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Fluvial Geomorphology1. Drainage Basins
Kite Stream, Victoria Valley, Antacrtica
Physiography of US & Canada
• Hunt, C. B. 1974. Natural regions of the United States and Canada. San Francisco: W. H. Freeman and Co. 725 p.
Classification Based on Frequency of Flow
• Perennial• Intermittent• Ephemeral
Scale of Map Influences Stream Networkby Determining the Contour Crenulations That Appear
Not shown or
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HORTON-STRAHLER SYSTEM OF STREAM ORDERS
• First - Stream with no tributaries, smallest drainage we can recognize
• Second - Confluence of two First order stream
• Third, 4th, 5th, etc.• Mississippi River: ~ 12th Order
What Constitutes a stream?NOT BLUE LINES ON MAP!
2 or 3 Contour Crenulations in Succession.
This is 3rd Order
Stream!
1st Order Stream?
4th Order Drainage Basin
Drainage Divide
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"Laws of Drainage Composition" Not in Bloom, 1998
Law of stream length:
L = 1.4 Ad0.6
(not 0.5 power)
D = Sum of Stream Lengths / Drainage Area
Law of Drainage Density:
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Bifurcation Ratio:Rb = Nu / Nu+1
Bifurcation Ratio Rb = N1/N2 = 3.2Rb = N2/N3 = 3.0
Drainage Divide
How Many First Order Streams in Mississippi River Basin?
Assume Mississippi River =12th order, Rb = 4.0
Use this Equation:
Nu (trib) = Rb(Os (basin) - Ou (trib) )
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Order Computation Number12 40 111 41 410 42 169 43 648 44 2567 45 10246 46 40965 47 163844 48 655363 49 2621442 410 10485761 411 4194304
Σ = A LOT
Precipitation (Rain or Snowmelt)
Infiltration Overland Flow (Sheetflow)(Recharge) “Zone of No Erosion”
(Raindrop Impact)
Ground- Bursting of Obstacle DamsWaterFlow Rills- Ephemeral Channels
Spring Discharge Gullies - Permanent
Streams
2 Likely Routes for Precipitation
Stan Schumm, 1977The Fluvial System
Zone 1
Zone 2
Zone 3
Sediment Production
Sediment Transport
Sediment Deposition
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Photo Source: Frederick Harrison Edmunds, “The Canadian Landscape,” U. of Saskatchewan Archives
Zone 1
Zone 2
Zone 3
Revised Universal Soil Loss Equation Bloom, 2004, p. 201-202
Dunne & Leopold, p. 521-531Handout Shows Nomograms
Developed for Calculating Soil Loss in Agricultural Areas
A = RKLSCPA = soil lossR = rainfall erosivity indexK = soil erodibility indexL = hillslope length factorS = hillslope gradient factorC = Crop-management factorP = erosion control practice factor
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Average Annual Rainfall Factor (R)
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stat
e.ed
u/A
ST32
4/Le
sson
5USL
E.pp
t
USLEFactor
Range “Typical”
R = rainfall erosivity index15 to >350 150 in Morgantown
K = soil erodibility index0.1 to 0.5 0.3 is typical
L = hillslope length factorS = hillslope gradient factor
0.1 to 20 500', 20% slope: LS = 6
LS Factor Nomogram
ww
w.a
be.ia
stat
e.ed
u/A
ST32
4/Le
sson
5USL
E.pp
t
Example: LS of 200 ft long slope with 10%
slope angle = 2.0
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FactorRange “Typical”
USLE
C = Crop-Management Factor 0.001 to 0.45 100% canopy to bare ground
P = Erosion Control Practice Factor0.1 to 1.0 terraced 2-7% slopes to none
Factor Range Importance
R 15 to >350 Style of Precip. Varies
K 0.1 to 0.5 Texture: little change
LS 0.1 to 20 LS: little change
C 0.001 to 0.45 Vegetation Change
P 0.1 to 1.0 N/A before Humans
Implications for Climate Change
Sediment Yield (= Sediment Load)
Total Amount of Sediment Transported
Out of Basin by Streams
How Determined?
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Sed Yield X 100Soil Loss
SDR not = 100% !
Why?
Sediment Delivery Ratio:
Production of Sediments in Zone 1:Slope ProcessesRill & Gully Erosion, Sheetwash
Downstream from Zone 1Decrease in Slope Processes, etc.Increase in Bank Erosion Decrease in New Sediment Production
Zone 2:
"The Transport Zone"
Dominated by Channel Processes
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Fundamentals of Stream Flow
Discharge (Q) = volume / time
Q = A V (area x velocity)
Stage: Height of
Water Surface
Typical Older-Style USGS
Stream GageStilling
Basin
Flow Meter
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Colorado River Rating Curve: Q vs. Stage
UT-CO State Line
Real-Time USGS Data
HydrographRainfall
Discharge
“Base Flow”New
“Base Flow”
Crest
Ris
ing
Lim
b
Falling Limb
0 cfs
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Cheat River at Hwy 50, Near Rowlesburg, WVStage Station Number 03069870
Drainage Area: 911mi2 Datum: 1405 ft a.s.l.http://www-wv.er.usgs.gov/rt-cgi/gen_stn_pg?station=03069500
Cheat River at Hwy 50, Near Rowlesburg, WVDischarge Station Number 03069870
Drainage Area: 911mi2 Datum: 1405 ft a.s.l.http://www-wv.er.usgs.gov/rt-cgi/gen_stn_pg?station=03069500
Velocity profiles, w/ isovels)
Shallow channel
Deep channel
Max Velocity
Max Velocity
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Empirical Stream-Flow Velocity Equations
Chezy Equation *** save for GEOL 427 ***
V = c (R S)0.5
c = factor varies w/ channel slope,bed roughness
R = hydraulic radius (≅ mean depth)= A/P (x-sect. area / wetted perim.)
