Coastal Intro

transcript

Introduction to Coastal Engineering

Harry C. Friebel, Ph.D., Harry C. Friebel, Ph.D., P.E.P.E.

U.S. Army Corps of EngineersU.S. Army Corps of Engineers

Philadelphia DistrictPhiladelphia District

Objectives

To review for students:To review for students:1.1. Answer the question: What is Coastal Answer the question: What is Coastal

Engineering?Engineering?

2.2. Introduction to the vocabulary used by coastal Introduction to the vocabulary used by coastal scientists and engineers.scientists and engineers.

3.3. Explain some similarities and differences Explain some similarities and differences between the principal US coastal regions: between the principal US coastal regions: geology, storm risk, etc.geology, storm risk, etc.

4.4. Provide an overview of important physical Provide an overview of important physical processes in the coastal zone.processes in the coastal zone.

Intro Vocabulary Differences Coastal Processes Summary

References

ER 1105-2-0100, Planning Guidance ER 1105-2-0100, Planning Guidance NotebookNotebook

EM 1110-2-1100, Coastal Engineering EM 1110-2-1100, Coastal Engineering ManualManual

Shore Protection ManualShore Protection Manual. 1984. 4th ed., 2 . 1984. 4th ed., 2 Vol., U.S. Army Engineer Waterways Vol., U.S. Army Engineer Waterways Experiment Station, U.S. Government Experiment Station, U.S. Government Printing Office, Washington, D.C., Printing Office, Washington, D.C., 1,088p.1,088p.Intro Vocabulary Differences Coastal Processes

Summary

What is Coastal Engineering?

The USACE Coastal & Hydraulics Laboratory The USACE Coastal & Hydraulics Laboratory defines coastal engineering as: defines coastal engineering as: A branch of A branch of civil engineering that applies engineering civil engineering that applies engineering principles specifically to projects within the principles specifically to projects within the coastal zone (nearshore, estuary, marine, and coastal zone (nearshore, estuary, marine, and shoreline). shoreline).

The University of Delaware defines coastal The University of Delaware defines coastal engineering as: engineering as: Coastal engineering is the Coastal engineering is the study of the processes ongoing at the study of the processes ongoing at the shoreline and construction within the coastal shoreline and construction within the coastal zone. The field involves aspects of nearshore zone. The field involves aspects of nearshore oceanography, marine geology, and civil oceanography, marine geology, and civil engineering, often directed at combating engineering, often directed at combating erosion of coasts or providing navigational erosion of coasts or providing navigational access. access.

Coastal Engineering Vocabulary

Water Wave - A deformation of the water’s surface.Water Wave - A deformation of the water’s surface.

Duration - length of time the Duration - length of time the wind blows.wind blows.

Wind speed – How fast the wind Wind speed – How fast the wind is blowing.is blowing.

Fetch – The horizontal distance Fetch – The horizontal distance (in direction of the wind) over (in direction of the wind) over which a wind blows.which a wind blows.

Figure from: http://geology.uprm.edu/Morelock/2_image/wavgenr.gif

Crest - highest point on a wave.Crest - highest point on a wave.

Trough - lowest point on a wave.Trough - lowest point on a wave.

Wavelength - horizontal distance, Wavelength - horizontal distance, either between the crests or either between the crests or troughs of troughs of two consecutive waves.two consecutive waves.

Wave height - vertical distance Wave height - vertical distance between a wave's crest and between a wave's crest and the next the next trough.trough.

Wave period - time it takes for Wave period - time it takes for two consecutive crests or two consecutive crests or troughs to pass a stationary troughs to pass a stationary point.point.

FACTFACT – Deep water particles do not move – Deep water particles do not move forward with water wave, but instead move in forward with water wave, but instead move in elliptical orbits. Waves are the forward elliptical orbits. Waves are the forward motion of energy, not water!motion of energy, not water!

Example of water wave refraction at Allenhurst, Lock Arbour, Asbury Park, 1987.Example of water wave refraction at Allenhurst, Lock Arbour, Asbury Park, 1987.

Refraction

Photo credit: Fjellanger Widerøe A.S.

Diffraction

Gif credit: http://upload.wikimedia.org/wikipedia/commons/2/2d/Propagation_du_tsunami_en_profondeur_variable.gif.

Shoaling

Photo credit:

http://pro.corbis.com.

Wave Breaking

Photo credit: www.niwa.cri.nz/pubs/wa/ma/13-1/flooding

Wave Run-up

Figure credit: www.coastal.er.usgs.gov

Wave Set-up

Tides are caused by the gravitational Tides are caused by the gravitational force exerted by both the sun and moon force exerted by both the sun and moon and by the centrifugal force produced and by the centrifugal force produced by the revolution of the earth .by the revolution of the earth .

Normal water levels are tidally Normal water levels are tidally influenced.influenced.

