coastal engineering introduction

Coastal Engineering Introduction

Engineering Applicationsby Msc. Jorge C. Palma

2013-04-15

PART ONE. INTRODUCTION TO COASTAL PROCESSES

1 Overview

1.1 Some Terminology of the Coasts

1.2 Examples of Coastal Engineering Projects

PART ONE. INTRODUCTION TO COASTAL PROCESSES. Typical

zones.

Examples of coastal engineering projects. Cuba. Western

Coasts

PART ONE. INTRODUCTION TO COASTAL PROCESSES. Beach

Nourishment. Planform and profile dynamic.

Examples of coastal engineering projects Varadero Beach

Nourishment. 5,0 million M3

Effects of groins interacting with longshore sediment

transport

Shore side Sea side

Maria La Gorda Beach & Groins. Forgetting big frame!

Maria La Gorda Beach & Groins. Forgetting big frame, but

lucky end!


lucky end!

Groins


lucky end!

Emerged terraces


lucky end!

Equilibrated beach profiles


lucky end!

Rocks on surface, yet beach profile is equilibrated

Cuba. Cristino Naranjo Breakwater. Tetrapods 25-ton

weight

Cuba. Cay Coco Roadway. 27 km with 15 bridges.

Cuba. Cay Coco Roadway. Bascule Bridge.

Spain. Cadiz. Camposoto beach

Camposoto Beach Study. Cadiz, Spain.

Camposoto Beach Study. Cadiz, Spain.

Cadiz Port

Ebb, Flood

currents

Ebb, Flood

currents

Estuaries

Sweden. Varholmen. Lile Varholmen Pier Enlargement

Sweden. Lile Varholmen Pier Enlargement

Denmark. Arkens Museum Channel

Coastal Engineering. Arken Channel Project

PART ONE. INTRODUCTION TO COASTAL PROCESSES. Sediment

Characteristics

2 Sediment Characteristics

2.1 Sand Composition

2.2 Grain Sizes

2.3 Shape

2.4 Porosity

2.5 Fall Velocity


Characteristics

2. Sediment Characteristics

2.1 Sand Composition (70 % from granitic mountains and quartz, 20 %

feldespar, there are from calcium carbonates precipitated and from

abrasion of coral reefs).

2.2 Grain Sizes. Representative normal diameter is D50, for bimodal

samples: Mean diameter=(D84+D50+D16)/3

2.3 Fall Velocity. According to Stockes law is:

where

ρs, sand density

ρ, sea water density

g, gravity

d, sand diameter

µ, dynamic viscosity for salt water (aprox. 1/1000 N s/m2), but depends on water temperature.


Characteristics. Scale of Sediment Size Classification.


3 Long-Term Processes

3.1 Relative Sea Level Change. For 2100 estimated between 0,5 and 1,0

m. higher due to earth warming process and climate changes

PART ONE. INTRODUCTION TO COASTAL PROCESSES. Goteborg

sea water levels

HHW 170 +11, 69

MHW 100 +10, 99

LHW 52 +10, 51

MW 0 +9, 99

HLW -40 +9, 59

MLW -62 +9, 37

LLW -112 +8, 87

The average values refer to the year 2012. Uplift Coefficient 0, 16 cm / year

The design level for structures near the sea in Gothenburg specified in

comprehensive plan and is set at +12.5 which includes 1 m sea-level rise

as a result of a warmer climate.

PART ONE. INTRODUCTION TO COASTAL

PROCESSES. Coastal Protection Policies


3 Long-Term Processes

3.2 Equilibrium Beach Profile

The concept of an equilibrium profile, - is the average beach response to the

natural forcing- makes it possible to determine several beach responses to

changes in forcing.

The equilibrium profile depends on sediment size, wave height and

period, and water level.

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE

Profile erosion due to storm tides and waves

PART ONE. INTRODUCTION TO COASTAL PROCESSES.Equilibrium profile response to sea level rise: Bruun’s rule.

Equilibrium profile response to sea level rise:

Bruun’s rule.

a. Volume of sand generated by horizontal

retreat R of equilibrium profile over vertical

distance (h∗ + B);

(b) volume of sand required to maintain an

equilibrium profile of active width W∗ owing to a

rise S in mean water level;

(c) landward (R) and upward (S) components of

profile translation to achieve equilibrium relative to

increased sea level.

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE

4 Tides and Storm Surges

4.1 Astronomical Tides (sea level variations by gravitational influence of

moon, ranging from cm. till several meters depending on location)

4.2 Storm Surges (wind velocities from scale 1: pressure<980 mbar, 96-

110 mph, surge 5 ft, moderate damage till scale 5: pressure <920 winds

>155 mph surge >18 ft damage Catastrophic)

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE. Water

waves and wave induced Hydrodynamics. Linear Theory.

