Review: Summary Hydraulic Geometry In Two...
Transcript of Review: Summary Hydraulic Geometry In Two...
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Review: Summary Hydraulic Geometry In Two Equations
Q = (width) (depth) (λ) / (slope)
Examples of Q+ and Q-
Qsed = (width) (λ) (slope) / (depth) (p)
Examples of Qsed+ and Qsed-
Stream Classification
• Suspended Load (Vertical Accretion),• Bedload (Channel Aggradation), vs.• Mixed Load (Lateral & Vertical Accretion)
Schumm, 1963
Bloom, 2004, p. 221after Schumm, 1981
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“Modern” Stream Classification
• One System Drawing Most Attention:
• Rosgen, David L. 1994. A classification of natural rivers. Catena 22 (1994) 169- 199.+ Rosgen, David L. 1996, Applied River
Morphology, Wildland Hydrology, Pagosa Springs. Co.
Dave Rosgen
After Montgomery & Buffington (1998)
Stream Classification Hierarchy
• Valley Segments (may be many miles)• Stream Reaches (~30 channel widths)• Channel Units (~1 channel width)
Rosgen Stream Classification Criteria
• Single Channel vs. Multiple Channels• Entrenchment Ratio• Width/Depth Ratio• Sinuosity• Slope• Bedload Texture
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Rosgen Level II Classification: Cross-Sectional Delineating Criteria
Entrenchment Ratio(Flood-prone Width / Bank-full Width)
Floodplain Width = Width @ 2 Times Maximum Bankfull Depth
Width/Depth Ratio(Bank-full Width/Bank-full Depth)
If You Don’t Know Bank-Full, ...
Flow Width @ 2X Bank-Full Stage
Bank-Full Width
“Entrenchment” Ratio =Flow Width @ 2X Bank-Full Stage
Bank-Full Width
“C” Type Stream, Deckers Creek, Monongalia Co.
Width-Depth Ratio
~12:1
~20:1
~40:1
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Rosgen Level II Classification: Plan-Form Pattern Delineating Criteria
Sinuosity (P) =
(Stream Length / Valley Length)
Meander-Width Ratio =
(Meander Belt Width / Bank-Full Channel Width)
λ = MeanderWavelength
Sinuosity = P = River Distance Along Thalweg /
Straight-Line Distance
Sinuosity Rosgen Class
1.0 - 1.2 Low1.2 - 1.5 Moderate1.5 + High
Radius of Curvature
Mea
nder
-Be
lt W
idth
Rosgen Stream Classification, Fig 5-3http://www.r6.fws.gov/pfw/images/Class2.gif
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Stream types: gradient, cross-section, plan view (from Applied River Morphology, Dave Rosgen and Hilton Lee Silvey, Wildland Hydrology, Pagosa Springs, Colorado, 1996.)
Longer Timescales
Review: Concept of Graded Stream
Unpaired Stream Terraces:
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Paired Stream Terraces:
Strath =Erosional (Unpaired) Terraces
Strath Terraces near Parsons, WV
1840’+
1800’+
1800’+
1620’+
1640’+
1760’+
1640’+
1680’+
1720’+
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Depositional (Paired) Terraces
© Michael R. Marty Snake River Terraces, Teton National Park, Wyoming
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Maximum Turbulence
.
Erosionwith SlightDownward Component
Deposition = Accretion
Slip-Off Terrace
Slip-Off Terrace
Erosion
Slip-Off Surface
Meander Development
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Slip-Off Terrace
Slip-Off Terrace
Slip-Off Terraces
Paw Paw, WV-MD
Photo
Slip-Off Terrace North of Paw Paw, WV
JS Kite Photo
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Valley Type ClassificationThornbury, 1969
• Antecedent (Predates Structures)• Superposed (Super-imposed)• Consequent (Flows Down Bedding Dip)
–vs. Obsequent (Flows Opposite Dip)• Subsequent (Eroded into Weak Rocks)
THEORIES OF LANDSCAPE DEVELOPMENT
(after Higgins, 1975)
3 Theories
W.M. Davis: Geomorphic CycleW. Penck: Parallel Slope RetreatJ.T. Hack : Dynamic Equilibrium
Davis:First Systematic, Genetic Landscape Classification on a Descriptive Basis
Normal Cycle (= Fluvial Cycle)Rapid Uplift of Landscape, Followed
by Prolonged Tectonic StillstandLandscapes Reflect Process & Time
Stages:Youth - Maturity - Old Age
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YOUTH:Dominated by Vertical Erosion and
Ungraded Streams
1. Numerous Short, Straight Tributariesand Gullies Extending Headward.
2. V-Shaped Cross Profile3. Poorly Developed Floodplain4. Broad, Poorly Drained Interfluves5. Falls and Rapids at Crossing of
Resistant Rocks6. Few Meanders
Black Canyon of the Gunnison,
Colorado
MATURITY:Lateral Erosion Important; Graded Streams1. Well-Integrated Drainage2. Some Structural Control of Tributaries3. Sharp, Well-Drained Interfluves4. Waterfalls & Lakes Obliterated5. Floodplains Considerable, with Shifting
Meanders6. Valley Floor Width = Meander Belt Width7. Most of Landscape in Slope
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Maturity - View from Backbone Mtn.