TIDESTIDES

Two bulges of water – one on the side Two bulges of water – one on the side of the earth facing the moon (and sun) of the earth facing the moon (and sun) and one on the opposite side.and one on the opposite side.

The bulges are stationary (relative to The bulges are stationary (relative to the Moon or sun), but the rotation of the Moon or sun), but the rotation of the earth about its polar axis causes the earth about its polar axis causes the bulges to move relative to the the bulges to move relative to the earth.earth.

TIDESTIDES

SpringSpring tide is when tide is when the bulges due to the bulges due to the sun and moon the sun and moon are aligned (full are aligned (full moon and new moon and new moon). moon).

NeapNeap tide is when tide is when the sun and moon the sun and moon are in quadrature are in quadrature (quarter moon) (quarter moon) and thus the and thus the respective bulges respective bulges are not aligned.are not aligned.

TIDESTIDES

http://www.rise.org.au/info/Res/tidal/image001.jpg

Diurnal Tide – one Diurnal Tide – one high and low per high and low per day.day.

Semi-diurnal Tide – Semi-diurnal Tide – two highs and two two highs and two lows per day.lows per day.

TIDESTIDES

Do the Great Lakes experience tides?

http://glakesonline.nos.noaa.gov/monitor.html

Similarities and differences between the principal US

coastal regions

Great Lakes

Atlantic Coast

Gulf Coast

Pacific Coast

Islands

GeologyGeology

Atlantic/Atlantic/Gulf CoastGulf Coast

Pacific Pacific CoastCoast

IslandsIslands Great Great LakesLakes

TopographTopographyy

Flat Flat Coastal Coastal PlainPlain

Steep Steep MountainsMountains

VolcanicVolcanic ContinentaContinentall

BathymetrBathymetryy

Wide Wide Shallow Shallow ShelfShelf

Steep Steep OffshoreOffshore

ReefsReefs

Glacier Glacier modifiedmodified

TopographyTopography

Laguna Laguna Beach, CA Beach, CA (1993)(1993)

St Joseph, MISt Joseph, MI

Westhampton, Westhampton, NY (1994)NY (1994)

BathymetryBathymetry

Atlantic/Gulf Atlantic/Gulf CoastCoast

Lake ErieLake Erie

Storm RiskStorm Risk

Storm Storm HazardHazard

Atlantic/Atlantic/Gulf CoastGulf Coast

IslandsIslands Great Great LakesLakes

TsunamiTsunami LowLow HighHigh HighHigh Very LowVery Low

HurricaneHurricane HighHigh Very LowVery Low Very LowVery Low Very LowVery Low

Extra-tropical storm Extra-tropical storm Forms outside the tropics. Forms outside the tropics. Center of storm is colder than the Center of storm is colder than the

surrounding air. surrounding air. Has fronts. Has fronts. Strongest winds in the upper atmosphere.Strongest winds in the upper atmosphere.

Tropical storm:Tropical storm: Forms over a tropical ocean. Forms over a tropical ocean. Center of storm is warmer than the Center of storm is warmer than the

surrounding air. surrounding air. Has no fronts. Has no fronts. Strongest winds are near the Earth's Strongest winds are near the Earth's

surface.surface.

The Perfect StormThe Perfect Storm

Important Hurricane parameters

1.1. Central Pressure DeficitCentral Pressure Deficit

2.2. Radius of Maximum Wind SpeedRadius of Maximum Wind Speed

3.3. Forward Speed and Angle of Forward Speed and Angle of Approach (Quadrant)Approach (Quadrant)

4.4. Storm SurgeStorm Surge

5.5. Timing (Tide)Timing (Tide)

1. Central Pressure Deficit

Hurricane Hurricane FloydFloyd

Figure courtesy http://cmn.dl.stevens-tech.edu/floyd/

2. Radius of Maximum Wind Speed

Figure credit: www.wunderground.com

3. Forward Speed and Angle of Approach

(Quadrant)

http://www2.sunysuffolk.edu/mandias/38hurricane/weather_history_38.html

1938 1938 HurricaneHurricane

4. Storm Surge

Components:Components:

A.A. Pressure surgePressure surge

B.B. Wind surgeWind surge

C.C. Wave setupWave setup

http://coastal.er.usgs.gov/hurricanes/impact-scale/images/fig1LG.gif

A. Pressure Surge

Pressure Surge - The light blue bulge represents Pressure Surge - The light blue bulge represents to water surface increase due to the reduced to water surface increase due to the reduced pressure in the eye of the storm.pressure in the eye of the storm.

ANALOGY - if several people sit around the edge of a waterbed, the center of the bed rises!ANALOGY - if several people sit around the edge of a waterbed, the center of the bed rises!

B. Wind Surge

Surface stress (due to the wind) is balanced by a water surface Surface stress (due to the wind) is balanced by a water surface slope.slope.

