienciesmoreefficiently,accurately, and cheaper thanpossiblebyvisualinspectiononly. KEYWORDS Keywords:dyke,peat,thermal,infrared,radiation,reflectance,resistivity,Reeuwijk,RSDYK LISTOFACRONYMS ADC Agriculturaldigitalcamera NAP Nationalmeansealevelreference NIR Nearinfrared TIR Thermalinfrared TAW TechnicalAdvisoryBoardforWaterBarriers ACKNOWLEDGEMENTS TheprojectcouldnothavebeendonewithouttheassistanceoftheHoogheemraadschapRijnland andthecitycouncilofreeuwijk.theownersofthelandatthethreetestsitesareacknowledgedfor theircooperation.

5 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page5of20 TABLEOFCONTENTS Summary Keywords ListofAcronyms Acknowledgements Tableofcontents 1 INTRODUCTION 1.1 FLOODCONTROL REMOTESENSING 1.3 PILOTPROJECTOBJECTIVES Specificobjectives 1.4 RESEARCHMETHODOLOGY 1.5 PROJECTPARTNERS 1.6 ACTIVITIES LIRETURTUREREVIEW 10 3 TESTSITES LOCATIONS Vreesterdijk Tempeldijk Tempeldijk North Tempeldijk South 3.2 GEOLOGICALENVIRONMENTANDTOPOGRAPHY 3.3 CLIMATE 3.4 GEOLOGICALSETTING 4 TEMPELDIJK SOUTHLOCATION 4.1 INTRODUCTION 4.2 SUBSURFACEMODELING Introduction Generalizedsubsurfaceconditions 4.3 ELECTRICALRESISTIVITY Introduction DResistivity Advantagesanddisadvantagesofthethreearrays DResistivitysurvey Correlationbetween3DresistivitySurveyandsubsurfacemodelattempeldijk south 5 IMAGING VISUAL,THERMALINFRARED(TIR)ANDNEAR INFRARED(NIR) GAMMARAYSURVEY HYPERSPECTRALSURVEY DISCUSSION,CONCLUSIONANDRECOMMENDATION 6.1 DISCUSSION Visual Elevationdata ThermalInfraRed(TIR) Resistivitysurveys 6.2 CONCLUSIONSPILOTSTUDY 6.3 RECOMMENDATIONS AppendixA Partiesandpersonsinvolvedinproject AppendixB Activities AppendixC Literaturereview

6 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 AppendixD Locations AppendixE Geology AppendixF BoreholesandCPTs AppendixG Subsurfacemodel AppendixH Resistivity AppendixI Remotesensing AppendixK GammaRaysurvey AppendixL Hyperspectralsurvey AppendixM Specificationinfraredcamera AppendixN References Page6of20

7 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December INTRODUCTION 1.1 FloodControl2015 Page7of20 DykesareafloodingprotectionmechanismintheNetherlandsandsomeothercounties.According to Van Baars (2005), the primary (3200km) and secondary (14000km) dykes in the Netherlands protectmorethan 50%ofthecountryfrom flooding.tomaintainthegroundwater level anddrain theprecipitationofthelowerlands,waterispumpedfromtheditchestothecanalsandfromthe canalsintothesea.manyofthesecondarydykesareso called peatdykes.thesedykesconsistof peatthathasnotbeenexcavatedwhilethesurroundingpeatwasexcavated.thepeatwasexcavated forfuelstartingfromtheearlymiddleages. ThepeatandclaydykesactasafloodingtemperingmeansincasealargefloodingoftheWestern part of the Netherlands occurs. The flooding is unlikely to be stopped by these dykes but the loweringof the flooding ratemaygiveopportunities to use dykes andthe roadsthatare oftenon top. Duetotheshearlargenumberofdykelengthitisimpossibletodoathoroughinvestigationoverthe fulllength.presentlythequalityofthedykesisestablishedbyvisualinspectionandonlyatlocations wherethequalityisvisuallydeemedtobelow;afurtherinvestigationtothequalityofthedykeis done.apartfromthefactthatavisualinspectionisslowandmaybebiasedandsubjective,amore important problem is that a dyke may in different seasons behave qualitative differently, even on differentdaysdependingontheweather.thevisualinspectionisgenerallyrestrictedtoaonceayear ormaybeacoupleoftimesmoreincasethesafetyofthedykeisnottrusted,butcertainlynotona basisthatcanascertainthatadykeisstableinallenvironmentalconditions. Remote sensing from the air allows for a far faster means of inspection. However, although it has been thought for a long time that remote sensing may be an attractive option it has never been systematically studied. Therefore this pilot project has been initiated to establish whether remote sensingisapossibleoptionfordykequalityassessmentbeforeandduringfloodingsituations. WithinthecontextoftheFloodControl2015project(FC2015project)thesecondarypeatdykeshave a specific function. Secondary dykes may reduce the flooding rate in the Westen part of the Netherlandswhenthemaindykesagainsttheseaandmainrivershavefailed.Importantisthenhow longthesedykesmaystillbeabletofunction.obviouslyinatimeofamajorfloodinginthewestern partofthenetherlandsnotimewillbeavailabletostartaninvestigationtothequalityofthedykes. Thequalityofthedykeshasthereforetobeestablishedbeforehand. 1.2 Remotesensing Anyvegetationpresentaroundthedykesislikelytobeinfluencedbychangesingroundwatertable ormoisturecontentofthematerialandviceversa.thehealthofthevegetationcanbeaffectedas the groundwatertable becomestoo shallow or toodeep. The most likelychanges are expectedto occurinthechlorophyllconcentrationsinthevegetationwhichareanindicatorofthehealthstate (Van der Meijde et al., 2004). Adams (Adams et al., 1999) showed that in stressed vegetation the absorptionefficiencyofthechlorophylldecreasesandtheirreflectancedecreasesduetochangesin thecellstructureoftheplant.thisleadstoareductioninreflectanceintheirsimultaneouswithan increaseinreflectanceinthered. The spatial distribution of surface temperature around the dyke can be related to the moisture content of the soil. The temperature variation in the subsurface depends on its thermal diffusivity which itself is also a function of water content. The effective soil water content is maximal at the beginning of the spring and then decreases until the end of summer (Behaegel et al., 2006). Soil

