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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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5USL

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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

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u/A

ST32

4/Le

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5USL

E.pp

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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

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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