OLD AGE:Lateral Erosion Dominant, Stream
Graded near Base Level, Little Erosion1. Valleys Broader than Meander Belt2. Large Floodplains
with Broadly Meandering Streams, Flood Basin, Swamps, etc.
3. Low Hills, Low Valley Slopes4. Effect of Lithology Obscure5. Extensive Areas at, or Near, Base Level:
Peneplain (Truncates Structure) -Monadnock (Resistant Bedrock Knob)
Old Age
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REJUVENATION
Large Meanders Juxtaposed withDeep V-Shaped Valleys
Interpretation:Development of PeneplainSubsequent Uplift
San Juan River
New River Gorge
Cheat Canyon,
WV
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Blackwater Canyon - Youth
Projected Peneplains: Cumberland - Ohio River.
Fridley, Harry M., and Nölting, John P., Jr., 1931, Peneplains of the Appalachian Plateau, The Journal of Geology, v. XXXIX, no. 8, p. 749-755
Geology Colloquium
Dr. Ellen HermanBucknell University
Interpreting Flow and Sediment Transport in Karst Springs
Thursday March 1stTalk at 4, refreshments at 345 PM
310 White Hall
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THEORIES OF LANDSCAPE DEVELOPMENT
(after Higgins, 1975)
3 Theories
W.M. Davis: Geomorphic CycleW. Penck: Parallel Slope RetreatJ.T. Hack : Dynamic Equilibrium
Do Davis’s Concepts Make Sense?
•Sure!
Geology: Epeirogeny• Continental-Wide Erosion Episodes in
Geological Record.• North American Craton - 6 Major
Unconformities in Last 600 My.– Base of Sauk - Tippecanoe - Kaskaskia -
Absaroka - Zuni - Tejas Sequences• Continent "Highstands"- Correlate with
Low Sea-Floor Spread Rates & Deep Ocean-Basin Geometry
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Peneplain Tracing Worldwide: 1899-1950
Dr. Harry M. Fridley, arrived WVU 1931Projected Profiles (1;62,500)
Accordant SurfacesFridley’s 2 Peneplains in This Area
Kittatinny (Schooley)Allegheny
Problems: Better Topo Maps Show Surfaces are Not Accordant?
Why Were Davis's Ideas Successful?
• Simple and Filled a Void.
Davis's Lasting Contributions
• Landforms Change in an Orderly Manner as Fluvial Processes Operate Through Time.
• Under Uniform Conditions, Orderly Sequences of Landforms Develop.
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Walther PENCK
"Die Morphologiche Analyse" 1924
- Translated by L.C. King.
PENCK
• Long Continued Crustal Movement• Parallel Slope Retreat
– Retreating Fluvial Knickpoints– Graded Slopes.
Canyonlands National Park
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Arches National Park, Utah
Walther PENCK
Long Lasting TectonicsParallel Slope Retreat
Retreating KnickpointsGraded Slopes.
Canyonlands National Park
Pediment
John T. HACK (1965)
Dynamic Equilibrium Concept: Much Inherited from Gilbert (1880s) &
Strahler (Columbia School of 1950s).Hack: Landforms Part of an Open
System Tending to Steady-State Equilibrium.
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Hack’s Assumptions:Balance Between Erosion & Rock
ResistanceAll Landscape Elements Down-
waste at the Same RateForm Is Explainable in Terms of
Bedrock Geology:“Accordant Summits” Have
Similar Structure and Lithology.
MacDonald Range,
Australia
Hack’s “Sequence”
• Short Early Ungraded Episode• Long Period of Uniform
Downwasting of Steady-State Landforms…
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Where Does Each Landscape Evolution Model Fit Best?
Davis: Cratons & Tectonic Landscapes
Not Rivers & Valleys of Appalachians Where He Came Up with Concepts.
Black Sea Coast near Varna, Bulgaria
Wasatch Range, Utah
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Where Does Each Model Fit Best?
Penck:
Arid & Semiarid Landscapes.
Canyonlands National Park
Canyonlands National Park© copyright nps.gov White Rim Road
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Where Does Each Model Fit Best?
Hack:
Erosional Landscapes with Varied Rock Types
Rivers and Valleys of Appalachians.
Ridge and Valley of PA
Ridge&
Valley of WV