BANNGLAADESHH
NETTWORRK
OFFIC
O
CE FO
OR

URBBANSAFEETY

B
BUET,
, DHA
AKA, BANG
B GLADESH
P
Prepareed By:

M di Ahm
Mehed
med Annsary

CONTENTS
PART-I: STRUCTURAL ASSESSMENT REPORT ON
EXISTING BUILDING VULNERABILITY EVALUATION……………………………………………………………………………………………………………………………
1
FOR MLSS QUARTER, BUET
PART-II: FIRE AT NIMTOLI RESIDENTIAL AREA IN OLD……………………………………………………………………………………………………………………………
9
DHAKA
PART-III: SEISMIC RISK ASSESSMENT OF SOME HISTORICAL
MOSQUE OF DHAKA USING NON-DESTRUCTIVE TESTING……………………………………………………………………………………………………………………………
METHODS
13
PART-IV: APPLICATION OF MICROTREMOR ARRAY FOR……………………………………………………………………………………………………………………………
23
ESTIMATING SHEAR WAVEVELOCITY IN BANGLADESHCONTENTS
PART-V: COMMUNITY UNDER FIRE THREAT: AN ASSESSMENT……………………………………………………………………………………………………………………………
OF FIRESTRUCTURAL
HAZARD VULNERABILITYWARDON
65 IN DHAKA CITY 3 1
PART-I:ASSESSMENTOFREPORT
PART-VI: BUILDINGGEOPHYSICALINVESTIGATIONAT PROPOSED GANGESEXISTING
VULNERABILITYEVALUATIONBARRAGESITE IN PANGSHA
1
FOR
MLSS QUARTER,
BUET RAJBARI AND AT BANGORA GAS……………………………………………………………………………………………………………………………
PLANT SITE
BRAHMANBARIA
43
PART-II:FIREINAT
NIMTOLI RESIDENTIAL AREA IN OLD
PART-VII: FIRE AT HAZARIBAG RESIDENTIAL AREA IN OLD
9DHAKA……………………………………………………………………………………………………………………………
DHAKA SEISMIC RISK ASSESSMENT OF SOME HISTORICAL
61
PART-III:PART-VIII:
AT A
READYMADEGARMENT FACTORYMOSQUEOF FIREDHAKA
USING
NON-DESTRUCTIVETESTING AT……………………………………………………………………………………………………………………………
63
NISCHINTAPUR IN ASHULIA INDUSTRIAL AREA
METHODS
13
PART-IX:COLLAPSE
OFAN
UNDER-CONSTRUCTIONFLYOVER
PART-IV: APPLICATION OF MICROTREMOR ARRAY FOR……………………………………………………………………………………………………………………………
AT BAHADDARHATIN CHITTAGONG
2639
ESTIMATINGSHEAR WAVEVELOCITY IN BANGLADESH
PART-X:COMMUNITY
VIBRATION MEASUREMENT
AND NDTA CEMENT
PART-V:UNDER FIRE THREAT:AN AT
ASSESSMENT……………………………………………………………………………………………………………………………
FACTORY
SITE VULNERABILITY OF WARD 65 IN DHAKA CITY 3711
OF
FIRE HAZARD……………………………………………………………………………………………………………………………
PART-XI:GEOPHYSICALDEVELOPMENTINVESTIGATION
OF FLOOD MAPAT
OFPROPOSEDDHAKA CITY
PART-VI:GANGES 103……………………………………………………………………………………………………………………………
PART-XII:TRAINING
COURSES, SEMINARSANDBARRAGE SITE IN PANGSHA RAJBARIAND ATBANGORAGAS129
WORKSHOP
PLANT SITE IN BRAHMANBARIA
43
PART-VII: FIRE AT HAZARIBAG RESIDENTIAL AREA IN OLD
DHAKA
61
PART-VIII: FIRE AT A READYMADE GARMENT FACTORY AT
63
NISCHINTAPUR IN ASHULIA INDUSTRIAL AREA
PART-IX: COLLAPSE OF AN UNDER-CONSTRUCTION FLYOVER
69
AT BAHADDARHAT IN CHITTAGONG
PART-X: VIBRATION MEASUREMENT AND NDT AT A CEMENT
71
FACTORY SITE
PART-XI: DEVELOPMENT OF FLOOD MAP OF DHAKA CITY
103
PART-XII: TRAINING COURSES, SEMINARS AND WORKSHOP
129

PART-I
STRUCTURAL ASSESSMENT REPORTON EXISTING BUILDING VULNERABILITYEVALUATION FOR MLSS QUARTER, BUETBANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: KM Khaleduzzaman
Ram K. MazumderMehedi Ahmed Ansary

ICUS Report 63

GeneralThe devastating social and economic impacts of recent earthquakes in urban areas haveresulted in an increased awareness of the potential seismic hazard and the corresponding
vulnerability of the built environment. Greater effort has been given to reasonably estimates,
predictions and mitigation of the risks associated with these potential losses.
This report is based on engineering judgment arrived at from the site visit, review of available
architectural drawings, and non-destructive test carried out at site. All possible efforts havebeen made to provide accurate and authoritative seismic vulnerability assessment of thebuilding in the given circumstances of information provided by the client and limited numberof field-tests. Therefore, neither BNUS nor any of its employees make any warranty,
expressed or implied, nor assumes any responsibility for the accuracy, completeness, orusefulness of the statement made in this report in case the starting information does not standcorrect.

Basic Information
Building Name
: BUET Staff Quarter Building
Building Type: Masonry
Construction Year:
Building Shape: RectangularNo. of Storey: 02
Occupancy Type: Residential
Number of Occupants :30-40
Name of Owner: BUET

Building Plan

Figure 1: Ground Floor Plan

1

March 2013

Load Calculation
Dead Load Calculation

Wall Load Calculation
Load Calculation for Ground Floor
Wt.
Height
Area
S.N.
1
2
3
6

3

Part

Wall
Window -Type1
Window -Type2
Doors -Type1(kN/m )
19.0
-19.0
-19.0
-19.0

Area

Weight, w

2

(m )
26.2
0.9
0.7
2.2

(kN)
1519.0-21.5-17.2-100.91379.3Area

Area

Weight, w

2

2

(kN)
1583.6
-21.5
-17.5
-50.4
1494.22

Ht. (m)mm
3.05 26212076
1.229295061.227436052.38 2230815

Load Calculation for 1st Floor
Wt.
S.N.
1
2
3
6

Part
Wall
Window -Type1
Window -Type2
Doors -Type1

Height3(kN/m )
19.0
-19.0
-19.0
-19.0

Ht. (m)
3.05
1.22
0.76
2.38

mm
27327483
92950612083581115408

(m )
27.3
0.9
1.2
1.1

Slab Load Calculation
Floor Level - 1
S.N.

Floor Level - 2
S.N.

Part
1 Slab - S1(1)Wt.
Thickness
Area
Area Weight2(kN/m3)
t (m)
mm
(m2)
(kN)
25.00
0.42 109588786.0 109.59 1141.53
109.59 1141.5

Wt.
Thickness
Area
Area Weight2
Part(kN/m3)
t (m)
mm
(m2)
(kN)
1 Slab - S2(1)25.00
0.42 109588786.0 109.59 1141.53
109.59 1141.5

Summary Dead Load
Floor Height hi (m)6.10
1st Floor
3.05
2nd Floor

2

Seismic Weight(KN)
2520.82713.7

BNUS Annual Report-2012

ICUS Report 63

Base Shear Calculation (Ref: BNBC)

No. of Stories = 2
StoreyHt (Level)1
2

Total StoreyHt (hn) =Ct =T=
S (Site Class) =Response reduction factor,R =C=
Seismic Zone =Z=
Importance factor, I =Seismic Weight,W =Base Shear, V =Ft =V Ft =

Each Story Ht(m)
3.05
3.05

6.1
0.049
0.19
2.0
6.0
2.75
2
0.15
1
5234.5359.870.00
359.87

Ht. from GL(m)
3.05
6.1

m
second
S4

KN
KN
KN
KN

Note: 1. V=ZICW/R,(2/3),
2. C=1.25S/T
3. T=Ct(hn)(3/4)

4.5 Seismic load distribution (floor wise):StoreyShearweightHeightwi (KN)hi (m)

2

2713.76.100 16553.57 245.74

12520.83.050 7688.44 114.13
Sum= 24242.01 359.87

Seismic load distribution(Floor)Wihi

Qi

Vi( KN)@1 Storey
245.74 Shear@0 Storey
359.87 Shear

3

March 2013

Structural Integrity Check
Direct Shear Test of Masonry
Destructive Test has been performed using Hi-Force Hydraulic Jack. Result of this test is
given below. Figure 2 shows application of Direct Shear Test.
jack diameter =Area =
Brick Size
Contact Area
Dial Gauge Reading

Shear strength for the sample,
Nos of brick above testing brickheight of wall above brickunit wt of wall
Vertical pre-stress on testing brick,*µ
Shear Stress due to mortar bond
only=

35 mm
962.5 mm2
LengthWidth247.65146.05sq.
89636.9175 mm
P bar
220
0.31195851
9
58
4.35
19
82.65
0.08265

Height69.85 mm

Force, N
27963

Shear Stress,
N/mm2
0.312

N/mm2
Nos.
m
KN/m3
KN/m2
N/mm2

- *µ
0.229 N/mm2

Figure 2: Direct Shear Test of Masonry for BUET Staff Quarter

Seismic load at the height of 1.35 m from the Ground level is 296.26 KN

4BNUS Annual Report-2012

ICUS Report 63

Shear Stress in Shear Walls (Ref: IIT KanpurGuideline)
wall = Vj / Aw
Vj = Storey shear at level j
Aw = Total area of walls in the direction of the loading.
For unreinforced masonry load bearing wall buildings, the average shear stress, wallshallbe less than 0.11 MPa (0.11 N/mm2)

Direction of earthquake
force
Along the Length
Along the width

Shear force(Vj)

Area of wall
(Aw)

KN
345.4
345.4

Shear stresses(Vavg)

Remark

2

Sq.m
13.29
12.92

N/mm
0.026
0.027

SatisfiedSatisfied

Height to Thickness Ratio Check (Ref: IIT Kanpur Guideline)

Wall Type

Zone II(z=0.15)

Top storey of multi-storey building

14

First storey of multi-storey building18

All other conditions

16

5

March 2013

Actual h/t Ratio Check
Floor height, hBl. No.
B1

Floor

ft

in

=height(in), h

thickness(in),th/tRemarkTop Storey

10

0

120

10 12.0

OkFirst Storey

10

0

120

10 12.0

Ok

Non-Destructive Test
In order to identify the resonance criteria, microtremor test has been performed. One sensor
was deployed on free field and other sensor was placed on roof of the building. Figure 3 andFigure 4 represent results of microtremor.

Figure 3: First Fourier Transform (FFT) for Sensor 1 (left) and Sensor 2

6

BNUS Annual Report-2012

ICUS Report 63

Figure 4: H/V Spectrum for Sensor 1 (Left) and Sensor 2

Laboratory Test
Compressive Strength of Brick: BUET Staff Quarter Building
Date : 12 December, 2011
Sample No.: 1
Special Remark: Wet Condition and Dark Red, Well Burnt
Surface Area Length
Width
Crashing Load
Crashing Strength
Sample No.: 2Special Remark: Dry and Light Red
Surface Area Length
Width
Crashing Load
Crashing Strength

117
108
150
11.9

mm
mm
kN
MPa

120
115
146
10.6

mm
mm
kN
MPa

7

PART-II
FIRE AT NIMTOLI RESIDENTIAL AREA
IN OLD DHAKABANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: Naima Rahman
Mehedi Ahmed Ansary

ICUS Report 63

Nimtoli at Old Dhaka often faces fire hazard due to mixed land uses in the residential areas.
Recently a devastating fire broke out on 26 March 2012 at a house at Mazed Sardar road of
Chankharpool area in Nimtoli. Local people said the fire originated from an electric shortcircuit at the ground floor of the five-story residential building at around 2:45pm andimmediately engulfed the whole floor. The building has polythene factory and paper store at
the ground floor. The other floors are used for residential purpose. The fire occurred at
polythene factory. On receiving information, four fire-fighting units from headquarters andPalashi fire stations went to the spot and extinguished the fire after more than one and a halfhour’s efforts at around 5:00 pm. Thus the fire could not be spread at upper level of the houseand also the paper store. Though only the factory was affected due to fire but the economic
loss was huge. Properties including hardware machineries, plastic materials and several raw
materials of the polythene factory worth about Tk. 60 lakh were gutted in the fire. The fireoccurred on a national holiday. Workers were absent in the factory. The inhabitants of thebuildings were also visited outside. They rushed the spot hearing the incident through cellular
phone by a neighbor. That’s why no human casualties happened due to fire. Somephotographs of the fire affected factory are showed as bellow:

Figure 1: Broken entrance of the factory

Figure 2: Burnt factory

Figure 3: Burnt machine

Figure 4: Burnt machine9March 2013

Figure 5: Burnt machine

Figure 6: Burnt machine

Figure 7: Burnt wire and electric switch

Figure 8: Burnt electric switch board

board

Figure 9: Burnt roof and wall

10

Figure 10: Burnt factory

BNUS Annual Report-2012

ICUS Report 63

Figure 11: Burnt machine and wall

Figure 12: Burnt electric wire

Figure 13: Burnt machine

Figure 14: Burnt materials

Figure 15: Burnt factory

Figure 16: Burnt floor and materials

11

PART-III
SEISMIC RISK ASSESSMENT OF SOMEHISTORICAL MOSQUE OF DHAKA USING NONDESTRUCTIVE TESTING METHODSBANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: KM Khaleduzzaman
Mehedi Ahmed Ansary

ICUS Report 63

Ancient masonry structures are particularly vulnerable to dynamic actions, especially seismic
actions. South Asian Cities are particularly at risk due to the large number of ancientmonuments (temples, mosques, churches etc.) and dwellings. Due to the ageing process andenvironmental factors, many cultural heritage buildings, as structures planned andconstructed in the past, are vulnerable to dynamic loads, which may unpredictably induce acollapse of a portion of the building or drive the whole structure to a rapid failure. However,
the high vulnerability of historical masonry buildings to seismic actions is mostly due toinsufficient connections between the various building parts.
The Seismic risk assessment of five heritage masonry mosques of Dhaka city using
nondestructive testing techniques have been presented in this paper. These mosques are Musa
Khan Mosque, Lalbag Fort Mosque, Khan Muhammad Mridha Mosque, Daira Sharif Mosqueand Aambur Shah Shahi Mosque. The simplified method of earthquake risk assessment
suggested by Lourenco and Oliveira (2004) has been applied and microtremor has been used
to determine the predominant period of the buildings.
2. STUDY AREA
The entire assessed mosques have been located in Dhaka city. Among these, Lalbag Fort
Mosque and Khan Muhammad Mridha Mosque are located in ward no.61. Daira Sharif
Mosque is in ward no. 62, Aambur Shah Shahi Mosque is in 39 and Musa Khan Mosque islocated in ward no. 56. The location of the mosques are shown in Figure 1.

Figure 1: Location of the study area (A - LalBag Fort Mosque, B - Khan Muhammad
Mridha Mosque, C - Daira Sharif Mosque, D - Musa Khan Mosque, E - Aambur Shah
Shahi Mosque)13

March 2013

3. METHODOLOGY
3.1 Simplified methods of analysis
The usage of simplified methods of analysis usually requires that the structure is regular andsymmetric, that the floors act as rigid diaphragms, and that the dominant collapse mode is inplane shear failure of the walls. The following simplified methods of analysis andcorresponding indexes are considered.
In-plane indexes:- Index 1: In-plan area ratio- Index 2: Area to weight ratio- Index 3: Base shear ratio
Out-of-plane indexes:- Index 4: Slenderness ratio of columns- Index 5: Thickness to height ratio of columns- Index 6: Thickness to height ratio of perimeter wall
3.1.1 In-Plane Area Ratio
The simplest index to assess the safety of ancient constructions is the ratio between the areaof the earthquake resistant walls in each main direction (transversal x and longitudinal y, withrespect to the central axis of the mosque) and the total in-plane area of the building.
According to Eurocode 8 (CEN-EC8 2003), walls are only considered as earthquake resistant
if the thickness is larger than 0.35 m, and the ratio between height and thickness is smaller
than nine. The first index, 1,i reads:
1,i = Awi / S

Where Awi is the in-plane area of earthquake resistant walls in direction “i” and S is the total
in-plane area of the building.
3.1.2 Area to Weight Ratio
This index provides the ratio between the in-plane area of earthquake resistant walls in eachmain direction and the total weight of the construction, reading
2,i = Awi / G
where Awi is the in-plane area of earthquake resistant walls in direction “i” and G is the quasipermanent vertical action. This index is associated with the horizontal cross-section of thebuilding, per unit of weight

14

BNUS Annual Report-2012

ICUS Report 63

3.1.3 Base Shear Ratio
The total design base shear in a given direction shall be determined from the following
relation (BNBC):V

ZIC / R * W

Where,Z = Seismic zone for a building site shall be determined based on the location of the site on
the Seismic Zoning Map provided in BNBC (1993)
I = Structure importance coefficient
R = Response modification coefficient for structural systems
W = the total seismic dead load
C = Numerical coefficient given by the relation:
C

1.25 S
T2 3

The value of C need not exceed 2.75
S = Site coefficient for soil characteristics
T = Fundamental period of vibration in seconds, T of the structure is determined from thefollowing methods:
For all buildings the value of T may be approximated by the following formula

T

Ct hn

3 4

Where, Ct= 0.083, for steel moment resisting frames= 0.073, for reinforced concrete moment resisting frames, and eccentric braced steel frames= 0.049, for all other structural systems
ht= Height in meters above the base to level n.

