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Performance of flood control works around Dhaka city during major floods in Bangladesh

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Dhaka city has been protected by flood protective embankments, flood walls and raised roads along with flood controlling regulators, sluices, and both temporary and permanent pump houses. This study describes the performance of various flood control works around Dhaka city and tries to find out the causes of external and internal flooding of protected Dhaka during major floods in the recent past. It has been found that flood embankment and raised road around the city functioned quite well during all floods except the1998 flood. Though the performances of three permanent pump stations were found satisfactory, temporary pumps were found poor performing. However, the flood control measures of the city has come under challenge by recent issues such as gradual increase of urban encroachments inside retention pond, fill up of low lying areas, increase of social conflicts around flood control structures etc.
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2nd International Conference on Water & Flood Management (ICWFM-2009)
PERFORMANCE OF FLOOD CONTROL WORKS AROUND DHAKA
CITY DURING MAJOR FLOODS IN BANGLADESH
Sujit Kumar Bala1, Akm Saiful Islam2, Jahir Uddin Chowdhury3, Md. Rezaur Rahman4, M.
Anisul Haque5, M. Shah Alam Khan and Mashfiqus Salehin
6 7
1 Institute of Water and Flood Management, Bangladesh University of Engineering and
Technology, Dhaka-1000, Bangladesh, e-mail: bala@iwfm.buet.ac.bd
2 Institute of Water and Flood Management, Bangladesh University of Engineering and
Technology, Dhaka-1000, Bangladesh, e-mail: akmsaifulislam@iwfm.buet.ac.bd
3 Institute of Water and Flood Management, Bangladesh University of Engineering and
Technology, Dhaka-1000, Bangladesh, e-mail: juc@iwfm.buet.ac.bd
4 Institute of Water and Flood Management, Bangladesh University of Engineering and
Technology, Dhaka-1000, Bangladesh, e-mail: rezaur@iwfm.buet.ac.bd
5 Institute of Water and Flood Management, Bangladesh University of Engineering and
Technology, Dhaka-1000, Bangladesh, e-mail: anisul@iwfm.buet.ac.bd
6 Institute of Water and Flood Management, Bangladesh University of Engineering and
Technology, Dhaka-1000, Bangladesh, e-mail: msalamkhan@iwfm.buet.ac.bd
7 Institute of Water and Flood Management, Bangladesh University of Engineering and
Technology, Dhaka-1000, Bangladesh, e-mail: mashfiqussalehin@iwfm.buet.ac.bd
ABSTRACT
Dhaka city has been protected by flood protective embankments, flood walls and raised roads
along with flood controlling regulators, sluices, and both temporary and permanent pump houses.
This study describes the performance of various flood control works around Dhaka city and tries
to find out the causes of external and internal flooding of protected Dhaka during major floods in
the recent past. It has been found that flood embankment and raised road around the city
functioned quite well during all floods except the1998 flood. Though the performances of three
permanent pump stations were found satisfactory, temporary pumps were found poor performing.
However, the flood control measures of the city has come under challenge by recent issues such as
gradual increase of urban encroachments inside retention pond, fill up of low lying areas,
increase of social conflicts around flood control structures etc.
Keywords: Dhaka city; embankment; flood wall; pump station; regulator
1. INTRODUCTION
Flood is a reality for Bangladesh. As the country is located at a floodplain delta of three major
river basins - the Ganges, the Brahmaputra and the Meghna (GBM), so every year, one quarter to
one third of the country is inundated during monsoon season through overflowing of the rivers.
However, floods of unusually large magnitude and long duration happen in the country affecting
the majority of the population of the country and severely disrupting the social and economic
activities. Such devastating floods are 1954, 1987, 1988, 1998, 2004 and 2007 and considered to
be the worst ones.
Flood 1988 was unprecedented and floodwater entered into the core places of Dhaka city, the
capital of Bangladesh, jeopardizing all important activities as a whole and compelled the policy
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makers to make flood free all important and vital places of Bangladesh. Dhaka city during flood
period always draws special attention due to its strategic importance. So, Dhaka West was given
flood protection after flood 1988. But unfortunately, protected Dhaka West was again flooded
during unprecedented flood of 1998.
Islam et al. (2002) have conducted a study on the Hydrologic characteristics of floods in 1998.
Chowdhury et al. (1998) have studied the impact of 1998 flood on Dhaka city and performance of
flood control works. Rahman et al. (2005) have investigated the hydrologic aspects of Flood 2004
in major rivers of Bangladesh and special emphasis has given on the floods of Dhaka city.
