Coastal structures are constructed along coastlines to protect the shoreline from erosion and flooding, and to support activities like navigation and recreation. Engineers build different types of coastal structures such as seawalls, revetments, breakwaters, and groins to slow erosion, increase access, and support development. Maintaining coastal structures is important for protecting infrastructure, harbors, and coastal communities.

1. Coastal structures
Prepared by
Ahmmed Zulfiqar Rahaman

2. Coastal structures
Coastal structures can be anything human-made in the
coastal area. They are constructed principally to protect
the coast line.

3. Coastal structures
Water resources engineers build these structures
to:
 slow down or prevent coastal erosion (for example,
groins and sea walls)
 increase access or mooring sites (for example,
marinas, bridges, causeways and boat ramps)
 support coastal subdivisions (for example, power
poles and storm water pipes)

4. What will
happen if
erosion occurs in
this structure?
Lets see……

5. cliff

6. crack

7. crack

8. cave

9. arch

10. pillar

11. stack

12. stump

13. reef

14. coastal retreat

15. To escape from
such kind of
erosion by wave
action coastal
structures are
needed
indeed……

16. More than 70 percent of all coastal structures are on the
shoreline for protection from probable damage by
storm surge or coastal erosion called Shoreline
protection

17. Coastal structures
On the basis of purposes
there are different types of
Coastal structures.
They are-
 Revetments
Bulkheads & sea walls
 Breakwaters
 Groins & jetties
 Coastal bridges & piers
 Dikes & levees.

18. Coastal structures
Revetments:
Fourth Cliff -Scituate, MA
Revetments are shoreline
structures constructed
parallel to the shoreline.
Revetments are structures
placed on banks or cliffs in
such a way as to absorb the
energy of incoming water or
explosives caused by water
waves & current.

19. Coastal structures
Revetments:
 A cheaper alternative to sea walls is the revetment
Usually built for shore protection
Point Allerton -Hull, MA

20. Revetments:
Modern revetments have concrete or shaped blocks of
rip rap stone laid on top of a layer of finer material.
Riprap has the advantage of good permeability plus it
looks more natural.
Fourth Cliff -Scituate

21. Coastal structures
Revetments components:
 Armor layer: using armor
stone(high wave energy
environments) or rip-rap
stone(lower wave energy
environments)
Filter layer: using smaller stone &
geo textile fabrics to act as a filter &
under layer, which support the
armor layer
Toe protection prevents under
cutting & provides support for all
about layer materials.

22. Coastal structures
Bulkheads:
Bulkheads are vertical retaining walls to hold or prevent
the soil from sliding seaward
Timber Bulkhead -Green Harbor Entrance Channel Marshfield

23. Coastal structures
Bulkheads reduce land erosion…..
Timber Bulkhead -Green Harbor Entrance Channel Marshfield

24. Coastal structures
Bulkheads……
secondary purpose is to protect upland
areas against damage from wave action.
Timber Bulkhead -Green Harbor Entrance Channel Marshfield

25. Coastal structures
Sea walls:
form of hard and strong coastal defense constructed on the
inland part of a coast to reduce the effects of strong waves
separate the land & water.
Maumeebay (seawall)

26. Coastal structures
Granite Block Seawall
Great Brewster Island Boston Harbor Islands

27. Coastal structures
Curved or stepped sea walls are designed to enable wave
to break and to dissipate wave energy and repel waves
back to the sea.
Concrete Seawall Lynn Shore Reservation Lynn

28. Coastal structures
Sea walls:
- seawalls are vertical
structures
constructed parallel
along the shore line.
- should last 20-30
years.
Seawall near Siwash rock in
stanely park

29. Coastal structures
Breakwaters:
 breakwaters are large scale structures constructed seaward of,
& usually to the shore line
 they attempt to break incoming waves before they reach the
shoreline or the facility (e.g. marina) they are protecting .

30. Coastal structures
Single breakwaters :
Single breakwaters may
be attached or
detached , depending
on what they are being
designed to protect

31. Coastal structures
Single breakwaters :
a single detached breakwaters may protect a small
section of shoreline
a single attached breakwater may a long structure
to shelter marines & harbors from wave action.