Finally, the base shear ratio provides a safety value with respect to the shear safety of theconstruction. The total base shear for seismic loading (VSd, base = FE) can be estimated from ananalysis with horizontal static loading equivalent to the seismic action (FE = G), where isan equivalent seismic static coefficient related to the peak ground acceleration. The shear
strength of the structure (VRd, base = FRd) can be estimated from the contribution of allearthquake resistant walls FRd,i = Awifvk, where, according to Eurocode 6 (CEN-EC6 2003),
fvk = fvk0 + 0.4 d. Here, fvk0 is the cohesion, which can be assumed equal to a low value orzero in the absence of more information, d is the design value of the normal stress, and 0.4
represents the tangent of a constant friction angle , equal to 22º. The index, 3, reads:
3,i = FRd,i / FE

15

March 2013

If a zero cohesion is assumed (fvk0 = 0), 3,i is independent from the building height, reading:
3,i = VRd,i / VSd = Awi / Aw × tan /For a non-zero cohesion, which is most relevant for low height buildings, 3,i reads:
3,i = VRd,i/VSd = Awi/Aw×[tan +fvk0/( × h)]/where Awi is the in-plan area of earthquake resistant walls in direction “i,” Aw is the total inplan area of earthquake resistant walls, h is the (average) height of the building, is thevolumetric masonry weight, is the friction angle of masonry walls, and is an equivalentstatic seismic coefficient. Here, it is assumed that the normal stress in the walls is only due totheir self-weight, i.e. d = × h, which is on the safe side and is a very reasonableapproximation for historical masonry buildings, usually made of very thick walls.
For indexes 1, 2 and 3 (in-plane indexes), assumed thresholds as functions of PGA/g areshown in Figure 2 (a), 2 (b) and 2 (c) respectively,

Figure 2: Assumed thresholds as functions of PGA/g: (a) index 1, (b) index 2 and (c) index 3(after Laurenco and Oliviera, 2004)

3.1.4 Out-of-plane Indexes
Besides the three indexes exposed above, other key indexes related to structural performance
were computed for the monuments under analysis. In this study, three geometric ratios
concerning the structural out-of-plane behaviour of columns and walls in main space wereadopted, when applicable; slenderness ratio ( 4), and thickness to height ratio of the columns( 5), as well as thickness to height ratio of the perimeter walls ( 6), were analyzed, reading:
1/2
4 = hcol / (I/A)

5 = dcol / hcol
6 = twall / hwall

where hcol is the free height of the columns, I and A are the inertia and the cross section areaof the columns, respectively, dcol is the (equivalent) diameter of the columns, and twall andhwall are the thickness and the (average) height of the perimeter walls, respectively. All of the

16

BNUS Annual Report-2012

ICUS Report 63

out-of-plane indexes are dimensionless and do not consider the local seismicity.. For indexes
4, 5 and 6, Assumed thresholds as functions of PGA/g are shown in Figure 3 (a), 3 (b) and 3(c) respectively,

Figure 3: Assumed thresholds as functions of PGA/g: (a) index 4, (b) index 5 and (c) index 6(after Laurenco and Oliviera, 2004)
3.2 Microtremor observation
Soil characteristics have been assessed by Microtremor measurement. Hard soil gives highfrequency and soft soil gives low frequency. A structure may experience a vibration period atwhich it oscillates in the earthquake vibration motion and will tend to response to that.
Natural frequency of structure is obtained based on the spectral ration of horizontal
component of the structure to that of ground. Wave propagation mechanism of Microtremor
and its relation with ground vibration characteristics were studied from the beginning ofMicrotremor studies (Aki, 1957; Kanai and Tanaka, 1961).

3.2.1 Data collection and processing
For Microtremor observation at the mosque, initially two sensors are deployed. One sensor isfixed on the roof of the buildings and another one on the free field near the structure. Aftertaking the observation with the help of microtremor, the time domain velocity data isconverted to frequency domain data and the natural period of the structures have been
estimated.
The computation steps of the spectrum analysis is shown in Figure 4 and described asfollows:
Pre-Processing:- 3-dimensional input (the accelerometer in northward direction to get North-South, EastWest and vertical components)- Windowing of the signal (in our case only the ambient parts are of interest, observe, in caseof transient excitation only the transient parts of the time response are of interest)
Main Data-Processing:17

March 2013

Hence the three different components of the signal were considered separately. The main dataprocessing is repeated for every input-signal (n-Steps according to the numbers of
preliminary separated windows).
- FFT is applied to obtain the several spectral amplitudes of the three components- Smoothing of the three spectral amplitudes with a bandwidth factor of 10 to 15- Afterwards the resulting horizontal component and vertical component are plotted to obtain
the amplitude in frequency domain.

4 RESULTS AND DISCUSSION
4.1 Findings of simplified methods of analysis
The relationship between the different indexes and PGA/g is shown in Figure 4. The Legends
used in the Figure 4 indicates the findings of the corresponding mosque provided at Table 1.
Table 1: Indicated meaning of Legends

N.B: For index 4 and index 5 the legends indicate the corresponding mosque only, not thedirection

18

BNUS Annual Report-2012

ICUS Report 63

Figure 4: Relationship between Indexes ((a) In-plane area ratio, (b)Area to weight ratio, (c)Base shear ratio, (d) Slenderness ratio, (e) t/h of columns, (f) t/h of perimeter wall) andPGA/g (after Kamruzzaman, 2011)

4.2 Findings of Microtremor Observation
Figure 5 shows individual time histories for X, Y and Z components for Khan Muhammad
Mridha Mosque. Figure 6 shows FFT of those time histories. Figure 5 also presents the
predominant frequency of the buildings in both directions. Figure 6 shows the H/V ratio of
the soil.

19

March 2013

Figure 5 : Time history of soil and building

Figure 6 : Fourier Spectrum of soil and building

Figure 7 : H/V ratio
The predominant period of mosque buildings and corresponding soil are given in Table 2.
Table 2: Predominant period of mosque buildings and corresponding soil
Name of Mosque
Soil Period (s) Structural Period (s)Boro Daira Mosque
No clear peak
0.40
Khan Mohammad Mridha Mosque No clear peak
0.50
Lalbagh Fort Mosque
0.25
0.20
Aambour Shah Shahi Mosque
0.50
0.33
Kurzon Hall Musa Khan Mosque
No clear peak
0.29
5. CONCLUSIONSIn this study, five historical mosques of Dhaka city have been assessed using analyticaltechniques and NDT. The analytical techniques have used six indexes, namely In-plane area
ratio, Area to weight ratio, Base shear ratio, Slenderness ratio, t/h of columns and t/h ofperimeter wall) and PGA/g. From this study, it has been found that all of those five masonry

20

BNUS Annual Report-2012

ICUS Report 63

structures are safe against their respective seismic loads. For those five structures,
microtremor observations have been carried out at the nearby free-field and on the top of themosque roofs. The results show that for four structures, no resonance between soil andstructure will occur. For Lalbagh Fort Mosque, there is high chance of resonance to occur
between soil and structure, and the structure may collapse.

6. REFERENCES
Aki, K. (1957). Space and time spectra of stationary stochastic waves, with special reference
to microtremors, Bull. of Earthquake Research Institute, 35, 415-456.
HBRI (1993). Bangladesh national Building Code.
CEN (2003). Eurocode 8: Design of Structures for Earthquake Resistance – part 1: General
Rules, Seismic Actions and Rules for Buildings, prEN 1998-1, Brussels, Belgium.
CEN (2003). Eurocode 6: Design of Masonry Structures, prEN 1996-1, Brussels, Belgium.
Kamruzzaman, M. (2011). Seismic Vulnerability Of Some Historical Masonry Structures In
Bangladesh, MSc Engineering Thesis, Department of Civil Engg., BUET, Dhaka,Bangladesh.
Kanai, K. and Tanaka T. (1961).On Microtremor VIII, Bull.Earthq.Res.Inst. Tokyo
University, Vol.39, pp.97-114.
Lourenco, PB and Oliveira, DV (2004). Seismic Vulnerability of Historical Churches, Proc.
of International Workshop on Masonry Walls and Earthquakes.

21

PART-IV
APPLICATION OF MICROTREMOR ARRAY FOR
ESTIMATING SHEAR WAVE VELOCITY IN
BANGLADESHBANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: EM Murad
Mehedi Ahmed Ansary

ICUS Report 63

Bangladesh is a small country situated at the south of The Himalayas. The Indian tectonic
plate and the Asian tectonic plate had a collision in The Himalayan region. Bilham et al.
(2001) has shown the high possibility of large earthquake occurrence around the Himalayan
region. Sylhet is one of the major cities of Bangladesh. There are several faults near Sylhet
with significant past earthquakes. Seismic activity in Sylhet is higher than any other region in
Bangladesh. According to Bangladesh National Building Code (BNBC, 1993), Sylhet issituated in the most vulnerable zone. Dhaka is one of those cities which remain in highest
relative earthquake disaster risk (Cardona et al, 1999). Both Sylhet and Dhaka city haveexperienced a lot of historical earthquakes like 1869 Cachar, 1897 Shillong and 1918
Srimangal earthquakes due to their geological location. Recently UNDP, Bangladesh has
conducted some studies (CDMP, 2009) to evaluate earthquake risk of Chittagong, Dhaka and
Sylhet cities. Several kinds of structural and geotechnical data have been collected for thispurpose. For evaluation of site amplification shear wave velocity of soil is the key parameter.
Static properties of soil can be determined easily by field tests like SPT, CPT, Vane shear
tests etc. but determination of dynamic soil properties is a complex and expensive task.
Dynamic properties like shear modulus (Gmax) and shear wave velocity (Vs) are importantparameters for estimating dynamic behavior of soil and for liquefaction susceptibility.
Determination of Vs can be done by different methods like seismic downhole method,crosshole method, spectral analysis of surface wave (SASW) etc. In this study, Shear wave
velocity of soil has been determined using a geophysical technique named microtremor array
method. This method has been developed and used in several projects like Network for
Earthquake Engineering Simulation (NEES) funded by National Science Foundation (NSF),
USA, and Site Effects Assessment Using Ambient Excitation (SESAME) in Europe. In
Bangladesh this is the first time this method has been applied.
2. METHODOLOGY
There are several methods of determining shear wave velocity from surface wave. SpectralAnalysis-of-Surface-Waves (SASW) have been proposed by Nazarian and Stokoe (1984).
Later a more easy and convenient method, Multi Channel Spectral Analysis (MCSA) has
been developed and proposed by Tokimatsu (1995) and later by Zywicki (1999). All thesemethods have one common disadvantage. An energy source is required to create vibration for
SASW and MCSA. That energy source usually makes too much noise and vibration. In urban
area those methods are not suitable. To recover from those problems, Louie (2001) proposed
Refraction Microtremor (ReMi) method. Ambient vibration is used in this method to get deep
profile of shear wave velocity of soil.
The steps to get shear wave velocity starts with data acquisition. Different array types
have been proposed by different researchers. An irregular array of microtremor has been usedin this research after Wathelet (2005). Five numbers of sensors are used in each site except
Zindabazar High School in Sylhet. Here due to space limitations, three sensors have beenused for data collection. To reduce the effect of noise and to detect low frequency vibration a
one hour reading has been taken in 100 data per second sampling rate. Using those data, at

23

March 2013

first Spectral Auto Correlation (SPAC) has been used to determine the correlation between
waves detected from different location at the same time. According to Aki (1957) spectral
auto correlation function between two sensors is defined by the following equation.
(1)is the distance between two sensors, T is the data acquisition time, vo and v
Here,are the signals recorded at the sensors of 0 anddistance respectively. If a narrowfrequency band filter is used of frequency 0 the auto correlation ratios are calculated for all
pairs of receivers by the following equation.
(2)ofAki (1957) has shown that, for a given inter sensor distance , the azimuthal average( , ) has the shape of Bessel function. That can be shown as,)

Here, J0 is the Bessel function of the first order and c ( 0) is the dispersion curve. Thanusing those correlation dispersion curve has been developed. There is a possibility ofobtaining different dispersion curves, so a theoretical dispersion curve has been used to findthe dispersion curve for the site. Theoretical dispersion curve developed for Sylhet has beenobtained from soil data collected by Comprehensive Disaster Management Program (CDMP,
2009). In the computation of theoretical dispersion curve, a program based on Eigenvalue
problem by Thomson (1950) and Haskell (1953) named GPDC has been used. For thecomputation, the assumptions are the soil layers are perfectly horizontal and isotropic (seeFigure 1), they are extended up to infinite horizontal distance. The soil parameters fordeveloping the theoretical dispersion curves for Dhaka and Sylhet have been presented inTables 1 and 2.

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Figure 1: Schematic one dimensional soil model (Wathelet, 2005)
Table 1: Soil parameters for development of theoretical dispersion curve for Dhaka
Vs (m/s)Density (kg/m3)
Thickness(m)Vp (m/s)
25
525
238
1600
42
700
339
1800
0
2000
1000
2200
Table 2: Soil parameters for development of theoretical dispersion curve for Sylhet
Vs (m/s)Density (kg/m3)
Thickness(m)Vp (m/s)
16
420
210
1600
24
800
400
1800
0
2000
1000
2200
The bottom most layer of thickness 0 m is actually the elastic half space. Here 0 m thickness
is given just because GPDC program considers the half space by reading 0 values inthickness. The obtained dispersion curves are presented in Figure 2.

(a)

(b)

Figure 2: Theoretical dispersion curves for (a) Dhaka and (b) Sylhet.
The inversion of those dispersion curves have been done by using Neighbourhood Algorithm
Program Dinver. In the inversion process the assumptions are, shear wave velocity increases
with depth of the layer and poison ratio is same for soil from any depth. Less attention is
given to the poison’s ratio of soil layers because the poison ratio does not have a significant
role in forward computation of dispersion curve from soil layer (Wathelet, 2005). It is also
necessary to relate shear wave velocity with p-wave velocity.
3.

COLLECTION AND ANALYSIS OF DATA

Mictrotremor data have been collected from several locations of Dhaka (two sites) and Sylhet(five sites) as shown in Figure 3. Two kinds of array have been used for data collection as
mentioned earlier. In each array five microtremor sensors have been used. Distances between
sensors have been varied according to the available space. Figure 4 presents a typical layoutof sensors in two arrays. Typical time histories and spectral auto-correlations of collected
data are shown in Figure 5.

25

March 2013

(a)
(b)

Figure 3:
Location of datacollection at (a)Dhaka and (b)Sylhet.

Figure 4: Typical array formations.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)

(i) (b)Figure 5: Time histories (vertical component) and auto-correlations of array data

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4.

RESULTS

Microtremor array method is an approximate method which is highly susceptible to somefactors like array formation, noise in collected data, the theoretical dispersion curve and theparameterization. The noise is very high in most of the cases. Generally long time reading iscollected to reduce the effect of noise. The shear wave velocity profiles found are averagesoil profile of all the soil profiles below each sensor. Positions of the sensors provide close
but different soil profile in the same field. The theoretical dispersion curve has been
estimated based on previous soil profiles. In the parameterization phase, the poison ratio anddensity of the soil strata are kept same for all the depth. It will not lead to a profile muchdifferent from real case.
In this study shear-wave velocity at seven locations (two at Dhaka and five at Sylhet) has
been estimated. For Aided School (Sylhet), up to a depth of 16m Vs is 200 m/s, below there
up to a depth of 28 m Vs is 320 m/s, up to 68m Vs is 560 m/s and below 68m Vs is around1000 m/s. From the geology of Sylhet it is found that the deep stratum of sylhet has been
formed at tertiary age during the formation of the Himalayans. But top soil of Sylhet isformed by sedimentation of the small channels which carry loose sandy soil from upstream.
The soil profile supports the geological information. At Aftab Nagar (Dhaka) at top 4m Vs isless than 200 m/s, than from 4 to 27 m Vs is around 240 m/s, than from 27 to 60 m average
Vs is around 320 m/s, from 60 to 76 m average Vs is around 470 m/s and below 76 m Vs isaround 950 m/s. From the soil exploration in Aftabnagar, it is found that top layer of soil isreclaimed, below that stiff clay has been obtained, below 20m dense sand is present. The
shear wave velocity profile supports the soil profile obtained through subsoil exploration.

(a)

(b)

27

March 2013

(c)

(d)

(e)

(g)

28

(f)

(h)

BNUS Annual Report-2012

ICUS Report 63

(i)

(j)

(k)
figure 6: Shear-wave velocity profile at (a) Aided School cross array, (b) Aided School longarray, (c) Upashahar long Array, (d) Upashahar cross array, (e) Raza G C School, (f)Zindabazaar High School, (g) Aftab Nagar I cross array, (h) Aftab Nagar I long array, (i)Aftab Nagar II cross array, (j) Aftab Nagar II long array and (k) Abdul Gafur High School
5. CONCLUSIONSIn this study, Microtremor array method has been used to obtain shear-wave velocity profileat seven locations of Sylhet and Dhaka city. Shear-wave velocity profile at Aided School,
Upashahar, Raza GC School, Zindabazaar High School and Abdul Gafur High School at
Sylhet and two locations of Aftab Nagar Land Fill Project at Dhaka have been obtained. This
non-destructive method has been also validated by subsoil exploration up to a depth of 30 m.

29March 2013

REFERENCES
Aki, K. (1957). Space and time spectra of stationary stochastic waves, with special reference
to microtremors, Bull. Earthq. Res. Inst. 35, 415-456.
Bilham, R., V.K. Gaur and P. Molnar (2001). Himalayan Seismic Hazard, SCIENCE, 293.
Cardona, C., R. Davidson and C. Villacis (1999). Understanding Urban Seismic risk Around
the World, Summary Report on the Comparative Study of the United Nations International
Decade for Natural Disaster Reduction, RADIUS Initiative.
CDMP (2009). Engineering Geological Map for Seismic Hazard and Vulnerability
Assessment of Dhaka, Chittagong and Sylhet City Corporation Area, Unpublished Report of
CDMP.
Haskell, N. A. (1953). The dispersion of surface waves on multilayered media, Bull. Seism.
Soc. Am. 43, 17{34.
Louie, J. N. (2001). Faster, better: shear-wave velocity to 100 meters depth from refraction
microtremor arrays, Bulletin of the Seismological Society of American, 91(2), 347-364.
Nazarian, S., and Stokoe, K. H., II (1984). In situ shear wave velocities from Spectral
Analysis of Surface Waves, Proceedings of the 8th World Conference on Earthquake
Engineering, Prentice-Hall, Inc., Englewood Cliffs, New Jersey, Vol. III, 31-38.
Thomson, W. T. (1950). Transmission of elastic waves through a stratied solid medium,
Journal of Applied Physics 21, 89-93.
Tokimatsu, K. (1995). Geotechnical site characterization using surface waves, Proceedings of
1st International Conference on Earthquake Geotechnical Engineering, IS-Tokyo '95,
Balkema, Rotterdam, 1333-1368.
Wathelet, M. (2005). Array recordings of ambient vibrations: surface-wave inversion, Ph.D.
Dissertation, Universite de Liege.
Zywicki, D.J. (1999). Advanced signal processing methods applied to engineering analysis ofseismic surface waves, Ph.D. Dissertation, Georgia Institute of Technology.