Similarly, Islam et al., (2008) carried out a study on Flood 2007. The findings of investigations on
major floods of 1998, 2004 and recent 2007 and their impacts on flood protection structures on
Dhaka city and their performances have been presented in this paper.
2. STUDY AREA
Dhaka is located in the central region of the flat deltaic plain of the three large rivers, the Ganges,
the Brahmaputra and the Meghna. The city is surrounded by distributories of these major rivers.
They are Buriganga at the south, Turag at the west, Tongi Khal at the north and Balu at the east.
Greater Dhaka city is divided into Dhaka West and Dhaka East (Figure 1).
Figure 1: Existing flood control and drainage infrastructures during 1998 flood.
A common Highway runs through the middle of Dhaka West and Dhaka East and several of its
parts are named as Mymensingh road, Pragati Sarani, DIT road and Biswa road. They were raised
after the devastating flood of 1988 to perform as road-cum-embankment. The combined area of
Greater Dhaka city is approximately 275 sq. km. (JICA, 1991). Dhaka East has an area of
approximately 119 sq. km. (JICA, 1992). So, Dhaka West has an area of approximately 156 sq.
km., which is protected from river flood by peripheral embankment as shown in Figure 1. Dhaka
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East is in the floodplain of Balu River and most of the area is low-lying and remains under water
for over half of the year, of which perhaps half is less than 2 m above mean sea level (JICA,
1992). Dhaka city is growing rapidly. The urban areas are forecast to be expanded from 200 sq.
km in 1990 to 366 sq. km by 2010 and the population is expected to reach 13.5 million by the year
2010 (JICA, 1991)
2.1 Flood control works in the study area
Dhaka West have been encircled by embankments, flood walls, raised roads to give protection
against riverine flood (JICA, 1991). Important components of flood protection measures are:
i) About 30 km of earthen embankment along Tongi Khal, Turag and Buriganga river,
ii) About 37 km of raised road and floodwalls in few locations of old Dhaka along the river
Buriganga where intensive infrastructures do not allow any further road improvement.
iii) A total of 11 regulators ( Figure 1) at the outfall of Khals to the surrounding rivers along
the embankment.
iv) 1 regulator and 12 sluice gates ( Figure 1) on the Khals at the crossing with Biswa road,
DIT road, Pragati Sarani, Mymensingh road and Railway line at Uttar Khan.
v) Three pump stations ( Figure 1) namely Kallyanpur, Goranchat Bari and Dholai Khal
pump stations and to drain out rainwater from some protected parts of Dhaka West.
They are all together called flood control structures and are supposed to keep Dhaka West free
from riverine floods, see Figure 1 (as per status of 1998). These flood control works were prepared
and rearranged based on the study of flood mitigation and storm water drainage plan in the Master
Plan for Greater Dhaka Protection Project (JICA, 1987, 1991, 1992).
3.
4.
DATA AND METHODOLOGY
3.1 Field and secondary data
Secondary information and field visits were the basis for the studies during 1998, 2004 and 2007
floods. Field visits were made to each flood control structure around the protected Dhaka West to
see in-flood functioning of the structure. Available flood data were collected from site during field
visits. Water level data at pump houses and at temporary pump stations were also collected during
field visits. The other relevant information was also recorded such as number of working pumps,
duration of pumping, pumping capacity, start date of pumping, pumping effect, management of
pumping, working condition of pumps and pump houses, etc.
3.2 Tools and techniques
Available water level data from water control structures and from pump stations have been utilized
to study performance of water control structures. Flood hydrographs were drawn to see the
pumping effect on floodwater. Photographic evidences of the impact of each flood are documented
and presented. Focus was given upon lessons learned during the flood of 1998 and their follow up
during 2004 and 2007 floods. Attention was focused upon people’s reaction upon flood control
structures around Dhaka West and their interactions with structures during flood time. Attention
was also made to new developments occurred with and around water control structures of
protected Dhaka West after 1998 flood to compare with the floods of 2004 and 2007.
PERFORMANCE OF FLOOD CONTROL WORKS
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4.1 Performance of embankment during Flood 1998
Embankment with regulators was visited during 1998 flood, when river flood level was the
highest. The flood level in the river was 1.5 to 2.0 m below the crest of flood protection
embankment. A section of about 2.2 km long between Lalbag Kellarmurkh to Shasanghat along
Buringanga River was not closed by flood protection embankment (Figure 2). Floodwater from
the Buringanga entered through this opening. The section was closed with soil filling, sand bags
piling promptly by Bangladesh Water Development Board (BWDB) with active participation of
local people. Unfortunately, the areas adjacent to raised sections of Mymensingh road, DIT road
were inundated by the intrusion of floodwater from the Balu River into Dhaka West. This
unexpected flooding was due to some unblocked culverts and unclosed regulator along the raised
roads (Figure 2). During 1998 flood, passiveness of Dhaka Water Supply Authority (DWASA),
BWDB, Dhaka city Corporation (DCC) was surfaced out and lack of coordination in between
them was clearly demonstrated in the management of the water structures. As a result, some water
control structures were remained open and areas like Maha Khali, Gulshan, Banani, Badda,
Baridhara etc. were the worst affected ones.