S = slope
Manning Equation *** know equation ***
V = (R0.667 S0.5) / nmetric units
V = 1.49 (R0.667 S0.5) / n"American" units
Manning Equation V = (R0.667 S0.5) / n metric
n = Manning coefficient of roughness
0.015 on large, smooth channel0.150 on bouldery mountain stream
R = hydraulic radius (nearly = mean depth)= A/P (x-sect. area / wetted perim.)
S = slope
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Flow Regimes: Laminar Flow
• No Mixing Between Layers
Laminar-Turbulent Threshold Defined by Reynolds Equation:
NR = Re = dimensionless Reynold's number
Re = ρ v R / μ
ρ = [Rho] = densityμ = [Mu] = viscosity
Re between 500 and 2500, marks transition from laminar to turbulent flow
Flow Regimes: Turbulent Flow
• Mixing Between Layers
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Test 1 Scores
>77: A66-76.9: B55-65.9: C44-54.9: D<44: not so good
Test 1 2006• Overall Mean: 68.9• Grad Students: **.*• Seniors: 71.2• Juniors: 69.3• Sophomores: 64.9• Freshmen: **.*
• **.* Data not shown if only 1 or 2 students in category
Test 1 2007• Overall Mean: 70.7• Grad Students: **.*• Seniors: 69.2• Juniors: 70.1• Sophomores: 72.6• Freshmen: n.a.
• **.* Data not shown if only 1 or 2 students in category
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Test 1 2007• Overall Mean: 70.67
• Geology & Pre-Geology: 75.48
• Soph- Geol & Pre-Geol: 77.29
• Other majors: 63.69** Includes Highest Grade (92)
Test 1 Undergraduate Grades
2002A: 11B: 10C: 6 D: 5F: 3
Mean:66.23
2000A: 4B: 15C: 12 D: 4F: 0
Mean:66.47
2001A: 10B: 11C: 11 D: 4F: 1
Mean:68.28
2004A: 18B: 12C: 6 D: 4F: 1
Mean:73.44Best Ever!
2005A: 4B: 5C: 8 D: 1F: 1
Mean:67.26
2006A: 6B: 12C: 11 D: 2F: 0
Mean:68.16
2007A: 14B: 10C: 6 D: 2F: 3
Mean:70.292nd Best Ever!
Turbulent flowFroude number = F = V / (g D)0.5
a. subcritical flow (F < 1) tranquil flow, streaming flow, lower flow regime (flat water)
b. supercritical flow (F > 1)jet flow, rapid flow, shooting flow, upper flow regime (white water)
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Turbulent Flow
• Tranquil = Subcritical Flow
Debris FanRapids
http:// ww
w.w
vout side.com/E
v ents/2000/ 10/1993.html
Copyr ight 2001 iPlayO
utside, Inc.
Rapids
SubcriticalFlow
SubcriticalFlow
SupercriticalSupercriticalFlowFlow
Upper Railroad Rapids, NRG: SubcritcialFlow Transforms into Supercritcal Flow
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WVU GEOL 621 Field Trip Supercritical Flow, Gauley River, West Virginia
I Swam!
I Swam!
I Swam!
I Didn’t, So the Guide Got an A!
Wave Train - NRG
TYPES OF TURBULENCE:
Type 1: surge phenomena -- - -- ->
Type 2: water rollersbank rollersbottom rollers
Type 3: eddies (local vortex, tornado-like)
Type 4: helical flow (like parallel coiled springs) may lead to meanders in streams.
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April 2004 Movies?
P4040031.mov
Where Is Maximum Turbulence in a Stream?
Maximum Turbulence
.
.
. .
.
Erosionwith SlightDownward Component
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Maximum Turbulence
.
Erosionwith SlightDownward Component
Deposition = Accretion
Lateral “Accretion”
Cut-BankErosion
Point-Bar Accretion
λ = MeanderWavelength
P = Sinuosity = River Distance / Straight-Line Distance
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Meander Development
Maximum Erosion Occurs Downstream from Outside Bend:
Thus, Meanders “Grow” & Migrate
Downstream with Time
Cut-BankErosion
Point-Bar Accretion
Cut-BankErosion
Point-Bar Accretion
Flow
Meander Development
Maximum Erosion Occurs Downstream from Outside Bend:
Thus, Meanders “Grow” & Migrate Downstream with Time
Constriction
Meander Development
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Meander Development
Meander Development
Meander DevelopmentNote “Kinks”
w/in Meanders
Meander Neck
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Ox-BowLake
Cut-Off Meander
Meandering Stream, Sinuosity >3
Abandoned Meanders
Ox-Bow Lakes
http://www.geosurv.gov.nf.ca/education/features/geomorph.html
Photo: Geolgical Survey ofNewfoundland & Labrador
Meander-Scroll Topography Showing Downstram Migration
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Oxbow Lakes
Point Bar
Neck
Cut Off
Meanders and Oxbow Lakes