8 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page8of20 thermalpropertiesarestronglyinfluencedbythesoilvolumetricwatercontent,volumefractionof solidsandvolumefractionofair. Hence, if the stability of peat and to a certain extend also clay dykes depend on the moisture content,andthehealthofthevegetationonadykeisdependentonthemoisturecontent,anditis possible to establishthe healthof thevegetationbyremotesensing, itshouldthenbe possibleto establisharelationbetweenremotelysensedimagesandthequalityofthepeatandprobablyclay dykes. In the context of the FloodControl 2015 project this pilot project is done to establish the possible correlations between terrestrial remote sensing techniques, geological information of the surroundingsubsurface,geophysicaldetailsofadykeandthequalityofpeatdykes.thepilotproject wasdoneatthreesitesinreeuwijk,thenetherlands. 1.3 Pilotprojectobjectives The main objective of this pilot project is to indicate possible relationships between terrestrial remote sensing, geological information of the surrounding subsurface, and weak areas in dykes mainlyconsistingofpeat.geophysics,boreholesanddutchconepenetration(cpt)testshavebeen donetoinvestigatethesubsurfaceofthedyke SPECIFICOBJECTIVES Theprojectaddressesthefollowingspecificobjectives: 1.4 Identifythespatialandtemporalvariationsofthethermalradiationofthedykematerialsaswell asreflectancefeaturesofthegrassusingthermalinfrared(tir)andnearinfrared(nir). Determine the variation in the composition of a dyke, the soil moisture condition and the material properties using two and three dimensional (2D and 3D) electrical imaging surveys, boreholesandcpts. Indicate possible relationships between the thermal infrared, near infrared, and visual remote sensingandthesubsurfacemodelofthedykeandpossibleweakareasofthedyke. Researchmethodology This pilot project comprises pre field, field data collection and post field data analysis works. A literaturereviewhasbeenmadeonterrestrialremotesensingtechniques(tirandnir)andphysical parameters of peat dykes such as moisture content, permeability, porosity, bulk density, organic contentandconsolidation.informationaboutthegeologicalsettingofthestudyareaalsogathered frompreviousworksofdifferentresearcherswhoworkedinthestudyarea. Duringthefielddatacollection,fieldimagesofTIR,NIRandvisualwereacquiredusinggroundbased sensorsinthreedykesites.thiswasdoneinthreedifferentseason ssummer,autumnandwinter.in addition, 2 D and 3Delectrical imaging surveys were conducted on twodyke sites. In the summer boreholes and Dutch cone penetration tests were done for referencing the geophysical subsurface model. Figure1 1showsasummarizedschematicworkflowthathasbeenusedtoachievetheobjectivesof theproject.

9 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page9of20 Figure1 1:Schematicworkflowdiagram. 1.5 Projectpartners ThepartnersintheprojectandthepersonsinvolvedintheprojectarelistedinAppendixA. 1.6 Activities TheactivitiesduringtheprojectarelistedinAppendixB.

10 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December Page10of20 LIRETURTUREREVIEW AbriefliteraturereviewisincorporatedinappendixC.Theliteraturereviewgivesanoverviewofthe characteristicsofpeatandremotesensingcharacteristicsofpeatandvegetationascommonlyfound ondykes.theconclusionsoftheliteraturereviewaremanybutcanbesummarizedasfollows: Remote sensing should give good opportunities to evaluate the homogeneity of the surface coverofdykesduringvariousseasons, thesurfacecoveriscoupledbythepresenceofwatertothedeepermaterialsinthedyke, the presence of water is often a good indicator of the possible problems with a dyke, such as excess water ( kwel ), unwanted water flows, or may indicate a situation that the dyke is jeopardizedbyashortageofwater,e.g.thematerialsinthedykearedriedout(forexample,the Wilnes case), surfacedeviationsofthedykeareeasilydetected,and remote sensing is a far faster method of investigation of dykes than traditional visual investigations.

11 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December TESTSITES 3.1 Locations Page11of20 ReeuwijkislocatedinapolderareaintheprovinceofZuidHolland,inthecentralwesternpartof The Netherlands. Maps and aerial photographs of the area and locations of the test sites are included in appendix D. In the area extensive excavation of peat has taken place since the early MiddleAges.Threetestsiteswereselected(Figure3 1).Inthisreportdescribingtheresultsofapilot project,onlythetestsitewithproblems, Tempeldijk South,isfullyevaluated. Figure3 1.Locationtestsides.TheurbanareainthebottommiddleisReeuwijk Dorp.(photoGoogleEarth,2008.Grid:UTM(WGS84, zone31nh) VREESTERDIJK TheVreesterdijkislocatedintheareawherepeathasbeenexcavatedandconsistsofaroadonan embankmentofnon excavatedpeat.thestructureofthedykeisnotknownindetail,butisassumed to consist of in situ peat in the lower part. Likely, the dyke has been covered by road pavement