After field inspection and discussion with local people, it was revealed that three drainage
structures namely FS8, located over the Begunbari Khal on DIT road (Figure 1) and called as
Rampura regulator, FS5, a 10 m wide Shajadpur bridge and located on Pragati Sarani and FS4, a
30 inch diameter Khilkhet pipe culvert located at Khilkhet and Nikunja served as flood carrying
channels (Figure 1 and Figure 2). Structure FS4 remained open for the whole period of flood and
caused flooding in Nikunja, adjacent to airport and cantonment areas. The locations of entry points
of floodwater in Dhaka West during 1998 flood through numerous openings are shown in Figure
2. Structures FS9, FS10 and FS11 on Biswa road were liable for partial flooding in Rajarbag,
Gopibag, Fakirapul area but they were quickly closed.
Lessons learned: The raised road cum embankment was upgraded after 1988 flood but design
height was not adequate to tolerate the flood of 1998. Moreover, coordinated efforts from the
organisations like DWASA, BWDB and DCC were not observed. As a result, some culverts and
regulators along the raised roads were left open in the beginning of the flood of 1998.
4.2 Performance of embankment during Flood 2004
Flood control structures during this flood functioned quite well. Some structures namely FS11,
FS10, FS9, FS7 and FS6 were fully abolished during the upgrading of the road cum embankment
after the flood of 1998. The coordination between DWASA, BWDB, and DCC for operation and
regulation of water control structures was better than that of the flood of 1998. Their in time
operation, regulation and coordination for closing of regulator and sluice gates stopped fully the
intrusion of the floodwater into Dhaka West. Increase of slum habitation, growth of whole-sale
markets like vegetables and fish, deposits of municipal garbage, boost of civil settlements, etc.
were observed at some locations near Kallayanpur Pump Station. A huge number of dredgers at
river side along the embankment after Ashulia road were observed for filling up of low-lying areas
of protected Dhaka. Some water intrusion was noticed only through the structure S11 at Lalbag.
The incomplete 2.2 km embankment from Kellarmukh to Buriganga Bridge-2 was found
completed and Dhaka West was free from river flooding.
Lessons learned: Flood protective embankment worked very well to stop any flood intrusion from
the river side. BWDB, DWASA, DCC were more coordinated during flood of 2004. But condition
flood protection embankment has deteriorated due to settlement activities around it. Internal
flooding is surfacing out as one of the disasters for protected Dhaka West. 2004 flood was
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accompanied with internal drainage congestion along the areas like Gulshan, Banani, Motijheel
commercial areas, BUET area, and etc. of Dhaka West.
Figure 2: Areas flooded by river water and floodwater intrusion points during 1998 flood.
4.3 Performance of embankment during Flood 2007
The embankment functioned well and did not allow any flood intrusion. Increase of growth of
slums, public settlements, industrial complexes, and other kinds of activities are observed.
Lessons learned: Flood protective embankment is still functioning well.
4.4 Performance of regulator during Floods 1998, 2004 and 2007
A 10-vent regulator located over the Begunbari khal is called Rampura Regulator and marked as
FS8 in Figure 1. It is a very important structure for regulating gravity drainage from Dhaka West.
It also prevents flood intrusion from the Balu River through the Begunbari Khal. A major part of
Dhaka West drainage water gets accumulated at upstream of this Rampura regulator and is
regulated by this structure. At present, there are temporary pumping facilities to reduce drainage
water from inside Dhaka West to outside Dhaka East. It was reported that the gates of the
regulator were not closed at right time and flood entered inside Dhaka West during flood of 1998
(Figure 2).
During field visit of 1998 flood, it was observed that 12 out of 20 pumps of individual capacity of
5 cusec (0.142 cumec) were pumping water from inside to outside at Rampura regulator. Water
level differences between river side and protected side for Rampura regulator were plotted for
floods of 1998, 2004 and 2007 (Figure 3). It is seen that river side and protected side water level
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differences were almost same at Rampura regulator for all the mentioned floods. The regulator
was not effective to stop flood water or to drain out congested rainwater from inside of Dhaka
West.
