Lectures 11Lectures 11--1313Hydrology & Hydrology &
Fluvial Fluvial GeomorphologyGeomorphology
Gauley River Imageshttp://www.youtube.com/watch?v=EulmUyeGtz4&feature=related
Ancients' (= Biblical) Model of Water (Hydrologic) Cycle
• Stream Water Came From the Earth.• Stream Runoff >> Precipitation.
• 1700s Idea: Streams Carve Valleys in Which They Flow !
http://www.touregypt.net/card3.html
St. Catherine's Monastery at the base of Mount Sinai painting by David Roberts
Strange Ideas?
Stream Water Came From the Earth
Runoff >> Precipitation
Not Strange in a Desert
Problem: How Does Salt Ocean Water Become Fresh Spring Water?
• This MODEL Makes Sense in a Desert,
• Where Streams Are Fed by Springs and Runoff From Far-Away Mountains
Modern Concept of the Water Cycle
Modern Concept of the Water Cycle (Figure 10.1)
H2O Volumes: Liter (l) = Quart +
• Oceans 1,350,000 X 1015 l• Glaciers 26,000 X 1015 l• Ground-water 7,200 X 1015 l • Lakes 220 X 1015 l• Atmosphere 13 X 1015 l• Streams 1 X 1015 l • Biomass (Plants) 0.7 X 1015 l
Rates of H20 Change - ApproximateOcean Evap 440 X 1015 l/yOcean Precip 404 X 1015 l/y Ocean -> Cont (vapor) 36 X 1015 l/yContinental Evap 70 X 1015 l/y Continental Precip 106 X 1015 l/y Cont -> Ocean Runoff 36 X 1015 l/y
only about 1/3 precip runs off continents
Outgassing + Comets 0.0003 X 1015 l/y“new” water
Outgassing:0.0003 X 1015 l/y
How was outgassingdetermined?
1,380,000 X 1015 liters (volume of oceans)
divided by 4,600,000,000 years (age of the earth)
New Hypothesis: Comet Origin for Water
Comet Hale-Bopp February 16, 1997 Observer: Stephane Potvin, St-luc Dorchester, Quebec
http://www.jpl.nasa.gov/comet/images97026.html
Runoff: Water in Streams
Comes From: Direct Precipitation in Stream
Surface (Overland) Runoff Spring Discharge ...
What Happens to Precipitation?
• Runoff (direct) = RO• Infiltration ⇒ Ground-Water Recharge ⇒
Spring Discharge ⇒ Runoff (RO)• Evaporation & Transpiration = ET• Precip - ET = RO ...
Drainage Basin Water Budgets:
Precip - ET = RO
Desert (AZ) 3" - 3 = 0”
Rain Forest 400" - 50" = 350"
Orographic Effect on Precipitation
Orographic Effect on Precipitation
Orographic Effect on Precipitation
Orographic Effect on Precipitation
Orographic Effect on Precipitation
Orographic Effect on Precipitation
Orographic Effect on Precipitation
Orographic Effect on Precipitation
Pickens Spruce Knob
Petersburg
Morgantown
Drainage Basin Water Budgets
Precip - ET = RO Morgantown 40” 25” 15” Pickens 65 25 40 Spruce Knob 50 20 30 Petersburg 32 25 7
Stream Geomorphology
Sandstone Falls, New River, WVphoto by John Remo
Streams• River• Creek• Run• Fork• Draft• Stream• Brook• others
Main Stem (= Trunk Stream)
• Tributaries flow into Main Stem
• Distributaries channels split flow from main stem (rare in WV)
Stream Classes Based on Frequency of Flow
• Perennial• Intermittent• Ephemeral
Kite Stream, Victoria Valley, Antarctica
Stream Order
• First - Stream with no tributaries, smallest drainage we can recognize
• Second - Confluence of two First order stream
• Third, 4th, 5th, etc.• Mississippi River - ca. 12th Order
4th Order Drainage Basin
Drainage Divide
Turbulent Flow
• Mixing Between Layers
Flow in Stream is Turbulent
• Tranquil Flow - Subcritical Flow– eddies, rollers, vortices
• Shooting Flow - Supercritical Flow– whitewater, standing waves, wave
trains
Turbulent Flow
• Tranquil = Subcritical Flow
Flatwater = Subcritical Flow -New River Gorge (= NRG)
Debris Fan Constricts New River
Causing Rapids
Bridge Day 2000
Copyright 2001iPlayOutside, Inc.