12 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page12of20 materialsmanytimes(probablyforhundredsofyears)andiscoveredbyabitumenlayeratpresent. Theextentindepthofthelayersisunknown.Thedykedoesnotfunctionasboundaryforawater canal,butasalocaldivisiondyke(dam)intheexcavatedarea,andasanaccessroadtoafarm TEMPELDIJK TheTempeldijkistheboundarybetweenahigh layingin situpeatdepositareawherethepeathas not been excavated and a low laying area where the peat layer has been excavated. The dyke functionsasadyke(e.g.dam boezemkade )forade wateringcanal.twotestsiteswereselected; one on both ends, e.g. Tempeldijk North and Tempeldijk South (originally these were named Tempeldijk 1andTempeldijk 2.Asthiscausedconfusionnameshavechangedtothemorelocation specificnamesoftempeldijk NorthandTempeldijk South) TEMPELDIJK NORTH Tempeldijk North location is chosen as reference. The dyke seems to function without known problems. Also on the surface of the dyke no features have been distinguished that may indicate seepage( kwel ),subsidence,orotherwisefeaturesthatcouldbeanindicationof problems TEMPELDIJK SOUTH Tempeldijk Southlocationisreportedtohaveproblemsduetoseepage( kwel )andpossibly subsidence.foramoredetaileddescriptionoftempeldijk Southisreferredtochapter Geologicalenvironmentandtopography Geologicallythestudyareaisadeltaicenvironment.Theareaisratherflatwithanaverageelevation of 1.6 m NAP (National Mean Sea Level Reference) with man made dykes and cannels. Polders resultingfromreclamationafterpeatextractionhaveelevationsaround 5.0mN.A.P. 3.3 Climate AccordingtoKöppen sclassification,thenetherlandshas amoderateseaclimatewithrain almost throughoutthewholeyear.ingeneral,thewintersaremildhavinganaveragemeantemperatureof 1.7oC.Themeantemperaturemaybebelowzerointhecoldestmonth.Insummerfivemonthshave amean temperatureover 10o Cwith a maximumtemperature of 17o C in July.Theprecipitation is evenly distributed over the year with a yearly average of 760 mm (Ten Cate, 1982). In Spring precipitationislowwhichcausesadeficitinsurfacewaterduetoevaporation. 3.4 Geologicalsetting Theinformationaboutthegeologicalsettingofthetestsitesissummarizedfrompreviousworksof researcherswhoworkedinthearea,fromregionalstudies,andfromthegeneralgeologicalhistoryof thenetherlands.asummaryisincludedinappendixe.thegeologicallithologyofthearearesulted from sedimentation in the Holocene period. During the Holocene, the area was located in the perimarinezone,wherethedepositswereformedundertheinfluenceofsealevelfluctuationsand sea level rising from the west interacting with river input from the east. This resulted in extensive areas where for a longer time stagnant water and swamps allowed the development of large and thickpeatlayers.occasionallymarineorriverinfluencecausedthedepositionofclayandsandlayers andlenses.

13 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December TEMPELDIJK SOUTHLOCATION 4.1 Introduction Page13of20 The test site location Tempeldijk South measures about 100 by 50 m along the Tempeldijk (Figure 4 1).Thetestlocation is the westsite ofthedyke. Thetop ofthe dyke is at about 2m while the bottomofthedykeisatabout 5m.Theareaiscoveredwithgrassthatisregularlycutinsummer. The firstlayerof material to adepthof around 0.3 m is a man made cover ofclay with peat(oral information,rupke,2008,andconfirmedbyboreholes).inthecanalandatthefootofthedykeat the western site of the dyke kwel occurs. Possible a part of the dyke has (slightly) subsided as indicatedbytheelevationcontourlinesbetweenp1andph1(figure4 1).Theelevationsarebased onthedataofthe ActueelHoogtebestandNederland. Figure4 1.Tempeldijk SouthtestsiteareaBoreholesandCPT AtthelocationofTempeldijk Southtwoboreholesand17CPTs(DutchConePenetrationtests)with pore water pressure measurement have been made. The locations, and borehole, including photo logs, and CPT logs are included in appendix E. Direct besides a borehole also a CPT test has been made to facilitate interpretation of the CPT. The boreholes are made with a so called Delft Continuous Soil Sampler (a type of triple tube core sampler). Borehole logs have been made by visualdescriptionoftheboreholecores.

14 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December Page14of20 Subsurfacemodeling INTRODUCTION TheboreholeandCPTlogsobtainedatTempeldijk Southhavebeenincludedinathree dimensional geologicalmodel.sectionsareincludedinappendixf.theinterpretationhasbeendonestartingwith the description of the boreholes coupled to the nearby CPT. In between the CPTs the lithology identificationhasbeendonelooselyfollowingthestandardscommonlyusedinthenetherlandsand international standards (Abu Farsakh et al., 2008, Robertson, 1990) for CPT interpretation. Interpretation of soil lithology based on CPT data only and in particular details in peat and peat containing layers isnotoriously difficult. Variations intypeof plantsremains orthecompetence of plantremainsgivechangesincptvalueswhicharedifficulttocorrelatetothevisualdescriptionof thepeatlayers.forthepurposeofthisinvestigationespeciallythehorizontalandverticalchangesin lithologyarelikelyveryimportant.thedifferentiationofthelithologybasedoncptvaluestherefore hasbeendoneinasmuchdetailaspossible GENERALIZEDSUBSURFACECONDITIONS The subsurface fromthe surface downwardscanbe generalized for thetempeldijk South location. The lithology names refer to the names used in the sections and 3D model in appendix G. The generalizedcompositionofthedykeis: 4.3 Fromthetopalayerofclayeypeatispresentwithathicknessofabout0.3mintheEastontop ofthedykereducinginthicknesstowardsthewest,thebottomofthedyke(peats).thislayeris likelyaman madetoplayer. Asequenceofpeatandsiltyorclayeypeatlayerswithsomethinsiltandclaylayersispresent betweentheman madetoplayerandadepthofabout 5m.Inwesterndirectionstheselayers truncateagainsttheman madetoplayer(peat7,clay5,peat6,silt3,andpeat5). Afairlyconsistentclayclayeypeatlayer(CLAY4)ispresentat 5m. Betweenabout 5and 9.5to 10.5asequenceofpeatandsiltyorclayeypeatlayerswithsome thinsiltandclaylayersispresent. Atabout 9.5to 10.5manundulatingsandlayersequencestarts(SAND2). Electricalresistivity INTRODUCTION Thepurposeoftheelectricalimagingsurveyistodeterminethesubsurfaceresistivitydistributionof thesites.theresistivityofthesubsurfacematerialsisdeterminedlargelybythewatercontentand secondarybytheresistivityofthesubsurfacematerialsandtheresistivityofthewater.2dand3d resistivity surveys have been done. The 2D survey has mainly been used for determining the best arraysetup(appendiceshandj) DRESISTIVITY A2 Delectricalimagingsurveyisusuallycarriedoutusingalargenumberofelectrodesconnectedto amulti corecable.thetypicalsetupfora2 Dsurveywithanumberofelectrodesalongastraight lineattachedtoamulti corecableisillustratedinfigure4 2.Acomputeroperated StingR1/IP has been used as measuring device. It is a single channel automatic resistivity imaging device with a multi electrodesystem.ithasabuilt insetofcommandfilesfordifferentelectrodearrays.typically, 28electrodesarelaidoutintwostringsof14electrodes,withelectrodesconnectedbyamulticore cabletoaswitchingboxandresistancemeter(figure4 3).Theelectrodespacinghasbeen1m.

