Chapter 1 introduction to coastal engineering and management strategies

CHAPTER 1: INTRODUCTION TO
COASTAL ENGINEERING AND
BEACH PROCESSES
DR. MOHSIN SIDDIQUE
ASSISTANT PROFESSOR
1
0401444 - Coastal Eng.
University of Sharjah
Dept. of Civil and Env. Engg.

COURSE OUTLINES*
Chapter 0: Introduction to the course
Chapter 1: Introduction to coastal engineering and
management
Chapter 2: Analysis of waves and tides
Chapter 3: Linear wave theories
Chapter 4: Coastal beach processes and
management strategies
Chapter 5: Introduction to coastal structures and
design
Chapter 6: Special topics by students**
* This is tentative and may change during the semester
**Student presentations
2

BOOKS
Text Book:
Robert M. Sorensen, Basic Coastal Engineering, 2nd Edition,
Reference Books:
Robert G Dean and Robert A Dalrymple, Water Wave Mechanics
for Engineers and Scientists, world scientific
Coastal Engineering Manual of US Army Corps of Engineers
3

INTRODUCTION
•Coastal
• Zone where the land meets the sea, region of indefinite width that extends
inland from the sea to the first major change in topography.
• Shores that are influenced by wave processes (oscillatory flow dynamics)
• Bays, and lakes, and estuaries, including that part of rivers subject to the
ebb and flow of the tide. (rivers, primarily influenced by unidirectional
currents, are not included).
4

INTRODUCTION
•Coastal Engineering
• Composite of many physical science and engineering disciplines which
apply to the coastal area, including geology, meteorology, environmental
sciences, hydrology, physics, mathematics, statistics, oceanography,
marine science, hydraulics, structural dynamics, and naval architecture.
• Primary Areas: Harbor works, navigation channel improvements, shore
protection, flood damage reduction, and environmental preservation and
restoration.
• Requires the rational interweaving of knowledge from many technical
disciplines to develop solutions for problems associated with
natural and human induced changes in the coastal zone
the structural and non-structural mitigation of these changes
the positive & negative impacts of solutions to problem areas on the
coast.
5

INTRODUCTION
•Coastal Engineering
• The Coastal Engineer must consider the processes present in the area of
interest such as:
Environmental processes (chemical, ecological).
Hydrodynamics processes (winds, waves, water level fluctuations, and
currents).
Seasonal meteorological trends (hurricane season, winter storms).
Sediment processes (sources, transport paths, sinks, and
characteristics).
Geological processes (soil and strata characteristics, stable and
migrating sub-aerial and sub-aqueous features, rebounding or
subsiding surfaces).
Long-term environmental trends (sea level rise, climate change).
Social and political conditions (land use, development trends,
regulatory laws, social trends, public safety, economics).
6

INTRODUCTION
•Coastal Science
• This field is a suite of interdisciplinary technologies applied to
understanding processes, environments, and characteristics of the
coastal zone.
• Coastal Engineers use these understandings to develop physical
adaptations to solve problems and enhance the human interface with the
coast.
7

BEACH PROFILE AND TERMINOLOGIES
8

Beach profile terminology (Coastal eng. manual)
BEACH PROFILE
(Continental
shelf)
9

Sand Dune: A dune formed of sand
Scarp: elongated and comparatively steep slope separating flat or gently
sloping areas on the seafloor or on a beach
Berm: nearly horizontal portion of a beach with an abrupt face, formed
from the deposition of material by wave action at high tide
Berm crest: ridge marking the seaward limit of the berm
Low Tide Terrace: A flat zone of the beach near the low water level
Step: The nearly horizontal section which more or less divides beach
from the shoreface
Longshore Bar: A sand ridge or ridges, running parallel to the shoreline
and extending along the shore outside the trough
Trough: A elongate depression or series of depressions extending along
the lower beach or in the offshore zone inside the breakers
10
MS2
MS4

MS2 Coastal Processes with eng applications by Dean Dalrymple
Mohsin Siddique, 18-Jul-17
MS4 page 6
Mohsin Siddique, 18-Jul-17

Mean low water: The average height of the low water over a 19-year
period.
Mean High water: The average height of the high waters over a 19
years period.
Coastline: The line that forms boundary between coast and shore.
Commonly, the line that forms boundary between land and water, esp.
the water of a sea or ocean.
Shore: A narrow strip of land in immediate contact with sea, including
the zone with high and low water lines.
Beach: The zone of unconsolidated material that extends landward from
the low water line to the place where there is marked change in material
or physiographic form, or to the line of permanent vegetation. The
seaward limit of a beach – unless otherwise specified- is mean low water
line. A beach includes foreshore and backshore.
11