5 Waves and Wave-Induced Hydrodynamics

5.1 Water Wave Mechanics

5.2 Cross-Shore and Longshore Currents

η (x,t) = (H/2)cos(kx-σt) k=2π/L and σ=2π/T

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE. Water

waves and wave induced Hydrodynamics. Boussinesq Theory. Shallows waters

Boundary conditions: Variable depth, propagation in x direction, depth

averaged velocity and free surface elevation.

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE.Wave refraction, difraction, and reflection.

Wave refraction is produced due to interaction of sea bottom in shallow waters with waves and

when bathimetry is parallel to the shore the Snell optical law can be applied with waves changing

direction to shallower waters.

Wave difraction happens around the border of obstacles.

Wave reflexion occurs in front of vertical walls producing stationary effects.

Wave breaking happens in shallow waters when the heigh of wave is about 0,78 water depth.

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE.Wave refraction, difraction, and reflection. Cuba. Bridges difraction.

PART TWO. HYDRODYNAMICS OF THE COASTAL ZONE.Cross shore and longshore currents. Schematic of vertically descending eddies with arrows showing

the direction of breaker travel

.

The energy radiation by obliquely incident waves and breaking produce

additional longshore currents.

Reflection of waves energy against shore produce crosshore currents

PART THREE. COASTAL RESPONSE

6 Field Measurement Techniques and Analysis

6.1 Beach Profile Measurements

6.2 Historical Shoreline Change. Planforms Charts

6.3 Sediment transport rates


8 Sediment Transport

8.1 Incipient Sand Motion and Depth of Closure

8.2 Longshore Sediment Transport

Forces on a sand particle in an inclined bed. Point A denotes the point of contact between two

particles. Cd and CL are drag and lift coefficient depending on Reynolds number R.

After moment balance:

Ʈc/( ρ s − ρ )gd= f (Re), Ʈc indicates critical bed

shear stress for Incipient motion for a uniform depth,

the left-hand side of Eq. is known as the critical

Shields parameter, denoted as Ψ c , which is used as

an indicator of incipient motion

PART THREE. COASTAL RESPONSE. Sediment transport

Shields curve for the initiation of motion for steady flow (Raudkivi 1967)

PART THREE. COASTAL RESPONSE. Sediment transport. Closure

depth.

Hallermeir Formula for closure depth:

The variables are here functions of time measured in years, H(t) e is the

significant wave height that is exceeded during only 12 h in the time t, and

T (t) e is the associated period.

Longshore sediment transport:

Bedload transport, which is either in sheet flow or rolled along the bottom

Suspended load, which is carried up within the fluid column and moved by currents

Swash load, which is moved on the beach face by the swash.

For littoral transport:


9 Modeling of Beaches and Shorelines

9.1 Physical Modeling of Coastal Processes (wave basins and wave tanks)

9.2 Analytical Modeling (analytical equations with exact solutions for

abstract models of problems, one, two or tridimensional equations)

9.3 Numerical Modeling (One, two or tridimensional equations using

computing techniques and processing capacities, calibrated with labs

measurements and real data under specific boundary conditions. Some use

Boussinesq equation). Represent Short-term & Long-term coastal evolution How is the randomness of the wave field to be included?

Should one representative wave train or a stochastic approach with different wave scenarios be used and the

results ensemble averaged?

How are the storms to be included, particularly because they play such a major role in the beach profile?

How are the tides to be included?

http://www.youtube.com/watch?feature=player_detailpage&v=X3lCXHxVFzU

https://www.youtube.com/watch?v=tg9IcMRg0Vc&feature=player_detailpage



9.1 Physical Modeling of Coastal Processes (wave basins and wave tanks)




9.1 Physical Modeling of Coastal Processes (wave basins and wave tanks.

Breakwater modeling)


PART THREE. COASTAL RESPONSE. Modular diagram for generic

tridimensional coastal model

PART FOUR. SHORELINE MODIFICATION AND ANALYSIS

10 Beach Fill and Soft Engineering Structures

10.1 Beach Nourishment (Beach Fill)

10.2 Submerged Berms (modifying the waves evolution)

11 Hard Engineering Structures

11.1 Perched Beach

11.2 Groins

11.3 Offshore Breakwaters

11.4 Revetments

11.5 Seawalls


10.1 Beach Nourishment (Beach Fill)


10.1 Beach Nourishment (Beach Fill, ”Rainbow method)


Beach Fill. Qualitative illustration of three components of shoreline recession following a

beach nourishment project shown for two background erosion rates and initial nourished width of

75 m.