15 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page15of20 Figure 4 2: The electrode arrangement for a 2 D electrical imaging survey and the sequence of measurements used to build up a pseudo section(lokem.h.,2000). Canal Poles(20mapart) Mainbody ofthedyke STINGR1/IP Electrodesattached bymulticables Figure4 3:A2 DelectricalimagingsurveyontheTempeldijk North.TheequipmentconsistsofaStingR1/IPand28electrodeshavinga 1mspacinglaidoutintwostringsof14electrodes.

16 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page16of ADVANTAGESANDDISADVANTAGESOFTHETHREEARRAYS In2 Dimagingsurveys,theelectrodesetups Schlumberger, Wenner and dipole dipole arethe electrodearraysthatarethemostcommonlyused.thechoiceofthe best arrayforafieldsurvey depends on the type of structure to be mapped, the sensitivity of the resistivity meter and the background noise level. The Wenner array is relatively sensitive to vertical changes (i.e. horizontal structures)inthesubsurfaceresistivitybelowthecentreofthearray.however,itislesssensitiveto horizontal changes (i.e. narrow vertical structures) in the subsurface resistivity. The dipole dipole array is most sensitive to resistivity changes between the electrodes in each dipole pair and the sensitivity contour pattern is almost vertical. This array is therefore very sensitive to horizontal changesinresistivity,butrelativelyinsensitivetoverticalchangesintheresistivity.unliketheabove arrays,theschlumbergerarrayismoderatelysensitivetobothhorizontalandverticalstructures.in areaswherebothtypesofgeologicalstructuresareexpected,thisarraymightbeagoodcompromise betweenthewennerandthedipole dipolearray DRESISTIVITYSURVEY Afullthree dimensionalresistivitysurveyhasbeendoneonthelocationtempeldijk South.The resultsareincludedinappendixg CORRELATIONBETWEEN3DRESISTIVITYSURVEYANDSUBSURFACEMODELAT TEMPELDIJK SOUTH TheresistivityimagingofthesubsurfaceatTempeldijk Southcanfairlyaccuratelyberelatedtothe subsurfacelithologymodel.thelowresistivityvalescorrelatetopeatlayersandinparticulartomore silty or sandy peat layers. In the top part of the dyke (e.g. above 5 m) the low resistivity values correlatewithasiltorsiltypeatlayer(refertoappendixh,figuresh 4andH 5)inwhichthesiltlayer isindicatedwithsilt3.

17 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December IMAGING 5.1 Visual,ThermalInfraRed(TIR)andNear InfraRed(NIR) InappendixIareincludedtheanalysisoftheremotesensingimages. 5.2 GammaRaysurvey InappendixKtheresultsofthegammaraysurveyareincluded. 5.3 HyperSpectralSurvey InappendixLareincludedtheanalysisofthehyperspectralsurvey. Page17of20

18 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December DISCUSSION,CONCLUSIONANDRECOMMENDATION 6.1 Discussion Page18of20 Thesoilmoisturecontentisoneofthemostimportantparameteraffectingsurfacestabilityinsoil structuresandhenceinthetypicalpeatdykesfoundinthewesternpartofthenetherlands.inpeat, theeffectivestressesandshearstrengththataredeterminingthestabilityaredirectlyrelatedtothe watercontent.sincethedistributionofwatercontentandalsothepropertiesofthematerialsin dykesvarybothverticallyandhorizontally,thestabilityofthepeatdykesisalsohighlyvariable verticallyandhorizontally.thishighlyvariablenatureandtheenormouslengthofso calledpeat dykesmakethatassessmentofthestabilityonaregularbasisisacostlyaffair.therefore,anymeans thatwouldbeabletoassessthestabilityoreventoindicateonlychangesinthestabilitythatare cheaperthanthepresentlyusedvisualinspectionsareworthwhiletobeinvestigatedontheirmerits. Remotesensingisthoughttobeapossibleassessmentmethod,andthereforeisinthisresearchis investigatedhowfarremotesensingtechniquescoulddeterminevariationsinwaterandsoil propertiesofthedykes VISUAL Thevisualimagesshowobviouslymainlythatsurfaceandthusthesurfacevegetationcoverofthe dyke. The vegetation cover, however, may show also differences in vegetation cover, such as the presenceofsmallyellowflowersinpartofthefootofthedyke(tempeldijk South,appendixI,Figure 6).Itisremarkablethatthislocationmoreorlesscoincideswiththelocationwherepossibleexcess waterflowsoutofthedyke.itisnotunlikelythatlocationsthatarewetteralsohaveavegetation coverthatisdifferentfromthosecoveringmoredryareas ELEVATIONDATA Although not intended to be investigated in this pilot study, the data from the Algemeen HoogtebestandNederlandmayshowdeficienciesinadyke.ThedatadeterminedbyLidarsurveysis accurate enough to determine surface patterns with high detail. The Tempeldijk South location showsapatternthatmayindicateadeficiency(subsidence)atalocationwherealsothelayersinthe subsurface (determined from the three dimensional resistivity survey and 3D subsurface model) showvariationsinelevation.visuallyanydeficiencyinthesurfaceofthedykehasnotbeennoted THERMALINFRARED(TIR) Thegeotechnicalpropertiesofpeatdifferfromthoseofclayinmanyaspects.Comparedtoclay,peat hasamuchhigherporosityandabilitytoholdwaterundernatural(unloaded)conditions.thiswas clearly indicated from their ability to absorb and emit electromagnetic energy. Apart from the emissivitypropertyofthematerialcomposition,theemissivityofanobjectishighlydependingon themoisturecontent.waterhasverydarktomediumgraytonesindaytirimagesandmoderately lighttonesinnighttirimages,comparedwiththesoil.thissimplymeansthatwateriscoolerinthe day and warmer in the night than most other materials present. This response is due in part to a rather high thermal inertia, relative to typical land surfaces, as controlled largely by water's high specific heat. After prolonged period of rainfall, in this research thus mainly in the autumn and winter,whenthetopsoilwatercontentishigh,theheatcapacityofthetopsoilisalsohighandasa result,moreenergyisneededtoincreaseitstemperature.inconsequence,thesurfacetemperature responsetosolarradiationandairtemperatureisslowerandweaker.however,afteralongperiod withoutrainthewatercontentofthesoilisless,andsurfacetemperaturesrespondsquickertosolar radiation and air temperatures. This feature is shown by the multi temporal TIR images of Tempeldijk South. During the summer following the reduction of the moisture content due to