Backshore: The zone of the shore or beach laying between foreshore
and the coastline comprising berm or berms and acted upon by water
only during several storms.
Foreshore: The part of the shore, laying between the crest of the
seaward berm (or upper limit of a wave wash at high tide) and the
ordinary low-water marks, that is ordinarily traversed by the uprush and
backrush of the waves as the tides rise and fall. (i.e., a zone between
mean high water and mean low water)
Shoreface: The narrow zone seaward from the low tide shoreline,
covered by water, over which the beach sands and gravel actively
oscillate with changing wave conditions.
Nearshore: (1) An indefinite zone extending seaward from the shoreline
well beyond the breaker zone. (2) The zone which extends from the
swash zone to the position marking the start of the offshore zone,
typically at a water depth of the order of 20m.
BEACH TOPOGRAPHY AND TERMINOLOGIES
12

Swash zone: The zone of wave action on the beach, which moves as
water level vary, extending from the limit of run-down to the limit of run-
up.
Surf zone: The zone of wave action extending from the water line out to
the most seaward point of zone (breaker zone) at which wave
approaching the coastline commence breaking, typically in water depths
of between 5 to 10m.
Breaker zone: The zone within which waves approaching the coastline
commence breaking.
Breaking: Reduction in wave energy and height in the surf zone due to
limited water depth
13
MS2
MS4

THE BEACH AND THE NEARSHORE
http://www.longbeachislandjournal.com/
14

NEARSHORE PROCESSES
Waves
• Shoaling
• Breaking
• Reflection
• Refraction
• Diffraction
Currents
• Longshore
• Rip
Mass transport
• Deposition
• Erosion
15

WAVE PROPAGATION
0=
∂
∂
+
∂
∂
x
P
t
η
0....
)/( 2
=++
∂
∂
+
∂
∂
+
∂
∂
brF
x
gd
x
dP
t
P η
Breaking Criterion:
Boussinesq Eq. + Surface roller model
Madsen et. al. (1997)
Simulation of wave propagation on sloping beach (Mohsin, 2011)
16

NEARSHORE PROCESSES
Conceptual drawing of cross‐shore sediment processes in the near‐shore region (Zandan, 2016)
Shoaling: Increase in wave height due to decrease in water depth
Breaking: Reduction in wave energy and height in the surf zone due to limited water depth
(Collapse of wave crest over its front face)
Wave transformation: Change in wave energy due to action of physical process (i.e., change in
wave form as it propagates)
17

NEARSHORE PROCESSES
• Reflection: Reflection involves a
change in direction of waves when
they bounce off a barrier
• Refraction: Refraction of waves
involves a change in the direction of
waves as they pass from one medium
to another. It is accompanied by a
change in speed and wavelength of
the waves
• Diffraction: Diffraction involves a
change in direction of waves as they
pass through an opening or around a
barrier in their path.
18

NEARSHORE PROCESSES
https://www.youtube.com/watch?v=YBERvQdztGQ&t=5s
19

NEARSHORE PROCESSES
https://www.youtube.com/watch?v=v9QSmdRhfDA
20

The beach and nearshore zone of a coast is a region where the forces of
the sea react against the land.
Motion of the sea supplies energy to the system and the shore absorbed
the energy
Because of complex physical interaction of air, water, and land, coastal
zones are unique, very complex and difficult to understand.
Coast of Collaroy, Australia
21

The beach and nearshore zone of a coast is a region where the forces of
the sea react against the land
Motion of the sea supplies energy to the system and the shore absorbed
the energy
Because of complex physical interaction of air, land and water, coastal
zones are unique, very complex and difficult to understand
The motion of sea which contribute to the beach and nearshore physical
system include:
• Waves,
• Tides,
• Currents,
• Storm surges and
• Tsunamis
(sea forces)
22

Waves: are traveling repeating forms of alternative highs and lows called
wave crests and wave trough- induced by wind
Sea waves are random in nature
Wave classification
23

Tides: These are created by gravitation forces of the Moon and to lesser
extend, the Sun. Tide motions of water masses are a form of very long
period wave motion, resulting in a rise and fall of water surface at a
point. There are normally two tides per day, but some localities have only
one per day. Tide constantly change the level at which waves attack the
beach.
24

https://www.youtube.com/watch?v=budXQlGL8Dc

Currents: When water in one area becomes higher than water in
another area, water from the higher elevation flows towards the lower
level, creating a horizontal movement of ocean water called current.
Currents can be caused by water elevation due to wind, wave breaking,
and river discharge.
www.geography.hunter.cun
26

