Rivers & Floods -...

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Unformatted text preview: !""#$"%&'&"()* Started October 25th, 2011 Geospatial literacy quiz available4.30 pm Tues Oct 25 - 8.00 am Mon Oct 31 You MUST complete this quiz (or zero on Lab #5) Preparation: read Chapter 8 of the handbook for the EES student Complete Geospatial Literacy pre-lab modules Week of Oct. 31 - Labs will be held in the Lloyd Reeds Map Collection (Mills Library, first floor). Arrive early! New Schedule: Oct 25 - Rivers and Floods Oct 27 - Mineral Resources Oct 28 - Intro to Topo Maps ! Nov 1 - Frozen World: Glaciers Nov 3 - Careers talk Nov 4 - Video- Queens of Diamonds oct 26, CIBC hall 308-309 !"#$%&'()*'+,--*&' +$(,-"&* Introduction terminology Stream and valley profiles Channel morphology Meandering streams Braided streams Urban systems ."(/#0$%(-#"* What is a stream? - a body of water confined within a channel, supplied with water by its drainage basin What determines the size of a stream? - climate - size of drainage basin - substrate - vegetation 1#'&*0&2-"-(-#")3*Stream valley - area between tops of slopes on both sides of the river Channel - trough through which water flows Fig. 14.2 thalweg - line connecting deepest parts of the channel discharge - volume of water flowing downstream/ unit time (m^3/sec) !"#$#%&'()*%+'(%#,-#./%/'%012*%/"#% "13"#4/%0)'&%5#)'.1/1#4%12%6%4/$#678% Straight areas !- centre of channel - just below water surface ! ! Around meanders - outside of meander bend Fig. 14.6 ! Meander wavelength: 10-14 times channel width Radius of curvature: 2-3 times channel width Helicoidal flow *45,,&6*7/#2-,&)* How does the shape of a valley change downstream? Cross sectional profiles - steep-sided, V-shaped near source, canyons - broader valleys downstream Fig. 14.2 9'&%*'#4%/"#%4)'-#%'0%6%4/$#67%."623#%*'&24/$#678% Longitudinal profile - steep gradients near source - low gradients downstream Fig. 14.35 Base level - deepest level to which streams can erode -most oftenly sea level but, not always (death valley) Fig. 14.34 !"6/%:12*4%'0%0'$7%.62%4/$#674%"65#8% Channel morphology sinuosity is used to classify channels - ratio of stream length : valley length ! ! ! ! ! ! valley length Low sinuosity valley length High sinuosity STRAIGHT or MEANDERING streams 8&5"0&/-"9*)(/&5')* - common in areas with low slopes - thalweg close to outer bend of meander Where would you expect to have most erosion? Outside bend of meander - deepest water, highest flow velocities (CUTBANK) Where would you expect deposition? Inside bend of meander (POINT BAR) * Erosion of cutbank, deposition on point bar = migration of meanders Fig. 14.20 8&5"0&/)*%5"*:#-"* *2#/'*"&%;*%$(<#22* * * * *******<!OXBOW LAKE ! Fig. 14.21 Oxbow Lake crescent shaped lake formed where a meander gets cut o from a stream ! =,##07,5-"* Broad strip of land built by sedimentation on each side of the channel covered with water when river floods coarsest material deposited closest to the channel - forms LEVEES finer-grained material carried further away - clays and silts Fig. 14.25 !"6/%:12*4%'0%4#*17#2/%*'%7#62*#$123% 4/$#674%*#-'41/8% On point bar - sands and silts (ripples & dunes) On floodplain - silts & plains Forms fining - ! Fig. 14.24 upwards sequence >/5-0&0*)(/&5')* Fig. 14.17 - multiple channels - common on steep slopes - common in glacial or arid regions What kinds of sediments? Coarse-grained - gravels & sands >/5-0&0*1(/&5')* Channels split & rejoin Areas of deposition between channels - BRAID BARS Highly variable Large amounts ?/@5"*/-A&/*)6)(&')* !"#$%"&'$()*+,-.+/-",$+00&1/$)-2&)$'3'/&4'5$ 1955 1975 Ground Surface less permeable less infiltration of rainwater more storm runo - increased flooding =,##0*B60/#9/57B* Shows eect of storm event on river discharge Urban rivers have 'flashy' discharge water enters river quickly, causes high flood peaks Fig. 14.31 =,##0-"9*#2*(B&*8-))#$/-*C-A&/D*1(*E#$-)D*FGGH* ! - erosion of stream banks, clogs channels - sediment poses.... ** Stream and creek modification Flood and erosion control * Reduced water quality - urban runo contains road salt, grease, oil >,$22&/)*I5/;D*1%5/@#/#$9BD*FGGF* ! X FLOW BALANCING SYSTEM: APRIL 2003 ! Finished October 25th, 2011 Things you have to do! Read Chapter 14: Streams & Floods Read Chapter 12: Geologic Resources ...
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