19 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page19of20 evaporation and evapo transpiration from the topsoil, the peat layer becomes dry and has higher temperatureswhereasduringthewinteritbecomeswetandhaslowtemperatures. Since the dykes are covered with grass, the radiation temperature values are the resultant of the emittedtemperaturesfromthetopsoilofthedykematerialandthegrass.itisdifficulttoestablish how much of this resulted from the grass compared to that from the topsoil. The variation in the radiationtemperatureofthegrassismainlyrelatedtotheaccumulationoftherainfallwater.fallen debris from the grass (dead leafs), the water content in the soil, the apparent roughness, and the positionwithrespecttothesunalsoinfluencetheradiation.theradiationtemperaturevariationof the dyke materials is mainly related to the seasonal variability of water content in the soil water contentandthereforecanprobablyberelatedtothegeotechnicalpropertiesofthedykematerials RESISTIVITYSURVEYS Theresultsofthe2 Delectricalimagingsurveysidentifythestratigraphicprofileofthetwositeson the Tempeldijk. The interpolated pseudo sections reveal the geological formation of the dyke. The boundarybetweentheclaylayerandthepeatlayerwasclearlydetermined.alsolateralvariations were established that may indicate heterogeneity of these layers, however, also variation in water content may be present. In the lower parts also more salt containing water from the sub surface seepagefromdeeperlayersmaybepresentwhichisshownbylowresistivityvalues. 6.2 ConclusionsPilotstudy Mainconclusionsofthispilotstudyare: The comparison of the reference site (Tempeldijk North) with Tempeldijk South (a known problem location)showsthatinallsurfaceandsubsurfaceinvestigationsthetempeldijk South surfaceandsubsurfacestructurearemoreirregularwhichareduetoorindicate problems such as kwel andsubsidence. Visual images showed differences in vegetation cover at locations where excess water is likely present. Thegammaraysurveyshowsapatternthatislikelyrelatedtotherealsubsurfacestructure,but furtherinvestigationsarerequiredtodeterminetheexactnatureofthisrelation. The3Dsubsurfacemodeland3Dresistivitymodelcorrelate. The data from the Algemeen Hoogtebestand Nederland may show patterns indicating deficiencies in a dyke. The data determined by Lidar surveys is accurate enough to determine surfacepatternswithhighdetail. AquantitativeanalysiswasusedtoevaluatetherelationshipbetweentheTIRandtheNIRimages. ScatterplotsweremadebetweentheradiationtemperatureandreflectanceDN values.mostofthe plotsillustrateaveryweakrelationship.someoftheinfluencingfactorsare: 6.3 Recommendations Thermalemissivityishighlydependentonthemoisturecontentofasoilandthustheemissivity of this moisture content can vary with diurnal period. Therefore, it is important to acquire thermalimagesindifferenthoursofthedayinordertoseethevariationintheemissivityofthe dykematerialsandtoindicatethedistributionofmoisturecontentofthetopsoil. Two objects might have the same Tkin (kinetic temperature) but have different Trad (radiation temperature)becauseofdifferencesintheiremissivityandtheiremissivitycanbeinfluencedby externalfactorssuchasmoisturecontent,color,andsurfaceroughness.insitumeasurementof the surface temperature of the dyke materials using digitalthermometers is very importantto understand the degree of the influence from these factors and to calibrate the results of the thermalimages.

20 Pilotproject:Strengthofpeatdykesevaluatedbyremotesensing (Gebiedsdekkendedijksterktebepalingmetremotesensing) ProgramFloodControl2015 RSDYK December2008 Page20of20 LocalmeteorologicalvariableshavetobemeasuredsimultaneouslywiththeTIRimaginginorder to characterize the conditions of the sensor ground surface continuum. These included air temperatureandtheglobalradiationreachingthesurface. Theremotelysensedimagingshouldhavetobeacquiredperpendiculartothestudyinterest,by increasingtheplatformabovetheground.thiswillhelptominimizethescatteringeffectinthe reflectionforthenearinfraredimaging. Vegetation stress can possibly be detected better using hyper spectral remote sensing. Using spectroscopyitwillbeeasiertodifferentiatethestressedgrassfromthehealthygrassbasedon their variation in the reflectance spectral signature. Therefore, it might be better to use hyper spectralspectroscopyinthefuturestudy.