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
Supercritical Flow - Standing Wave, NRG
Supercritical Flow - Standing Wave, Pillow Rock, Gauley River
Wave Train - NRG
Whitewater Images
• http://geology.csun.edu/jeff/esci.html• http://www.try-
rivers.com/gauley_river.html• http://www.nps.gov/neri/photo.htm
2009 Lecture• The Floods lecture was given on 26 Feb, because it was
the anniversary of the most deadly WV flood: the 1972 Buffalo Creek Flood that killed 125 in Logan County.
http://www.wvgazette.com/static/series/buffalocreek/bridge.JPG
Sediment Transport (Load)
• Dissolved Load – Ions in Solution
• Suspended Load – Clay, Silt, Sand - Kept in Water by
Turbulence • Bed Load
– Sand, Gravel - Moved by Traction Sliding, Rolling, Saltating
Sediment Transport
Which is difficult for streams to erode, but easy to transport?
(A) clay, (B) silt, (C) sand, or (D) boulders.
Sediment Transport
Which is difficult for streams to erode and transport?
(A) clay, (B) silt, (C) sand, or (D) boulders.
Sediment Transport
Which material is most easily transported, once eroded?
(A) clay, (B) silt, (C) fine sand, or (D) coarse sand.
Sediment Transport
Boulder Transported in Nov 1985 Flood, Cheat Narrows
Bed Load
• Bernoulli Principle - lift
Airplane Wing
Bernoulli Principle
Low P
High P
Bernoulli Principle & Lift
High P
Low P
Bed Load
• Bernoulli Principle - lift
Cobble
Channel Bed
Bed Load
• Bernoulli Principle - lift
Hign V, Low P
Low V, High P
Bed Load
• Bernoulli Principle - lift
Hign V, Low P
Low V, High P
Bed Load
• Bernoulli Principle - liftLow P
High P
Meandering Stream Flow
Meanders and Oxbow Lakes
Oxbow Lakes
Point Bar
Neck
Cut Off
Meander Cut-Off: Oxbow Lake
ChannelSediments
What might you expect to occur after a stream is straightened (channelized)?
(A) the stream erodes its bed to create a shallower channel, (B) the stream will erode its banks and construct point bars, re-creating a channel similar to its original channel, (C) the stream will shift from a third order stream to second order, or (D) base level will fall until the stream incises its bed, leaving a terrace or similar feature.
Straight Channel (Meandering Thalweg)
Meandering Channel
Braided Channel
Straight Channel = Rare, Most are Man-made or in Rock Gorges
Meandering Channel Bedload Energy > “Work”
Braided Channel Bedload Energy < “Work”
Stream Equilibrium• Balance of Energy & Work• Discharge (Water Volume / Time ) +
Channel Slope Provides Energy
• Work of a Stream?–Transporting Water–Transporting Sediment
• Especially Bedload– Ecological Template – Not in GEOL 101
Stream Adjusts to Sediment Under-Supply
• Deep Channel• Lengthen Channel - Meander Growth• Bank Erosion - Meander Growth
Stream Adjustments to Sediment Over-Supply
• Straighten Channel• Gravel or Sand Bars Clog Channel• Braided Channel Pattern
Glacier Fed Braided Stream, Denali National Park, Alaska
J.S. Kite Photo
Sediment Supply Boosters
• Steep Slopes – Commonly after Uplift of Mountains
• Easily Eroded Parent Material• Sparse Vegetation• Cold Climates• Glaciers
What might happen to a graded stream that has its sediment supply cut off by the construction of dams upstream?
(A) the stream would build up (aggrade) its channel and floodplain, (B) the stream would erode (degrade) its channel and floodplain, (C) nothing, once a stream is in grade it never changes, or (D) the channel will begin to braid.
Over-Supply of Sediment Can Cause Terraces
Over-Supply Builds Up Floodplain
Later
Stream Cuts Down Through Deposits When Supply is Reduced
Ohio River Terraces
• http://www.emporia.edu/S/www/earthsci/student/forge/ohio.htm
Stream Profile• Slope & Energy Decrease as Bedload
Becomes Finer GrainedSteep: Coarse
BedloadShallow: Fine
Bedload
The “Sea”
Immature SedimentsImmature Sediments
Mature SedimeMature Sedime
FaciesFacies
Maturity
Base Level• Lowest Point to which Stream Can Erode• Ultimate Base Level vs. Local Base Level
Sea Level= Base Level
Stream Adjustments to Lower Base Level
• Incision to Adjust Profile
Stream Adjustments to Higher Base Level
• Deposition to Adjust Profile
What would happen to stream whose base level drops by 100 meters.
(A) the stream will deposits sediment, raising its channel.(B) the stream will not change its profile. (C) the stream will meander and braid. or (D) the stream will erode its bed.
A rise in base level for a stream will produce:
(A) erosion, (B) deposition, (C) no change, or (D) a graded stream.
Base Levels
New River: 2nd Oldest River in the World?
photo by John Remo
New River: 2nd Oldest River in the World?
Spokane Flood
• ChannelledScablands
• Washington (State)
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