During floods of 2004, all sluices and regulators were closed in time to prevent floodwater
intrusion. During field visit of flood 2004 on 28th July, 35 numbers of pumps out of 40 were found
on workable condition at Rampura regulator. It was also reported that pumping was started on 12th
July with only 15 numbers of pumps. Still the inside water level was not getting reduced. During
field visit on 8th August, 2004, additional 4 numbers of dredger pumps of higher capacity of 0.426
cumec and 1 dredger pump of 0.142 cumec were found at site and were in operation by turns.
Thus, water level at Rampura regulator was reduced to some extent.
During flood 2007, about 50 small pumps operated at Rampura regulator. Similarly, it was not
possible to reduce inside water level by small temporary pumps. The pumping again was an eye
wash (Figure 3). From the Figure 3 and water level curves, it is clear that inside and outside water
levels at Rampura regulator for all flood events were almost same.
The pumping experience of permanent pump house at Goranchat Bari during 2004 and 2007
showed that though the pump house has a higher pumping capacity (22 cumec), still it started
pumping quite earlier with lower inside water level and attained higher pumping effect during full
flood time and rains. So, it is our strong conviction that if pumping could be started earlier during
low inside water level with sufficient number of pumps then pumping effect could be attained
keeping water level much lower. Of course, if a large enough pumping station was provided then it
would have an impact on flood levels.
Lessons learned: Rampura regulator is an important component of flood protection structures
around Dhaka West for maintaining drainage function between Dhaka West and Dhaka East.
Experiences gained from the three major floods taught us that pumping of drainage water from
Dhaka West during flood time at Rmpura regulator is futile and eye washing. Not external
flooding but internal water logging problem in Dhaka West is getting worse for each incoming
flood and needs special attention.
4.5 Performance of large scale pumping stations during Flood 1998
During 1998 flood, there were three pumping stations in Dhaka city, namely Kallyanpur Khal to
Turag with capacity of 10 cumec, Dholai Khal at Narinda with capacity of 9.6 cumec and Dholai
Khal at Mill Barrack to Burigange with capacity of 22 cumec. Narinda pumping station was very
old with low efficiency. Dholai Khal pump station has been designed such to include the drainage
area of this Narinda pump station also. So, Narinda pump station had been dismantled by the
Dhaka city Corporation in 2002. All the three pumping stations were in operation during 1998
flood.
The Kallyanpur pump station was quite effective in draining the rainwater during 1998 flood. It
was observed that low lying areas such as Kallyanpur, Shyamoli, etc were dry. These areas
suffered from severe flooding during 1988 flood. The water level differences between river side
and protected side at the pump station are plotted in Figure 3 based on the data obtained from the
records at pump station. The water level analysis supports that Kallyanpur pump station performed
effectively during 1998 flood.
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As a result of operation of other two permanent pump stations (one at Narinda and the other at
Mill Barrack to Buringanga) on Dholai Khal, large part of Old Dhaka city was dry during 1998
flood. Water level differences at the new Dholai Khal pump station are plotted in Figure 3. This
figure also shows water level differences at the crossing of Segunbagicha Khal with Biswa road. It
is seen that the pumping station was quite able to reduce the protected side water level compared
to that in Segunbagicha Khal, which is very close to Dholai Khal pump station. It is seen from
Figure 3 that the protected side water level at the new pump station was increased suddenly on the
5th September of 1998. As per opinion of local people, an earthen bund was constructed to stop the
flow over the submerged sluice gate (FS13 in Figure 1) on the Zerani Khal. The earthen bund
suddenly collapsed resulting on rush of water.
Lessons learned: Large scale pumping house is very effective to reduce inside water level. Internal
flooding is to become a problem after flood protection of Dhaka West.
4.6 Performance of large scale pumping stations during Flood 2004
All three large pump stations were actively pumping during 2004 flood (Figure 3). Due to in time
pumping, catchment areas under pumping influence, were free from both water logging and
internal flooding. During the flood of 1998, Goranchat Bari pump station on Degun Khal was
under construction. It could function during the flood of 2004.
The effectiveness of Kallyanpur pump station may be seen from the Figure 3, where water level
differences between river side and protected side are quite high. The retarding area of Kallyanpur
pump station has been encroached through filling land and converting them into residential areas.
Significant land filling has been done in several locations around Kallyanpur pump station. The
area of the retention pond is gradually decreasing leading to the reduction of lead time of
accumulation of drainage water in the retention pond. As a result, the pumping pressure on the
existing pumping station is gradually increasing and can ultimately result in ineffective operation
of the structure. It is informed during field visit that additional one pump house would be
constructed at Kallyanpur pump station to manage this future anticipated increased drainage water.
