10. Sea Wall (page8,Q2d)
• The sea wall is a retaining wall built on
and parallel to coast
• It is made of concrete and rocks and can
be sloping or vertical
• It absorbs the energy of waves and
reflects the waves from the coast to
reduce the effects of strong waves. This
will cut down erosion
11. Problems with Sea Walls
• But it has a problem.
• It does not reduce the energy of waves. It
only reflects it to the area beneath and in
front of the wall. This will cause the beach
material at this area to be eroded and
removed
• The bottom of the wall is undercut, and will
weaken and collapse. The wall will need
to be repaired and replaced.
16. BUILDING BREAKWATER & ITS EFFECTS
Concrete / rock structure built parallel to coast some distance away
17. BUILDING BREAKWATER & ITS EFFECTS
Concrete / rock structure built with one end attached to the coast
18. Breakwaters
• Break the force of the
waves some distance
from the coast
• Reduce erosion along
the coast
• Calm waters behind
the breakwater caused
deposition and
formation of beach
• Erosion in areas not
protected by the
breakwater
22. Breakwaters
• Breakwaters are made of rocks and concrete
• The most common type of breakwater is built
parallel to and some distance from the coast
• Breakwaters break the force of waves some
distance away from the coast. When waves hit
the breakwaters, they will lose their energy and
there will be less erosion.
• The strength of the waves behind the
breakwater is reduced so deposition takes place
and a beach is formed behind the breakwaters.
23. Problems with Breakwaters
• The problem with breakwaters is erosion will
take place on the part of the coast that is not
protected by the breakwater.
• (CONCLUSION – Need to give conclusion
because this is level marking question)
Therefore I conclude that all the methods help to
reduce erosion. However, they are not totally
effective because all of them have some
problems.
25. BUILDING GROYNE & ITS EFFECTS
Perpendicular structure
to stop sediment carried
by longshore drift
Sediment deposited on side of groyne facing longshore drift – builds up
beach
26. BUILDING GROYNE & ITS EFFECTS
Erosion and no supply of sediments behind groyne
33. Groynes
• Built at right angles to the sea – trap
sediments on the side facing the
longshore drift – stops the removal of
sediments by longshore drift – build up a
beach
• Protects existing beaches behind the
groyne from erosion
• Protects cliff behind groyne from wave
erosion
34. Problem with Groynes
• Beach on the other side may disappear
because there is no new addition of
sediments. Also existing sediments
removed by erosion
• The solution is to build more groynes
along the coast – but this makes it very
unattractive
42. Gabions
• Gabions are wire cages filled with crushed
rocks and piled along the shore
• They help to weaken wave energy and will
reduce or prevent erosion
43. Problems with Gabions
• The problems is they do not last very long
because they get rusty very fast. Also,
they are easily damaged because people
keep stepping on it.
• They have to be maintained regularly as
the wires can be a danger for people
walking along the beach.
• Furthermore, they look quite ugly
48. Soft Engineering Approach
• Does not involve building physical
structures – no need for regular
maintenance – so easier and cheaper to
carry out
• Also called non-structural approach
• Involves proper planning, management
and use of the coast
70. Hard vs Soft Engineering Methods
Hard Engineering Methods Soft Engineering Methods
• Some physical structure has to • Does not involve building any
be built. Requires money, physical structure. Only
manpower and technology. (eg involves the proper planning,
seawall, groyne, gabion and management and use of the
breakwater) coast as well as encouraging
• The physical structure does not minimal human interference
last very long and needs to be along the coast. So saves a
regularly maintained (eg the wire lot of money. (eg stabilising
cages or gabions will rust and dunes)
must be changes regularly) • As it involves educating people
• Protects only one part of the on how to use the coast, it is
coast, but it creates new more long term
problems elsewhere along the • It is environmentally friendly
coast (eg breakwaters only and beautifies the environment
protect the coast behind it) (eg mangrove trees are
• May cause harm to humans (eg protected so that their roots
gabion are steel cages that have will trap the sand)
sharp edges…)
71. • Level Marking
• Eg Do you agree that gabions are the only
measures used to protect the coast from
erosion?
Explain gabions
3 others – hard and/or soft methods
72. • Assess the effectiveness of hard engineering
methods to protect the coast. (8 – Level
Marking)
Intro- Hard engineering methods are effective only
to a certain extent because it has advantages as
well as problems.
Para 1- Eg Describe what seawalls are, how it
helps and its problems.
Do the same for 3 other methods
Conclusion- Therefore all the methods have
advantages and problems and are not totally
effective.
73. Video on Coastal Erosion
• http://www.youtube.com/watch?v=zUh3WeilFN4
• Pay attention to what the video says about Coastal
Erosion.
74. What factors are identified in the
video?
[Deposition]
(1) Strength of waves
[4 Processes of Coastal Erosion]
Factors:
1. Geology – type of rock present
75. Video on Coastal Management
• http://www.youtube.com/watch?
v=HiNGGwRfdMU
