Yan Ding, Ph.D.
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Transcript of Yan Ding, Ph.D.
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ENGR 691, Fall Semester 2010-2011Special Topic on Sedimentation Engineering
Section 73Coastal Sedimentation
Yan Ding, Ph.D. Research Assistant Professor, National Center for Computational
Hydroscience and Engineering (NCCHE), The University of Mississippi, Old Chemistry 335, University, MS 38677
Phone: 915-8969Email: [email protected]
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Objective
• The lectures are to introduce morphodynamic processes driven by waves and currents in coasts, estuaries, and lakes. Emphasis is placed on understanding the features of sediment transport and morphological changes induced by combined waves and currents. Numerical modeling in morphodynamic process simulations will be briefly introduced.
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Outline • Introduction of morphodynamic processes driven by waves and
currents in coasts, estuaries, and lakes• Initiation of motion for combined waves and currents• Bed forms in waves and in combined waves and currents• Bed roughness in combined waves and currents• Sediment transport in waves• Sediment transport in combined waves and currents• Transport of cohesive materials in coasts and estuaries• Mathematical models of morphodynamic processes driven by
waves and currents• Introduction of a process-integrated modeling system (CCHE2D-
Coast) in application to coastal sedimentation problems
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Course Mechanics
• Grades – Grades will be based on the homework assignments and the lecture
• Lecture notes: http://www.ncche.olemiss.edu/~ding/Teaching/Engr691_73_Fall_2010/
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References• van Rijn, L.C., (1993). Principles of sediment transport in rivers, estuaries and
coastal seas, Aqua Publications, ISBN: 90-800356-2-9. http://www.aquapublications.nl/page9.html
PART I: EDITION 1993; 715 pagesPART II: SUPPLEMENT/UPDATE 2006; 500 pages
• Dean, R. G., and Dalrymple, R. A. (2002). Coastal Processes with Engineering Applications, Cambridge Press.
• Sorensen, R. M. (1993), Basic Wave Mechanics for Coastal and Ocean Engineering, Wiley-Interscience (ISBN 0471551651).
• Coastal Engineering Manual (2002). Coastal Engineering Manual, Part II: Coastal Hydrodynamics, US Army Corps of Engineers, ERDC, Report Number: EM 1110-2-1100. (http://140.194.76.129/publications/eng-manuals/em1110-2-1100/PartII/PartII.htm ).
• Mei, C.C. (1989). The Applied Dynamics of Ocean Surface Waves, World Scientific, Singapore.
• Dean, R.G. and Dalrymple, R.A. (1992). Water Wave Mechanics for Engineering and Scientists, World Scientific, Singapore.
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Beautiful Coasts
Sunrise at Turtle Bay Resort Hotel, Honolulu, Hawaii, 04/14/2008
Turtle Bay Resort Hotel, Honolulu, Hawaii, 04/15/2008
Waves in Turtle Bay, Honolulu, Hawaii, 04/15/2008
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Estuaries and Coastal Waters
Mouth of Columbia River, WA Coastal Inlet
Ocean City Beach looking north, Maryland
Barrier Island Breaching
A small estuary
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Wave crashed against a boat that washed into Highway 90 in Gulfport, MS, AP Photo
Vulnerable Coasts
Storm Surge, Hurricane Katrina
Water spilled over a collapsed levee in New Orleans on Tuesday (8/30/2005)
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Erosion in the beach
A beautiful beach before 13 years
Embankment and groin for
shore protection
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Hurricane IsabelHatteras Island Breach,
21 Sep 03
(Breached ~ 18 Sep 03 )
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Vulnerable Coasts Structure Failure by Katrina
US 90, Bilox, MS, Feb 26, 2006
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NWLON Station Analyses New Global Station Analyses
Long-term Variations in Sea Level and Analysis of Trends:
Exceedance Probability Analyses and the 100-year Event :*
* In development 2008
Annual Exceedance Probability Curves 1%, 10%, 50%, 99% Exceedance Probability Levels
Honolulu
Return Period (years)
300200100504030201054321
met
ers
abov
e M
HH
W
.9
.6
.3
0.0 99% 50% 10% 1%
Analysis of Climate Changehttp://www.tidesandcurrents.noaa.gov/sltrends.html
12
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USGS Published Landloss Since 1932 and Projected For the Next 45 Years
1932 1956 1978 1988 2000 2050NWRC
Landscape Change: Predicted Landloss in Louisiana
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Spatial and Temporal Multi-Scales of Hydrodynamics and Morphology in Coasts and Estuaries
•Small-Scale Processes (0.1mm-10m; 0.1s-1day) Fluid and sediment motions in turbulent wave-current bottom boundary layer
•Intermediate-Scale Processes (1-10km; 1s-1yr) Wave breaking across surf zone, wave-induced nearshore current, lower frequency infragravity wave motions by storm surges, sediment transport alongshore and crossshore, fresh water and sediment from rivers during floods, and tidal motions
•Large-Scale Processes (1-100km; months-decades) Ocean circulations, sea-level rising, global scale weather change, long-term shoreline change, etc.