30

BNUS Annual Report-2012

PART-V
COMMUNITY UNDER FIRE THREAT: AN
ASSESSMENT OF FIRE HAZARD VULNERABILITY
OF WARD 65 IN DHAKA CITYBANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: Naima Rahman
Mehedi Ahmed Ansary

ICUS Report 63

1. INTRODUCTION
Dhaka City has been experiencing many fire accidents at present and in most cases lack ofproper precautionary measures along with the institutional inefficiency, insufficientequipment support and lack of public awareness. In this study, a traditional community ofward 65 of Dhaka has been selected for vulnerability assessment. Community Vulnerability
Assessment Tool (CVAT) (Lisa et al, 2002) method has been applied to assess community’s
fire hazard vulnerability. At first, a hazard map showing the different risk zones of fire has
been developed by land use in the study area. Then four vulnerability analyses have been
conducted namely social vulnerability, critical facilities vulnerability, economic vulnerability
and structural vulnerability. Different field surveys have been conducted for getting complete
scenario of the community. By using some parameters and attributes, community
vulnerability has been evaluated with respect to fire hazard. Finally some recommendations
have been provided to improve the present condition of the community.

2. BACKGROUND
Fires hazards occur frequently in Bangladesh especially in urban areas. Table 1
describes number of fire accidents originated by various causes in the last three years in
Bangladesh. Electric fault, kitchen fire, cigarette, naked fire, burning ash, fireworks, frictionof machine, sabotage, mob, unknown and misc (engine misfire, spontaneous ignition, andchemical reaction) are different causes of fire. Among these most of the fire occur due toelectric fault and kitchen fire.
Table 1: Causes of Fire in Bangladesh
S
Number of Fire Incident
Cause of Fire
L
2009
2010
2011
1
Electric Fault
375 43.27 318 39.44 376 43.8
4
%
8
%
0
6%
2
Kitchen Fire
225 25.98 216 25.67 213 24.8
4
%
6
%
7
9%
3
Cigarette
865 9.97
789 9.75
828 9.64%%%
4
Naked fire542 6.24
528 6.52
450 5.24%%%
5
Burning Ash
229 3.41
267 3.16
358 4.17%%%
6
Fire Works
162 2.41
204 2.41
161 1.87%%%
7
Friction of
134 1.99
170 2.01
244 2.84
Machine%%%8
Sabotage85
1.26
149 1.76
104 1.21%%%

31

March 2013

9

Mob

113

1.68
%
-

241

10

Unknown868

11

Misc (Engine
536 6.17
4.61
464 5.40
misfire,%%%spontaneous
ignition, Chemical
reaction)
Total
121
146
130
82
82
41
Source: Bangladesh Fire Service and Civil Defense, 2012

110
5
389

2.85
%
-

78

0.90
%
-

726

Residential fire events are increasing in every year tremendously and it causes loss ofproperty and injures many people badly. Industrial fire is also in increasing trend.
(Bangladesh Fire Service and Civil Defense, 2011) Economic loss due to fire incidents ishigh. Figure 2 describes amount of loss due to residential fire in Taka crore from 2002 to
2010. Among these years the highest amount of loss (Tk. 272.64 crores) is seen in 2005. In
most of the years the loss amount is above Tk. 100 crores. As Bangladesh is a developing
country it cannot afford the huge amount of loss due to fire accidents every year.
300

272.64250

238.7

213.78

200
150
100

172.78112.21 110.59

92.9

107.42

2009

2010

56.45

50
0
2002

2003

2004

2005

2006

2007

2008

Year

Figure 2: Extent of losses due to fire hazards in recent years(1 Million USD = Taka 8.6 crore)(Source: Bangladesh Fire Service and Civil Defense)
Dhaka the capital of Bangladesh often faces fire hazards due to its dense building
concentrations, narrow roads, flammable building materials, aging water supply and electricalwire, chemical factory in residential areas as well as the lack of preparedness and response
skills among local people and the fire authority. Figure 3 shows the trend of fire in Dhaka
City in the last six years. Most of the fire events occurred in 2010 than the other statistical
year.

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BNUS Annual Report-2012

ICUS Report 63

2500
2000
1500
1000
500
0

1775
1220

1100

2068

1110
638

2006

2007

2008

2009

2010

2011 ( (Up to
March)

Year

Figure 3: Number of fire event in Dhaka city
(Source: Bangladesh Fire Service and Civil Defense, June 2011)
In 3rd June 2010, a devastating fire broke out in the densely-populated part of Old
Dhaka called Nimtoli. Fire killed at least 117 people and caused injury to a hundred people.
Most of the affected peoples were women and children. Initially it was thought that explosionof two transformers at Nimtoli started the fire but later it has been known the fire originatedfrom an oil stove and spread to the chemical warehouses nearby and resulted high casualties
and damages.
Old Dhaka comprises of mixed land use of buildings where most of the buildings havesmall factories like chemical, plastic, rubber etc., and Warehouse and food shops up tosecond floor of the residential building. In Old Dhaka no house is equipped with fire fighting
equipments like extinguisher, hose pipe etc. They don’t have sufficient width of staircase letalone the emergency exit. In this respect, assessment of fire hazard vulnerability in Dhaka
City especially in the old part is very important. The old part ‘Puran Dhaka’ is the mostvulnerable area in Dhaka City. In this study Ward 65 (Map 1) of Old Dhaka is selected forthe vulnerability assessment. This ward is one of most vulnerable to fire hazard than otherbecause of its traditional land use and population density. Fire incidents are very common
phenomenon in this area. It is also one of the oldest areas of Dhaka City. This ward is mainly
used as manufacturing industrial area. Besides several land uses like Warehouse, commercial
use, chemical shop, clamber storage and processing shops are also prominent. Land use ofthis area makes it more unique than the other area of Dhaka City. In this study, assessment offire hazard vulnerability of the community has been conducted to examine the existing risk offire in the area and prepare the residents to face this sort of disaster.

33

March 2013

Map 1: Study Area (ward 65 of Dhaka city)
Source: Dhaka City Corporation

3. METHODOLOGY
3.1 Study Design and Sampling
For achieving the objectives, depending on the literature review a checklist for the study has
been designed which has been modified on the basis of findings from pilot survey. The total
number of buildings of Ward 65 is 3210. For this sample size, total 1078 buildings survey has
been conducted keeping the confidence level at 95% and confidence interval is 2.5.
(http://www.surveysystem.com/sscalc.htm, accessed on 25th March, 2011).
3.2 Data Collection
A base map of the study area was collected from Dhaka City Corporation (DCC) office tobecome familiar with the environment of the study area. Field survey of the buildings was
conducted on the basis of the DCC base map. A checklist survey was conducted in the study
area to find out the existing socio-economic condition of the residents.
3.3 Fire Hazard Vulnerability Analysis
To assess the community vulnerability of Ward 65 in Old Dhaka, Community Vulnerability
Assessment Tool (CVAT) is used to find out the existing scenario of the area. This tool has 7
steps including:Hazard identification
Hazard analysis
Critical facilities analysis
Social analysis
Economic analysis
Environmental analysis

34

BNUS Annual Report-2012

ICUS Report 63

Mitigation opportunities analysis
In this study only critical facilities analysis, social vulnerability analysis, economic
vulnerability analysis and in addition structural vulnerability analysis has been done to assess
the vulnerability of the community.

4. FIRE HAZARD VULNERABILITY ANALYSISThe study area is divided into three risk zones including high risk zone, moderate risk zone
and low risk zone according to their land use. The total area of Ward 65 is 118.1668 acres
among which high risk zone is 52.84 acres (44.72%), moderate risk zone is 30.89 acres(26.14%) and low risk zone is 27.95 acres (23.65%). (From GIS Map) The livelihoods of the
inhabitants of Islambag are primarily based on plastic processing industries like plastic
manufacturing, recycling and processing factories. This zone is considered as high risk area.
In the moderate risk area processing factory and different Warehouse (plastic Warehouse,
cattle food storage) are dominant. Residential use with commercial (retail shop, office, bankand storage) use is considered as the low risk area.

Map 3: Fire risk zone in Ward 65

4.1 Critical Facilities Analysis
There are total 22 numbers of critical facilities including educational institution and religious
center in the study area. Critical facilities that are in and within close proximity to high risk
areas were identified by overlying the critical facilities location over the map of firevulnerable areas. Map 4 shows critical facilities map in Ward 65.

35

March 2013

Map 4:: Critical faccilities Map in Ward 65
Figure 4 shows that 27.27% crittical facilitiees are located at the highh risk zone i.e. Islambagg,
9.09% arre located att moderate riisk area andd 63.64% aree located at llow risk zonne i.e. Lalbagg.
In Islambbag, plastic industriesiarre located to very close proximitypto critical faciilities. Criticalfacilities of the studyy area are not vulnerable to fire. Besiides these arre located maainly adjacennt
to wider roads. In casse of any firee, these can be used as shelter for the inhabitantss.
High risskarea%
27.27%
Low riskarea
63.64%
Moderraterisk arrea
9.09%%

Figure 4: Percenntage of critical facilitiess in differentt risk zones
al Vulnerab
bility Analyssis
4.2 Socia
Number of populatioon in any buuilding of thhe study areea varies froom 0 to 400. Most of thhebuildingss (28.53%) haveh
11 to 20
2 people. 222.03% have 21 to 30 persons and 188.93% have 6
to 10 perrsons. Buildiing having populationpmmore than 100
0 is very low
w (1.6%). Buut most of thhedensely populatedpbu
uildings are situated in thet high riskk zone (Map 5) which mainlymconsisstsof plasticc recycling and processsing factoriees. In these factories
fgennerally wom
man and chilld
laborers work. Withh respect to these condiitions of thee area it cann be said that the area isvulnerablle to fire hazzard.

36

BNUS Annual Report-2012

ICUS Report 63

28.53

30.00
25.00

18.93

20.00
15.00
10.00
5.00

9.70

22.03

11.11
5.65

2.45

0.00

1.13

0.38

0.09

Number of Population

Figure 5: Population distribution in Ward 65.

Map 5: Population Map of Ward 65
4.3 Economic Vulnerability Analysis
Among the surveyed households, 57.22% have different types of economic activities. Plastic
manufacturing and processing industry is dominating (20.22%); others are different type offactory (15.19%), warehouse (8.95%), iron/metal shop/factory (2.8%), gold and silver shop
(1.49%), electric goods shop (1.3%), chemical shop/factory (1.21%) and other (6.06%) etc.
Grocery shop, grocery shop and bank, medicine shop, tailoring shop/laundry, clamberstorage, paper shop, bank/services, cloth store, hotel, market and phone shop are in othercategory. Figure 6 shows different types of economic activities of the study area. Someeconomic activities make the study area vulnerable to fire hazard. Among them plastic
manufacturing industry is totally based on chemicals which promote fire to spread within few
seconds to the locality.

37March 2013

45
5
40
0
35
5
30
0
25
5
20
0
15
5
10
0
5
0

42.78

22
20.2

15.19

95
8.9

2.8

1
1.49

1.3

1.21

6.06

Figure 6: Economic A
Activities of thet Study Arrea
4.4 Strucctural Vulnerability An
nalysisThere aree other factoors in the areea which maakes it vulnerrable to fire hazard. Theese factors arre
width off staircase, road width of the areaa and accesssibility to thet buildingg, position ofotransform
mer and elecctricity pole etc. If the rroads are nott accessible to fire service vehicle totextinguissh the fire it
i may cause a loss to the commuunity. For thhe emergenccy evacuatioon
process staircaseswiddth is a vitall issue to thee resident off a building. That’s whyy these factorrs
get impo
ortance to thhe vulnerabiility assessm
ment. The arrea consists of total 3210 structurees.
Among these,t
55.66%% of the strructures are situated in highhrisk zonne; 24.45% structures arre
situated ini moderate risk zone annd 19.89% sttructures aree situated in low
l risk zonne.
4.4.1 Agee of Structurre
From thee field surveey, 2011, it is found thaat Ward 65 is composeed of both oldo and newlly
developeed buildings. 23.3% of surveyed buuildings hav
ve been connstructed 0-110 years ago.
These arre the newesst structuress of the areaa. Most of the buildinggs have beenn constructeedaround 11-20 years ago (25.7%)). 23.2% and 11.6 % sttructures havve been buillt 21-30 yeaars
and 31-50 years befoore respectivvely. 15.9% bbuilding are 51-100 yearrs old and 0..4% buildinggs
are more than 100 yeears old.
61 70
51 60 3.3%
2.5%
5
41 50
6.8%

71 80
1.6%
%

81 90
0.3%

91 1009
1.4%

above 100
0.4%
0 10
23.3%

31 40
11.6%
21 30
23.2%

11 20
25.7%

Figure 8: Age of buuilding in thee study area
4.4.2 Number of Flooor
From fieeld survey itt has observved that in thhe study areea most of tthe buildinggs (29.64% ofosurveyedd buildings) are one storied. 22.27%% buildings are two stooried and mainlymused asa

38

BNUS Annual Report-2012

ICUS Report 63

residentiaal and plasttic processinng activity. 3 storied arre 14.35%, 4 storied arre 13.05%, 5storied arre 12.3% andd 6 to 14 stooried are 7.366%. 1.03% buildingsbaree under construction.
35.0
00
30.0
00
25.0
00
20.0
00
15.0
00
10.0
00
5.00
0.00

29.64
22.227
14.35

13.05

12.3307.36

1.03

Figgure 9: Numbber of floor of the buildiing in the stuudy area
4.4.3 Sta
aircase WidthhIn the oldder portion ofo Dhaka cityy it is a tradiition that thee width of staaircase is sm
maller than thhe
new partt of Dhaka.. From the field surveyy it has beeen observedd that stairccase width ofobuildingss varies fromm 1-5 feet. Most
M of the buildings (441.82%) havve 3 feet widde staircase. 4
feet widde staircasess are seen ini 28.09% buildings. In
I case of some newlyy constructeedbuildingss the width is 5 feet (11.73%). Wideer staircase iss essential foor any buildiing during thheevacuatioon process foor any disastter. In this reespect the stuudy area is vulnerablev
too fire hazard.
Above 5feet
1.54%
5 feet%11.73%

1 feett
0.61%%
2 feet16.2%

4 feet28
8.09%
3 feet41.82%

Figuure 10: Stairccase width (f(feet) of buildding in the study area
4.4.4 Roaad Width/ Accessibility to Building
Road wid
dth varies frrom 1 foot tot 33 feet inn the study area.
a
Most ofo the residennts have 6-110
feet roadds in front off their housees (44.73%). 16.31% havve 11-15 feeet roads and 20.42% havve
above 15
5 feet roads. 18.55% hoouseholds haave only 0-5
5 feet roads which is inaaccessible foor
fire truckk. These narrrow roads arre totally imppossible for evacuation and recue prrocess. In thhis
respect th
his commun
nity is also vulnerable tto fire hazarrd. People oof the studyy area are nootaware abbout wideninng the road.

39

March 201321 25 feet
4.85%

26 30
10.72%

16 20 feet
4.57%

ab
bove 30
00.28%

0 5 feet
18.55%
1

11 15
1 feet16..31%
6 10 feet
44.73%%

Figure 111: Road widtth (feet) / acccessibility too building in the study arrea
ansformer an
nd Electriciity Pole
4.4.5 Tra
Position of transform
mer and electtricity pole too a building is also assesssed in this studysbecausse
these maay cause serrious fire haazard to the locality. Am
mong the suurveyed buildings electrricpole is loocated in froont of 13.511% buildingss and transfo
former is loccated in fronnt of 11.37 %building.
Electricc Pole

Transfformer
Yes%
11.37%

Yes
13.51%
No86
6.49%

Figuree 12: Electriic pole in theestudy arrea

No
88.63%

Figurre 13: Transfformer in thee studyarrea

4.4.6 Exiistence of Fiire Source
Most of thet buildings of the studdy area havee different ty
ype of fire soources. Gas stove,selectric
wire, cheemical factorry and plastiic factory are the main sourcessof firre. Besides, there are alsso
some orn
nament facto
ories, metal factories,freccycled plastic shop, prinnting press anda wholesaale
paper maarket in the area all of whichw
can be source of great fire haazard. Residdential housees
are vulneerable due too gas stove (38.4%)(
andd electric wirre (15.84%)). Householdds with mixeed
use are mainlymvuln
nerable due to plastic factoryfa(17.88%), chemiccal shop (166.59%), mettal
factory (2.8%) and goldgornameent factory (1.5%).
(
3.266% buildings have no firef source. In
I
this respeect this commmunity is vuulnerable to firef hazard.

40

BNUS Annual Report-2012

ICUS Report 63

45
40
35
30
25
20
15
10
5
0

38.4

17.8

16.59
3.26

0.19

0.56

1.49

3.07

15.84
2.8

Figure 14: Existence of fire sources in the study area

5. CONCLUSIONS
Urban fire incidents have been determined to have a high likelihood of occurrence in ourcountry. In this study after conducting vulnerability assessment using Community
Vulnerability Assessment Tool (CVAT), it is found that ward 65 is vulnerable to fire hazard.
The land use pattern of ward 65 indicates the possibility of this kind of hazard. The area
comprises of residential use as well as commercial and industrial uses like plastic
manufacturing and processing factory and chemical factory which may induce massive fire.
As being a mixed use residential area, the loss due to fire may be catastrophic. To minimize
the social and economic loss, Mitigation Planning is required. A change in present land use
pattern is required. Chemical factory and plastic factory should be relocated. Road network as
well as staircase of building should be wider to evacuate the community people. Community
awareness should be raised. Although CVAT has been applied in this small area of Dhaka
city, it can be applied to any type of hazard in any location of the country both at micro andmacro levels.

REFERENCES
Lisa, K. Flax, Russell, W. Jackson and David, N. Stein (2002) “Community
Vulnerability Assessment Tool Methodology” Natural Hazards Review Vol. 3 (ISSN
1527-6988), 162-176.
http://www.surveysystem.com/sscalc.htm, accessed on 25th March, 2011.
BNUS field survey, 2012.

