Costal protection-purpose and devices, sea wall protection-sea wall revetment, bulkhead. Dredging, dredgers-types and suitability, usage of dredged materials

1. “SEAPORT
MAINTENANCE”
1
PREPARED BY : ASST. PROF. VATSAL D. PATEL
MAHATMA GANDHI INSTITUTE OF
TECHNICAL EDUCATION &
RESEARCH CENTRE, NAVSARI.

2. COASTAL ZONE AND BEACH PROFILES
 The coastal zones have certain aesthetic and practical
advantages and this has resulted in the concentration of
recreational, residential and industrial areas in the zone.
 The important beach characteristics are:-
Average sizes of the beach sand particles.
Range and size of sand particles.
Slope and steepness of the foreshore.
General slope of the under water.

4. CAUSES OF BEACH EROSION
 Direct wave action
 Interception of littoral drift
 Sea level changes
 River mouth changes
 Anthropogenic activities
 Effect of storms and tides

5. COASTAL PROTECTION WORKS
 The shoreline is likely to undergo continuous changes due
to effects caused by various natural phenomena. Hence,
shore protection works are necessary.
 The various shore protection works are:
Sea walls
Bulkheads
Groynes
Offshore breakwaters
Revetments
Protective beaches
Sand dunes

6. SEA WALLS
These are the
structures constructed
parallel to the shore
line to develop a
demarcating line
between land area and
water area.
These are used where
land to be protected is
a developed one and
wave effects are severe.

7. BULKHEAD
These are constructed
along the shoreline to
prevent encroachment
of the sea by direct
wave action.
The walls may be
made up of timber, steel
or concrete.

8. GROYNES
These are structures
which are built to protect
the beach erosion by
trapping littoral drift.
Different types of groynes
are:-
• Permeable or Impermeable.
• High and Low.
• Long and Short.
• Fixed or Adjustable.
These are used to stabilise
the beach, to reduce the
littoral transport, to widen
a beach by trapping littoral
material, to prevent loss of
material by dividing a
beach into compartments.

9. Revetment
Offshore Breakwater
REVETMENT
It protects the land
from wave erosion. It is
constructed either of
stone, or cement
concrete ,etc,.
OFFSHORE
BREAKWATER
These protect the area
from wave action and
serve as an aid to
navigation.

10. Protective Beaches
Sand Dunes
PROTECTIVE
BEACHES
Some beaches of
suitable dimensions can
prove to be effective to
grant protection to the
adjacent upland from
the effects of waves and
tides.
SAND DUNES
These are the sand
formations along the
coast due to wind and
they prevent the
movement of tides and
waves into the areas
behind them.

11. DREDGING
 Dredging is the technique and operations of removing
material from the sea bed or a lake to increase the depth of
water.
 It makes the harbour clean enough from the suspended
materials, to make navigation suitable inside the harbour.
 Objectives of Dredging :-
 Creation of artificial depths for new harbours.
 Maintaining the navigable depths in the existing harbours.
 Providing the filler material for protection of beaches.
 Reclamation of low lying areas.
 Improving the flow capabilities of rivers.
 In the construction of sea walls and breakwater.
 Replacing unsuitable foundation materials with suitable ones.

12. CLASSIFICATION OF DREDGING
 Capital Dredging: It is the initial removal of bed material
at the time of building a harbour.
 Maintenance Dredging: After the harbour is
commissioned due to various factors silt materials will be
getting deposited and eroded in the bed so this type of
dredging is necessary.
 Sundry Dredging: If dredging is to be carried out for
reclamation or sanitation purpose.

13. TYPE OF DREDGERS
 A machine which is specially useful for removing bed
material from under water is called a dredger.
 Various types of dredgers are:-
Bucket-Ladder dredger.
Dipper dredger.
Grab dredger.
Hydraulic dredger.

14. HYDRAULIC DREDGER
BUCKET-LADDER DREDGER
-- An endless chain of buckets
-- Mounted and running round
-- Lowered or raised
-- Cutting edge

15. DIPPER DREDGER
-- Floating vessel
-- Inclined frame
-- Revolving boom
-- Dipper stick
-- Hoisting cable

16. GRAB DREDGER
-- Mechanical dredger
-- Suspended by a cable
-- Grab can be opened or closed
-- Fall by gravity

17. HYDRAULIC DREDGER
-- Soil is removed by suction
-- Sand pump is adequate
-- Rotating cutter at the end
-- System of water jets

18. USAGE OF DREDGED MATERIAL
 Worldwide millions of cubic meters of material are
removed each year from ports, harbour and waterways in
order to optimize navigation, remediation and food
management. The destination of this dredged material is
often one of the greatest challenges facing dredging project.
 Over the last few decades, however, research and
experience have shown that dredged material can be reused
and is not inevitably a waste to be disposed. When dredged
material has a purpose, it can be used, for instance, for
environmental improvements, giving the material added
value and creating a win-win situation.

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