The Dholai Khal pump station was good enough to keep the whole old Dhaka city free from
internal flooding. Figure 3 demonstrated the truth.
Field visit to Goranchat Bari pump house during 2004 flood revealed that pumping was started
quite earlier and continued keeping close observation on water level rise inside protected Dhaka as
well as on rainfall so that water level could not go beyond the control of pump house. The
approach gave good results and continuous pumping made it possible to keep inside water level
much lower than outside (Figure 3).
Lessons learned: The areas under pumping house were free from water logging inside Dhaka West
during 2004 flood. Pump house is essential for effective pumping of drainage water from inside of
protected Dhaka West. Internal flooding of protected Dhaka West during any major flood has
already become a permanent problem and needs its proper management. Encroachment of
retarding areas of respective pumping house is also a threat for the station.
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Figure 3: Difference of riverside and protected side water level during floods in (a) 1998, (b) 2004
and (c) 2007 of the surrounding major flood control works
4.7 Performance of large scale pumping during Flood 2007
During flood in 2007, the performance of Goranchat Bari pump station was very well and
pumping was also started quite early to avoid any mishap. On the other hand, Kallayanpur pump
station showed satisfactory performance during all the three major floods. The difference of water
level was always below the flooding level of that area. It was also found from the plots that it
should start pumping when water level is below 4.0 meter above datum. The permanent pump
station in Dholai Khal shows satisfactory performance during all the three major floods. Water
level difference was very high in this pump station even after a high intensity of rainfall.
Lessons learned: Large scale pump station functioned well in all floods of 1998, 2004 and 2007.
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4.8 Performance of small scale temporary pumping during Floods 1998, 2004 and 2007
A total of 66 small pumps were installed at different locations by Dhaka WASA to drain out the
accumulated water inside protected Dhaka West during flood of 1998. The capacity of each pump
was 5 cusec (0.142 cumec). The internal water was accumulated rainfall, intruded flood water and
domestic waste water. There were 20 pumps at Rampura regulator, 30 pumps at the crossing of
Segunbagicha Khal with Biswa road, 1 pump at Goran Chadbari regulator and a total of 15 pumps
along the embankment from Hazaribagh to Kellarmukh as illustrated in Figure 4.
The pumping at Rampura regulator was ineffective. The reasons have been explained earlier with
the help of observed data. The total pumping capacity was also insufficient compared to the
drainage area of Begunbari Khal at Rampura regulator. The pumping from Segunbagicha Khal
was effective. The temporary pumping at other locations along the flood protection embankment
from Hazaribagh to Kellarmukh was also moderate effective during flood in 1998.
Figure 4: Locations of pumped drainage in Dhaka West during 1998 flood.
During the flood of 2004, no flood intrusion was happened from the river side to protected side.
Major efforts were focused on how to drain out water from inside of Dhaka West. As Begunbari
Khal is the main drainage path to drain water from a vast area of Dhaka West, so in total of 70
temporary pumps (if compared with 0.142 cumec) were in operation at Rampura regulator. The
total pumping capacity was insignificant compared to the drainage area of Begunbari Khal at
Rampura regulator. Drainage of Begunbari Khal was only then effective, when the Balu River
water level was lowered i.e., gravity drainage happened. Thus, there were 70 pumps at Rampura
regulator, 16 pumps at the crossing of Segunbagicha Khal with Pragati Sarani and a total of 20
pumps along the embankment from Rayer Bazar to Kellarmukh. The pumping effect at
Segunbagicha Khal was not effective in the beginning of the flood in 2007 due to connection of
Dhaka city Corporation (DCC). Pumped water again returned into Segunbagicha Khal through the
connection. The incidence again showed that development of infrastructures by different
development organisations like DCC, DWASA and BWDB suffers from lack of coordination.
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At least 50 small pumps were operating at the Rampura regulator and 30 small pumps were
operating in Segunbagicha kjhal during the flood of 2007. Along the embankment of the
Buriganga between Dholai Khal pump station and Kallayanpur pump station, temporary pumps
were found in more than 27 locations. In these locations 1 to 4 pumps were installed temporarily
during the flood of 2007. The main purpose of these pumps was to drain out congested water
inside the embankment i.e., from protected Dhaka city.
Lessons learned: The three flood studies around Dhaka city indicated that water logging as well as
internal flooding inside protected Dhaka city during flood time is on increase. The protected
Dhaka city faces the challenge of water management not from external flooding but from internal
flooding.