41

PART-VI
GEOPHYSICAL INVESTIGATION AT PROPOSEDGANGES BARRAGE SITE IN PANGSHA RAJBARIAND AT BANGORA GAS PLANT SITE IN
BRAHMANBARIABANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: Mominul Haque
Mehedi Ahmed Ansary

ICUS Report 63

Dispersion, or change in phase velocity with frequency, is the fundamental property utilized
in surface wave methods. Shear wave velocity can be derived by inverting the dispersive
phase velocity of surface waves. Surface wave dispersion can be significant in the presenceof velocity layering, which is common in the near-surface environment (upper 100 meters).
There are other types of surface waves (waves that propagate along the earth’s surface), but
for this application we are concerned with the Rayleigh wave, also known as “ground roll”.
Although there are other wave types, the term “surface wave” when used in the SASW
(Spectral Analysis or Surface Waves), MASW (Multi-channel Analysis of Surface Waves),
or MAM (Micro-tremor Array Measurement) context has come to mean the Raleigh wave.
There are two ways surface waves are generated. “Active source” means that seismic energy
is intentionally generated at a specific location and recording begins when the source energy
is imparted into the ground. This is in contrast to “passive source” or “micro-tremor”
surveying where there is no time break and motion from passive, ambient energy generated
by cultural noise, traffic, factories, wind, wave motion, etc. is recorded.
Surface wave energy decays exponentially with depth beneath the surface. The energy oramplitude of any particular frequency is dependent on the ratio of depth to wavelength.
Thus, for each frequency, the amplitude decreases by the same factor when the depth
increases by a wavelength. This means that the longer wavelength (longer-period, lowerfrequency) surface waves travel deeper and they contain more information about deeper
velocity structure and shorter wavelength (shorter-period, higher-frequency) surface waves
travel shallower and thus contain more information about shallower velocity structure.
In this context, by their nature and proximity to the geophone spread, it can be said that active
source surface waves resolve the shallower velocity structure and passive source surface
waves sample the deeper velocity structure. Since the shallower section can have a relatively
large impact on the average shear-wave velocity profile, it is important to sufficiently sample
the shallower depths. In SeisImager/SW the results from active and passive source surveys
can be combined to maximize the depth of investigation and yield a composite highresolution result over all depths (to the maximum depth of penetration).

Seismic energy for active source surface wave surveys can be created various ways, but werecommend using a sledgehammer to impact a striker plate on the ground since it is a lowcost, readily available item. To signal to the seismograph when the energy has been
generated, a trigger switch is used as the interface between the hammer and the seismograph.
When the sledgehammer hits the ground, a signal is sent to the seismograph to tell it to start
recording.
Table 1 summarizes the parameters used for active source MASW surveys. Most parameters
are self-evident, but one setting to consider further is the geophone interval and resultant
spread length.
There is a general rule of thumb that surface waves sample to an approximate depth of theirwavelength divided by two. In surface wave surveying it is assumed that the longest
wavelength that can be sampled is as long as the spread length. When combining active and43March 2013

passive results, because the passive source survey will be used to sample the greater depths,
the active source survey spread length need not be two times the depth of interest.
To determine the spread length, we suggest that you consider the maximum distance thatsource energy propagates and the shallowest depth of interest.
For an active source survey with a 10 to 20-pound sledgehammer, a geophone interval of 5 to
10 feet is suggested. Using a 24-channel seismograph, this would give a spread length of 115
feet using the 5-foot geophone interval. Applying the one-half-wavelength rule of thumb, thedepth of penetration would be about 58 feet. Depending on the site materials and conditions,source energy may not strongly propagate to an offset of 115 feet, and stacking may beneeded and/or the geophone interval may need to be reduced.
Note that the spread length has more importance on data resolution than geophone interval.
You need to find the balance between signal propagation and maximizing the spread length.
Site-specific testing and judgment should always be applied to confirm that the suggested
recording parameters are appropriate.
If you were only doing active source survey and would not have passive data to resolve
greater depths, it is recommended that the spread length equal about two times depth ofinterest. Additionally, the active source testing can include two (or more) spreads, one with ashorter and lighter weight hammer and one with a longer spread length and heavier weighthammer, to sufficiently sample a range of depths.

Figure 1: Schematic linear active source spread configuration.

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March 2013

Figure 2: A 24 channel active source data

The Earth’s surface is always vibrating weakly. This vibration is known as microtremors.The micro-tremors are generated by the various sources, such as winds, ocean waves
at ther sea shore, traffic noises, heavy machinery factories and household appliances. Microtremors are generated on the ground surface and are mainly consist of surface waves. The
vertical component of the micro-tremors can be considered as Rayleigh waves. The
dispersion curve of the vertical component of the micro-tremors is the dispersion curve ofRayleigh waves. Micro-tremors of surface waves consist of a wide range of frequency fromthe period of 0.1 second to 10 seconds. Wide range of frequency allows obtain S wave
velocity model down to several kilometers using passive surface waves.
Okada (2003) has developed a large scale passive surface wave method, so called microtremors array measurements, using long period micro-tremors. The penetration depth of themethod is from 100m to several kilometers. By selecting high frequencies depth can be
restricted to few 10s of meters and can be applied it to solve shallower problems like geotechnical, environmental and earthquake engineering. Unlike the active source surface wave
methods, the passive method does not need any sources and needs two dimensional arrays,
such as triangles, circles or crosses. The sources of micro-tremors are distributed randomly inspace, the micro-tremors do not have any specific propagation direction and need to have two
directional arrays for calculating the phase velocity of micro-tremors.

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During a passive source survey the system will “listen” and record the energy generated bycultural noise, traffic, factories, wind, wave motion, etc. There is no timing device to trigger
the seismograph.
The preferred noise sources are steady, at a constant level. The fundamental assumption of
micro-tremor array measurements (MAM) analyzed using the spatial autocorrelation methodof SeisImager/SW is that the signal wavefront is planar, stable, and isotropic (coming fromall directions). A high level of intermittent noise (like passing cars) is tolerable if the sources
are relatively distant (greater than one array length). Even if the intermittent noise sources arenear, this will usually be countered by recording long records (a minimum of 10 minutes total
recommended). Such a body of data will provide a statistically steady representation of noise.
Table 2 summarizes the recommended passive source acquisition parameters.

Four types of passive source spread or array configurations as noted in Table 2. Figure 4
illustrates the L shape configuration. In Figure 4, the black line represents the spread cableand the green inverted triangles represent the geophones.

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Figure 4: Schematic of passive source L-shape spread configurations with 11 (L11), 9 (L9),and 7 (L7) geophones. The Angle between the branches of the L is typically 60 to 90 degrees,buttechnically can be as small as 0 degrees, which is a linear array. Both branches are thesame length;Array size equals the length of the branches.
For a L-shape array, the velocity curve is representative of a point between the two branchesof the L, close to the origin. The L-shape array is the two-dimensional array that is easiest to
construct in the field. The L-shaped array can easily be constructed after an active source
survey by turning one-half of the spread 90 degrees. A typical passive source record is shown
below.

Figure 5: A typical passive source record

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B. ELECTRICAL RESISTIVITY SURVEY
Introduction
The electrical properties of the subsurface vary with the ground material, the presence andsaturation level of fluids, and the presence of buried objects. Electrical techniques
seek to describe the distribution of these properties as a function of depth and horizontal
distance. The most commonly used electrical technique is Electrical Resistivity Imaging(or Electrical Resistivity Tomography, ERT). Measurements of ground resistance are
made by introducing an electric current into the subsurface via two metal stakes(current electrodes) planted into the ground. The current passing through the ground sets up
a distribution of electrical potential in the subsurface. The difference in electrical potential
between two additional electrodes (potential electrodes) is measured as a voltage. Using
Ohm’s law, this voltage can be converted into a resistance reading for the ground between thetwo potential electrodes. Main types of procedure related to the resistivity survey are:Vertical electrical sounding (VES), Constant separation traversing (CST), and 2D resistivity
imaging.
2D Resistivity Imaging:To build a cross-sectional image of ground resistance, a string of connected electrodes are
deployed along a straight line with an inter-electrode spacing of a. Once a measurement ofground resistance has been determined for one set of four electrodes, the next set offour electrodes is automatically selected and a second measurement of resistance ismade. This process is repeated until the end of the line is reached. The line is then resurveyed with an inter-electrode spacing of 2a, 3a, 4a, etc. Each increase in interelectrode spacing increases the effective depth of the survey. The measured resistancevalues are converted to value of apparent resistivity, r (in ohm-meters) which can then be aused to model the true subsurface resistivity distribution.
Electrical resistivity imaging can be used for Mapping buried dykes and other ore bodies,
Locating fissures, faults and mineshafts, Landslide assessments, Buried foundation mapping,
Time-lapse infiltration studies, Cross-borehole tomography, Assessment of aquifer
heterogeneity, Soil corrosivity assessment, Landfill Investigation, Mapping and monitoringleachate plumes, Mapping and monitoring of groundwater pollution, Determination of depth
to bedrock, Locating sinkholes / cave systems, Stratigraphic mapping, Locating buried
channels, etc..

49March 2013

Figure 6: 2D imaging Wenner configuration showing the
Subsurface imaging points

Figure 7: A typical resistivity imaging survey, above comprises an array ofground electrodes connected to a resistivity meter. The length of line
determines the depth penetration and resolution of the data.

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RESULTS OF GEOPHYSICAL INVESTIGATION AT GANGES BARRAGE SITE
In the study area 3 shallow seismic with source (profile) and without source (L pattern) and3 2D imaging following Wenner configuration were carried out to delineate the subsurface
geology and to calculate the shear wave velocity to a depth of 30m (average Vs 30 m). The
study area is a plain agricultural land on the river bank and is mostly covered by silty/sandy
clay soil. The 2D resistivity imaging and the shallow seismic (SS) locations are shown infigure 8.

Figure 8: Location Map showing the 2D Electrical Resistivity imaging (ER) and the Shallow
Seismic (SS) Survey Points

Shallow Seismic Survey Results:
Shallow seismic survey was carried out at three SS 1, SS 2 and SS 3 locations (Fig.
8) to decipher the shear wave velocity Vs average 30m. The spread without active source was
L pattern and consists of 11 geophones (5 geophones on each side) with 3m spacing between
geophones. The active source spread was 30m along a line with 11 geophones. In each station
both ambient and artificial fields are recorded. The record length and the sampling interval
were selected 500ms and 2ms respectively. The software used for collecting and processing
the data is Pickwin. The active source data provided shear wave velocity with reliability to51

March 2013depth of around 5 to 10m. Shear wave velocity for the deeper part of the section is achieved
through the interpretation of the passive source data.
Shallow Seismic Profile 1 (SS1)
The final velocity model (Fig. 9) obtained through combining active and passive
sources data processing shows that shear wave velocity (Vs) average 30m for SS 1 is 256
m/s. The distribution of the points on velocity-density curve shows the reliability of the data.
S-velocity (m/s)
0.0

0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0 320.0 340.0 360.0 380.0 400.0

5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0

S-velocity model :Average Vs 30m = 256.5 m/s

Figure 9: Shear wave velocity (Vs) average 30m model obtained combining active andpassive source data for SS 1
Shallow Seismic Profile 2 (SS2)Shear wave velocity model for shallow seismic at location SS 2 (Fig. 10) showsthat the shear wave velocity (Vs) for SS 2 is 280m/s. Passive source data is reliable to depthof 48m and the shear wave velocity can be calculated to a depth of 48m.

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S-velocity (m/s)
0.0

0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0 320.0 340.0 360.0 380.0 400.0

5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0

S-velocity model :Average Vs 30m = 279.7 m/s

Figure 10: Shear wave velocity (Vs) model obtained combining active andpassive source data for SS 2

Shallow Seismic Profile 3 (SS3)
Shear wave velocity model for shallow seismic at location SS 3 with source (Fig. 11)
shows that the first layer with thickness of 5m has the velocity of 130m/s. The second layer
continuing to depth of 15m has the velocity of 230m/s and the third layer has the velocity of
340m/s. The second layer showing the velocity of 230m/s may act as the supporting layer.
Shear wave velocity models for recordings with source and without source show almost
identical models indicating that shear wave velocity model is independent on the type ofrecording whether it is with or without source.

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S-velocity (m/s)
0.0

0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0 320.0 340.0 360.0 380.0 400.0 420.0

5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0

S-velocity model :Average Vs 30m = 271.0 m/s

Figure 11: Shear wave velocity (Vs) model obtained combining active and passive source
data for SS 3 (with source)
2D Resistivity Imaging Results:
2D Imaging Profile 1 (ER 1)
Profile 1(ER 1) is located about 5m west of the bench mark (fig. 8). The length of the
profile is 30m and the selected electrode spacings are 1, 3, 5, 7 and 10m. The direction of the
profile is N-S parallel to the flood protection road. 2D resistivity pseudo section (Fig. 12)
prepared based on the profiling data shows that the surface layer (top soil) resistivity ranges
from 15 to 22 m. The resistivity of the top soil at the centre of the profile is maximum
reaching about 22 m. Top soil is composed of silty sand and the variation in the resistivityof the top soil is related to the variation in the moisture content of the soil. Resistivity thenreduces to 12 to 15 m at the middle depth of the section reflecting the water saturated zone.
At the deeper part of the section resistivity again increases indicating the presence of morecompacted sandy soil.

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Figure 12: 2D resistivity imaging along profile1 (ER 1)
Imaging Profile 2 (ER 2)
Profile 2 (SSER 2) is located about 100m west of the bench mark (Fig. 8). The lengthof the profile is 30m and the selected electrode spacings are 1, 3, 5, 7 and 10m. The directionof the profile is E-W parallel to the barrage axis. 2D resistivity pseudo section (Fig. 13)
prepared based on the profiling data shows that the surface layer (top soil) resistivity ranges
from 18 to 60 m. The resistivity of the top soil increases from east to west with maximum
values reaching about 60 m at the west corner. The elevation of the land increases to thewest towards the river bank. Top soil is composed of silty sand and the variation in theresistivity of the top soil is related to the variation in the moisture content of the soil. At the
deeper part of the section resistivity ranges from 15 to 30 m.

Figure13: 2D resistivity imaging along profile 2 (ER 2)
Imaging Profile 3 (ER 3)
Profile 3 (SSER 3) is located about 300m west of the bench mark and is about 10m
east from the river bank (Fig. 8). The length of the profile is 30m and the selected electrodespacings are 1, 3, 5, 7 and 10m. The direction of the profile is N-S. 2D resistivity pseudosection (Fig. 14) prepared based on the profiling data shows that the surface layer (top soil)
resistivity dominantly is around 18 m with some isolated patches showing lower resistivity(about 15 m). Middle part of the section shows resistivity around 25 m while theresistivity of the deeper part of the section is about 45 m.

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Figure 14: 2D resistivity imaging along profile 3 (ER 3)

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RESULTS OF GEOPHYSICAL INVESTIGATION AT BANGORA GASPLANT SITE
In the study area 2 shallow seismic with source (profile) and without source (L pattern) and2 2D imaging following Wenner configuration were carried out to calculate the shear wave
velocity to a depth of 30m (average Vs 30 m) and to delineate the subsurface geology. The
study area is a sand filled land and gas production and supply facilities are installed there.
The shallow seismic (SS) and the 2D resistivity imaging (ER) locations are shown in figure
8.

Figure 8: Location Map showing the Shallow Seismic (SS) and the 2D Electrical Resistivity
imaging (ER) Survey Points

Shallow Seismic Survey Results:
Shallow seismic survey was carried out at three SS 1 and SS 2 locations (Fig. 8) todecipher the shear wave velocity Vs average 30m. The spread without active source was L
pattern and consists of 11 geophones (5 geophones on each side) with 3m spacing between
geophones. The active source spread was 30m along a line with 11 geophones. In each station
both ambient and artificial fields are recorded. The record length and the sampling interval
were selected 500ms and 2ms respectively. The software used for collecting and processing
the data is Pickwin. The active source data provided shear wave velocity with reliability to57

March 2013depth of around 5 to 10m. Shear wave velocity for the deeper part of the section is achieved
through the interpretation of the passive source data.
Shallow Seismic Profile 1 (SS1)Profile SS1 is located close to bore hole BH 1 at the north-west corner of thesurveyed area (Fig. 8). The final velocity model (Fig. 9) obtained through combining active
and passive sources data processing shows that shear wave velocity (Vs) average 30m for SS
1 is 145 m/s. The distribution of the points on velocity-density curve shows the reliability ofthe data.

S-velocity (m/s)

0.0

0.0

50.0

100.0

150.0

200.0

250.0

300.0

5.0
10.0
15.0
20.0
25.0
30.0

S-velocity model : 17.dat-21.dat
Average Vs 30m = 145.0 m/s

Figure 9: Shear wave velocity (Vs) average 30m model obtained combining active
and passive source data for SS 1
Shallow Seismic Profile 2 (SS2)
Profile SS2 is located close to bore hole BH 2 at the central-west of the surveyed
area (Fig. 8). Shear wave velocity model for shallow seismic at location SS 2 (Fig. 10) showsthat the shear wave velocity (Vs) for SS 2 is 207.5m/s.

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S-velocity (m/s)
0.0

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

5.0
10.0
15.0
20.0
25.0
30.0

S-velocity model : 32.dat-38.dat
Average Vs 30m = 207.5 m/s

Figure 10: Shear wave velocity (Vs) model obtained combining active andpassive source data for SS 2
2D Resistivity Imaging Results:
2D Imaging Profile 1 (ER 1)
Profile 1(ER 1) is located close to borehole BH 1at north-west corner of theinvestigated area (fig. 8). The length of the profile is 30m and the selected electrode spacingsare 1, 3, 6 and 9m. The direction of the profile is E-W parallel to the northern boundary of the
Tullow installations. 2D resistivity pseudo section (Fig. 11) prepared based on the profilingdata shows that the surface layer (top soil) resistivity ranges around 80 m. Top soil iscomposed of filled dry sand. At the middle depth of the section resistivity in the western part
increases to more than 100 m. At the deeper part of the section resistivity varies from 12 to
40 m.

Figure 11: 2D resistivity imaging along profile1 (ER 1)

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Imaging Profile 2 (ER 2)
Profile ER 2 is located close to bore hole BH 2 at the central-west of thesurveyed area (Fig. 8). The length of the profile is 30m and the selected electrode spacingsare 1, 3, 6 and 9m. The direction of the profile is E-W. 2D resistivity pseudo section (Fig. 12)
prepared based on the profiling data shows that the surface layer (top soil) resistivity ranges
from 85 to more than 100 m. The resistivity of the top soil at the west of the profile ismaximum reaching to more than 100 m. Top soil is composed of filled dry sand and thevariation in the resistivity of the top soil is related to the variation in the moisture content of
the soil. Resistivity then reduces to 33 to 64 m at the middle depth of the section. At the
deeper part of the section resistivity varies from 12 to 24 m.

