Water Club 18th March, 2010, IWM, Dhaka
Performance of Flood Control
Works around Dhaka City during
Major Floods in Bangladesh
(Part-1)
A.K.M. Saiful Islam
Institute of Water and Flood Management (IWFM)
Bangladesh University of Engineer and Technology (BUET)
Outline
• Hydro-Meteorology and Drainage
System of Dhaka City
• Hydrological Characteristics of Major
Floods
• Recent Extreme Rainfall event in
Dhaka City
The Ganges, Brahmaputra, and
Meghna (GBM) River Basins
• 93% water comes outside of Bangladesh
Recent Major Floods in
Bangladesh
Flood is a reality for Bangladesh.
Devastating floods like 1954, 1987,
1988, 1998, 2004 and 2007 are
considered to be the worst ones
affecting the majority of the population of
the country and severely disrupting the
social and economic activities.
Floods in Major Rivers
1988
2004
1998
2007
Height of Peak above DL
2007
2004
1998
1988
Brahmaputra
0.88
0.68
0.87
1.12
Ganges
-
-
0.94
0.62
Meghna
0.69
1.53
1.08
1.41
Duration of flood above DL
2007
2004
1998
1988
Brahmaputra
21
15
67
16
Ganges
0
0
26
23
Meghna
37
38
67
75
TRMM Rainfall (May-Sep, 2004)
TRMM Rainfall (May-Sep, 2007)
Flood Inundation Map 2007 based
on MODIS Satellite Data
Location of Dhaka
City with regional
river system
Greater Dhaka City : Rainfall
 Four climatic seasons:
 Pre-monsoon (March-May)
 Monsoon (June-September)
 Post-monsoon (October-November)
 Dry (December-February)
 Mean annual rainfall: 2060 mm (70% occurs
during monsoon)
 Mean monthly rainfall during monsoon: 300 to
450 mm
 Peak monthly rainfall usually occurs before
the surrounding rivers attain the highest
stage
Source: Khan et al., 2010 IWFM, BUET
Height of Peak above DL
2007
2004
1998
1988
Turag
0.02
0.7
1.23
1.58
Balu
0.68
1.35
2.03
2.41
Buriganga
0.78
1.05
1.46
1.75
Tongi Khal
0.5
-
-
-
Duration of flood above DL
2007
2004
1998
1988
Turag
1
17
56
22
Balu
25
26
69
30
Buriganga
29
22
65
25
Tongi Khal
20
-
-
-
Recent Events of Urban
Flooding
14 September 2004
•Recorded highest
daily rainfall (341
mm) and 5-day
cumulative rainfall of
600 mm
•Both 1-day and 7day rainfall had return
period of about 100
years
Kallyanpur
Gulshan
Sept. 2004 Rainfall in Dhaka
400
300
Rayer
bazar
250
200
Motijheel
150
100
50
Date
28-Sep
25-Sep
22-Sep
19-Sep
16-Sep
13-Sep
7-Sep
10-Sep
4-Sep
0
1-Sep
Rainfall (mm)
350
Source: Khan et al., 2010 IWFM, BUET
Storm water flooding
in 14 September 2004
Mirpur Road
Motijhee
l
Source: Khan et al., 2010 IWFM, BUET
BUET Campus on 14 September 2004
Heavy rain storms on May 22, 2006
• The metrological
office recorded 52
mm rainfall in Dhaka
since the midnight of
Thursday till 6:00 pm
at May 22, 2006.
• The city experienced
38 mm rainfall 3
hours from 6:00 to
9:00 am in the
morning at May 22,
2006.
Water logging on July 23, 2007
• The worst affected were Azimpur, and the old parts of the
city. The Meteorological Office recorded 134 millimeters of
rain in Dhaka between 6:00am and 3:00pm
• WASA sources said the drains can deal with only 10
millimeters (mm) of rain an hour. The city has 150 square
kilometers of storm drains, whereas it needs at least 260 sq
kms to collect runoff from heavy shower.
July 28, 2009
• The heaviest rain in 53 years battered Bangladesh's
capital Tuesday, leaving at least six people dead and
stranding thousands in their swamped homes.
• The national weather office said 333 mm of rain fell
in 12 hours in Dhaka, an overcrowded city of about
10 million people - the most in a single day since
1956
Causes of Aggravated Stormwater Flooding
• Unauthorized development on the drainage
routes
• Encroachment of the lakes, detention areas
and retarding ponds
• Reduced conveyance capacity of storm sewers
by accumulation of solids
• Inadequate passage for storm runoff through
newly constructed roads
Source: Khan et al., 2010 IWFM, BUET
Contd..
• Late starting of temporary pumping
operation when detention storages are
already filled up from antecedent rainfall
• Malfunction and power outage of
permanent pumps
• Unauthorized discharge of domestic
sewage into storm sewers
Source: Khan et al., 2010 IWFM, BUET
The Way Forward
• Integrated management of water
supply, wastewater, stormwater, solid
waste and aquatic ecosystem is
necessary to ensure sustainable
management of urban water systems.
• This will lead to reducing pollution and
health problems, reducing flood impacts
and improving the water quality in
waterbodies.
Source: Khan et al., 2010 IWFM, BUET
Thank you