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: 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/Teaching/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 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.

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

Mouth of Columbia River, WA Coastal Inlet

Ocean City Beach looking north, Maryland

Barrier Island Breaching

A small estuary

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)

Erosion in the beach

A beautiful beach before 13 years

Embankment and groin for

shore protection

Hurricane IsabelHatteras Island Breach,

21 Sep 03

(Breached ~ 18 Sep 03 )

Vulnerable Coasts Structure Failure by Katrina

US 90, Bilox, MS, Feb 26, 2006

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

USGS Published Landloss Since 1932 and Projected For the Next 45 Years

1932 1956 1978 1988 2000 2050NWRC

Landscape Change: Predicted Landloss in Louisiana

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 layerwave deformationNearshore circulationSediment movementShoreline changeBar and tough

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 …

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

Wave Transformation

Columbia River Entrance, WA/OR, 1966

Breaking

Refraction

Reflection

Shoaling

Smith & Cialone (2000)

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 　

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

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

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

Wave Breaking in beach

Deep wave breaking

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

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

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

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

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

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

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