Surface currents and storm surge: Wind creates currents as it blows
over the surface, producing stress on surface water particles and starting
the movement of the particles in the direction in which the wind is
blowing, thus surface current is created.
When the surface current reaches a barrier, such as coast, water tend to
pile up against land. Strong winds create higher pile up of water (called
wind setup or storm surge).
The height of storm surge depends upon wind speed, direction, fetch,
atmospheric pressure, offshore bathymetry, and nearshore slope.
27

https://www.youtube.com/watch?v=b4ZhjwbNTXk
28

Longshore current: When waves approach the beach at an angle, they
create a current in shallow water parallel to the shore known as
longshore current.
Rip current: longshore current, under certain conditions, may turn and
flow seaward in what is known as a rip current.
www.ec.gc.ca
29

Tsunamis: The are waves created by earthquakes or other tectonic
disturbances on the ocean bottom. These long-period waves can travel
across entire ocean at speeds exceeding 800 km/hr. Tsunamis can
cause extensive damage at times, but fortunately major tsunamis do not
occur frequently.
30

The areas most directly affected by the forces of sea are the beach and
the nearshore zone regions that experience full impact of the sea energy.
Consequently, beach sediment moves alongshore by the wave and
currents. This process is called longshore transport and it’s a continuous
process and great volumes of sediments may be transported.
31

DYNAMIC BEACH RESPONSE TO SEA
Littoral transport: movement of the sediment in the nearshore
zone by waves and currents.
It is divided into tow general classes:
1. Longshore transport (transport parallel to the shore)
2. Onshore-offshore transport or cross-shore transport
(transport perpendicular to the shore).
The material that is transported is called littoral drift.
32

Boston Science Museum Wave Flume

Beach Sediment: Ranges from fine sand to cobbles
Composition:
• Weathered mountain rocks (sand) supplied by rivers and streams
• Fragments of coastal formation
• Sediment from deeper water
• Marine shell fragments,
• Coral reef fragment, and
• Volcano material
Clays and silt usually do not exist on ocean beaches
34

Beach Characteristics:
These are usually described in terms of:
Average size of sand particles, range and distribution of sizes, sand
composition,
elevation and width of berm, slope or steepness of the foreshore, the
existence of a bar and the general slopes of the inshore zone fronting
the beach.
Generally, the larger the sand particles the steeper the beach slope.
35

Barrier island: These are important part of the physical system in some
areas. The are long narrow island or spits laying parallel to the mainland.
Tombolo is a deposition landform in which an island is attached to the
mainland by a narrow piece of land such as a spit or bar.
36

Lagoons: The area shallow bodies of water separating the barrier beach
from the mainland.
The are usually connected to the sea by narrow channels through tidal
current flow. These provide a habitat for a wide variety of wildlife and
many lagoons serve as safe harbors and navigation water ways.
Inlet: It is the narrow opening between the lagoon and the sea.
Blue Lagoon (Oludeniz Beach) TurkeyAl Khaled Lagoon Sharjah
37

The beach constantly adjust its profile to provide most efficient means of
dissipating incoming wave energy. Although an equilibrium is sometimes
reached between beach and the sea, the “peace” is short lived and the
“battle” soon begins a new.
There are two general types of dynamic beach response to wave motion:
1. Response to normal conditions: It prevails most of the time and
the wave energy is easily dissipated by the beach natural defense
system
2. Response to storm conditions: In storm conditions, the coast must
responds with extraordinary measures such as sacrificing large
section of beach and dune. In time beach may recover but often not
without permanent loss
38

Ref. Shore protection manual 39

https://www.youtube.com/
40

Beach and dune recovery from storm attack
Following a storm there is return to more normal conditions which are
dominated by low long swells.
The wave transports sand from the offshore bar build during the storm
and place the material on the beach.
Wind then transport the sand onto the dunes where it is trapped by the
vegetation.
In this manner the beach begins to recover from the storm attack.
The rebuilding process takes longer than short span of erosion during
storm event.
Sometime full recovery of the beach never occurs because sand is
deposited too far offshore during the storm to be retuned to the beach by
normal wave conditions.
41

Effects of Inlets on Barrier Beaches:
Inlets may have significant effects on adjacent shores by interrupting the
longshore transport and trapping onshore-offshore moving sand.
During ebb-tide (lowest tide), sand transport to the inlet by wave is
carried seaward a short distance and deposited on an outer bar. When
the bar becomes large enough, the waves start to break on it, moving
the sand over the bar back towards the beach.
During floodtide, when the water flows through the inlet into the lagoon,
sand in the inlet is carried short distance into the lagoon and deposited.
This process creates inner bars. Later ebb flows may return some of the
material in these shoals to the ocean but some is always lost from the
system
In this way, tidal inlets store sand and reduce the supply of sand to
adjacent shore.
42