21 AppendixA RSDYK2008 Partiesandpersonsinvolvedintheproject Page1of2 APPENDIXA RSDYK2008 PARTIESANDPERSONS INVOLVEDINTHEPROJECT

22 AppendixA RSDYK2008 Partiesandpersonsinvolvedintheproject Page2of2 Theprojectwasexecutedbythefollowingparties: International Institute for Geo Information Science and Earth Observation (ITC) (project leader) Deltares Haskoning TNOScience&Industry StichtingIJkdijk GemeenteReeuwijk HoogheemraadschapvanRijnland Thepersonsinvolvedintheprojectare: YonnasHaddishAwaju,MSc(ITC) Dr.SallyBarritt(ITC) Dr.RobertHack(ITC)(projectleader) Jaapvan'tHof(MonitoringSystemsTNOScience&Industry) Ir.JosMaccabiani(Deltares) SabineMaresch,MSc.(ITC) Dr.MarkvanderMeijde(ITC) DanielPerezCalero(MonitoringSystemsTNOScience&Industry) Dr.ArthurReymer(MonitoringSystemsTNOScience&Industry) Dr.JanRupke(GemeenteReeuwijk) Ir.JoostvanderSchrier(Haskoning) TimoSchweckendiek(Deltares) JaapStoop(HoogheemraadschapvanRijnland) HenkWilbrinck(ITC) WouterZomer,Ing(StichtingIJkdijk

23 AppendixB RSDYK2008 Activities APPENDIXB RSDYK2008 ACTIVITIES Page1of2

24 AppendixB RSDYK2008 Activities Table1showsanoverviewoftheactivitiesinthisproject. Table1.Overviewactivities. 15Aug Aug Oct Dec Dec Dec2007 9Jan Jan2008 7Feb Feb2008 6Mar2008 7Mar Mar Mar Jun Jun2008 4Jun2008 4Jun2008 5Jun Jul Aug2008 fieldworkreeuwijk visual,tirandnirimages fieldworkreeuwijk 2Dresistivitysurvey fieldworkreeuwijk visual,tirandnirimages fieldworkreeuwijk visual,tirandnirimages meetingcitycouncil Reeuwijk meetingonlocation,reeuwijk meetingdelft meetingdelft workshopfc2015 meetingdelft conference Waterkeringen,Amersfoort meetingdelft meetingdelft meetingreeuwijk fieldworkreeuwijk visual,tirandnirimages fieldworkreeuwijk 3Dresistivitysurvey fieldworkreeuwijk gammaraysurvey fieldworkreeuwijk hyperspectralsurvey meetinghhrijnland,leiden fieldworkreeuwijk visual,tirandnirimages fieldworkreeuwijk boreholesandcpt Page2of2

25 AppendixC RSDYK2008 Literaturereview APPENDIXC RSDYK2008 LITERATUREREVIEW Page1of7

26 AppendixC RSDYK2008 Literaturereview Page2of7 Contents 1 GENERALCHARACTERISTICSOFPEAT REMOTESENSING INTRODUCTION PEATASDYKEFOUNDATION DIFFERENTIALSETTLEMENT WATERCONTENTANDHOMOGENEITY 3 THERMALINFRARED REFLECTANCEFEATURESOFVEGETATION REFERENCES

27 AppendixC RSDYK2008 Literaturereview 1 GENERALCHARACTERISTICSOFPEAT 1.1 Introduction Page3of7 Continuesdetectionandmonitoringofpeatdykesisveryimportanttosecuretheirstabilityand protect the major impact on the environment and casualties (McCahon et al., 1987). Previous studiesshowthat,thereisstilllackindetailedunderstandingofpeatmassmovements(carling, 1986a; Dykes and Kirk, 2001). However, the hydrological and geotechnical conditions are the main issues of peat dykes. These conditions are usually affected by seasonal variations, which canbeconsideredasamaincauseoffailureinmanyengineeringstructures(tallisetal.,1997; Evansetal.,1999). 1.2 Peatasdykefoundation Wardhasbeendescribedtheriskofapeatlayerunderadyke(Ward1948andWard1955).He indicated that dykes founded on very weak peat might collapse within a short period after construction. Instability can occur in peat dykes even if they are on the top of an impervious material like clay (Carling, 1986a). This is because peat dykes can have less weight than the resultant water force especially when the crest of the dyke dries out (Van Baars, 2005). This resultantforcecanbeaffectedbyariseofwaterlevelinthecanals,ditchorstreams. 1.3 Differentialsettlement IncountrieswithlargepeatdepositsatsurfacesuchasCanadaandIreland,wherepeatcoversas much as 16 18% of the area, construction activities face a serious problem to engineers with respecttothedifferentialsettlementanddeformation.thisisalsoawell knownprobleminthe testsitearea,reeuwijk,thenetherlands. 1.4 Watercontentandhomogeneity The distribution of water content and total unit weight vary in both vertical and horizontal directions in peat layers. Saiyid (Saiyid Hassan, 1994); Dalton (1954) and Radforth (1964) postulatedthat,theretentionofwaterinpeatmayberecognizedasfreewaterinlargecavities, capillary water in narrower cavities and water bound (physically, chemically ). This indicated thatanyvariabilityinthewatercontentwouldaffectthestabilityofpeatstructures. Inpeat,theeffectivestressesandshearstrengththat aredeterminingthestabilityaredirectly relatedtothewatercontent.thewatercontentofthetopsoilvarieswithrespecttotheseasonal variations.followingthereductionofthewatercontentofthetopsoilduringthedryconditions inthesummercanresultindryingandshrinkageofthepeatlayer.thiswillcausenewcracking, reactivation of old cracks, and opening of peat fuel cuttings (Long, 2006). During the intense rainfall, water can rapidly percolate to the base of the peat through the new and old cracks. Therefore, any increase in stability due to lowering of the water content is likely to have been offset by the reduction in unit weight of the peat by drying. Pore pressures in the peat would haveincreasedsignificantly,reducingtheeffectivestressesandtheresistancetosliding.itisalso possible to speculate that repeated drying and wetting cycles caused shrinkage and swelling movements in the peat (Warburton et al., 2004). The soil moisture content is also a key parameter in computing the surface energy balance and important in many applications includinghydrology,agricultureandmeteorology(petroneetal.,2004).otherfactorslikespecific gravity, organic content, heterogeneity in soil texture, vegetation, land use, topography and surfacetemperaturealsoaffectthestabilityofpeatdykes(tansey,1999;liandislam,1999).

