Vietnam presentation coastal processes

Coastal processes: question • The large deltas are found on leading or trailing edge coasts • Leading edge coasts • Trailing edge coasts... • The large deltas are found on leading or

Introduction to coastal processes and structures

Ir K Lendering

Introduction: About the Netherlands

• Flat low delta, precarious location,

‘best’ flood control system in the world

Several Dutch companies are involved in

Water projects Conservation projects and land

reclamation throughout the world

• Lowest altitude: 6.74 meter below sea level

(near Rotterdam)

• Highest altitude: 323 meter (near Maastricht)

TUDelft

Delft University of Technology

Dredging and Engineering firms

Hydraulic Engineering and Water

Management at Delft University

Delta Urbanism

Coastal Engineering Hydraulic Engineering

Ports Flood Risk Management

Water Management

• 2006 – 2012 BSc/MSc

• Hydraulic Engineering

Kasper Lendering

Contents of guest lecture

Coastal engineering

Start with thinking / understanding processes

Then design / engineer possible solutions

Cyclic process

What has happened?

What has happened?

aground

stranded ship on land

reduced wave heights

MOOC coastal processes

Types of coasts

• Three main types of coasts:

• Leading edge coasts

• Trailing edge coasts

• Marginal coasts

Types of coasts

Coastal processes: question

• The large deltas are found on leading or trailing edge

coasts

• Leading edge coasts

• Trailing edge coasts

• The large deltas are found on leading or trailing edge

coasts

• Leading edge coasts

• Trailing edge coasts

• These coasts combine ample sediment supply with wide and flat shelves This combination ensures a rapid building out of the coast

Coastal processes: question

• Large deltas have a surplus or deficit of sediment from their catchment areas?

i Surplus of sediment

ii Deficit of sediment

Coastal processes: question

• Large deltas have a surplus or deficit of sediment from their catchment areas?

i Surplus of sediment

ii Deficit of sediment

Coastal processes: question

MOOC coastal processes: recap

• Sea level rise is actually a secondary factor

(absolute SLR)

• Primary problem factors for coasts are:

• Availability of sediment

• Subsidence of the land (due to groundwater

extraction)  relative sea level rise

Purposes of hydraulic engineering

interventions

• Energy generation

• Water supply (deltas and estuaries)

• Navigation

• Safety (deltas and estuaries)

• Ecological and societal functions

View of a coastal area

Purposes of coastal interventions

• Ecological and societal functions

• control of shoreline erosion

• development of coastal functions (recreation)

MOOC coastal interventions

Break

MOOC coastal interventions: recap

• Main problems faced along a coast:

• Interruption of alongshore transport

• Coastal squeeze

• Relative sea level rise

Coastal problems: question

• Coastal squeeze refers to (select two):

A Narrowing the shelf width

B Changing a leading edge to a trailing edge coast

C Decreasing the sediment supply to a coast

D Narrowing the dune, beach and surf zone

Coastal problems: question

• Coastal squeeze refers to (select two):

A Narrowing the shelf width

B Changing a leading edge to a trailing edge coast

C Decreasing the sediment supply to a coast

D Narrowing the dune, beach and surf zone

Coastal problems: question

• How can one resolve coastal squeeze? (select two)

A Creating enough coastal space to absorb extreme

events so that recovery is possible

B Enlarging the coastal shelf

C Increasing sand supply to the coast

D Changing a leading edge to a trailing edge coast

Coastal problems: question

• How can one resolve coastal squeeze? (select two)

A Creating enough coastal space to absorb

extreme events so that recovery is possible

B Enlarging the coastal shelf

C Increasing sand supply to the coast

D Changing a leading edge to a trailing edge coast

Alongshore transports

Alongshore currents

Alongshore transport problems

• When the alongshore transport is interrupted

• When the alongshore transport is (gradually)

changing alongshore

• Do we need to solve these problems?

To protect or not to protect?

To protect or not to protect?

What to do in case of coastal erosion ?

3a If yes: You have the possibility to give this problem to your

children 3b If no: Make a retreat policy

 observe erosion carefully

 define good set-back lines

Building codes in eroding areas

How to combat erosion?