Beach Stability:
Although a beach may temporarily eroded by storm waves and later
partly or wholly restored by swells, and
erosion and accretion patters may occur seasonally,
the long-range condition of the beach –eroding, stable, accrediting
(deposition)—depends on the rate of supply and loss of littoral material
(sediment).
The beach is considered stable when the long-term rate of supply and
loss are equal. Thus, conservation of sand is an important aspect of
shore protection.
43

COASTAL ZONE: USES AND ISSUES
USES:
Residential, Recreational
Industrial (Shipping, Transportation)
Military
Commercial (Fishing, Mining)
These uses drive engineering requirements …
Problems (existing/future) and Issues:
Sea Level and Tectonics
Beach sand budgets
Coastal erosion / armoring
Public Access
Beach Nourishment
Urban Ocean
Harbors and dredge disposal
Marine minerals and energy resources
Management
44

CAUSES OF SHORELINE EROSION
45Ref. Shore protection manual

46Ref. Shore protection manual

47
Ref. Shore
protection
manual

SHORE PROTECTION/MANAGEMENT STRATEGIES
Five generic strategies are
involved in coastal defense
1. Abandonment
2. Managed retreat or realignment,
which plans for retreat and adopts
engineering solutions that
accommodate natural processes of
adjustment
3. Armoring by constructing seawalls
and other hard structures
4. Construct defenses seaward of the
coast
5. Adapting vertically by elevating
land and buildings
The choice of strategy is site-specific, depending on pattern of sea-level change,
geomorphological setting, sediment availability and erosion, as well as social,
economic and political factors.
Management strategies are physical management of the coast to control natural
processes such as flood and erosion.
48
wikipedia.org

49
Managed retreat is an alternative to constructing or maintaining coastal
structures. Managed retreat allows an area to erode. Managed retreat is often a
response to a change in sediment budget or to sea level rise. The technique is
used when the land adjacent to the sea is low in value.
Holding the line typically involves shoreline hardening techniques, e.g., using
permanent concrete and rock constructions.
In some cases a seaward strategy can be adopted. An upside to the strategy is
that moving seaward (and upward) can create land of high value which can bring
investment.
Limited intervention is an action taken whereby the management only
addresses the problem to a certain extent, usually in areas of low economic
significance.

50
Management strategies are physical management of the coast to control natural
processes such as flood and erosion.
Construction Techniques:
Soft Engineering:
Soft engineering options make use of natural systems. These are often less
expensive than hard engineering options. They are usually more long-term
and sustainable, with less impact on the environment.
Hard Engineering:
Hard Engineering options involve construction of coastal structures.
These tend to be expensive, short-term options. They may also have a high
impact on the landscape or environment and be unsustainable.
These fall in two classes:
1. Structures to prevent wave from reaching harbor area
2. Manmade structures to retard the longshore transport of littoral drift (sediment)
https://en.wikipedia.org/wiki/Coastal_management#cite_note-auto-3

51
Soft Engineering:
Soft engineering options make use of natural systems. These are often less
expensive than hard engineering options. They are usually more long-term
and sustainable, with less impact on the environment.
Beach nourishment:
Beach reprofiling:
Dune regeneration:
Offshore reef:
Managed retreat:

55
Hard Engineering:
Hard Engineering options involve construction of coastal structures.
These tend to be expensive, short-term options. They may also have a high
impact on the landscape or environment and be unsustainable.
Examples of coastal protection structures:
Groynes
Sea wall
Gabions
Revetment
Armor layer/riprap
Breakwater

CONSERVATION OF SAND
Because the sand is diminishing resource in many coastal areas, its
conservation is an important factor in the preservation of our coastal
areas and must be included in long-range planning.
Sand from streams and rivers was once available in abundance by
natural, however, watershed development has significantly reduced the
supply of sand to coasts
Nature provides extensive storage of beach sand in bays, lagoon, estuaries,
offshore area and dunes that may be used when balance is disrupted
however it my incur heavy cost.
Mechanical techniques (sand bypassing, sand dredging) may be useful
Through careful planning, adequate management and sound engineering, it
will be possible to do the job of protecting coastal areas properly and
economically
62

REFERENCES
Coastal engineering manual, 2002
Shore protection manual, 1984
Wikipedia
etc
63

Chapter 1 introduction to coastal engineering and management strategies

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