A challenging goal: a realistic coupled waves-currents-morphologic-ecological evolution model
See http://www.coastal.udel.edu/coastal/
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• Coupling of the small-, intermediate-, and large-scale process:
turbulent boundary layerwave deformationNearshore circulationSediment movementShoreline changeBar and tough
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Physical Processes in an Estuary
Wind Input, Storm Surge, River Inflow
Tide and Waves
Wave-Induced Currents Tidal Currents
River Discharges
Sediment Transport Morphological Change
• Coastal Structures
• Beach Maintenance
• Dredging
• …
Water Quality
Fishing Water Withdrawal
Sewerage …
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Wave Transformation
Columbia River Entrance, WA/OR
Breaking
Refraction
Reflection
Shoaling
after Smith & Cialone (2000) Wave breaking in a tidal front of an inlet
Wave breaking in Turtle Bay, HI, 4/14/08 Wave breaking in a tidal front of the Fraser Estuary, BC, Canada (after Baschek)
Strait of Georgia River flow
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Wave Transformation
Columbia River Entrance, WA/OR, 1966
Breaking
Refraction
Reflection
Shoaling
Smith & Cialone (2000)
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Seminar for Course ENGR 691 20
Deformation of Irregular Wave (1)
Deformation of wave• Refraction• Diffraction• Reflection• Wave Breaking• Bottom Friction• ……
Incident W
ave
Nearshore wave processes
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Seminar for Course ENGR 691 21
Nearshore Current System (Schematically)
Incident Wave
Longshore
Rip C
urre
ntCurrents generated by breaking wave
One Cell
Mass Transport
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Wave Parameters
Figure. Definition of wave parameters
Parameter (SI Unit) Conventional Notation NotesWave Height (m) H
Wave Period (s) T
Wave Length (m) L
Wave Celerity /Speed (m/s) C C = L/T = σ/k
Wave number (1/m) k k=2π/L
Wave Angular Frequency (1/s) σ (ω) σ = 2π/T,
Wave Steepness H/L
Relative Water Depth d/L
kdgk tanh2
trough
crest
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Wave Celerity (1)• Solution of nonlinear equation (Newton’s method)
A good estimate of initial value of L (deep wave length)
LdgTL
2tanh
2
2
02tanh2
)(2
LdgTLLf
Newton’s method
)()(
1n
nnn Lf
LfLL
n = 1,2, ……
Dispersion relation:
2
2
0gTL
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Wave Breaking in beach
Deep wave breaking
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Small Wave CharacteristicsShallow
(d/L <=0.05)Intermediate Deep
(d/L >=0.5)
Celerity
Wave Length
Wave Number 2π/L
Wave Period T T T
22gTgL
2
2gT
2
2)2(gT
kdkg tanh gd
LdgT
2tanh
2
2Tgd
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Small Wave Characteristics (3)Shallow
(d/L <=0.05)Intermediate Deep
(d/L >=0.5)
Velocity Potential φ
Surface Profile η
Particle velocityu
Particle Velocity w
Pressure P
Group Velocity Cg C nC C/2
sin2dTkH
cos2H
cosTkdH
)sin(cosh
)(cosh2
tkxkdzdkgH
,tkx
sinkzekTH
cos2H cos
2H
coskzeTH
cossinh
)(coshkdzdk
TH
sin)1(dz
TH
sinkzeTH
sinsinh
)(sinhkdzdk
TH
where
cos21 gHgz cos
21 kzgHegz cos
cosh)(cosh
2 kdzdkgHgz
kdkdn
2sinh21
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Near-bed Orbital Velocities
Applying linear wave theory, the peak value of the orbital excursion (Aδ) and velocity (U δ) at the edge of the wave boundary layer can be expressed as
2sinh( )HAkh
sinh( )HU A
T kh
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Longshore Sediment Transport in Coasts
Observations on natural beaches as well as in laboratory wave basins have confirmed that the longshore current is largely confined to the surf zone. This longshore current drives the shoreward movement of longshore sediment transport.
Ocean City Beach looking north, MarylandDownloaded from: http://images.usace.army.mil/main.html
Wave
Current &
Sediment
Brea
king L
ine
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Longshore and Cross-shore Sediment Transport in Local Scale(2D Morphological Change in River Mouth)
The total longshore sediment transport model is not useful for this case.
Sediment alongshore ql=?Sediment cross-shore qc=?
Deposition of littoral sand
Movement of littoral sand
Erosion Protection (Artificial Headland) River Mouth
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Jetty and Navigation Channel
Portage Lake Harbor, Onekama, Michigan
From Digital Virtual Library, U.S. Army Corps of Engineers
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Detached Breakwater
Physical model testing of detached breakwaters and beach morphology in CHL's Longshore Sediment Transport Facility (LSTF)
http://cirp.wes.army.mil/cirp/gallery/gallery.html
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Scour holes at Indian River Inlet, Delaware
Aerial Photo Scour: view looking seaward
http://cirp.wes.army.mil/cirp/gallery/gallery.html
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Hydrodynamic and Morphodynamic Processes in River Mouths and Estuaries
Touchien River Estuary Tidal Inlet
Flood Shoal
River
River
Waves
Tides
Longshore Current
Yangtze River Estuary
Ocean
Longshore C
urrents
Flood Ebb
Estuary
Wave
Longshore C
urrents
River Inflow
Alluvial Sediments
An estuary: a semi-enclosed coastal water body with a river inflow