• protection of the boundary between land and water

Different causes, different

measures

• In case of a longshore problem, solutions are:

• prevent sand leaving the section

• decrease the eroding forces

• supply the sand needed

Prevent sand from

leaving the section

North to South

Decrease the eroding forces

Offshore breakwaters

• Salients

Supply the sand needed

• Nourishments

Different causes, different

measures

• In case of a cross-shore problem, we distinguish

two cases:

• Acute erosion is erosion due to a single storm; i.e it is an

adaptation of the profile to a new wave condition

Basically it is a cross-shore problem

• Chronic erosion is erosion which takes place during a long

term; is caused by a gradient in longshore transport capacity Basically it is a long-shore problem

Acute erosion by storm surge

Dune erosion after a storm surge

Cross-shore erosion solutions

• Allow the coast to erode; after the

storm the sand will recover This requires a buffer space

• Construct an erosion barrier, and

allow erosion at the toe; this erosion may recover after some time

Erosion by sea level rise

Measures can be divided in soft

and hard solutions:

• Soft solutions are those that make use of natural

(soft) material (sand), such as nourishments,

maintenance dredging and land reclamation

• Hard solutions are those that make use of hard

material, such as seawalls, breakwaters, groins and jetties

Dutch Coastal Engineering

in the 21 st century

The Zandmotor

Combination of hard and soft

measures along Dutch coast

or northeast

Groynes

Groynes

Soft solutions

Holland Coast: context

Shortage of natural sediment

Consequence: Structural erosion

Solution: Nourishments (10-15 mln m3/yr)

Coastal retreat in Netherlands

Increase in nourished volumes

building with nature?

young dune formation

why not have nature do part

of the work

while creating new

Instead of local nourishments

Mega nourishment:

a shift in Nourishment strategy ??

• From direct protection to a feeder

strategy

(Building with Nature)

• Alongshore non uniform nourishment

strategy

Mega nourishments

Is it the way to go for the future??

• Benefits:

+ Less (frequent) nourishment

disturbance of the beach

+ Variability in the coast

(good for nature)

• Drawbacks:

- Uncertain development

Pilot Project ‘De Zand Motor’

‘Hook’ altenative

70 M Euro

21 M m3 of sand

Design

• Pumping sand ashore

Construction Techniques

15-03-2011

Construction, first 6 weeks

28-03-2011

Actual development

July 2011

Jan 2012

March 2012

Monitoring the Zandmotor

Summary of 2 years of

development

• 1.14 million m 3 of sand is moved north

• 0.68 million m 3 of sand is moved south

• 0.74 million m 3 is moved outside measurement area (long shore and/or cross shore)

of the nourishment project

Zandmotor is Dutch !!

problem Big Dutch dredging companies and large amounts

of sand available

itself

(socio-economic & institutional aspects)

Break

Summary: coastal problems

• Main problems faced along a coast:

• Gradient in alongshore transport  erosion/accretion

• Coastal squeeze  cross shore erosion

• Relative sea level rise  coastal retreat

Purposes of coastal interventions

• Navigation:

• development of channels and ports

• Ecological and societal functions

• control of shoreline erosion

• development of coastal functions (recreation)

• Safety (lecture by Prof Jonkman)

• defence against flooding by storms, tides and

tsunamis

2nd Maasvlakte and sand engine

2nd Maasvlakte port expansion

2 nd Maasvlakte port expansion

• Port of Rotterdam expansion to accommodate large vessels

• No room in existing port

• Large reclamation in North sea(240 mln M3 sand)

• Combination of hard and soft sea defence

2 nd Maasvlakte port expansion

Stone breakwater

2 nd Maasvlakte port expansion:

breakwater north

2 nd Maasvlakte port expansion

sand dunes southwest

Cuba, port of Batabano

Example: Cuba, port of Batabano

sures

What happened?

Example: Cuba, port of Batabano

How to solve this issue?

Example: Cuba, port of Batabano

• Short term solution:

dredging

• Long term solution:

combination of breakwaters

will reduce the accretion in

the harbour significantly

and create a bypass

project are reduced when

choosing long term solution

Coastal development: palm island

Coastal development: world

Coastal development: Hong Kong

International airport

Example: beach creation on Curacao

Example: beach creation on Curacao

• How would you create a

sandy beach?

Example: beach creation on Curacao

Reduce wave action with offshore

breakwaters and create beach with nourishments

Example: beach creation on Curacao

Example: beach creation on Curacao

Safety: Storm surge barriers

What has happened?

What has happened?

aground

stranded ship on land

reduced wave heights

What has happened?

aground

stranded ship on land

reduced wave heights

• Any questions?

Thank you