Figure 12: 2D resistivity imaging along profile 2 (ER 2)

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PART-VII
FIRE AT HAZARIBAG RESIDENTIAL AREA
IN OLD DHAKABANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: Naima Rahman
Mehedi Ahmed Ansary

ICUS Report 63

A devastating fire broke out at around 3:00 am of 18 November 2012 (Sunday) throughHazaribagh's Bou Bazar slum which is situated at the south-west periphery of Dhaka City.
The fire caused death of at least 11 people including six women and five children dead andgutted 700 shanties.
From the point of view of local residents the fire originated from a cigarette butts, mosquito
coils or kerosene stove in a rickshaw garage right in front of the slum. Just minutes after it
broke out, the fire engulfed the nearby houses after coming in contact with some kerosene
drums, which had been kept for sale. The fire spread quickly and destroyed 150 rickshaws
and six auto-rickshaws in the garage, and some 700 shanties. These shanties were the homesof about 3,000 low-income people who have lost everything in the fire. Besides thirty shops,
two bakeries, five rickshaw garages and a mosque were also burned while five adjacentbuildings were partly damaged.
All the fatalities occurred in the 'Shamsu Professor's Slum' which is generally a compound;
occupies over nearly five-katha land, surrounded by a wall and has a two-storied concretebuilding with tin-shed roof and temporary shanties on the edge of the Bou Bazaar slum.
There is only one entrance of the slum which is a six-feet high and four-feet wide.
The 11 dead were the tenants of the two-story tin-shed house, where 46 families lived. The
two-storied concrete building has kitchens, bathrooms and toilets. As the fire began to spread,
all the tenants ran for their lives through a common exit. But the 11 victims, being womenand children, could not run as fast. So instead of getting out of the house, they took shelter ina bathroom and a kitchen. But soon the blaze, gushing through the exit, engulfed thebathroom and the kitchen and burned them alive. Some people, mostly men and youths,
escaped the fire by jumping over the boundary walls. Others cut through their bamboo
boundaries and jumped outside. Seventeen fire fighting units from seven stations
extinguished the fire after two and a half hours of hectic efforts at around 7am in themorning.
Government has announced to provide aid for the affected families. Families of deceased
would receive Tk 20,000 from the local administration and Tk 10,000 from the City
authorities. In addition Tk 900,000 will be handed later to rebuild their houses. The prime
minister gave 6,000 pieces of blankets, 3,000 pieces of saris, 3,000 pieces of three-pieces,
3,000 pieces of sweaters, 3,000 pieces of shawls and 409 pieces of lungis for the affected
people. The relief materials were handed over to the deputy commissioner of Dhaka for
distribution among the victims.

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62

Burnt Household Materials

Burnt Rickshaws

Affected Adjacent Buildings

Affected Water Supply

Temporary Shelter

Temporary Shelter

BNUS Annual Report-2012

PART-VIII
FIRE AT A READYMADE GARMENT FACTORY AT
NISCHINTAPUR IN ASHULIA INDUSTRIAL AREABANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: Naima Rahman
Mehedi Ahmed Ansary
At the night of November 24, 2012 a catastrophic fire attacks a nine-storey garment building
named Tazrin Fashion of Tuba Group Ltd. The factory is situated at Nischintapur which is apart of Ashulia industrial belt near Dhaka City.

ICUS Report 63

The fire, started at 7:30 PM at the ground floor of the factory seemed to be caused by anelectrical short circuit. The fire spread quickly to other floors because of the large amount of
fabrics and yarn which was stored in front of the staircase at the ground floor the factory.
Thus the workers at the upper floors were trapped and could not come out of the building
using the staircase. The fire burned for more than seventeen hours before firefighters
succeeded in extinguishing it. Due to lack of water in surrounding areas, the dousing
operation was delayed.
Most of the victims at least 69 bodies were found on the second floor, 21 from the third floor
and 10 from the fourth floor. 12 victims died leaping from windows to escape the flames,
some of them dying of their injuries after being taken to area hospitals. Other workers who
had escaped to the roof of the building were successfully rescued.
Many workers had been unable to escape through the narrow exits. The fire department's
operations manager stated that the factory lacked emergency exits that led out of the building.
All three staircases of the building led through the ground floor, making them unusable in thefire. Some workers who managed to escape the fire by jumping from windows complainedthat after hearing the alarm of fire they rushed to the supervisors. But they told them thealarm was not working properly and locked the collapsible gate. Fire Service started rescue
operations on the ninth floor in the morning after dousing the blaze. The fire fighters also
found the gate locked and they had to cut the padlock to enter at upper floor. Thus the rescue
operation was delayed. Army's Ninth Infantry Division, police; RAB and Border Guard
Bangladesh members took part in the rescue. Meanwhile, relatives of the trapped workers
thronged the factory area and spent a sleepless night there in the hope of getting their loved
ones back alive. In the morning, rescuers started retrieving burnt bodies from inside thebuilding and gathering them at the Nischintopur Government Primary School premises.
Prime Minister Sheikh Hasina stated her shock at the death toll, called for thorough searchand-rescue operations and also suspected the incident as sabotage. Home Minister Mohiuddin
Khan Alamgir also supported the suspicion, citing a series of recent fires at clothing factories.
In one incident, two employees were caught on CCTV attempting to set fire to stockpiled
cotton. But some recent enquiries found no involvement of the suspect in this fire accident.
The administration, police and Fire Brigade have formed three separate committees toinvestigate the cause of the devastating fire. Three supervisors from the factory were arrested
on 28 November on charges of criminal negligence. Police accused them of padlocking exits
and preventing workers from leaving the building.
The Bangladesh Garment Manufacturers and Exporters Association (BGMEA) offeredsupport to the victims' families and announced giving Tk 100,000 each to the families of thedeceased. The Ministry of Labour announced giving Tk 10 million for the injured. The
district administration announced Tk 20,000 each for the families of the victims as funeral63March 2013

costs. Hong Kong sourcing giant Li & Fung which has orders placed with Tazreen Fashions
offered to give $1,200 to each of the families of those who died in the blaze.
According to the website of Tuba Group it has 13 other garment factories other than Tazreen.
Around 1,500 people used to work at Tazreen Fashions. Authorities said there were around
300 employees in the nine-storied factory to ensure fire safety. They comprised fire fighters,
rescue workers and primary medics. However, there were no visible efforts on their part toextinguish the fire. Eight fire-extinguishers placed on each floor from the first to the seventh.
The equipments were last tested on the fifth of this month and bore the authority's signatureson them. The 'open rings' of two of the fire extinguishers found lying on the second and third
floors were intact. There was evidence of using one of the extinguishers on the seventh floor.
The thread warehouse on the ground floor was found burned to ashes. Fire brigade officials
assumed fire to have originated from there.
Opened in 2009, the Tazreen Fashion factory employed 1,630 workers, who produced Tshirts, polo shirts and jackets. The factory produced clothes for various companies, including
Dutch company C&A, American company Walmart and Hong Kong company Li & Fung.
The Tuba group is a major exporter of garments from Bangladesh to the U.S., Germany,
France, Italy and the Netherlands, whose clients include Wal-Mart, Carrefour and IKEA.
According to Tazreen Fashions' web site, the factory was flagged in May 2011 with anorange grade by a Walmart ethical sourcing official for violations and/or conditions whichwere deemed to be high risk. The notice said that any factory receiving three suchassessments in two years would not receive Wal-Mart orders for one year. The orange rating
was the first the company had received, and was followed by a yellow medium risk rating thefollowing August, which pertained to the factory where the fire occurred.
On 27 November, Walmart America ended its relationship with Tuba and stated that theTazreen factory was not authorized to produce merchandise for Wal-Mart. A suppliersubcontracted work to this factory without authorization and in direct violation of theirpolicies. The corporation also said that it would be working with suppliers to improve fire
safety.
Three trade unions demanded that US retailer Walmart compensate the families of those who
were killed or injured in a deadly fire at Tazreen Fashions Ltd in Ashulia on November 24.
Apart from compensations, the unions in a letter asked Walmart to bear all expenses of therequired treatment of the injured. Leaders of the workers' rights groups requested the world's
largest retailer not to stop outsourcing to Bangladeshi factories. Cancellation of orders would
only add to the plight of garment workers, leaving many of them jobless. It should be
mentioned that Walmart is the largest buyer of Bangladesh's readymade garment products,
purchasing items worth over $1billion annually.

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Prime Minister Sheikh Hasina handed over Tk 2.58 crore to the families of 43 of the 112
victims on 4 December 2012 at the Prime Minister's Office. Each of the family was given Tk.
6 lakhs. The amount needed for the families of all the 112 dead workers will total Tk 6.72
crore. Of the Tk 6 lakh given to each family, Tk 2 lakh came from the Prime Minister's Relief
and Welfare Fund and Tk 1 lakh each from the labour and employment ministry, BGMEA,
Bankers Association of Bangladesh and Hong Kong-based readymade garment (RMG)
importer Li & Fung.
Tazreen Fashions will get a fire-insurance of Tk 18 crore as a compensation for thedevastating blaze killing 112 workers of the RMG industry. The RMG had a one-year fireinsurance with Karnaphuli Insurance Company Limited in 2011. The Tazreen Fashions isgoing to get the compensation as tenure of the year-long insurance would be effective till
December in 2012, just before a month of the completion of the tenure.

Figure 1: Blaze

Figure 2: Fire fighting operation

Figure 3: Burnt machineries

Figure 4: Injured worker

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Figure 5: Crowd at outside

66

Figure 6: Mourning relative

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Insurers worried over rising RMG accidents
Insurance companies are concerned over the growing number of accidents in apparel factories
as the insurers' compensation for their clients in the garment sector has been on the rise over
the years. In a move, the companies have decided to devise new policies to handle themenace, especially the fire accidents that kill people and occur mainly due to poor factory
management. “We are the worst sufferers of accidents in factories as we are the leading
insurer in the country,” said Nasir A Chowdhury, managing director of Green Delta
Insurance Company. Green Delta paid Tk 5.6 crore as compensation for fire accidents ingarment factories in 2010. The amount rose to Tk 12.20 crore in 2011. Till September thisyear, the insurer has paid Tk 4.5 crore as compensation. According to the Clean Clothes
Campaign, an alliance of organisations in 15 European countries, more than 500 Bangladeshi
workers have died in factory fires since 2006. In February 2006, at least 57 workers were
killed and more than 100 seriously injured when fire engulfed KTS, a textile factory in
Chittagong. Fire at Spectrum, a garment factory near Dhaka killed 29 people in the same
year. The latest fire incident in Tazreen Fashions claimed more than 100 lives. Fire insurance
is a must for factories. The companies that are engaged in export-import business have tocover some additional risks. Before issuing insurance coverage, insurers need to inspect thefactories to know about their safety measures and compliance. “We think twice before
insuring a hazardous factory, such as garments,” said Sabir Ahmed, chief financial officer of
Reliance Insurance, one of the top two companies in the country. “We inspect factories on
our own,” said Ahmed. “We did not need to pay a big amount of compensation last year.”
Chowdhury said they also carry out survey of the factories before issuing any coverage.
Insurers usually ignore minor loopholes, he said. “But we find a lot of shortcomings when afactory goes for claims settlement,” he said. “And, we minus the cost for negligence.” Theissue has become a worry for the insurers' association as well. “We have convened a special
board meeting after the fire accident in Tazreen Fashions. We've formed a committee todevise new policies to handle the growing number of accidents,” said Sheikh Kabir Hossain,
president of Bangladesh Insurance Association. Hossain said insurers face problems during
claims settlement as the policyholders do not cover all the machinery and risks.“When we
carry out survey for claims settlement we find major loopholes,” he said. Hossain, who is also
the chairman of Sonar Bangla Insurance, said his company is witnessing a rise in claims for
accidents in garment factories. He said factory owners do not insure their workers, theirpolicies only cover the factories. The garment industry having more than 5,000 factories
produces clothes for the western countries. Garments account for 80 percent of Bangladesh's
exports, with earnings of nearly $19 billion in the last financial year. Nearly 3.5 million
people, mostly women, are employed in the industry.

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PART-IX
COLLAPSE OF AN UNDER-CONSTRUCTIONFLYOVER AT BAHADDARHAT IN CHITTAGONG

BANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: Naima Rahman
Mehedi Ahmed Ansary

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Three concrete girders of an under-construction flyover at Bahaddarhat in Chittagong
collapsed on 24 November 2012 evening, burying a makeshift kitchen market andpassersby.Each concrete girderwas 42 metre in length and two-and-half metres in height.At
least 13 people died and more than 50 were injured when the concrete girders collapsed.
Eyewitnesses said at around 8:00pm three concrete girders of the flyover fell on some people,
mostly vegetable vendors of the kitchen market. The accident occurred when workers were
shifting the girders on the flyover, said Hasanul Islam, a student of the Chittagong Universityof Engineering and Technology, who observed the whole thing from a close distance. At one
stage, he saw one girder which was in the middle go off balance and push the other two to theroadside and adjacent pond.
Communication experts said that there were faults in the construction and safety measures in
the project. The construction company did not issue any warning to the public while carryingout the shifting work of the girders And the Chittagong Development Authority (CDA), whois constructing the flyover at a cost of Tk 106 crore, had failed to ensure security at the siteand had apparently no supervisory role when the work was going on. They should haveensured enough precautionary measures in the entire project area for the flyover. And the
district administration was allowing pedestrians, peddlers and others to move about freely
and use the place. Meanwhile, a girder on the pillar numbers 20 and 21 has been foundvulnerable by the. People have been advised to remain cautious while travelling through thearea,
On June 29, a concrete girder connecting pillars No. 22 and 23 of the same flyover fell on theroad below, slightly injuring a rickshaw-puller. Luckily, the accident happened on a Friday
during Juma prayer time when the road was almost empty.
The construction work of the four-lane flyover began in December 2010.

The girder which collapsed at 29 June,2012

The girder which
November, 2012

collapsed

at

24

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PART-X
VIBRATION MEASUREMENT AND NDT AT A
CEMENT FACTORY SITEBANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: KM Khaleduzzaman
Raquib Ahsan
Mehedi Ahmed Ansary

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1.0
Measurement of Vibrations
Figure 1 shows the location map (showing the point of measurement) of the area over which
vibration measurements were made. Figure 2 shows the microtremor observation system.
The BRTC, BUET team conducted the measurement of vibrations using a 15-channel
recorder at five locations of the plant, simultaneously, as shown in Figure 1. Each of thesensors has three components in X, Y and Z directions. For this study, however, only thevertical components (Z-directions) at the selected locations were measured. The following
channels were assigned: Ch 3 (for free-field - at the river side), Ch. 6 (for Gear-box
foundation), Ch. 9 (for Ball Mill outlet foundation), Ch. 12 (for Ball Mill inlet foundation)
and Ch. 15 (for free-field - within the plant). For the initial several minutes, the ball mill was
kept shut off and it then was started until the machine ceases to work after two days. Even
after the cease of the ball mill readings of vibrations were also taken for another 48 hours
continuously.
Ch15

Outlet:Inlet:

Gearbox:Fig. 1 Locations of Vibration

Ch3River Side

Measurement

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Fig. 2 Measurement of Plant Vibration using Microtremor System

Fig. 2 (Continued) Measurement of Plant Vibration using Microtremor System
2.1 Vibration Plots at Channel 6 (Gear Box Base) for Different Time Segments
In the following figures (Fig. 3), the collected data are presented for several time segments. In
the following sections they are described and analysed.

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Time: 18:23 on 06/10/2012

Time: 22:30 on 06/10/2012

Time: 2:44 on 07/10/2012

Time: 2:53 on 07/10/2012

Time: 7:25 on 07/10/2012

Time: 11:30 on 07/10/2012

Time: 15:44 on 07/10/2012

Time: 20:00 on 07/10/2012

Time: 00:08 on 08/10/2012

Time: 06:25 on 08/10/2012

Time: 11:11 on 08/10/2012

Time: 15:18 on 08/10/2012

Time: 19:26 on 08/10/2012

Time: 23:57 on 08/10/2012

Time: 06:06 on 09/10/2012

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Fig. 3 Vibration Plots at Channel 6 (Gear Box Base) for Different Time Segments
2.2 Comparison of Vibrations at Channel 6 (Gear Box Base) for Different Time
Segments
Figure 4 shows the Fourier Spectrum of the vibrations at gear box base (Channel 6). The
Fourier Spectrum shows the predominant frequency of the Mill to be 7.5 Hz when the mill isrunning (October 6: 22:30 and October 7: 20:00). The amplitude of the vibration is around 7.
The machine did not show any peak while the Mill is at rest (October 6: 18:23 and October 8:
19:26).

Fig. 4 Fourier Spectrum of the vibrations at Gear Box Base (Channel 6) at Different Time
Segements
2.3 Comparison of Vibrations at Channel 6 for Different Time Segments Including theTime when the Mill Ceases
Figure 5 shows the Fourier Spectrum of the vibrations at gear box base (Channel 6) atdifferent time segments including at the time when the mill ceases. The Fourier Spectrum
shows the predominant frequency of the Mill to be 7.5 Hz when the mill is running (October
6: 22:30 and October 7: 20:00). The machine did not show any peak while the Mill is at rest
(October 6: 18:23). The machine shows a slightly amplified peak just before it ceases(October 8: 00:08). The amplitude of the vibration is around 13.

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10

06_1823
06_2230
07_2000
08_0008

Amplitude

1
0.1
0.01
0.001

5E-5

Fig. 5
2.4

0

5

10

15

20

25

30

35

Frequency (Hz)

40

45

50

Fourier Spectrum of the vibrations at Gear Box Base (Channel 6) at Different Time
Segments Including the Time Prior to The Mill Ceases
Comparison of Vibrations at Different Channels for Particular Time Segment

Figure 6 shows the Fourier Spectrum of the vibrations at different channels at a fixed time
segment. The predominant frequency, for all the Fourier Spectra, peaks at 7.5 Hz when themill is running. The amplitude of the vibration is less than 10.

Amplitude

10
5

ch6-06_2230
ch9-06_2230
ch12-06_2230
ch15-06_2230

2
1
0.5
0.2
0.1
0.05
0.02
0.01
0.005
0.002
0.001

0

5

10

15

20

25

30

Frequency (Hz)

35

40

45

50

Fig. 6 Fourier Spectrum of the Vibrations at Different Channels
2.5 Comparison of Vibrations at Different Channels for the Time Segment When theMill Broke Down
Figure 7 shows the Fourier Spectrum of the vibrations at different channels at a fixed time
segment prior to the Mill ceases. The predominant frequency, for all the Fourier Spectra,
peaks at 7.5 Hz. The amplitude of the vibration is around 13 at all the channels except atchannel 9 where the amplitude is around 35.

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March 201350

ch6-08_0008
ch9-08_0008
ch12-08_0008
ch15-08_0008

Amplitude

10
1
0.1
0.01
0.001
0.0002

0

5

10

15

20

25

30

Frequency (Hz)

35

40

45

50

Fig. 7 Fourier Spectrum of the Vibrations at Different Channels at Different Time Segments
Including the Time Prior to The Mill Ceases
3.0 Shear –Wave Velocity Estimation through Microtremor Array Observation
Figure 8 shows the estimated value of shear-wave velocity profile for the site. The average
shear-wave velocity for a depth of 30 m is 288 m/s. The predominant frequency of the freefield (soil) is 2.4 Hz.

