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GEOL100(PlanetEarth)#24Sculp9ngEarthwithWater-Rivers

Smith River in northwest California

RiversandCiviliza9onRivers play huge role in society. Civilizations developed around rivers, e.g., Nile River - Ancient Egypt.

Nile River and Pyramid of Cheops

Nile River and its delta from space

RiversandCiviliza9onAncient Mesopotamia, “Cradle of civilization”, between Tigris, Euphrates rivers

RiversandCiviliza9onMany US cities, including Pittsburgh, St. Louis, New Orleans, located along rivers. Gateway Arch and St. Louis -

next to Mississippi River

Allegheny, Monongahela, and Ohio Rivers - Pittsburgh

New Orleans and Mississippi River

ImportanceofRiversWhy are rivers so important to society?

Societal Benefits Hazards Geological Study

ImportanceofRivers-SocietalBenefitsRivervalleyciviliza0ons,e.g.,Egypt,Mesopotamia,usedspringfloodsassourceofirriga9onwater(drinkingwater),fer9lesoil

Colorado River water for irrigation

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ImportanceofRivers-SocietalBenefitsBarges-cheaptomovebulkycommodi0es,e.g.,coal,ironore,grain

Towboat pushing barges with coal along Ohio River

ImportanceofRivers-SocietalBenefits

Food

Fly fishing for trout

ImportanceofRivers-SocietalBenefitsHydroelectricity-rela0velyclean,reliable,cheaprenewableenergy

Hoover Dam - along Colorado River

SocietalBenefitsofRiversRecrea9on

White water canoeing along Big South Fork of Cumberland River, Tennessee

Tubing in Jamaica

swimming,boa0ng,fishing,tubing

ImportanceofRivers-SocietalBenefitsScenicbeautyLarge bend in Moselle River, Germany

Ecosystem

HazardsofRivers-FloodsFloods,e.g.,quicklydeveloped,devasta0ngflashfloods

Stillaguamish River, WA record flood in 2006

VideoofflashfloodinToowoomba,AustraliaonJanuary10,2011(YouTube,0:25-3:30,4-4:10,5:15-5:30;hUps://www.youtube.com/watch?v=kYUpkPTcqPY)

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HazardsofRivers-FloodsLargerrivers-slowlydeveloped,longlas9ngfloodsaffecthugeareas

2009 Red River flood in Moorhead, MN

GeologicalStudyofRivers

Sedimentarydeposi9onalenvironment

Mississippi River Delta - river-deposited sediment

GeologicalStudyofRiversShapeslandscapes-erosion,deposi0on Gunnison River at Black Canyon

of Gunnison National Park, CO

RiverDefinedFlowingwateratEarth'ssurfaceusuallyconfinedtolowarea(channel).Flowingwaterdis0nguishesriversfromlakes(liUleflow).AtEarth'ssurfacedis0nguishesriversfromgroundwater(undergroundflowingwater)Confinedtochanneldis0nguishesriversfromunchannelizedsurfacerunoffa^erheavyrainstorm.

Rouvre River in France’s Normandy Region

River-SourceofWater,FlowRiverwaterfromrain(snowmelt),movesoverlandorthroughgroundintoriver.Riversflowdownhillduetogravity,headtowardsocean.

Pouring rain in river in Adirondacks, NY

RiverLoadMaterialcarriedbyriver=load,includesgrains(clay!boulders)carriedinsuspensionorrolledalongboUom.With↑velocity,riverscancarry↑sedimentload,largergrains.Loadincludesdissolvedsalt.

Big Muddy River, Illinois, has high sediment load

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River-LongitudinalProfileRiverGradient=slope,changeineleva0ondividedbyhorizontaldistance(rise/run)

Coarse grains deposited near river’s source

Typical longitudinal profile of river

Characteris0cgradient=longitudinalprofile,eleva0onalongflowdirec0on(figure).Majorriverso^enbegin(source)inmountains,i.e.,steepgradient.Sedimentgrainsofallsizesproducedbyweathering,erosion;coarsegrainsdeposited;medium,finegrainscarrieddownstream

River-LongitudinalProfileRiverflowsintoplains,flatgradient.Sand,graveldeposited;finegrainscarrieddownstream.

Fine grains deposited at river’s mouth

Sand deposited by river in plains

Eventually,riveremp0esintooceanorlake(liUle!nocurrent),finegrainsdepositedatriver’smouth

RiverVelocityTrendsRivers’maximumvelocityusually↑slightlydownstreamfrommountainstoplains.Counterintui0ve;steepgradientshouldcreatefasterflowthanflatgradient.

Whydoesmaximumrivervelocity↑downstream?

Mississippi River near Memphis, Tennessee

KindsofRivers-MountainRivers

Severalkindsofrivers,emphasizingmountainrivers,meanderingrivers.

Yellowstone River in Wyoming

Mountainriversfoundinmountainousareasnearsource.Cross-sec0on-valleysshapedlikeleUerv,channeloccupies~allofvalleyboUom.Mapview-channelfollows~straightpath,waterseeksshortestdistancedownsteepslope.

KindsofRivers-MeanderingRiversMeanderingriversmovebackandforthacrossfloodplain-broad,flatareawithsedimentdepositedduringflood;broadvalleys;riverbend=meander;plainsnearmouth

Cuckmere River in England

MeanderingRiversMeandering river on Yamal tundra, Siberia, Russia

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MeanderingRivers MeanderingRiversMeandering river in flood stage

KindsofRivers-MeanderingRiversMeanderingriversconstantlychangecourse,erosionanddeposi0onalongmeanders.Whenriverchangesdirec0on,maximumvelocityzoneshi^sfrommiddletoouterpart(iner0a),causeserosionthere.Innerpartofmeanderhas↓velocity,causesdeposi0onofsandandgravelthere.

Sand deposit on inner part of meander, Innoko River, Alaska

Whichdirec0onwillmeandersonrightmoveover0me?

KindsofRivers-MeanderingRivers

Sand deposit on inner part of meander, Innoko River, Alaska

Whichdirec0onwillmeandersonle^moveover0me?

Migra9onofRiverMeanders

Meanderswingscangetexaggerated,rivercutsstraighterchannelpath,abandonedrivermeander(oxbowlake)

Migra9onofRiverMeanders-OxbowLakesAbandonedrivermeander(oxbowlake)

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Migra9onofRiverMeanders-OxbowLakes OxbowLakes

OxbowLake Migra9onofRiverMeanders-OxbowLakesMeander scars and oxbow lakes in floodplain of Rio Negro River, Argentina

Migra9onofRiverMeanders-PropertyDamageMeanderingriversaredynamicsystems,constantlychangingcourse.

January,1965

Twomonthslater

Canthreatennearbystructures

DrainageBasinAreadrainedbyriverandtributaries(smallriversdrainintolargerones);bigorsmall

Continental divides of North America

Highgroundseparatesdrainagebasins,e.g.,drainagedivide,con0nentaldivide(separatesflowtodifferentoceans)

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Dendri9cDrainagePaYernPaUernofriverandtributariesthatresemblesleafveins;commonDendritic drainage pattern of Yarlung Tsangpo River, Tibet, from space: snow cover melted in valleys

DeltaLandformofdepositedsedimentatrivermouth.Mapview-deltashapeo^entriangle,GreekleUercapitaldelta(Δ)

Satellite photo Nile Delta (false color)