14 Shoreline Management

14.1 Options and Factors

14.2 The Role of Setbacks and Construction Standards (frozen

construction shorelines spaces areas up to 500 m.)

14.3 Protective Value of a Wide Beach


Adaptation of flood protection.


1. Climate Change will have direct and indirect effects on Coastal Areas

- water levels will increase

- wave heights may increase in some areas

- wave directions will change

- frequency and intensity of storms will increase at least in some areas,

which might also cause more intensive wave conditions

This will result in:

2. Higher loads on the coast and on coastal structures

- retreat of the coast

- changed long-shore sediment transport


3. without adaptation

- increase in probability of failure

- increase of flooded area

- increase of water level in flooded area

- higher risks in coastal areas

4. with adaptation

- higher costs for coastal protection


Swedish approach on sustainable use of coastal zones.

Varholmen. Existing Pier and Berthing Dolphins

Varholmen. Pier Enlargement Project

Varholmen. Rays of wind

Varholmen. Pier Enlargement Project. Varholmen waves

hindcasting SMHI

Varholmen. Pier Enlargement Project. Varholmen

Bathimetry

Coastal Engineering. Arken Channel Project

Channel Typical Section A-A and slopes. Concept Solution

+ 1,65 m. surface level

28 m.

15,5 m. 3,15 m.2,5 m. 6,85 m.

Existing soil

Crushed rocks and

gravels

+ 0,35 m. water level

Concrete slabs

and blocks

Centerline

- 1,90 m. channel bottom

Channel Typical Section B-B and sheet pile walls. Concept

Solution


10,0 m.

Existing soil

+ 0,35 m. water level

- 1,90 m. channel bottom

- 9,30 m. sheet pile foot

Existing soil

- 9,30 m. sheet pile foot


sheet pile walls

Coastal Engineering. Arken Channel Project. Budget.

Coastal Engineering Design data

Maritime boundaries

Coastal topography and bathymetry

Geology and soil parameters

Existing coastal defences and maritimes structures

Erosion trends. Land cover changes (50 years). Aerial photography,

satellites and surveys.

Winds

Waves regimes

Currents

Water sea level rise (long term, global changes)

River and coastal sediment transport

Areas of high ecological values and protection structures

Coastal Management planning

General methods and toolkits in Coastal Engineering

Databases

Surveys and local campaings

Numerical models

Physical models

Engineering references and projects

Regional guidelines and coastal management policies

Approach to Coastal Engineering Problems

Information review and analysis. Review of existing BBDDs, studies, projects and related technical information

Problem definition of client and stakeholders needs, goals and guidelines

Definitions of spacial/time scales and evaluation of main natural and human actions and influences

Site visual inspection and gathering of preliminary data

Preliminary estimations and evaluation with existing data, by row mathematical and numerical tools, physical modeling or empirical

formulations.

Review of projects of references.

Preliminary hypothesis of natural and physical functioning of coastal processes

Determination of needed detailed data and location of surveys (local winds, waves, flow velocities, sea levels, sediments, topography,

batimetry, geological and geotechnical information) for models selection, validation and callibrations*.

Project budget estimation, presentation and approval by client

Surveying, measurements, data filtering and process

Model calibration

Testing hypothesis, chek-out of results and validation.

Coastal System Diagnostic. Sensitiveness analysis –what if?-

Alternatives of solutions, impacts, risk and consecuences.

Dimensions and Concept Design of Solution.

Cost benefits analysis. Selection of best alternatives. Detailed measurements and adjustments.

Final evaluation. Discussion of results, final solution (Description, construction specifications, BOQ, Drawings, Program)

Delivery of final solution.

Monitoring and Control of Coastal Project System

Lessons learnt

* To counter the recurring problem of lack of data (waves, currents, other), a major tenet of coastal engineering should be to design flexibility wherever possible

into every project to correct for unknown parameters and poorly estimated factors and to allow for fine-tuning of the project afterwards.

Engineering approach to coastal engineering

The best understanding of coastal processes, including the nearshore flows

and the resulting sediment transport, and the ability to transform it into

effective engineering measures require the following:

A blend of analytical capability,

An interest in the workings of nature,

The ability to interpret many complex and apparently conflicting

pieces of evidence, and

4. Experience gained from studying a variety of shorelines and working with

many coastal projects.

Engineering approach to coastal engineering

End of presentation.Thank for attention!

coastal engineering introduction

Documents

gorda beach groins

coastal processes

groins maria

big frame

lucky end

m3 effects of groins

longterm processes

sediment characteristics2