Fig. 8 Estimation of Shear-Wave Velocity at the Plant Site through Microtremor Array

4.0

76

Remarks on Ball Mill Foundation Vibrations

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4.0 Remarks on Ball Mill Foundation Vibrations
The predominant frequency of the Mill foundation during operation is 7.5 Hz and for the soil,
it is 2.4 Hz. The probability is low for resonance to occur between the Mill foundation andthe free field soil.
5.0 Ball Mill Foundation Design
The ball mill foundation consists of P3 type (as designated in design drawings) of bored piles.
The salient features of the pile foundation are provided below in Chart 1.
Chart 1: Salient Features of the Pile Foundation of Ball Mill(i)Type of foundation(ii)

Total number of piles used in Ball
Mill area(iii) No. of piles in a group in Inlet(iv) No. of piles in a group in Outlet(v) No. of piles in a group in gear box& motor base(vi) No. of piles in Other areas(vii) Arrangement of piles(viii) Length of piles(ix) Diameter of piles(x) Minimum c/c spacing of piles(xi) Main reinforcement used in pile(xii) Design
strengthofpile
reinforcement(xiii) Design strength of concrete in pile(xiv) Dimensions of pile cap(xv) Thickness of pile cap(xvi) Type of pedestals
5.1

:
:

Bored cast in situ group pile with continuous pile cap& pedestals at the inlet and outlet of ball mill
24 as shown in APPENDIX-B:::

Six (6)Six (6)
Eight (8)

:
:
:
:
:
:
:

Four (4) in square
Rectangular arrangement beneath common pile cap(rectangular irregular shaped)
20 m
600 m
1.8 m
12-20 mm
415 Mpa::::

27.5 Mpa(3.50 m × 18.6 m) + (3.50 m × 9.9 m)
1.5m
Wall type with rectangular sections

Subsoil Condition

The subsoil condition of the site was investigated by Development Design Consultants,
Dhaka. It is understood from subsoil investigation report that three bore holes (BH. Nos. 15,
16 & 17) were done to a maximum depth of 27 m in the ball mill areas for the purpose
designing foundations of the ball mill. Standard Penetration Test (SPT) and other soil
parameters were determined. It appears from borehole log and soil report that the soils at all
the locations investigated are typical of alluvial sand deposits with a significant depth(approximately 8 meters) of soft soil deposit. The borehole logs are attached as APPENDIXC.
The soil at the site, in general, consists of four (4) layers of sandy soil deposits. The top layerof 8 m thick is loose fine sand (Av. Field SPT 2), followed by a thin layer of 3 m of loose
to medium dense fine sand (Av. Field SPT 9) under lain by two thick layer of medium
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dense to dense fine sand with average field SPTs of 15 and 35 respectively. The water table isapproximately at 5.0 m.
5.2
Basic Criteria for Machine Foundation Design
The existing foundations of ball mill can be termed as piled block foundation. According to
Srinivasulu & Vaidyanathan (1990), the following criteria should be satisfied from the design
point of view for machine foundations.
(a) The machine foundation should be able to carry the superimposed loads withoutcausing shear or crushing failure.
(b) The settlements should be within the permissible limits.
(c) The combined centre of gravity of machine and foundation should as far as possible
and be in the same vertical line as the centre of gravity of the base plane.
(d) No resonance should occur, hence, the natural frequency of foundation-soil systemshould be either too large or too small compared to the operating frequency of themachine. For low-speed machines, the natural frequency should be high, and viceversa.
(e) The amplitudes under service conditions should be within permissible limits. The
permissible limits are generally prescribed by the machine manufacturers.
(f) All rotating and reciprocating parts of a machine should be so well balanced as tominimize the unbalanced forces or moments.
(g) Where possible, the foundation should be planned in such a manner as to permit a
subsequent alteration of natural frequency by changing base area or mass of thefoundation as may subsequently be found necessary.
From the practical point of view, the following requirements should be fulfilled:(a) The ground-water table should be as low as possible and ground-water level deeper
by at least one-fourth of the width of foundation below the base plane. This limits thevibration propagation, ground-water being a good conductor of vibration waves.
(b) Machine foundations should be separated from adjacent building components bymeans of expansion joints.
(c) Any steam or hot air pipes, embedded in the foundation must be properly isolated.
(d) The foundation must be protected from machine oil by means of acid resisting coatingor suitable chemical treatment.
(e) Machine foundations should be taken to a level lower than the level of the foundationsof adjoining buildings.
Keeping the above important points in mind, the foundation design was checked for vertical
capacity, settlement and lateral deflection of the pile foundation used. The natural frequencyof the piled foundation was also estimated. In the following articles results are reported anddiscussed.
5.4 Static Analysis of Foundation Capacity and Settlement
The allowable load compressive downward load carrying capacity, vertical settlement andlateral deflection of the pile foundation under inlet and outlet was calculated using the soil
parameters as obtained from subsoil investigation report. The results are presented in Chart 3.
Chart 3: Load Carrying Capacity of Pile Groups
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Soil Data Taken
From

Borehole 15
Borehole 16
Borehole 17

Allowable
Compressive
Load Capacitywith FS =2.5
(kN)
619
590
624

Settlement at
Ultimate
Compressive
Load (mm)LateralDeflection at
applied Loadof 70 kN (mm)

21.8
22.8
22.5

2.4 - 8.8
2.4 - 8.8
2.4 - 8.8

The results indicate that the maximum design capacity of 1034 kN as used in ball millfoundation is an over estimation, while compared to the results using a BNBC recommended
factor of safety of 2.5 (Chart 3). However, results appear to be adequate only with a factor ofsafety of 1.5. The estimated settlement of the foundation is high, thus the expecteddifferential settlement would also be high. It is suggested to carryout a precision topographic
survey for the differential settlement at the inlet and outlet pedestals. The lateral deformation
is in the range of 2.4mm to 8.8 mm. This should be verified with allowable design deflection.
[
5.5 Dynamic Analysis for Natural Frequency of Piled Foundation
The natural frequency of vertical vibrations ( n) of an end bearing pile carrying a load W
may be obtained from the relation:

tan
Where,(1)is the ratio of self weight of the pile to the external load carried by it, and

n

H

Eg

(2)

E and are the modulus of elasticity and density of pile material; and H is the height of thepile, g is the acceleration due to gravity. Table 1 shows the values of for various values of. For a pile of known characteristics the natural fequency may be obtained using Eq. (2) andTable 1.
Table 1 Coefficients for Natural Frequency of Piles (after Srinivasulu & Vaidyanathan,
1990)

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Now load coming to a pile at the inlet end are basically from mill ball, pile cap and pedestal,and the load can be calculated as 593 kN. The weight of a single pile is 130kN (Chart 2).
Therefore,

Weight of pile
Load on the pile

130
593

0.22

Corresponding to this value of , the value of
frequency may be calculated as:

0.43

n

20

23.5
24.8 106 9.81

may a taken as 0.43. Thus the natural

n

69.2

The circular natural frequency of the pile is 69.2 rad/sec. This corresponds to a natural
frequency of 11 Hz. The predominant frequency of the Mill foundation during operation wasmeasured as 7.5 Hz. The frequency ratio is 0.68 which may result in an amplitude
magnification factor of approximately 2.
6.0 Analysis of Vibration Data recorded at Crown Cement Factory
Vibration data has been collected for almost one hour to a nearby Crown Cement Factory.
The gearbox in this factory is located axially with the inlet and outlet of the Ball Mill. The
BRTC, BUET team conducted the measurement of vibrations using a 15-channel recorder atfive locations of the plant, simultaneously. Each of the sensors has three components in X, Y
and Z directions. For this study, however, only the vertical components (Z-directions) at the
selected locations were measured. The following channels were assigned: Ch 3 (for freefield), Ch. 6 (for Gear-box foundation), Ch. 9 (for Ball Mill outlet foundation), Ch. 15 (forBall Mill inlet foundation) and Ch. 12 (on the pilecap). Figure 9 shows the Fourier Spectrumof the vibrations at different channels at a fixed time segment. The predominant frequency of
the gearbox foundation is 16.5 Hz. The maximum amplitude of the vibration is lower than 1
at all the channels except at channel 6 where the maximum amplitude is around 3.5.
.

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Fig. 9 Vibration analysis at the Crown Cement Factory
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7.0

Predominant Frequency of Pile-Foundation System Using Thin Layered Element
Method (TLEM)

The dynamic impedance of a groped pile is evaluated by an equivalent single upright beam
method, which is first proposed by Konagai et al [2000]. A brief description about theequivalent single upright beam analogy is given in this paper. See Ref. [5] for its details. The
present single upright beam is a composite of np piles and the soil caught among them.
Following the assumption of Thin-Layered Element Method (“TLEM”), the soil deposit
overlying its rigid bedrock should include a cylindrical hollow of radius R0. The single
upright beam is assumed to be embedded in this hollow. The cross-section R02 of this hollow
is assumed to be identical to the cross-section of the beam AG enclosed with the broken line
circumscribing the outermost piles in the group (Fig. 10). The motion of the hollow isassumed to be compatible with that of the beam. The soil-pile composite together with its
exterior soil is divided into nL horizontal slices as shown in Fig. 10. The following
assumptions are adopted to derive the stiffness matrix of the equivalent single beam.
(a) Pile elements within a horizontal soil slice are all deformed at once keeping their intervals
constant, and the soil caught among the piles moves with the piles.
(b) Frictional effects due to bending of piles are ignored.
(c) The top ends of piles are fixed to a rigid cap.
(d) All upper or lower ends of the sliced pile elements arranged on the cut-end of a soil slice
remain on one plane.

Fig.10 Assumption for evaluation of equivalent single

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For the Pile-Soil System in the Emirates Cement Factory:
Predominant frequency for lateral vibration of the whole pile group under an excitation of
7.5Hz has been determined assuming that the superimposed load/mass from the machine andthe foundation behaves together as a Single Degree of Freedom (SDOF) system. Total load
has been assumed to be 465 ton. Stiffness of the pile group has been determined using Thin
Layered Element Method (TLEM) which considers pile-soil-pile interaction of the pile group.
To incorporate pile-soil-pile interaction, soil properties were obtained using Microtremor
measurements. Soil is assumed to be saturated. Following pile properties have been
considered in the present analysis.
Pile length = 20 m
Pile diameter = 600 mm
Number of Piles = 24
Pile locations – as provided in the drawing
Young’s modulus of pile = 2.1 E6 ton/m2
Unit weight of pile = 2.4 ton/m3
From the TLEM analysis, it is found that the lateral stiffness of pile group under 7.5 Hz
excitation is almost 160,000 ton/m. Thus the predominant frequency of the SDOF systemwith this stiffness becomes 9.25 Hz.

8.0

Concluding Remarks

The analyses of the data obtained from field observations and scrutiny of the design drawing
lead to the following conclusions regarding vibrations and ceasure of ball mill operations ofemirates cement factory at East Mukterpur, Munshigonj.
(i) The predominant frequency, for all the Fourier Spectra, peaks at 7.5 Hz when the Ball
Mill is running. The amplitude of the vibration is around 10. Just before the Mill ceases,
the amplitude of the vibration is around 13 at all the channels except at channel 9(outlet) where the amplitude is around 35.
(ii) The design static load creates a settlement of approximately 23 mm; this reveals that
their might be differential settlement between inlet and outlet of the ball mill. A
precision survey should be carried out.
(iii) The circular natural frequency of the pile is 69.2 rad/sec. This corresponds to a natural
frequency of 11 Hz. The predominant frequency of the Mill foundation during
operation was measured as 7.5 Hz. The frequency ratio is 0.68 which may result in an
amplitude magnification factor of approximately 2.
(iv) The fixing arrangement of gear box and motor should be checked against any damage
in the arrangements.
(v) At the Crown Cement Factory: The predominant frequency of the gearbox foundation is16.5 Hz. The maximum amplitude of the vibration is lower than 1 at all the channels
except at channel 6 where the maximum amplitude is around 3.5.
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83March 2013(vi) From the TLEM analysis, it is found that the lateral stiffness of pile group under 7.5 Hz
excitation is almost 160,000 ton/m. Thus the predominant frequency of the SDOF
system with this stiffness becomes 9.25 Hz. The frequency ratio is 0.81 which may resultin an amplitude magnification factor of almost infinity. This high amplification of
displacement may be a cause for failure of the gearbox system.
Bibliography:
Konagai, K., Ahsan, R. and Murayama, D. : “Simple Expression of the Dynamic Stiffness ofGrouped Piles in Sway Motion”, Journal of Earthquake Engineering 4(3), 2000: 355-376
Saran, S. (2010), Soil Dynamics
Srinivasulu, P. & Vaidyanathan, C.V. (1990), Handbook of Machine Foundation, Tata
McGraw-Hill Publishing Company Ltd., New Delhi.

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APPENDIX-B Arrangements of Pile Foundation in Ball Mill

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APPENDIX-C Borehole Logs

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2.0
NDT Using Schmidt Hammer and Ultrasonic Pulse Velocity Meter (UPV)
Figure 1 shows the location map (showing the point of measurement) of the area over which
NDTs have been carried out. Figure 2 shows the use of Schmidt Hammer and Ultrasonic Pulse
Velocity Meter at the Ball Mill area.
2.1 Crack Detection Using UPV
UPV has been mainly used to detect cracks on the top of the grouted pad on the gearbox
foundation. Although some superficial cracks have been observed but their depth of penetration is
negligible.
2.2 Concrete Strength Using Schmidt Hammer and UPV
Schmidt Hammer and UPV have been used to estimate concrete strength at the Ball Mill area asshown in Fig. 2. Figure 3 shows the location of the Schmidt Hammer test. Figure 4 shows theconversion curve for Silver Schmidt from rebound number (Q) to concrete strength. The collected
rebound number and corresponding concrete strength, and UPV data have been presented in Table
1.

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N

Outlet

Inlet

Foundation
below the Mill

GearboxFig. 1 Locations of NDT Measurement

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Fig. 2 Use of Schmidt Hammer to estimate concrete strength at the Inlet foundation and use of
UPV to detect cracks on the top of gear box

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Fig. 3 Location of Schmidt Hammer test

Fig. 4 Conversion curve for Silver Schmidt ST/PC Type N (Valid range 20–62Q, 10100 MPa)

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Table 1 Point location and number, Rebound Coefficient, Compressive Strength and Pulse
Velocity
Point location

Inlet top grout
Inlet Foundation

GearboxFoundation

Outlet wall

Inlet wall

Point
NumberReboundCoefficient,Q

Compressive
Strength,
MPa

1
2
3

57
50
61

74
47
93

F1
F2
V-1
V-2
V-3
V-4
V-5
V-6

57
55
59
63
56
53
55
55

74
65
82
109
66
57
64
64

V-8
V-10
V-11
1
2
3
4
5
1
2
3
4

50
49
47
64
58
57
54
59
59
54
55
58

47
43
38
113
76
75
61
80
80
58
64
77

AverageCompressive
Strength, MPa

71
70

76

38

81

70

Pulse Velocity(m/sec)
4115
3355
10000
8000
4405
9900
4201
10000
8264
7352
5988
4310
4524
4000
6756
10000
10000
7194
6329
10000
10000
5128
5154

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3.0 NDT Using Ground Penetrating Radar (GPR)
Different frequencies of GPR (1.6 GHz and 400 MHz) have been used to identify the location ofreinforcement at different points of the Ball Mill area.

3.1 NDT Using 1.6 GHz GPR
Figure 5 shows an area on the foundation top and a wall to identify the reinforcement locations.
Figures 6 to 10 show reinforcement locations on top of the inlet foundation (at a depth of 2 inch)
and on wall (at a depth of 1.5 inch), top of the gearbox foundation (at a depth of 1.5 inch) and on
wall (at a depth of 1.5 inch), and on the top of the foundation below the Ball Mill (at a depth of
3.5 inch).

3.2 NDT Using 400 MHz GPR
Figure 11 shows an area on the foundation top below the Ball Mill to identify the reinforcement
locations. Figure 12 shows reinforcement location on the top of the foundation below the Ball
Mill (at a depth of 12 inch).

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Fig. 5 GPR tests being carried out on the top of the gear box and on the outlet side wall (1.6 GHz)

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Fig. 6 Analysis of GPR results on the top of the inlet foundation (2i h)BNUS Annual Report-2012

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Fig. 7 Analysis of GPR results on the sidewall of the inlet foundation (1.5
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Fig. 8 Analysis of GPR results on top of the gearbox foundation (1.5 inch)

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Fig. 9 Analysis of GPR results on the sidewall of gearbox foundation (1.5

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Fig. 10 Analysis of GPR results on the foundation below the Ball Mill (3.5 inch)
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4.0

Concluding Remarks

The analyses of the data obtained from field observations and scrutiny of the design drawing leadto the following conclusions regarding Ball Mill foundation area of Emirates Cement factory at
East Mukterpur, Munshigonj.
(vii) No substantial crack has been observed on the grouted area of the foundation top.
(viii) Concrete strength at different locations of the Ball Mill area have been estimated andpresented in tabular form using Schmidt Hammer. Additionally pulse velocities of the same
locations have been reported.
The obtained concrete strength is quite high (around 70 MPa), then mentioned
in the existing design sheet supplied by CEMAG (around 25 MPa).

(ix) GPR has been used to locate the reinforcement at different foundation and wall locations.
Reinforcement has been detected at a depth of 1.5 inch from the surface at the top of theoutlet and inlet foundations and wall of the outlet and inlet foundations. Reinforcement has
been detected at a depth of 3.5 inch and at a depth of 12 inch for the foundation (pile cap)
below the Ball Mill area.
The location of reinforcement identified through this study matches with the location ofreinforcement shown in the design sheet supplied by CEMAG.

Bibliography:
The Silver Schmidt Reference Curve (2009).
Turgut, P. (2004). Research into the correlation between concrete strength and UPV values
NDT.net • Dec 2004 • Vol. 12 No.12.