32. Coastal structures
Breakwaters…….

33. Coastal structures
Head land breakwaters(HB):
-a series of breakwaters
constructed in an “attached”
fashion to the shoreline & angled
in the direction of predominant
waves
-the shoreline behind the
structures evolves into a natural
“crenulate” or log spiral
embayment.

34. Coastal structures
Detached breakwaters:
 detached breakwaters
are constructed away from
the shoreline, usually a
slight distance offshore
they are designed to
promote beach deposition
on their leeside.

35. Groins:
 groins are the oldest and most common shore-connected, beach
stabilization structure
they help to create or widen beaches by capturing sand moving
along the shoreline.
Mortared Stone Groin “The Five Sisters”Broad Sound
Winthrop

36. A groin is an active structure extending from shore into
sea, most often perpendicularly or slightly obliquely to
the shoreline

37. Coastal structures
Types of Groins:
 normal or straight
 inclined or angled
 submerged
Permeable
 single
groin system or field
T L or Y shaped
Rubble-mound and sand-filled bag
attracting, deflecting or repelling

38. Coastal structures
Types of groins

39. Coastal structures
Characteristic of Groins:
 they are usually made of
tropical hardwoods which are
more resistant to marine borers
and erosion.
a few are made of concrete, steel
or in more recent times large
rocks.
they are spaced about 50-100
metres apart.
may have a life of 15-20 years

40. Coastal structures
Concrete groins…….
Ukraine ( the black sea)

41. Coastal structures
Shoreline response to groins

42. Coastal structures
Jetties and piers
 a structure extended into a sea, lake, or river to
influence the current or tide or to protect a harbor
 a protecting frame of a pier
 a landing wharf
Timber Pier -George’s Island Boston Harbor Islands

43. Jetties & piers……..
Tybee

44. Jetties are shore-normal stone structures commonly
used for training navigation channels & stabilizing inlets

45. Coastal structures
Characteristics of jetties:
they prevent intrusion of long-
shore sediment transport
 they cause higher flow velocities
that scour the channel to a depth
required for safe navigation.

46. Coastal structures
Coastal bridges and piers
Biloxi bridge

47. Coastal structures
Coastal bridges and piers
Cuba bridge

48. Coastal structures
Dikes & levees
 dikes are typically earth
structures
 they keep elevated
water levels from
flooding interior
lowlands.
 sometimes they refer to
as dam

49. Coastal structures
Dikes & levees
Levees…..

50. Coastal structures
Emergency shore protection:
for emergency shore
protection gabions are used.
gabion is a metal cage filled
with rocks, about 1 metre by 1
metre square
Gabion

51. Coastal structures
Gabion:

52. Coastal structures
Gabion:
they are stacked to form a simple wall.
used to protect a cliff or area in the short term only
gabions have the advantage of ease of use and are
relatively cheap but their life span is short.

53. Coastal structures
Now-a-days X-block & Tripodal blocks are vastly used for
building such coastal structures.

54. Coastal structures
Tripodal block……

55. Coastal structures
Coastal structures in Bangladesh
Bangladesh has 710 km long coastline

56. Coastal structures
Natural calamities or storm
surge visit our country
every year
So to protect our coastline
from wave action or coastal
erosion, coastal structures
are obviously needed
Sonadia dip

57. Coastal structures
The coastal region of Bangladesh has 123 embanked
Coastal structures in Bangladesh
polders, constructed in late sixties to protect the land

58. Coastal structures
St. Martin island jetty….. Kutubdia

59. Coastal structures
Importance of coastal structures
Coastal structures are important assets for the economic health of
many coastal communities to:
Protect harbors and inlets that are important commercial and
military navigation links
Protect shore-based infrastructure
Provide beach and shoreline stability control
Stabilize navigation channels
Protect navigation, coastal communities, roadways, bridges, etc.
Provide flood protection
Provide recreational activities

60. Why should we let such coastal area
disappear…….???

61. Coastal structures
Summary
Coastal structures influence waves currents
sediment transport in the near shore
environment
A systematic approach is needed in order to
minimize negative effects