The Work of Streams

8/19/2019 The Work of Streams

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The Work of Streams


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The Work of Streams

• Streams generallyerode their

channels liftingloose particles byabrasion,

grinding, and bydissolvingsoluble material .

http://soer.justice.tas.gov.au/2003/image/10/p!"ater#erosion!stream!m.jpg


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The Work of Streams

• Streams transport materials oferosion in three "ays:

1. In Solution (dissolved load)2. In Suspension (suspended

load)

3. Scooting or Rolling alongthe bottom (bed load)


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$issolve% &oa%

• 'ost of the dissolved load (n%s its "ay into streams via

groundwater .• )sually e*presse% as

%issolve% material per millionparts of "ater + parts permillion,.


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The Work of Streams

• Streams %eliveralmost - illion

metric tons of%issolve%sustances to theoceans eachyear.

hoto y . o"sey


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Suspen%e% &oa%

• 'ost streams carry thelargest part of theirloa% in suspension.

• The visile clou% ofse%iment suspen%e%in the "ater is the

most ovious portionof a streams loa%.

http://rpme%ia.ask.com/tsu4/"ikipe%ia/commons/thum/1/10/Ska"a#iver526#olan%526#7oo%#2001.jpg/218p*!

Ska"a#iver526#olan%526#7oo%#2001.jpg


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Suspen%e% &oa%

•

Streams usuallyonly carry sand,silt, and clay in

this fashion.• igher velocity in

a stream may allo"

it to carry larger particles insuspension.

http://""".geomorph.org/gal/mslattery/9;-. jpg


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6ompetence an% 6apacity

• The aility of a stream tocarry a loa% is %etermine% y

t"o factors:1. "ompetence

2. "apacity


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6ompetence

• "ompetence of astream measures the largest

particles it cancarry.

• streams

competenceincreases withvelocity .

http://amyglenn.com/images/stream#loa%.gif

http://uregina.ca/=sauchyn/geog323/hjulstrom.gif


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6apacity

• streams capacity is thema#imum load it can carry.

•

6apacity is %irectly related to astreams discharge.

• The greater the volume of a

stream> the greater itscapacity for carrying se%iment.


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$eposition

• s a streamsvelocity decreases +slo"s %o"n,> itscompetence%ecreases an%

se%iment egins to%rop out> largest particles $rst .

Click forDeposit

ionAnimati

on


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$eposition

• $eposition occursas stream%ow

drops below thecritical settlingvelocity o& a

certain particlesi'e.

http://""".northcoastjournal.com/011?03/co

ver011?!se%iment.jpg


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Sorting

• Stream transport separatessoli% particles of various si@es>

large to small.• This process is calle% sorting.

•

9t e*plains "hy particles ofsimilar si@e are %eposite%together.


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lluvium

• The sorte%material %eposite%y a stream is

calle% alluvium.• 'any %iAerent

%epositional

features are ma%eof alluvium.

http://"""."in%o"s.ucar.e%u/earth/geology/images/alluvial#fan#lg.jpeg


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$eltas

• delta is anaccumulation

o& sediment&ormed wherea stream

enters a laeor ocean.

http://uploa%."ikime%ia.org/"ikipe%ia/commons/thum/e/ef/9n%us#iver#$elta.jpg/300p*!9n%us#iver#$elta.jpg


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Batural &evees

• naturallevee is a ri%ge

ma%e up mostlycoarsese%iments that

parallels somestreams.

http://sepmstrata.org/'9BCSC$9'CBTS/%elta/9mage8.gif


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Batural &evees

• natural levee forms "hena stream repeatedlyover%ows its bans.

http://""".google.com/imgresimgurl4http://""".u"sp.e%u/geD/faculty/o@svath/images/natural#levees.jpgEimgrefurl4http://F"ickstep.com/search/natural!levees.htmlEusg4##2Gl9k"DrvsT#@8p#1*f&1$H


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Barro" Jalleys

• narrow vshaped valley

in%icates that astreams primary"ork has een

downcuttingtowards baselevel .


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Barro" Jalleys

•

The *ellowstoneRiver is an e*cellente*ample of a narro"

valley.• Rapids an%water&alls are the

pre%ominantfeatures of a narro"valley.

hoto y . o"sey


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Barro" Jalleys

hoto y . o"sey hoto y . o"sey


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Barro" Jalleys

hoto y . o"sey


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Wi%e Jalleys

•

Dnce a stream has cut its channelcloser to ase level> %o"n"ar%erosion %ecreases.

•

'ore of the streams energy isthen %irecte% from side to side.

• The result is a widening o& the

valley as the river cuts a"ay at(rst one ank an% then the other.


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Oloo%plain

• The si%e to si%ecutting of a

streameventuallypro%uces a %at

valley %oor > or7oo%plain.

http://""".u"ec.e%u/jolhm/CG/$isru%e/images

/7oo%plain.gif


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Oloo%plain

• Streams that 7o"on 7oo%plains move

in meanders.• mean%er is alooplie bend in

the course o& astream.http://1.p.logspot.com/#m-@a0KBgt$M/TeJO%n9/Bc/o@!hgBt%WK0/s-00/okvangoQriverQmean%erQ!Qrohig.jpg


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'ean%ers

•Dnce a mean%eregins to form>it gets larger.

• +ost erosion occurs on the

outside of themean%er.http://""".scioly.org/"/images/?/?8/'ean%er.jpg


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'ean%ers

• The outsideban in a

mean%er issometimescalle% the cut

ban .http://""".scioly.org/"/images/?/?8/'ean%er.jpg


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6heck for )n%erstan%ing

• Why is the cut ank +outerank, the area of greatest

erosion in a mean%er

he cut ban is the 'one o&greatest stream velocity .


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D*o" &ake

• n o*o" lake is acrescentshaped(o&ten temporary)

lae that is &ormedwhen a bend in ariver is cut o- &rom

the main channelby the &orces o&erosion.

http://""".ny"etlan%s.com/o*o"lake.html

http://""".geosociety.org/Carthcache/9ma

ges/Oorming520an520D*o"52011123200H.jpg


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D*o" &ake

• n o*o" lake"ill slo"ly e

create% as soilero%es an% re!%eposits>

changing theriverRs originalcourse.

http://homepage.ntl"orl%.com/harry."ickens/orneo/orneo!0I0.jpg


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D*o" &ake

• D*o" lakeformation !vi%eo%emonstration+click left,.

http://elmont.s%?2.c.ca/teacher/geology12/photos/erosion!"ater/mean%er!o*o".gif


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9n%epen%ent ssignment

• )se your notes an% yourkno"le%ge of iology to

ans"er the Fuestions on your"orksheet.


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eferences

• %apte% from:

Taruck E &utgens +200H,. CarthScience. rentice Gall>

Documents

The Work of Streams