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PART-XI

DEVELOPMENT OF FLOOD MAP OF DHAKA
CITY

BANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: Naima Rahman

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Introduction
1.1 Background
Bangladesh is known as the ‘land of rivers’ and major rivers that flow through Bangladesh
are the Ganges, the Brahmaputra and the Meghna with a complex network of 230 rivers
including 57 international trans-boundary (cross boundary) rivers. The Ganges (Padma), theBrahmaputra (Jamuna) and the Meghna are the large rivers systems in the world covering a
total combined catchment area of about 1.6 million sq km and extending over Bhutan, China,
India and Nepal of which only 7% falls in Bangladesh (FFWC, 2001). Topography of thecountry is mostly flat except some part in the northeast and southeast, which are hilly. The
land elevation varies from 3 to 90 m above MSL. More than 50% of the floodplain is within
the 5m level above MSL. The very location and the topography make the country vulnerable
to floods.
Because of the geographical location Dhaka City is vulnerable to flood more or less. The Cityis surrounded by Buriganga to the south, Turag to the west, Tongi khal to the north, and Baluto the east. The elevation of Greater Dhaka is 2 to 13 meters above the mean sea level, andmost of the urban area located at elevation of 6 to 8 meters above the mean sea level. The
land area above 8 meters above mean sea level covers only 20 square kilometers while
Dhaka’s city area is 360 sq. Kilometers. The land ranging from 6 to 8 meters above mean sea
level covers 75 square kilometers, while 170 square kilometers of Greater Dhaka is below 6
meters above mean sea level (JICA 1987). Because of being surrounded by the distributaries
of several major rivers, the city has been subjected to periodic flooding since its early days.
Major floods in the Greater Dhaka area have been occurred in 1954, 1955, 1970, 1974, 1980,
1987, 1988, and 1998 due to spillover from surrounding rivers. Among these occurrences, the1988 and 1998 floods were catastrophic. During the 1988 flood about 85 percent of the city
was inundated with water depth ranging from 0.3 to over 4.5 meters. About 60 percent of citydwellers were affected by the then 1988 flood. It also disrupted city life, air travel, andcommunication from the capital city to the outside world. The 1998 flood was most severe interms of extent and duration. It was estimated that about 56 percent of the city was inundated,
including most of the eastern and 23 percent of the western parts of the city.
Because of internal water logging in the city, Dhaka has also experienced flood. It is basicallyfor human activities rapid urbanization of the city. The 1998 flood of Dhaka has been
occurred due to internal water logging. During the 1998 flood, excessive rainfall in Dhaka
caused short-duration flooding in the areas of Shantinagar, Nayapaltan, Rajarbag, Dhanmodi,
Azimpur, and Green Road. Beside this, flood also occurred in 2000, 2004 and 2007 due towater logging. Among these characteristics of flood of 2004 was almost similar to the floodof 1998.
As the City has been facing frequent flooding, it requires vulnerability assessment as thebasis of proper planning for Dhaka City. Keeping this in sense the authors tried to indentify
the vulnerable area in Dhaka City to flooding. Flood vulnerability refers to the degree of lossof damage due to flood and this damage due to flooding depends of several factors such as

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flood depth, duration of the flood, flow velocity, sediment concentration and pollution. The
present study only focuses on water depth in preparing the vulnerability map for Dhaka City.
1.2 Objective
The study has been conducted with the following objectives:
To prepare a flood vulnerability map of Dhaka city.
To Develop Connectivity Index for Drain

1.3 Scopes
During the last 25 years, so rapid urbanization has taken place in Dhaka City. Substantial increase inbuilt-up areas has taken place due to development of residential and commercial areas mostly throughprivate land developers and real estate business. These activities resulted in substantial increase inimpervious area, created obstruction to natural drainage pattern, and reduced detention basins, which
in turn lead to shortening of the overflow concentration time and an increase of the peak flow. As aresult flood occur frequently causing devastating water logging in the city. It is important to find out
the most vulnerable areas of flood and also to realize that very few urban drainage systems. Thus thestudy focuses to find out the vulnerable areas of flood by preparing vulnerability map of Dhaka City,
which will be helpful to take appropriate steps for better management of the problem due to flood.

1.4 Limitations
Some limitations were encountered during the study period to complete research work
according to the selected objectives. Very few studies were conducted related to flood anddrainage system of Dhaka City. As a result, there was no sufficient literature to enrich theanalysis of this study by reviewing their study findings. There was no sufficient secondary
data to collect related to past drainage system in terms of width, length, depth, capacity, pickflow rate, drainage coefficient etc. and their layout. Due to the lack of detailed elevation data,sometimes it was very hard to measure the actual depth of flood.
Review
2.1 Flood
A flood is an overflow of an expanse of water that submerges land. The term "flood" is a
general or temporary condition of partial or complete inundation of normally dry land areasfrom overflow of inland or tidal waters or from the unusual and rapid accumulation or runoff
of surface waters from any source.
Flooding and flash flooding are the deadliest of natural disasters. Floodwaters claim
thousands of lives every year and render millions homeless. One of the more frightening
things about flooding is that it can occur nearly anywhere, at any time. It can result fromexcess water jams on rivers, even moderate rain, or a single very heavy downpour.
(http://www.vigyanprasar.gov.in/comcom/feature64.htm)
2.2 Flood Risk Assessment
The assessment of the flooding risk hazard requires a multidisciplinary approach; coupledwith the hydrological/hydraulic modeling, the contribution of geomorphology can play an
exhaustive and determining role using the GIS tools (Townsend & Walsh, 1998).
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Georgakos et al (1997) undertook an estimation of flash flood potential for large areas inUnited States of America. A methodology for determining the potential for flash floods insmall basins within large geographical area was presented. Geographical Information System(GIS) technology was used to assimilate digital spatial data, remotely sensed data withphysically-based hydrological – hydraulic models catchment response.
Okoduwa (1999) applied Geographic Information System (GIS) in the prediction of urban
flooding in Benin City. Nigeria. This was achieved by creating a digital database of selectedvariables such as land use, land cover and soil strength. The software used was Arcview 3.1
and the overlay technique in GIS was used for analysis. In carrying out the overlay operation,
the researcher first carried out the land use and the reclassified Digital Elevation Model(DEM). The land use map and the relief map were overlayed using the union function withthe geo-processing hazard contained in the Arcview. The union function was used to create
new theme by overlaying two polygons of the input theme. That is, the land use them andrelief theme, were split at their intersection. The dissolved function contained in the geoprocessing wizard was used to enhance the merging of the feature of the two themes which
generated a theme called land Relief Map. The land relief map was then overlayed on the soil
strength, and high intensity of land use as well as areas with low relief, are areas that areprone to high flooding, while areas with high soils strength, low intensity of land use, as wellas with high relief are prone to low flooding. Also areas with medium soil strength, medium
intensity of land use as well as areas with medium relief are prone to medium flooding.
Having overlayed the land Relief map on the soil strength map, the overlay gave a map (ofBenin City), showing areas that are prone to high flooding areas prone to medium flooding,and areas that are prone to low flooding respectively.
A study was carried out to create flood vulnerability map of Munshiganj district using
satellite and GIS techniques. Landsat TM data was used to generate a land cover, and JERSSAR and RADASAT data were combined to map flooded area in a normal flood event.
Combining them with population data a population distribution map was produced according
to land use types. Subsequently, this outcome was compared with flooded area mapped using
satellite data in creating population that is at risk during a normal flood event. Attempt wasmade to identify shelters in a flood event based on information such as existing
schools/hospitals location, topography and accessibility. Prioritization of shelters was carriedout based on population at risk during a normal flood event. Finally, a flood mitigation planfor Munshiganj district based on evacuation was proposed considering selected center
capacities and the accessibility. (Prathumchai, 2006)
2.3 Floods in Bangladesh
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Bangladesh is prone to the natural disaster of flooding due to being situated on the Ganges
Delta and the many tributaries flowing into the Bay of Bengal. The coastal flooding twinned
with the bursting of Bangladesh's river banks is common and severely affects the landscapeand Bangladeshi society. 75% of Bangladesh is less than 10m above sea level and 80% isflood plain, therefore rendering Bangladesh a nation very much at risk of further widespread
damage despite its development, especially as its present flood defenses are unsustainable
and somewhat amateur. Flooding normally occurs during the monsoon season from June to
September during the monsoon. The convectional rainfall of the monsoon is added to byrelief rainfall caused by the Himalayas. Melt water from the Himalayas is also a significant
input and flood every year.
Each year in Bangladesh about 26,000 km2, (around 18%) of the country is flooded, killingover 5,000 people and destroying 7 million homes. During severe floods the affected area
may exceed 75% of the country, as was seen in 1998. This volume is 95% of the total annual
inflow. By comparison, only about 187,000 million m3, of stream flow is generated byrainfall inside the country during the same period. The floods have caused devastation in
Bangladesh throughout history, especially during the years 1966, 1987, 1998 and 1988. The
2007 South Asian floods also affected a large portion of Bangladesh.
Small scale flooding in Bangladesh is required to sustain the agricultural industry, as
sediment deposited by floodwaters fertilizes fields. The water is required to grow rice, so
natural flooding replaces the requirement of artificial irrigation, which is time consuming andcostly to build. Salt deposited on fields from high rates of evaporation is removed during
floods, preventing the land from becoming infertile. The benefits of flooding are clear in El
Niño years when the monsoon is interrupted. As El Nino becomes increasingly frequent, andflood events appear to become more extreme, the previously reliable monsoon may besucceeded by years of drought or devastating floods. Also, some 3 thousand people were left
homeless or killed. (Wikipedia)
In Bangladesh, the following types of floods are normally encountered.
Flash floods in the eastern and northern rivers are characterized by a sharp rise followed by arelatively rapid recession, often causing high flow velocities that damage crops and property.
Local floods due to high localized rainfall of long duration in the monsoon season often
generate water volumes in excess of the local drainage capacity, causing localized floods due
to drainage congestion.
Monsoon floods from the major rivers generally rise slowly and the period of rise and fall
may extend from 10 to 20 days or more. Spilling through distributaries and over the banks ofthe major rivers causes the most extensive flood damage, particularly when the three majorrivers rise simultaneously.
Floods due to storm surges in the coastal areas of Bangladesh, which are generated bytropical cyclone, cause extensive damage to life and property. These cyclones are
predominant during the post-monsoon (October and November) and pre-monsoon (April toJune) period. (Wikipedia)

2.4 Floods in Dhaka City
The occurrence of floods in and around Dhaka City can be traced back to as early in 1787-88
when terrible inundation occurred and the streets of Dhaka were submerged to a depth
sufficient to admit boats sailing along them. Again in 1833-34, 1870 devastation due to
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floods were reported (Hunter, 1877). Major floods also occurred in 1954, 1955, 1962 and
1966, which severely affected the city of Dhaka (Rizvi, 1969). Floods that occurred during
1970, 1974, 1987, 1988 and 1998 also affected the city. Among these the floods of 1988 and1998 were catastrophic. It was estimated that about 77 per cent of city area were submerged
to depths ranging between 0.3 to over 4.5 metres and that about 60 per cent of city population
were directly affected in the 1988 flood (FAP, 1991). The return period for a 1988 flood wasestimated at 70 years but in just 10 years another flood occurred in 1998.
The 1998 flood of Bangladesh was an unprecedented event of its kind in terms of duration,
inundation of areas and damages (DMB, 1998). It was estimated that 79 per cent of Dhaka
City area were inundated ranging between 0.3 to over 3.0 metres and that about 60 per centcity population were under inundation for about 10 weeks – the longest time in memory. The
city experienced colossal loses in housing, infrastructure, industry and commerce sectors.
According to DCC estimates, two-thirds of the city roads and 75% of kutcha and semi-pucca
houses were affected in the flood. It was reported that 1000 km of city streets, 400 km of
drains, 40 km of foot paths, 400 switch points and 1 lock gate were affected and these were
estimated at Taka 4.0 billion or US$ 89 million (DCC, 1998). The total damage in housing
sector was estimated at Taka 2310.9 million or US$ 48.2 million (Islam, 1998).
Poor drainage has been identified as the principal cause of flooding in the metropolitan areasof Bangladesh. Flooding in Dhaka City is mainly caused by heavy rainfall, drainage
congestion, high surrounding water and overflow of rivers. In whatever way flood occurs, itdisrupts city life and inflicts major damages. Local flooding due to poor drainage affects 65
per cent of slums and squatter dwellers and 22 per cent of city dwellers are regularly flooded
during minor rainfall (FAP, 1991).

Dhaka city, the capital of Bangladesh and home for more than 10 million people, has been
affected by seasonal flooding almost in every year, however, the situation aggravates
depending on rainfall and surrounding river waters. The unplanned growth of the city andfilling of water bodies has made the flood situation worse. The catastrophic events of 1988
and 1998 flood affected the whole capital that widely impacted in the financial growth as
Dhaka contributes 16.7% to the national development (Dewan et al. 2006). Hydrometeorological assessment of these events revealed that the 1988 flood was severe due to thelack of flood protection in the city together with trans-boundary flow of the major rivers
while the 1998 flood was become deluge due to incessant monsoonal downpour along withearly peaked of the river water levels (Dewan et al. 2003). The 1988 event has done colossal
damage to the city compared to the 1988 event. Remote sensing techniques have been usedparticularly to map the flood concentrating in the capital. The following two case studies
show that how the flood maps were developed for Dhaka city for the 1988 and 1998 events.
This is to mention that the use of RS techniques in Bangladesh for mapping flood is quite
recent. So studies for mapping floods in Dhaka city for the 1988 event is not available
widely. Still to provide a basic idea of the process for 1988 event the case study is included.
However the case study for the 1998 event is detailed in this paper.

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Sado et al. (1997) in his research tries to estimate the flood area based on land coverclassification. To map the flooded area of 1988 in Dhaka city, two images were consideredusing MOS 1-, MESSR data. The first image was of October 17, 1988 which was during theflood and the other was of January 27, 1989 which was the dry season. Sun scenes wereextracted from the MOS-1, MESSR full scenes of 2400 pixels and 1800 lines with thinningout rate of 1. Geometric correction was performed to avoid distortions. To establish therelationship between the image coordinate system and the geographic coordinate system
positions, seven ground control points (GCP) were chosen. The GCPs were selected from theeasily identifiable points on the satellite image and topographic map of Dhaka city. The
geometric corrections were performed by using Affine transformation. For applying land
cover classification, rectangles were cut out from each original image for different
classification. Three corner points of the rectangle were selected on the basis of the
topographical map. Resampling was performed using nearest neighbor method from the oldimage. For land cover classification Parallelepiped classification was used. Composite false
color image was created from the two satellite images and then was classified by comparing
with the Dhaka city land use map. The classification was broadly segmented into two: Water
area and Non-water area. The different spectral characteristics of the rivers, lakes and thedeposit water helped to establish the relationship. The CCT count for river water was higher
than of lake and deposit water as it had more turbidity during flood which influenced theamount of energy back scattered. Extracting the water area from the non-water area finallyhelped to develop the map of the flood inundated areas which provided an estimating of thetotal flood area affected in that catastrophic event.

Dewan et al. (2006) delineated flood hazard areas for the greatest flood of 1998 in the capital.
Six RADARSAT SAR images were acquired that covered the whole flood season of 1998
(July – September). SAR data were despeckled using the GMAA-MAP filter with 5X5window size. Geometric corrections were carried out using a referenced 1999 Landsat TM
image of the same area until the root mean square resulted in less than 1 pixel. A second
order polynomial fit was applied and the pixel values were resampled to 50m. As the digitalformat of GIS data was absent for Dhaka city, an elevation map was developed by slicing theDEM into different categories. The land cover map was generated in a GIS platform using
IRS-1D Panchromatic data of February 29, 2000. Ground data and topographic maps wereassigned to develop the land cover categories from IRS image. A geomorphic map was also
developed by using a Landsat TM of 1999. The projection was transformed to BTM for rasterbased flood hazard assessment. Flood frequency map based on flood duration was developed
using the multi-date SAR imagery. The images were classified to water areas and non-water
areas based on algorithms. And the six images were combined to 3 images for each month ofJuly, August and September respectively. The images were superimposed to characterize theinundated areas. Four flood frequency categories were obtained showing high, medium, low
and non-damaged areas. Multi-temporal SAR images were also used to estimate the flood
water depth. A land level map was extracted from the DEM that consisted of four heights ofclasses and the ground truth data was created and brought to GIS. The signatures were
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collected to extract training pixels. A minimum distance supervised classification was applied
to classify into four depth categories. In order to assess flood hazard for each category of land
cover, elevation height and geomorphic category, a weighted score was estimated and hazard
map was decided. Drainage network was overlaid on each flood hazard map to depict theriver networks. Several flood hazard maps were constructed to attain the best combination. It
was found that two maps produced the highest resemblance.

2.6 Theoretical Framework
2.6.1 Concept of Graph Theory
Graph theory deals with abstract configurations consisting of lines and points, and is suitable
for representing the topological properties of transport systems such as for roads, water
bodies. Important graph theory concepts and their transport equivalents are:
Link: Imaginary straight line that represents a finite length of road, railway, bus route orwater body.
Node: Imaginary points where links intersect. Nodes represent road intersections and railway
junctions; on public transport networks nodes also indicate the location of stations or bus
stops.
At the highest level of abstraction, networks can be represented by a series of vertices(representing nodes on a network) and a set of edges (representing network linkages),
together with a relationship of incidence that associates each edge with two vertices. When so
defined, the network is a minimal one in terms of its information content- only the presenceor absence of connection between nodes. Measures of spatial properties of such a network are
structural and deal with the geometrical pattern of the network.
2.6.2
ConnectivityThe degree of connection between all vertices is defined as theinterconnected.
When a network is abstracted as a set of edges (linkages) that are related to a set of vertices
connectivity of the network. It is the most important structural property of the network.
(nodes), a fundamental question is the degree to which all pairs of vertices are interconnected.
Twodegreeof theofmost
commonly
employedgraphis theoretic
ofof
connectivity
The
connection
betweenall vertices
defined asmeasurements
the connectivity
the network.areItismost important
structural
thetheGammaand Alphaindices.property of the network.
Two of the most commonly employed graph theoretic measurements of connectivity are the
The Gamma
Index
Gamma
and Alphaindices.
The
The Gamma
gamma Index
index is simply the ration of the number of edges in a network to the
The gamma index is simply the ration of the number of edges in a network to the maximum
maximum number possible in that network:
number possible in that network:ɤ = (actual edge) / (maximum edge)= =e/ee/emaxmax
Here, emax = 3 (v-2)
Here,emax = 3of(v-2)
The
inclusion
one additional node to a network of more than 2 nodes increases the numberof possible linkages by a value of 3. There is no intersection of linkages except a node.
The numerical range for the gamma index is between 0 and 1. For convenience ininterpretation, the numerical value may be expressed as a percentage of connectivity.
The Alpha Index
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If one linkage is removed, the network is divided into two completely separates parts. On theother hand, if one or more linkages are added to the network, the connectivity is increased
beyond the minimal configuration in which only a single and unique path can be identified
between all pairs of nodes. Additional linkages in a network create circuitry. A circuit isdefined as a finite, closed path in which the initial node of linkage sequence coincides withthe terminal node.
In a finite connected network in which the number of linkages is e and the number of nodes isv, the number of linkages is equal to 1 (one) less than the number of nodes i.e. (e= v-1) only
when the network is minimally connected. When circuits exist in the network, the number oflinkages is greater than (v-1) or (e>v-1). The number of circuit is obtained by subtracting thenumber of linkages needed for a minimally connected network (v-1) from the actual numberof linkages (e). This may be expressed as e- (v-1) or (e-v+1). It is a measure of the number of
independent circuits in the network.
The alpha index is the ratio measure of the number of actual circuits to the maximum numberof circuits.
= (actual circuit) / (maximum circuit)= (e-v+1) / (2v-5)
The range of index is from a value of zero (0) for a minimally connected network to a valueof one (1) for a maximally connected one. For convenience the numerical value may be
expressed as a percentage of circuitry in network.
2.6.3 Application of Graph Theory on the Study Area
The study of the researchers is based on connectivity of drain of Dhaka city. In this case theconnectivity index has to be identified by using graph theory. This will show the blockages
and the missing links of the drains. The indices will give a numerical value of connectivity ofdrains. With the help of Gamma Index it will reveal the percentage of connectivity of thedrains. The Alpha Index will show the degree of connection i.e. whether the drains areminimally connected or maximally connected.
2.7 Operational Definition
Vulnerability: Vulnerability is the weaknesses or gaps in a system that can be exploited by threats. A
vulnerability assessment is the process of identifying, quantifying, and prioritizing (or ranking) thevulnerabilities in a system.