28 AppendixC RSDYK2008 Literaturereview 2 Page4of7 REMOTESENSING Remote sensing in all ranges of the electro magnetic spectrum has many applications in geotechnical investigations (Figure 1). It is also used for mapping the top soil moisture over a varying landscape (Famiglietti et al., 1999; Li and Islam, 1999) and in identifying engineering structures.rijswaterstaat,thenetherlands,hasmadeaninventoryofthepossibilitiesofremote sensingapplicationsforthepurposeofdykequalityassessment(swart,2007).inthispublication thepossibleoptionsforusingremotesensingaredescribedbasedonaliteraturereview. Figure1.Theelectro magneticspectrum. 2.1 Thermalinfrared Thermalremotesensingiswidelyusedformanyapplicationsincludingcoalfiredetection(Yang. 1995),damleakagemonitoringetc.Thermalremotesensingisbasedontheinfraredrangeofthe electro magnetic spectrum. According to Planck s Radiation law, all objects above 0 K emit thermalelectromagneticenergyinthe3.0 14μmwavelengthregion.Theemissivepowerofa black body at any wavelength and temperature, as well as the amount of emitted energy per wavelengthdependsontheobject stemperature.differentmaterialscanhavewidelydifferent valueswithintherangeof0to1.therangeofemissivityforgroundcomponentsinsituofsoil, vegetation and rocks, varies at a given wavelength according to their physical properties and water content (Fuchs and Tanner, 1966, Van de Griend et al., 1991, Blumberg, D.G et.al., 2000 and2001). Planck's law gives the spectral radiance of electromagnetic radiation at all wavelengths from a blackbodyattemperaturetasafunctionofwavelengthλ:

29 AppendixC RSDYK2008 Literaturereview M,T C1 Page5of7 C1 CT2 e 1 [1] 5 InwhichMλ,Tisthespectralradiancein(Wm3),λisthewavelengthin(m),Tisthetemperatureof theblackbodyin(k),c1isthefirstradiationconstant, (Wm2)andC2isthesecond radiationconstant, (mk). The emissivity power increases with temperature at each wavelength and the position of the maximum emissive power shifts towards the shorter wavelengths. Relatively more energy is emittedatshorterwavelength(figure2). Figure2.Theblackbodycurveat3500,4000,4500,5000and5500k Manyresearchers(Idsoetal.,1975;Reginatoetal.,1976;Price,1980)assessedandmappedsoil moisturebythermalinfraredusingradarmicrowavetechnology,satelliteimagesand/orairborne sensors for studying bio physical processes on a micro scale. Jackson (2002) showed the difficultiesforretrievalofsoilmoistureduetotheinfluenceofsurfacevariableslikevegetation cover. Recent studies use terrestrial thermal remote sensing for detection purposes. Thermo tracer (TH9100) is one of the high sensitive radiometric cameras that measures the infrared radiationemittedfromobjects.preliminaryanalysesusingthisthermalcamerashowasignificant relationshipbetweeninfrared basedtemperatureandsurfacesoilmoisture.atasmallscale,the thermalinfraredimagesbyathermotracerisshowntobeusefultomapareascharacterizedby differentsoilmoisturecontent(p.mora,etal.,2007). 2.2 Reflectancefeaturesofvegetation Changesinvegetationcanaffectthesurroundingengineeringstructuresandlocalgroundwater level(fredlund,2001).adifferenceinthereflectanceofgrass,whichcoversapeatdyke,might relate to the soil moisture variation of the material. Remote sensing allows the detection of hazardousgasleakageofpipelinesfromthereflectancespectralsignatureofstressedvegetation (VanderWerffetal.,2007).Thehealthofplantsisreflectedinitschlorophyllcontent(Vander Meijdeetal.,2004).Adamsdemonstratedthathealthyvegetationshowshighreflectanceinthe greenandnirregion(figure3).however,thechlorophyllofstressedordryvegetationdecreases its absorption efficiency and increase in reflectance in the red (Gausman 1974, Tucker 1979,

30 AppendixC RSDYK2008 Literaturereview Page6of7 Adams M.L. et al., 1999). Environmental factors such as soil, geomorphology and vegetation apparentroughnessinfluencethereflectancevalues.variationsinclimaticfactors,inparticular precipitationandtemperature,havethereforeastronginfluenceonvariationinthereflectance. Figure 3. This general diagram shows the stress indicated by a progressive decrease in Near IR reflectance accompanied by a reversalinshort WaveIRreflectance

31 AppendixC RSDYK2008 Literaturereview 3 REFERENCES ForthereferencesisreferredtoappendixN. Page7of7

32 AppendixD RSDYK2008 Locationtestsides APPENDIXD RSDYK2008 LOCATIONTESTSITES Page1of3

33 AppendixD RSDYK2008 Locationtestsides Page2of3 Mapsandaerialandsatellitephotosofthetestsiteareaandthelocationsofthetestsites. Figure1.LocationReeuwijk(map:Routenet Routeplan,

34 AppendixD RSDYK2008 Locationtestsides Page3of3 Figure2.TestsitesinReeuwijk(photoGoogleEarth,17Feb2009).(Reeuwijk DorpisjustsouthofTempeldijk Southtestlocation)

