ã2017CaliforniaInstituteofTechnology.Governmentsponsorshipacknowledged.

NISAR:TheNASA-ISROSARMission

LeveeandDamMonitoringfromEarthOrbitThe U.S. is protected by tens of thousands of miles ofleveesandhundredsofdams,mostofwhichwerebuiltinthe last century. This aging infrastructure requires bothroutinemonitoringandmaintenanceandintensivesurveyfollowingstressfromfloodsorearthquakes.Today,byand

large,theintegrityofthedamsandleveesisdeterminedfrom visual inspectionsmade by experienced personnelfrom vehicles or on foot, infrequent ground-based landelevationsurveyofsmallsections,andverylimitedsemi-permanentinstrumentsinstalledin-ground.

LeveesandDams:FloodDefenseforU.S.Communities

AvastnetworkofdamsandleveesprotectcommunitiesthroughouttheU.S.fromfloods.Maintainingthesestructuresisabsolutelycriticalandrequiresconstantvigilance.RadarremotesensingwithNISARcanprovideearlywarningofmovementandseepageintimetopreventdisaster.

Dams & Levees: Flood Prevention, Water Conservation, Energy Generation, and Sports and RecreationLeveesanddamsservemultiplefunctionsbesidestheirprimaryfunctionoffloodprevention.Damsprovidehydroelectricpower,storeandprotectthewatersupply,andproviderecreationareaswherepeoplerelax,andwherefish,birds,andgameliveandbreed.Leveesdon’tjustkeepwaterfrominundatingtheland,butalsochannelwatertocommunitiesandbusinesseswhereitisneeded.Monitoringleveesanddamsistime-consumingandpersonnelintensive,causinginfrequentmonitoringofmostareas.Remotesensingcanincreaseinspection,imagingtheentireU.S.every12daysregardlessofseason,light,andweather,todetectchangesbeforetheybecomedisasters.

TheNISARMission–OpenAccessRadarImagesNISARisscheduledtolaunchin2021andwillprovideall-weather,day/night imaging of nearly the entire landmass of the Earthrepeated2-3timespermonth,withthecapabilityofmonitoringdeformationofsurfaceandstructuresovermuchofthearea.Allthedatafromthemissionwillbemadeavailablefreeofchargesothat it is available toall communities, largeor small: engineersidentifying structural changes, water resource managers, damowners,andscientistsstudyinggeologicalhazardsalike.Thedataproducts will be hosted through the Alaska Satellite Facility inFairbanks, one of NASA’s Distributed Active Archive Centers.[Photocredit:NASA]

Photos(clockwise):CaliforniaDWR,USACE,USACE,NASA/JPL-CaltechS

ã2017CaliforniaInstituteofTechnology.Governmentsponsorshipacknowledged.

Continuedfromfrontpage

NISAR:TheNASA-ISROSARMission

Modernradarremotesensingmethodscanrevolutionizethewaythatleveeanddamsaremonitored,significantlyincreasing the spatial coverage, frequency ofmeasurement, and consistency of the observationmethods.Remotesensingcanimproveuponandaugmentthe traditional methods of detecting slope failures,subsidence,andseepage,allofwhichareindicatorsofthehealthoftheinfrastructure.Insteadofdetermininggroundmovementfromachangeintwoormoremeasurementsofelevation,itispossibleusing NISAR to measure surface movement directlywithout knowledge of absolute surface elevation. Thetechnique used to measure ground displacement reliesupon repeat imaging of an area with a high-resolutionsyntheticapertureradar(SAR)instrumentandperforminga specific type of processing known as interferometry(InSAR).Thistechniquemeasureschangesinthedistancebetween the radar antenna and the ground along thedirectionofradarillumination,atthescaleofafractionofthe radar wavelength. Synthetic aperture radarinterferometry is a remote sensingmethod that can be

usedtomeasuresurfacedeformationdirectlyacrosslargeareas at one time with far greater accuracy than ispossiblewithtraditionalground-basedlevelingsurveysorLiDARdifferencing.Radarhasadditionaladvantagesoverthosemethods,includingtheabilitytoseethroughclouds,smoke,andhaze,andto imagethesurfacedayornightwithoutrelyingonsolarillumination.SARcanalsobeusedto detect developing seeps through changes in soilmoisture,whichcanbeveryusefulduringfloodresponsewherenobaseline,pre-floodimageryisavailable.NASA’sspace-basedEarthobservingradarinstrumentwillbe a cost-effective tool for both long-term failuremitigation and short-term rapid response in emergencysituations. It makes economic sense to apply our besttechnology to protecting levees and dams in the U.S.through frequent, repeated and consistent imaging.Space-based resources such as this could be routinelyusedtoguidedecision-makersandcommercial interestsalike in order to more effectively and efficiently targetrepairandupgrades.

NationalAeronauticsandSpaceAdministration Formoreinformation,visithttp://nisar.jpl.nasa.gov/applications

JetPropulsionLaboratory/CaliforniaInstituteofTechnology/Pasadena,California/www.jpl.nasa.gov

MapshowingrateofgroundmovementalongoneoftheleveesthatpreventsfloodingofanislandintheSacramento-SanJoaquinDelta[Deverel2016].Theinsetphotoshowsaviewlookingeasttowardstheareaofmostrapidmovement(red/orangecolor).Thesignal,clearlyvisibletotheradar,isnotobvioustoanobserverontheground.

Radar-based Measurement of Levee Conditions

ObservationsoftheEarth’slandsurfacesfromspaceusingactivemicrowavesensorsenablereliableandrepeatedmeasurementstobemadethroughouttheyear,buildingupabaselinesetofobservationsthatshowtypicalchangeinthegeneralvicinityoffloodprotectionstructures(e.g.,dams,levees,spillways)fromwhichabnormallylargelocalizedmovementorrapidlychangingpartsofthestructurescanbeidentified.Informationlikethisisusedtoquantifythestatusofallleveesanddamsthatareimagedfromspace,bothinurbancommunitiesandremotefrompopulatedareas.Thisvaluableinformationwillenablesmarttargetingofresourcesformaintainingdamsandlevees,andwillproviderapidreassessmentoftheirhealthfollowingastressorevent,suchasincreasingfloodwaterlevel,earthquakes,orhuman-initiatedthreats.ShownatrightisalandmovementmapderivedfromimagesacquiredbyUAVSAR,theNASAairborneinstrumentthatistheprototypeforNISAR.Thesedatawerecollectedtodevelopnewremotesensingmethodsforleveemonitoring,andarebeingactivelyusedtodaytotargetgroundobservationsandleveerepairandtoprepareforemergencyresponsetoleveebreaksinthefuture.