ENGR 691, Fall Semester 2010-2011
Special Topic on Sedimentation Engineering
Section 73
Coastal 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: 915-8969
Email: ding@ncche.olemiss.edu
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.
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
Course Mechanics
• Grades – Grades will be based on the
homework assignments and the lecture
• Lecture notes:
http://www.ncche.olemiss.edu/~ding/Teachin
g/Engr691_73_Fall_2010/
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 pages
PART 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/engmanuals/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.
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
Estuaries and Coastal Waters
Barrier Island Breaching
Mouth of Columbia River, WA
Ocean City Beach looking north, Maryland
Coastal Inlet
A small estuary
Vulnerable Coasts
Wave crashed against a boat that washed into
Highway 90 in Gulfport, MS, AP Photo
Storm Surge, Hurricane Katrina
Water spilled over a collapsed levee in New Orleans on Tuesday (8/30/2005)
Erosion in the beach
A beautiful beach
before 13 years
Embankment
and groin for
shore
protection
Hurricane Isabel
Hatteras Island Breach,
21 Sep 03
(Breached ~ 18 Sep 03 )
Vulnerable
Coasts
Structure Failure by Katrina
US 90, Bilox, MS, Feb 26, 2006
Analysis of Climate Change
http://www.tidesandcurrents.noaa.gov/sltrends.html
Long-term Variations in Sea Level and Analysis of Trends:
NWLON Station Analyses
New Global Station Analyses
Exceedance Probability Analyses and the 100-year Event :*
Honolulu
.9
.6
.3
99%
0.0
1
50%
2
10%
3
4
5
10
1%
20
30
40 50
100
200
300
Return Period (years)
Annual Exceedance Probability Curves
1%, 10%, 50%, 99% Exceedance Probability Levels
* In development 2008
12
Landscape Change: Predicted Landloss in
Louisiana
USGS Published Landloss Since 1932 and Projected
For the Next 45 Years
1932
1956
1978
1988
2000
2050
NWRC
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/
•
Coupling of the small-,
intermediate-, and large-scale
process:
turbulent boundary layer
wave deformation
Nearshore circulation
Sediment movement
Shoreline change
Bar and tough
Physical Processes in an Estuary
Wind Input, Storm Surge, River Inflow
Tide and Waves
• Coastal
Structures
Wave-Induced Currents
Tidal Currents
River Discharges
Water Quality
• Beach
Maintenance
• Dredging
•…
Sediment Transport
Morphological Change

 Fishing
Water Withdrawal
 Sewerage
 …
Wave Transformation
Strait of Georgia
Wave breaking in a tidal front of the Fraser Estuary, BC,
Canada (after Baschek)
Wave breaking in Turtle Bay, HI, 4/14/08
Shoaling
Refraction
Reflection
Breaking
Columbia River Entrance, WA/OR after Smith & Cialone (2000)
Wave breaking in a tidal front of an inlet
Wave Transformation
Shoaling
Refraction
Breaking
Reflection
Columbia River Entrance, WA/OR, 1966
Smith & Cialone (2000)
Deformation of Irregular Wave (1)
Deformation of wave
• Refraction
• Diffraction
• Reflection
• Wave Breaking
• Bottom Friction
• ……
Nearshore wave processes
Seminar for Course ENGR 691
20
Nearshore Current System (Schematically)
One Cell
Mass Transport
Longshore
Currents generated by breaking wave
Seminar for Course ENGR 691
21
Wave Parameters
Parameter (SI Unit)
Conventional Notation
Notes
Wave 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)
2
σ = 2π/T,   gk tanh kd
Wave Steepness
H/L
Relative Water Depth
d/L
crest
trough
Figure. Definition of wave parameters
Wave Celerity (1)
• Solution of nonlinear equation (Newton’s method)
Dispersion relation:
gT 2
2d
L
tanh
2
L
gT 2
2d
f ( L)  L 
tanh
0
2
L
Newton’s method
f ( Ln )
Ln 1  Ln 
f ( Ln )
n = 1,2, ……
A good estimate of initial value of L (deep wave length)
gT 2
L0 
2
Wave Breaking in beach
Deep wave breaking
Small Wave Characteristics
Celerity
Wave Length
Wave Number
Wave Period
Shallow
(d/L <=0.05)
Intermediate
gL gT

2 2
g
tanh kd
k
gT 2
2
(2 ) 2
gT 2
T
gT 2
2d
tanh
2
L
Deep
(d/L >=0.5)
gd
gd T
2π/L
T
T
Small Wave Characteristics (3)
Shallow
(d/L <=0.05)
Velocity Potential
φ
H
k 2 dT
Surface Profile
η
Particle velocity
u
Particle Velocity
w
Pressure P
where
gH cosh k (d  z )
sin( kx  t )
2
cosh kd
H
cos 
2
H
Tkd
H
cos 
2
H cosh k (d  z )
cos 
T
H
z
(1  ) sin 
T
d
 gz 
Group Velocity Cg
sin 
Intermediate
1
gH cos 
2
sinh kd
H sinh k (d  z )
T
 gz 
sinh kd
C
cosh kd
nC
  kx  t , n  1 
2
kd
sinh 2kd
H
kT
e kz sin 
H
cos 
2
cos 
sin 
gH cosh k (d  z )
2
Deep
(d/L >=0.5)
H
T
H
T
cos 
 gz 
e kz cos 
e kz sin 
1
gHe kz cos 
2
C/2
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
H
A 
2sinh(kh)
U   A 
H
T sinh(kh)
Longshore Sediment Transport in Coasts
Ocean City Beach looking north, Maryland
Downloaded from: http://images.usace.army.mil/main.html
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.
Longshore and Cross-shore Sediment Transport in Local Scale
(2D Morphological Change in River Mouth)
Deposition of
littoral sand
Sediment alongshore ql=?
Sediment cross-shore qc=?
Movement of
littoral sand
Erosion Protection (Artificial Headland)
River Mouth
The total longshore sediment transport model is not useful for this case.
Jetty and Navigation Channel
Portage Lake Harbor, Onekama, Michigan
From Digital Virtual Library, U.S. Army Corps of Engineers
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
Scour holes at Indian River Inlet, Delaware
Aerial Photo
Scour: view looking seaward
http://cirp.wes.army.mil/cirp/gallery/gallery.html
Hydrodynamic and Morphodynamic Processes
in River Mouths and Estuaries
Flood Shoal
Tidal Inlet
Touchien River Estuary
Longshore Currents
Ocean
Ebb
Estuary
Flood
Alluvial Sediments
Longshore Currents
River Inflow
Wave
Yangtze River Estuary
An estuary: a semi-enclosed coastal water body with a river inflow