ANALOGY - blowing on a hot cup of coffee.!ANALOGY - blowing on a hot cup of coffee.!

Wind surge becomes more pronounced in shallow water.Wind surge becomes more pronounced in shallow water.

C. Wave Setup

This gradient of the This gradient of the SSxxxx radiation stress term is balanced by a slope radiation stress term is balanced by a slope of the water surface.of the water surface.

From linear wave theory, it can be shown that the mean water level From linear wave theory, it can be shown that the mean water level at the shoreline is elevated by more than 20% of the wave height.at the shoreline is elevated by more than 20% of the wave height.

5. Timing (Tide) Assume Category 2 Hurricane or 8 foot surge

Compare peak at 18:00 July 1 vs. 01:00 July 2

Slide credit: Harley Winer

TsunamisTsunamis is Japanese for “Big Wave.”is Japanese for “Big Wave.”

TsunamisTsunamis can be earthquake or landside can be earthquake or landside Induced.Induced.

TsunamisTsunamis considered long period or shallow considered long period or shallow water wave.water wave.

TsunamisTsunamis has small amplitude in deep ocean has small amplitude in deep ocean and shoals to great heights near shore.and shoals to great heights near shore.

Pacific CoastPacific Coast

TsunamisTsunamis

Slide credit: Harley WinerSlide credit: Harley Winer

TsunamisTsunamis

Slide credit: Harley WinerSlide credit: Harley Winer

Coastal ProcessesCoastal Processes

Beach profiles

Littoral transport (cross-shore and longshore)

Sediment budgets

Accretion/Erosion

Berm Crest

Beach Beach ProfileProfile

Slide credit: Randy Wise, NAP

https://www.maine.gov/doc/nrimc/mgs/explore/hazards/erosion/shape.gif

Seasonal Profiles

Depth of Closure

Sand Movement

Cross-shore transport

Slide credit: Randy Wise, NAP

http://pubs.usgs.gov/circ/http://pubs.usgs.gov/circ/c1075/images/longshore.gifc1075/images/longshore.gif

Longshore transport

Sediment Budgets

Generally waves come from Generally waves come from a predominate direction, so a predominate direction, so net transport will generally net transport will generally be in that directionbe in that direction

Gross transport is the sum Gross transport is the sum of the transport in the two of the transport in the two directions directions

Net transport is the Net transport is the difference between the difference between the transport in the two transport in the two directionsdirections

South = 100,000 c.y./year

North = 80,000 c.y./year

Gross Transport = ?

Net Transport = ?

Sediment Budgets

It is important to identify It is important to identify rates of erosion when rates of erosion when building on the coast. A building on the coast. A beach can remain in beach can remain in equilibrium if the incoming equilibrium if the incoming sediment matches outgoing sediment matches outgoing sediment.sediment.

Empirical equations estimate Empirical equations estimate longshore transport.longshore transport.

Conservation of mass (check Conservation of mass (check book analogy) book analogy) – when outgoing is greater when outgoing is greater

than incoming - erosion than incoming - erosion – when incoming is greater when incoming is greater

than outgoing – accretionthan outgoing – accretion

Accretion/Erosion

Sources (+)Sources (+)RiversRiversEroding headlandsEroding headlands

Sinks (-)Sinks (-)Sediment TrapsSediment TrapsInletsInletsOffshore DepthsOffshore DepthsLittoral Drift InterruptionsLittoral Drift InterruptionsSea Level RiseSea Level Rise

Eroding Headland

River Delta

Sources (+)Sources (+)

www.truecolorearth.comwww.truecolorearth.com

SinksTidal Inlets - Canaveral, Fl

19931950

www.nww.usace.army.mil/dmmp/report.htm

Offshore Depths Disrupt Littoral Drift

Sediment Trap

Implications of Sea Level Rise

Absolute Sea Level RiseAbsolute Sea Level Rise Relative Sea Level Rise – i.e. subsidence (land Relative Sea Level Rise – i.e. subsidence (land

sinking)sinking) Adjustment of Equilibrium Beach ProfileAdjustment of Equilibrium Beach Profile Sea level rise will be very significant in the Sea level rise will be very significant in the

evaluation of future with and future without project evaluation of future with and future without project conditions.conditions.

Summary

In this session, we have:In this session, we have:

1.1. Defined Coastal EngineeringDefined Coastal Engineering

2.2. Introduced common vocabulary used by Introduced common vocabulary used by coastal scientists and engineers.coastal scientists and engineers.

3.3. Explained some of the similarities and Explained some of the similarities and differences between the principal US differences between the principal US coastal regions.coastal regions.

4.4. Provided an overview of the important Provided an overview of the important physical processes in the coastal zone.physical processes in the coastal zone.

Coastal Intro

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