35 AppendixE RSDYK2008 Geology Page1of7 APPENDIXE RSDYK2008 GEOLOGY

36 AppendixE RSDYK2008 Geology 1 Page2of7 GEOLOGICALSETTING Theinformationaboutthegeologicalsettingofthetestsitesissummarizedfrompreviousworks of researcherswho worked inthearea,from regional studies, and from the general geological historyofthenetherlands. 1.1 RegionalGeologichistory AccordingtoVanStaalduinen,attheendoftheearlyTertiary,theNorthSeaBasindevelopedin northwesterneuropeandthelaterterritoryofthenetherlandswaslocatedatthesoutherntip of the basin. During the Tertiary and the Quaternary, the basin subsided gradually due to the continuousfillingupwithsediments(vanstaalduinenetal.,1979;tencate,1982). According to Ten Cate (1982), the configuration of the coastline of the Netherlands was determinedbythetectonicallyactiveareaofthecentralgrabenandlowerrhineembaymentin the southeast in the latest part of the Tertiary. The river Rhine had its course towards the northwestandbuiltadeltainthecentralgrabenarea.inthenortheast,deltawherebuiltonby NorthGermanonancientBalticrivers.Thisindicatesthatthelargepartofthedepositshasbeen laid down in a coastal area at the end of the Tertiary. These deposits are referred deposition eitherinashallowseanotdeeperthantenmeters,orincoastalswamps,lagoonsandlowerriver courses.however,atpresenttheyarefoundatconsiderabledepthbelowsealevel,sometimesas lowas400to600m.variationsinintensityoftectonicmovement,changesinrivercoursesand climaticchangeswithglacialandinterglacialperiodshavedeterminedthegeologicalgenesisof thesubsidingbasininthenetherlandsduringthequaternary(tencate,1982). During the Saalian glaciation (Figure 3.2) the inland ice covered Northern Europe again, as in several glacial periods before Quaternary, but this time it included the northern half of the Netherlands. This event had a profound influence on both the sedimentation pattern and the morphology of the landscape. The rivers Rhine and Meuse were forced into westerly courses. Theicesheetthatpushedbypre glacialandriversedimentsformedthehillsinthecentraland easternpartofthecountry. The Saalian glaciation was followed by the melting of the inland ice during the Eemian interglacial and attheendoftheweichselian (remained inthe Per glacial zonewithoutinland ice)resultedinariseofsealevelandtheseapenetratingfarmoretotheeast.accordingtoten Cate, during the sea level rising at the end of the Weichselian, there were three zones of sedimentation:alittoralsandyzoneofcoastalbarriersanddunes,aclayeyzoneoftidalflats,salt marshesandbrackishlagoonsand,atagreaterdistancefromthesea,azoneofpeatformation in a fresh water environment. These zones were shifted towards the east as the sea gradually floodedtheformerdrynorthseafloor.

37 AppendixE RSDYK2008 Geology Page3of7 Figure1.PalaeogeographicmapoftheNetherlandsduringtheUpperTertiaryandtheQuaternary(TenCate,1982) 1.2 Holocenegeologyofthestudyarea The regional geological setting of the study area was formed largely in the quaternary by the directandindirectactivitiesoftheriverandthesea(tencate,1982).thedutchcoastalareawas drowningduetothemeltingoftheweichselianglacialicesheet.themeltingofthisglacialicein combinationwiththetectonicmovementsresultedinsealevelrising.thewesternnetherlands wasgentlywestwardsloppingplainattheendofthepleistocene.thisindicatesthatthegeology ofthewesternnetherlandsisgreatlyinfluencedbytheholocenedeposits(figure3.3). AtthestartoftheHolocene,climatechangecausesaveryrapidlysealevelriseaccompaniedby ariseofregionalgroundwatertable.astheresultoftheriseofthewatertable,peatgrowthtook placeinvariousplaces(tencate,1982).sedimentationintheholoceneperiodstartedwiththe formationofpeat(basalpeat).thebattlebetweenthelandandthewaterincreasedasthesea levelcontinuedtoriserapidly.astheresult,thecoastlinemovedfurtherinwardandreachedthe Dutchterritoryinabout8000BP(Bijlsm,1982).ThePalaeo geographicalmapaboveshowsthat themarinesedimentsdepositedinthecoastalareawhilethefluvialsedimentswasdepositedin the perimarine area (Figure 3.3a). According to Bijlsma, the rate of sea level rise reduced to 27cm/100years during 5000BP (Bijlsma, 1982) and the extension of marine deposit reduced significantly(figure3.3b).thesealevelriseratewasextremelyslowinabout3700bpandmore stableriverpatternwasformed;however,thegroundwaterlevelwasstillhightodevelopathick peatlayeroverthemarineandfluvialdeposits(figure3.3c).thispeatformingprocesscontinued until 700BP in the central part of the Netherlands (Figure 3.3d). When the peat layer was inundatedand/orerodedbythewater,themarineorfluvialsedimentsdepositedoverit(figure 3.3e).

38 AppendixE RSDYK2008 Geology Figure2.PalaeogeographicmapoftheNetherlandsduringtheHoloceneperiod(source:tookfromMahabubur2007) Page4of7 Duringthis Holocene period,the area was located in theperimarine zone, wherethedeposits wereformedundertheinfluenceofthesealevelrisinginteractingwithriverinputfromtheeast. Specifically the study area is located on the Holocene deposits of The Netherlands, which are dominatedbythethicklayersofpeatandclay.accordingtoboschandkok,thesedepositshave two mainorigins;namely marine and fluvial deposits. In the Netherlands,the Holocene fluvial deposits are named as Gorkum and Tiel depending on their correlation to Calais and Dunkirk marinedeposits(boschandkok,1994). Themarine(CalaisandDunkirk)depositswereformedinatidalflatdepositionalenvironment, normallyaplaingentlydippingtowardstheseacoastswithmarkedtidalrhythms.thedeposits compriseverysiltyandmoderatelysilty,massiveclayscoarseningupward(boschandkok,1994). AccordingtotheclassificationmadebyReineckandSinghbasedonthesedimentationprocess, thefluvialdepositsoftheareaaregroupedintothreemaingroups(reineckandsingh,1973): The channel deposits: are sediment deposits formed mainly from the activity of river channels.itcompriseschannellag,pointbardeposits,channelbardepositsandchannelfill depositsofsand. Bankdeposits:areriverbanksediments,whicharedepositedduringthefloodperiod.Levee depositsandcrevassesplaydepositsofsandandclayareincludedinthesedeposits. Flood basin deposits: are essentially fine grained sediment deposits formed during heavy floodswhenriverwaterflowsovertheleveesintothefloodbasin.theyincludefloodbasin depositsandmarshdeposits. The Holocene deposits of the study area belong to Westland and Kreftenheye Formation and bothformationsbeingmainlyformedbyriverdeposits(bosch&kok,1994). Different layers are distinguished within the westland formation. This formation overlies the KreftenheyeFormationcomprisesthefluvialsediments(GorkumandTieldeposits)togetherwith the clastic marine deposits and intercalated peat layers (Bosch & Kok, 1994). In the Reeuwijk, area the formation consists predominantly of complex alternations of floodplain clay deposits