5. CONCLUSIONS
The performance of three permanent pump stations at Dholai Khal, Goranchat Bari and
Kallayanpur was found satisfactory. The water levels of protected side were far below than that of
river side. On the other hand, the difference of the water level between country side and protected
side of the Rampura regulator where temporary pumps installed was close to zero during all the
major floods. Performance of the temporary pumps is insignificant and has very little effect on the
drainage congestion in flood season. It was found during field visits that urban encroachments
gradually have increased and reduced retention pond area of the Kallaynpur and Goranchat Bari
pump stations. This will enhance water logging from a small amount of intense precipitation.
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Dhaka City and Performance of Flood Control Works. Dhaka: Institute of Flood Control &
Drainage Research, Bangladesh University of Engineering & Technology.
Islam, A. S., and Chowdhury, J. U. (Eds.). (2002). Hydrological Characteristics of the 1998 flood
in major rivers, Engineering Concern of Flood. Dhaka: Bangladesh University of Engineering
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Area), FAP 8A, Main Report and Supporting Reports I and II. Flood Plan Coordination
Organization. Dhaka: Japan International Cooperation Agency.
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Coordination Organization. Dhaka: Japan International Cooperation Agency.
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Hydrologic Aspects of Flood-2004 with Special Emphasis on Dhaka City. Dhaka, Bangladesh:
Institute of Water and Flood Management (IWFM), Bangladesh University of Engineering and
Technology (BUET).
... At present, the management of flood control measures is the combined responsibility of several organizations (Table 11.1), which might create a jurisdictional impediment. In the past, lack of coordination between stakeholders resulted in a bad management of the culverts and regulators during the 1998 flood (Bala et al. 2009). Dewan (2013) noted that organizations tend to blame each other for critical failures, and are sometimes unwilling to take responsibility for the damage. ...
... Dewan (2013) noted that organizations tend to blame each other for critical failures, and are sometimes unwilling to take responsibility for the damage. However, during the 2004 flood, Bala et al. (2009) observed that the level of coordination improved and, as a result, the flood situation was managed more efficiently. Existing methods for flood mitigation are traditionally divided into two broad groups: structural and non-structural measures (Dasgupta et al. 2015). ...
... Furthermore, some open culverts 1 and unclosed regulators of the embankment facilitated water intrusion from outside. The embankment worked well during the 2004 and 2007 floods, but the condition of the protection bunds has degraded as settlements have increased and encroached onto them (Bala et al. 2009). ...
Chapter
Dhaka, the capital city of Bangladesh, is susceptible to floods because of its topography, large population, and inadequate infrastructure. Almost half of Dhaka’s population live in the low-lying and flood-prone areas, and the local communities suffer from economic stress due to flooding as well as having an absence of flood protection measures in these areas. The economic damages caused by flooding have a severe impact on national economic development and growth. Unplanned urbanization intensifies damage from flood incidents, including caused by the migration into Dhaka from rural areas as people move to the city in search of jobs and to recover from the impacts of natural disasters like cyclones, droughts, and river erosion in rural areas. This chapter outlines Dhaka’s current situation with regards to flood exposure and risks from climate change as well as summarising key measures to reduce flood risk in recent years.
... Possible solutions to the flood problem: Solutions to the flood problem in Bangladesh can be divided into two basic types: structural solutions and geologic solutions [4][5][6]13,23,31,39 . ...
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A substantial body of work supports a teleconnection between the El Niño-Southern Oscillation (ENSO) and cholera incidence in Bangladesh. In particular, high positive anomalies during the winter (Dec-Feb) in sea surface temperatures (SST) in the tropical Pacific have been shown to exacerbate the seasonal outbreak of cholera following the monsoons from August to November. Climate studies have indicated a role of regional precipitation over Bangladesh in mediating this long-distance effect. Motivated by this previous evidence, we took advantage of the strong 2015–2016 El Niño event to evaluate the predictability of cholera dynamics for the city in recent times based on two transmission models that incorporate SST anomalies and are fitted to the earlier surveillance records starting in 1995. We implemented a mechanistic temporal model that incorporates both epidemiological processes and the effect of ENSO, as well as a previously published statistical model that resolves space at the level of districts (thanas). Prediction accuracy was evaluated with “out-of-fit” data from the same surveillance efforts (post 2008 and 2010 for the two models respectively), by comparing the total number of cholera cases observed for the season to those predicted by model simulations eight to twelve months ahead, starting in January each year. Although forecasts were accurate for the low cholera risk observed for the years preceding the 2015–2016 El Niño, the models also predicted a high probability of observing a large outbreak in fall 2016. Observed cholera cases up to Oct 2016 did not show evidence of an anomalous season. We discuss these predictions in the context of regional and local climate conditions, which show that despite positive regional rainfall anomalies, rainfall and inundation in Dhaka remained low. Possible explanations for these patterns are given together with future implications for cholera dynamics and directions to improve their prediction for the city.
