Embankment

An overview of Embankment

3. An embankment is an artificial barrier that
typically is used to hold back water or to
support a roadway, railway, or canal.

It is a ridge to prevent water from passing
beyond desirable limits.

These man-made mounds mainly consist of
stones, rocks, and earth.

Most have sloping sides, much like small hills.
Generally, embankments are longer than they
are in height.

8. The Place Embankment along the Neva River in
Saint Petersburg, Russia

9. The Embankment along the Daniub River in
Europe

10. The Embankment along the DEE River in North
Wales, England

11. Eagle eye view: The Place Embankment
along the Neva River in Saint Petersburg,
Russia

12.  To hold back water in order to prevent
flooding from seas, lakes, or rivers onto
adjacent land.

Typically strong barriers provide
protection to lower-lying grounds by
acting as a levee, as well.

Helps to confine the movement of
water by allowing it to flow faster and
higher without overflowing.

13.  A transportation embankment usually is
used to support a roadway, canal or
railway by keeping land flat or straight and
uninterrupted.

It also may be used to support lowlands,
such as valleys, that may need to be
crossed.

Most embankments are built so as to be
immune to surface erosion.

(CONTD.)

14. An embankment may be either
earth-filled
Or,
rock-filled.

An earth-filled barrier usually is the
simpler of the two, consisting mainly
of earth and natural materials.

15. A rock-filled barrier generally is
made up of more granular
components, consisting mostly of
large varieties of rocks, stones, and
other fragmented particles.
Rock-filled mounds usually are more
ideal to cover wider areas.

(CONTD.)

16. Fig: The river bank of the Brahmaputra river in a
village in the Kamarjani Union

17. (Geotextiles
are permeable
fabrics which,
when used in
association
with soil, have
the ability to
separate,
filter,
reinforce,
protect,
or drain )
Components of an embankment:

18. CONSTRUCTION OF EMBANKMENTS:
EARTH CUTTING

19. BREACHING OF EMBANKMENTS

20. EMBANKMENT UNDER CONSTRUCTION

21. Embankment condition after rainy season.
Displacement
of cc block

23. x

26. Map Showing
existing
embankments
in Bangladesh

27. Notable Embankments at a glance:
Brahmaputra Right Bank
Embankment

Gumti River Embankment

Khowai River Embankment

28. Brahmaputra Right Bank Embankment:

Brahmaputra
right bank
embankment
Brahmaputra view
from satellite

29. Brahmaputra Right Bank Embankment:
One of the first embankments
constructed in 1960s to provide flood
protection to about 230,000 ha lying on
the western side of the Brahmaputra-
Jamuna and Tista rivers.
It is 217 km long and extends from
Kaunia in Rangpur at the northern end
up to Bera upazila in Sirajganj district at
the southern end.

30. Brahmaputra Right Bank Embankment:
Construction of the embankment
started in 1963 and was completed in
1968 at a cost of about Tk. 80 million.
The average height is 4.5m, crest
width 6m and side slope 1:3 on both
sides.
The embankment has been under
constant threat of erosion by the
Jamuna river and needs relocation
further away from the riverbank.

31. Gomti River Embankment
Gomti River
Embankment

32. Gumti River Embankment:
 located in Comilla district

Comprises 67 km of embankment
on the left bank of the river Gumti
from Katak Bazar and 64 km on
the right bank from Golabari up to
Gauripur of Daudkandi.

33. Khowai River Embankment
Khowai River
Embankment

34. Khowai River Embankment:

Lies in HABIGANJ district and

Provides flood protection to 25,790 ha of land.

This 40 km embankment on the right bank of
the river Khowai extends from Habiganj to
CHUNARUGHAT and 47 km on the left bank up to
Rajabazar.

35. Dhaka-
Narayanganj-
Demra (DND)
Project

36. DND PROJECT
Located between the cities of Dhaka and
Narayanganj and bounded by the Buriganga and
the Shitalakshya river.

It was started in 1964 and completed in 1968
at a cost of Tk. 22.9 million.

 A dual purpose pumping station is located at
Shim rail having a total capacity of 4.2 cusec. The
project provides flood control for 4,860 ha,
irrigation for 6,070 ha, pumped drainage for
4,860 ha and gravity drainage for 2,470 ha of
land.

37. •But as the project is
located close to
Dhaka city,
urbanization is taking
place rapidly. So the
initial objective has
been distorted.
•The area gets clogged
in the rainy season.
HAZARDS CAUSED BY DND PROJECT

38. Nearly two million people have
become marooned as unplanned
urbanization left the rainwater trapped
inside the Dhaka-Narayanganj-Demra
Protection Embankment.

The urbanization, which is taking
place rapidly in the DND irrigation
project, posed a severe threat to the
project as well as to the people in the
area.
HAZARDS CAUSED BY DND
PROJECT

40.  CEP Covers the coastal districts of Bangladesh
and includes Cox's Bazar, Chittagong, Feni,
Noakhali, Lakshmipur, Bhola, Barisal,
Patuakhali, Jhalokati, Barguna,Pirojpur, Khulna,
Satkhira and Bagerhat districts.
The Coastal Embankment Project (CEP)

The project was implemented between
1961 and 1978 by the Bangladesh water
development board in two
phases.