... Therefore, concerns are growing over the contaminated sediments in river beds because it may cause substantive damage to the aquatic ecosystems. Moreover, monsoon flood caused by the overflow of rivers inundates about one-third of Bangladesh (Bala et al. 2009). This may pose risks to agricultural soils as a result of the mobilization and deposition of contaminated sediments in the floodplain. ...
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Trace metals accumulation in soil irrigated with polluted water and human health risk from vegetable consumption was assessed based on the data available in the literature on metals pollution of water, soil, sediment and vegetables from the cites of Bangladesh. The quantitative data on metal concentrations, their contamination levels and their pollution sources have not been systematically gathered and studied so far. The data on metal concentrations, sources, contamination levels, sample collection and analytical tools used were collected, compared and discussed. The USEPA-recommended method for health risk assessment was used to estimate human risk from vegetable consumption. Concentrations of metals in water were highly variable, and the mean concentrations of Cd, Cr, Cu and As in water were found to be higher than the FAO irrigation water quality standard. In most cases, mean concentrations of metals in soil were higher than the Bangladesh background value. Based on geoaccumulation index (Igeo) values, soils of Dhaka city are considered as highly contaminated. The Igeo shows Cd, As, Cu, Ni, Pb and Cr contamination of agricultural soils and sediments of the cities all over the Bangladesh. Polluted water irrigation and agrochemicals are identified as dominant sources of metals in agricultural soils. Vegetable contamination by metals poses both non-carcinogenic and carcinogenic risks to the public. Based on the results of the pollution and health risk assessments, Cd, As, Cr, Cu, Pb and Ni are identified as the priority control metals and the Dhaka city is recommended as the priority control city. This study provides quantitative evidence demonstrating the critical need for strengthened wastewater discharge regulations in order to protect residents from heavy metal discharges into the environment.
... Although flooding has a long history in the country and the city, it is projected to be further exacerbated by climate change, i.e. erratic and heavy rainfall, river flow changes caused by sea level change. The location of the city also intensifies its risks to flooding as it is located in the central area of the flat deltaic plain of the GBM basin (Bala et al., 2010). Moreover, it is situated in the active river tidal zone which holds up water in low lying areas during high tides (Haque et al., 2012) (Figures 5 and 6). ...
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The developing countries are suffering the most because of climatic variability and they have an enormous backlog in basic infrastructure to protect their cities. In addition, the resources and technical expertise are limited. Therefore, the adaptation measures to protect their cities are needed to be planned and prioritized carefully to reduce the vulnerability simultaneously considering the risk reduction, local constraints and development goals. A framework for prioritization of adaptation measures is lacking in the decision making in this context which could immensely assist in informed and structured decisions during the planning process of adaptation strategies in developing countries. This paper is exploring the potential of Multi-Criteria Analysis as a methodology for climate adaptation assessment in order to prioritize the adaptation measures to be undertaken. Hence in this paper Adaptation assessment is conducted within the framework of Multi-Criteria Analysis methodology which allows both normative judgement and technical expertise in the assessment process. Such a participatory integrated assessment of adaptation options is a new approach in flood management in least developed countries. The assessment framework has been applied and tested at the Eastern fringe of Dhaka city which is highly vulnerable to flooding. Based on the assessment and analysis, adaptive measures are prioritized to enable more effective action. Copyright
Chapter
The focus of this study is placed on inspecting the Turag River dyke in Dhaka by using the Ground Penetrating Radar (GPR) which is often damaged during the monsoon season due to erosion caused by flooding and overtopping. The dyke was inspected to identify the weak zones at several locations by using GPR which is a non-destructive investigation technique. It requires no physical penetration into the ground, can perform quick survey and hence low cost involved compared to other surveys. GPR survey has been conducted in three selected stretches of the dyke. These selected stretches are Mirpur Sluice Gate, Rostampur Cross Dyke and Prottasha Bridge areas. GPR investigations on these particular portions of the dyke have done to monitor the health of the dyke and to locate any disturbed or weak zones which may need strengthening before monsoon. Radargram of Mirpur Sluice Gate area shows four distinct reflection layers of pitch (tar) mixed with brick; brick chips with sand; pre-existing footpath and compacted soil. Compacted soil below the pre-existing footpath formed by silty clay to clay materials found with slight variation of materials types, materials compactness and wetness, indication comparative weak zones in silty clay to clay. The lines representing the reflections from the ground layers suddenly end from both sides in the radargram indicating the existence of the sluice gate. In Rostampur Cross Dyke three subsurface layers can easily be identified from the radargram. The uppermost unit is mainly composed of brick chips and silty clay materials. Below the top layer, lithology of second layer has not been identified. Underneath the second layer the main dam materials are silty clay to clay. Variation of materials, compactness and wetness are also observed here. Radargram from GPR measurement on the highway beside Prottasha Bridge clearly shows that the bridge structure of the section is different from the adjacent sections at both sides. Reflections from pipes or cables under the highway are strongly visible. Although dyke materials are comparatively fine textured and wet but results were satisfactory and encouraging.
Chapter
Flood mapping and monitoring was performed using both Landsat and Radarsat data from 1988 to 2009. Multi-temporal satellite data were digitally classified using a threshold algorithm to determine the spatial and temporal distribution of floods. In addition, flood depths were calculated using the highest water-level data with a DEM. Synthetic depth–damage curves were prepared for three housing categories and for major roads. Flood maps were evaluated using classified satellite images with ground truth data. It was found that 25% of the study area is flooded every year which could rise to more than 40% during abnormal events such as those that occurred in 1988 and 1998. Flood damage estimations revealed that the greatest damage occurred to katcha houses rather than semi-pucca and pucca houses. Variable accuracies were found for satellite-derived flood maps; however, the overall accuracy was highest for radar-based classifications.
Chapter
This chapter illustrates the physical environment together with the built and socioeconomic characteristics of the megacity of Dhaka. An account of historical floods with damage statistics is discussed, revealing that flood loss in the city has increased over time. This is clearly attributed to unplanned and ill-structured development planning. A number of factors are accountable for the increase in flood vulnerability, including extreme population density, intense inequality in resource distribution, and dilapidated drainage systems. Although various adaptation strategies have been suggested for flood management, their success depends on a number of issues such as restricting urban expansion in flood-prone areas.
Chapter
The objective of this chapter is to evaluate flood risk in Dhaka with geospatial techniques. Multi-temporal flood data, derived from digital elevation model and satellite imagery, were used to determine flood hazards. Census and spatial databases were used to evaluate flood vulnerability and risk zoning at a community level. The analytic hierarchy process (AHP) and weighted linear combination (WLC) methods were used to determine flood vulnerability within a geographic information system framework. The results revealed that 45 % of the study area was estimated as highly hazardous, accounting for 7 % of the total study population. Around 40 % of the communities in the study area are highly vulnerable to flood, with 8 % being extremely vulnerable. Further, more than 22 % of the population are in areas that are at high to very high risk of flood. Forty per cent of housing units are located in the high- to very high-risk zone, and around half of these were katcha houses, built using fragile construction materials—28 % of the communities in Dhaka were at high risk of flood.
Hydrological Aspects of Flood
  • A S Islam
  • A Haque
  • S K Bala
Islam, A. S., Haque, A., and Bala, S. K. (2008). Hydrological Aspects of Flood 2007. Dhaka, Bangladesh: Institute of Water and Flood Management (IWFM), Bangladesh University of Engineering and Technology (BUET)
Investigation of Hydrologic Aspects of Flood-2004 with Special Emphasis on Dhaka City
  • R Rahman
  • A Haque
  • S A Khan
  • M Salehin
  • S K Bala
Rahman, R., Haque, A., Khan, S. A., Salehin, M., and Bala, S. K. (2005). Investigation of Hydrologic Aspects of Flood-2004 with Special Emphasis on Dhaka City. Dhaka, Bangladesh: Institute of Water and Flood Management (IWFM), Bangladesh University of Engineering and Technology (BUET).
Impact of 1998 Flood on Dhaka City and Performance of Flood Control Works
  • J U Chowdhury
  • R Rahman
  • S K Bala
  • A S Islam
Chowdhury, J. U., Rahman, R., Bala, S. K., and Islam, A. S. (1998). Impact of 1998 Flood on Dhaka City and Performance of Flood Control Works. Dhaka: Institute of Flood Control & Drainage Research, Bangladesh University of Engineering & Technology
Hydrological Characteristics of the 1998 flood in major rivers
  • A S Islam
Islam, A. S., and Chowdhury, J. U. (Eds.). (2002). Hydrological Characteristics of the 1998 flood in major rivers, Engineering Concern of Flood. Dhaka: Bangladesh University of Engineering and Technology.