BACKGROUND:

41. The Coastal Embankment Project (CEP)
Within the CEP more than 4,000 km of
embankment and 1,039 drainage sluices
have been constructed.
BACKGROUND: (CONTD.)
Phase I comprises some 92 polders
providing protection to one million ha of land
Phase II consists of 16 polders covering
another 0.40 million ha. Polder is a Dutch
word meaning an area enclosed by dikes.

42. The Coastal Embankment Project (CEP)

Main Purposes:
The CEP comprises a complex network of
dikes and drainage sluices and was the first
comprehensive plan for providing protection
against flood and

To prevent saline water intrusion in the
coastal area.

43. The Coastal Embankment Project (CEP)

Within the CEP more than 4,000 km of
embankment and 1,039 drainage sluices
have been constructed. Such as_

Sea dike embankment

Interior dike embankment

Marginal dike embankment

44. The Coastal Embankment Project (CEP)


 Typical dimensions of three types of
embankments are as follows:
Embankment
type
Side slope Crest
width
(m)
Freebo
ard (m)
Set
back
distanc
e (m)
Country
side
Sea side
Sea dike 2:1 7:1 4.2 1.5 75
Interior dike 2:1 3:1 4.2 0.9 50
Marginal dike 2:1 2:1 2.4 0.9 40

45. The portion of Bangladesh map
showing Coastal Embankment protected area
The Coastal
Embankment
Protected Area

46. The Coastal Embankment Project (CEP)

More than 4,000 km of
embankment and 1,039 drainage
sluices have been constructed in the
Coastal area.
providing protection against flood
and saline water intrusion in the
coastal area

47. The Coastal Embankment Project (CEP)

oThese embankments are intended to protect
land from tidal inundation but cannot prevent
overtopping and damage from cyclonic surges
and tidal bores.

oIn addition to increased agricultural
production, these embankments have provided
good road communication and contributed
towards improvement of the overall socio-
economic condition in the coastal zone.
(CONTD.)

48. Embankment Erosion

The instability in river regime coupled with
huge discharge and sediment load cause
erosion, scouring and also deposition, and
thus a chain action proceeds. This is almost a
recurring phenomenon. As per the latest
information available from BWDB, it is found
that 441 projects/sub-projects are either fully
or partially damaged due to the severe floods
of 1998. The total estimated cost of the
rehabilitation works is about US$143.17
million.

50. Embankment
Collapse of
Embankment

51. River No. of location of
bank/embankment
erosion
Length of erosion
(km)
Brahmaputra-
Jamuna
41 162.50
Ganges-Padma 26 94.0
Meghna 8 72.0
Teesta 11 34.90
Minor river 112 92.30
Flashy river 75 23.0
Tidal river 32 85.80
Total 305 565.10
Main areas of erosion in Bangladesh8

52. Rainfall impact (from both the regular
monsoon rains and torrential rains)

53. Wave action (daily/periodic and
created by constant wind):
 Tidal waves cause damage to the
embankments located too near to the
sea.
A severe hydraulic load is steadily
exerted on the toes and slopes and
causes
erosion.
CAUSES OF EROSION (Contd.)

54. Cyclonic storms in the coastal zone
(occurring repeatedly) act upon the
water surface, causing it to advance
towards the shore with enormous
hydraulic loads.
The waves thus formed eventually hit
the embankment toe and slopes.

55. Creating force
towards
Embankment

56. Turbulent water currents (mainly in
rivers and at coastlines):


·

57.  The high velocity flow of water
associated with vortex motion in rivers
and estuaries often causes erosion of
the banks by undermining, and the
eventual collapse of the embankment
threatens unless protective measures
are taken.
Source: Bangladesh Meteorological Department

·

58. The presence of continuous borrow-
pits on a river:

59. · The presence of continuous borrow-
pits on a river or seaside induces
undercutting of the embankment toes
and slopes due to complete inundation of
the riverbank or seashore during the
monsoon. The borrow-pits and adjoining
lowlands thus inundated induce a parallel
water current to flow along very near the
embankment toes and slopes, thereby
eroding the surfaces rapidly.

60. Human Interference:
The human interference responsible
for major embankment erosion is
quite diverse in nature and often
varies according to the lifestyle and
manner of using the embankments of
the inhabitants of different areas.

61. Human Interference:

REMOVAL OF EMBANKMENT STONES BY
IGNORANT PEOPLE

62. Excessive grazing:

Excessive grazing also make the
embankment vulnerable.

63. At different locations protective
measures are taken by any of the
following methods:
· Mattressing along the bank line
· Revetments either by boulders or by
concrete/brick boulders
· Permeable spurs
· Groynes
· Guide bundle

64. Rehabilitation of Embankments

65. · Artificial loop cut
· Porcupines
· Retards (palisade fences)
· Gravel drains
· Bandals
· Biological treatment eg.
afforestation in the foreshore and
embankment.