Risk: Risk is the potential for loss, damage or destruction of an asset as a result of a threat
exploiting vulnerability and the risk assessment is the procedure to predict the probability ofloss and damage due to potential hazard.
Hazard: Hazards have the potential to cause disaster. Natural hazards are the forces of nature
which have the potential to cause loss of life and damage of properties of human being.
Drainage System: Channels, either constructed or natural, passes through surface orunderground or both that are usually used to drain out the flood or rain water.

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Khals: Canals passes through Dhaka City that are created naturally and used as drainage
channel to drain out the flood as well as rain water of the city to the surrounded outfall rivers.
Begunbari khal, Dholai khal, Shegunbagicha khal, Tongi khal etc. are some major khals in
Dhaka City.
Mega City: A metropolitan area having population more than 5.0 million is termed as mega
city (Population Census, 2001). According to population census 2001, Dhaka is the only
mega city of the country.
Retention Area: Natural or man-made depression usually reserved in urban area to retain theflood or rain water.
Water logging: Flooding in built up areas caused by rainfall, where water remains stagnant
for long time due to lack of proper drainage system and creates many adverse impact on daily
life.
Methodology
Methodology of the study was developed with due consideration to achieve the objective of
the study. As such the following methodological procedures were adopted.
3.1 Formulation of Objective
An objective has been formulated to carry out the study.
3.2 Literature Review
A review of relevant literature has been carried out. It included review of international
journal, books, thesis, and local newspaper etc specifically addressing flood issues.
3.3 Study Area Selection
Dhaka City has been selected as the study area. There are two main reasons of choosing thiscity as the study area. The first reason is that it is the capital of Bangladesh and the mostimportant city. The second reason is data availability.
3.4 Data Collection
Shape files of spot height, structures, land uses, drainage and administrative boundary of
Dhaka City have been collected from reliable sources. Flood depths of Dhaka City anddanger level of surrounding rivers have been collected from literature review.
3.5 Map Preparation using GIS
ArcGIS 9.2 software has been used to prepare flood map. Collected shape files of spot height,
structures, land uses, drainage and administrative boundary of Dhaka City have been added in
an mxd layer of ArcMap. Land use map, structure use map, drainage map and flood map
have been prepared using the following methodology.
3.5.1 Preparation of Flood map
There are two steps of preparing flood map. First a Digital Elevation Model (DEM) has been
produced and then the DEM has been reclassified using the following methodology.

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3.5.1.1. Preparation of a Digital Elevation Model (DEM)

A Digital Elevation Model (DEM) has been prepared on the basis of spot height of Dhaka
City. Spatial resolution of spot is average 10 m. The lowest spot value is 0.11 m and thehighest value is 17.62 m. The following process is followed to prepare DEM:
3-D Analyst
Options General Working Directory: Working Folder; Analysis Mask:
Dhaka; Extent Analysis Extent: same as layer Dhaka; Cell Size Analysis cell size: As
specified bellow; Cell Size 9.
3-D Analyst
Interpolate to Raster Inverse Distance Weighted Input Points:
Spot_height; Z value field: RL; Output cell size: 9; Output raster: fix the location & name thefile Ok.
3.5.1.2 Preparation of a flood map from the DEM
DEM is reclassified into four categories as elevation 0 to 3 m = High Flood Zone, 3 m to5.5 m =Moderate Flood Zone, 5.5 m to7.2 m = Low flood Zone and above7.2 m = No Flood Zone. The
reclassified map is the flood map of Dhaka City. The following methodology is the process of
preparing flood map using GIS
3-D Analyst Reclassify Input raster: DEM Classify Method: Equal Interval; Classes:
4 Old Value: 0-3, 3-5.5, 5.5-7.2 and 7.2- 17.2; Output raster reclassified Ok.

3.5.2 Flood vulnerability map
Flood vulnerability map has been generated by overlaying Structure use Map with Flood Mapof Dhaka City.
3.6 Calculation of Drainage Connectivity Index
By using graph theory, the connectivity index of Dhaka city drains has been developed andthen analyzed by calculating their percentage of connectivity.
3.7 Analysis
Analysis has been divided into two parts. Firstly, flood affected areas/Wards have been
identified. Then the drainage condition of those areas has analyzed by calculating
Connectivity Index of drains.

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Formulation of objectives

Literature Review

Study area selection

Data collection

Map Preparation using GIS
PreparationofaDigitalElevation Model (DEM) on thebasis of spot height
Structure use Map

Flood Map

Preparation of a flood map byreclassifying the DEM

Flood Vulnerability Map By overlaying Structureuse Map with Flood Map

Finding of connectivity of drainage line by Graph

Data Analysis

Major findings

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Study Area Profile
Dhaka city has two parts. The Greater Dhaka having an area of 258.78 km2 and the DND
area having an area of 56.79 km2. The Greater Dhaka includes both flood protected westernpart (142.75 km2) and unprotected eastern part (116.03 km2). With the rapid urbanizationand development of City infrastructure, combined with the reduction of water storage andpercolation areas, recent flooding and water logging from local rainfall combined with river
spills have reached a dangerous magnitude. Dhaka is located in the central part of
Bangladesh. It is almost 200 kilometers from Meghna estuary. The distance hinders any
impact of the sea therefore sea water intrusion is not feasible for Dhaka city. The increased
amount of the rainfall affects Dhaka is more likely. Because day by day Dhaka is becoming
more populated and the excessive population is causing harmful effect to the city sewer
system. For this reason even small amount of rainfall is causing water logging and Excessive
population is causing all sorts of water related problems.
There are two kinds flood occurs in Dhaka city. Main cause of this flood is water level rising,i.e. river flooding and another is rainfall flooding due to Heavy rainfall & drainage
congestion..Based on this two causes of flood this study develop and analysis the reason
behind flood vulnerability for Dhaka city.
Map 4.1: Dhaka City Map

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Analysis and Findings
5.1 Identification of Flood Affected Areas/Wards
Ground elevation of Dhaka City ranges from 0.16 m to 17.2 m at 10 m spatial resolution.
Low lands are found in Ward No. 04, 05, 06, 09, 10, 15, 21, 22, 23, 24, 37, 54 and 55. Large
portion of high lands are found in northern part of the city. Most of the wards of the city fallin the category 5.84 m to 9.63 m. Map 5.1 show the Digital Elevation Model (DEM) of
Dhaka City.
DEM has been reclassified to prepare Flood Map (Map 5.2) on the basis of the following four
categories:
No Flood Zone: Ground elevation is above 7.2 m
Low Flood Zone: Ground elevation is from 5.5 m to 7.2 m
Medium Flood Zone: Ground elevation is from 3 m to 5.5 m
High Flood Zone: Ground elevation is from 0 m to 3 m

There are 90 wards in Dhaka City. In this study, Dhaka Cantonment and Uttara (Ward No.
01) have been excluded in the map as well as in the analysis due to data unavailability. Rest
89 wards have been categorized according to the flood zone. The following table 4.1 shows
the distribution of Wards according to Flood Zone.
Table 5.1: Distribution of Wards according to Flood Zone
Flood
Ward Coverage
Total
Total Area
Percentag
Zone
Number of(acres)e
Wards
No Flood 3, 7, 8, 38, 39, 40, 45, 47, 52, 1914074.06
45.59
Zone
53, 56, 57, 59, 58, 59, 61, 62,
63, 64
Low Flood 11, 12, 13, 14, 16, 17, 18, 19, 52
12516.7
40.55
Zone
20, 25, 27, 29, 30, 31, 32, 33,
34, 35, 36, 41, 42, 44, 46, 48,
49, 50, 51, 54, 60, 65, 66, 67,
68, 69, 70, 71, 72, 73, 74, 75,
76, 77, 78, 79, 80, 81, 82, 83,
84, 86, 87, 90
Medium23, 26, 28, 43, 85, 88, 89
72816.35
9.12
Flood
Zone
High
2, 4, 5, 6, 9,10, 15, 21, 22, 121461.4
4.73
Flood24, 37, 55
Zone
Total
89
30868.51
100

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Structure Map has been overlaid on Flood map to produce Flood Vulnerability Map(Map5.3).
Map 5.1: Digital Elevation Model of Dhaka City

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Map 5.2: Flood Map of Dhaka City

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Map 5.3: Flood Vulnerability Map of Dhaka City

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nerability An
nalysis of Sttructures off Flood Affeected Areas//Wards
5.2 Vuln
od Zone: Noo flood zonee consists off 19 wards coveringcalm
most 14074.006
Analysis of No Flooacres areeas (45.59%)) of Dhaka City. Most of these wards are situaated in the northernnparrtsand the centre
cof thee city. Total 103754 num
mbers of stru
uctures are siituated in th
his zone. Moostof them are residentiial (78.23%)), pucca (466%) and onee storied (622.9%). This zonezcontainnsain Dhaaka City. Tabble 5.2 and figuref
5.1 shhows the struucture use annd
the most developed areas
N Flood Zoone.
the structture type of No
Table 5.2
2 Structure use
u of No Floood Zone
Frequenc
Structuure UseyPercentagge
Agricultture
64
0.006
Commercial Activitty
6527
6.229
Commu
unity Servicee
811
0.778
Educatioon & Researrch
1411
1.336
Governmmental Serviices
415
0.440
Manufaccturing and Processing
P
Activity
A
1730
1.667
Miscellaaneous
29
0.003
Mixed Use
U
8181
7.888
No Information
499
0.448
Non Goovernment Seervices
18
0.002
Office Use
U
119
0.111
Open Sp
pace
23
0.002
Open/Coommunity Space
S
36
0.003
Recreatiional Facilitiies
120.001
Residenntial
81163
78.223
Restricteed Area45
0.004
Service Activity
2478
2.339
Transpoort & Commuunication
193
0.119
Total
1037541000
Sttructure Typpe
Seemi
Puucca42
2%Katcha12%

No_Info
0.1%

Puccaa46%

Figure 5..1: Type of Structure
Sof No
N Flood Zoone

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Analysis of Low Floood Zone: Low flood zoone consists ofo 52 wards covering almost 12516.7
C
Most ofo these wardds are situateed in the whhole southeaast
acres areeas (40.55%)) of Dhaka City.
parts, som
me portion of west parrts and northhern parts of the city. Total
T
1490666 numbers ofostructures are situatted in this zone. Mostt of them area residentiial (81.13%%), semipuccca%). Table 5.3 and figuree 5.2 shows the structurre use and thhe(40.36%)) and one storied (67.4%
structure type of Low
w Flood Zonne.
3 Structure use
u of Low FloodF
Zone
Table 5.3
Structuure UseAgricultture
Commercial ActivittyCommuunity Servicee
Educatioon & Researrch
Governmmental Serviices
Manufaccturing and Processing
P
ActivityyMiscellaaneous
Mixed UseU
No Info
Non Goovernment Seervices
Office Use
UOpen Sppace
Open/Coommunity SpaceS
Recreatiional Facilitiies
Residenntial
Restricteed Area
Service Activity
Transpoort & Commuunication
Total

Freq
quency Peercentage
30
0.02
8528
5.72
909
0.61
1143
0.77
191
0.13
1749
47
11815
782
15
43
21
14
19
120935432451
331149066

1.17
0.03
7.93
0.52
0.01
0.03
0.01
0.01
0.01
81.13
0.03
1.64
0.22
100

Sttructure Type
e
Seemi
Pucca
40.3
36%

Katch
ha
20%
%

No__Info
0.1%

Pucca
40%

S
of Low
L Flood ZoneZ
Figure 5..2: Type of Structure

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Analysis of Medium
m Flood Zon
ne: Medium flood zone consists of 7 wards covvering almoost
2816.35 acres areas (9.12%) of Dhaka Cityy. Most of thhese wards are situated in the fringgeMof themmareas of the city. Total 28968 nuumbers of structures aree situated inn this zone. Most%). Mainly sllum areas arre
are residential (90.233%), semipuucca (43%) and one stooried (84.5%
built up in
i this zone. Table 5.4 annd figure 5.33 shows the structure usee and the struucture type ofoMedium Flood Zone.
4 Structure use
u of Mediuum Flood Zoone
Table 5.4
Frequenc Perrcentag
Structuure UseyeAgricultture
5
0.02
Commercial Activitty
886
3.06
Commu
unity Servicee
124
0.43
Educatioon & Researrch
129
0.45
Governmmental Serviices
14
0.05
Manufaccturing and Processing
P
219
Activityy
0.76
Miscellaaneous
31
0.11
Mixed Use
U
996
3.44
No Information
121
0.42
Office UseU
4
0.01
Open/Coommunity Space
S
10
0.03
Residen
ntial
26138
90.23
Restricteed Area3
0.01
Service Activity
216
0.75
Transpoort & Commuunication
72
0.25
Total
28968
100

S
Structure
Typ
pe
S
Semi
Pucca
4
43%

Katcha
K
34%
Pucca
23%

No
o_Info00.1%

Figure 5..3: Type of StructureSof MediumM
Floood Zone
ood Zone: HighH
flood zonezconsistss of 12 wardds covering almosta1461.4
Analysis of High Flo
acres areas (4.73%) ofo Dhaka Ciity. Most of these wards are situatedd in the fringge areas of thhecity. Totaal 1858 num
mbers of struuctures are siituated in thhis zone. Moost of them area residential

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March 2013(94.3%), katcha (60%%) and one storied (92.44%). Mainlyy slum areas are built upp in this zonne.
5 and figure 5.4 shows thhe structure use and the structure typpe of High FloodF
Zone.
Table 5.5
Table 5.5
5 Structure use
u of High FloodF
Zone
Structuure UseFreequency Percentage
P
Agricultture2
0.1
Commercial Activitty
16
0.9
Commu
unity Servicee
6
0.3
Educatioon & Researrch
10
0.5
Manufaccturing and Processing
P3
0.2
ActivityyMixed UseU
28
1.5
No Information
5
0.3
Residen
ntial
1752
94.3
Service Activity
35
1.9
Transpoort & Commuunication
1
0.1
Total
1858
100

Semi
Pucca
27%

Puccaa13%%

Sttructure Typee

Kattcha60%

Figure 5..4: Type of StructureSof HighH
Flood Zone
nectivity Ind
dex Develop
pment for Drain
D
5.3 Conn
This chap
pter briefly describeddthhe connectiviity index dev
velopment forf drain in Dhaka
Dcity byb
applying graph theoory. On the basis of deegree of nettwork comppleteness byy connectivittyn(allpha) and (gamma)(inddices that ap
pply the Graaph theory too measure thheindices namely
network system of drain.
dWherre, the netwoork of drainns can be reepresented byb a series ofo(g nodes on a network) annd a set of eddges (repressenting network linkagess),vertices (representing
together with a relattionship of incidence thhat associatees each edge with two vertices. Thhedegree off connectionn between alll vertices is ddefined as thhe connectivvity of the neetwork.
The draiins of Dhakka city shouuld carried water towarrds the surrrounding rivvers. So it isnecessaryy to find outt the degree of connectiivity of drainns with rivers (Map 5.44). It will givve
the resultt whether thhe drains carrry water to the rivers orr not and alsso show theeir circulationn.
For this reason,r(alpha) and (gamma)(inddices developped to know about the coonnectivity ofodrain in Dhaka
Dcity. Drainage
Dmaap has been overlaid on FloodF
map (Map(
5.4).
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5.3.1 Connectivity index calculation for Ward 23 drain in Dhaka city
All types of flood zone are presented in Ward 23 (Map 5.5).So, the calculation of α
5.3.1 Connectivity index calculation for Ward 23 drain in Dhaka citya ɤ (gamma)
for ward
below:
All(alpha)types andof floodzone areindex
presented
in no.23
Ward is23given(Map5.5).So, the calculation of (alpha)and a (gamma) index for ward no.23 is given below:
Table 5.6: Connectivity Index Calculation
Table 5.6: Connectivity Index Calculation
Flood Zone
Number of
Number of Gamma Index, Alpha Index,
Flood Zone
Number of
Number of Gamma Index, Alpha Index,
ɣNodes,v v
Links,eeαNodes,
Links,

MediumMediumFlood
Flood 8 8
Zone
Zone

55

0.28
0.28

-2/11==-0.18
-0.18
-2/11

Low
Flood 5851
0.3
-4/151 = -0.27
Low
Flood 5851
0.3
-4/151 = -0.27
Zone
Zone
*emax
= 3(v-2)
5.3.2 Analysis of (gamma) index for Ward 23
For2.6
mediumflood Frameworkzone the connectivity index of drains is 0.28 and 0.30 for low flood zone.
Theoretical
It meansthatthedrains
2.6.1 Concept of Graphconnected
Theory 28% and 30% connected for moderate flood zone and low
flood zone. Both of the indexes are near to 0 i.e. the drains are minimally connected in ward
Graph theory deals with abstract configurations consisting of lines and points, and is
no. 23.
suitablefor representing
topologicalof transport systems such as forindex
for Wardproperties
23
5.3.3
Analysisof (alpha) theroads,
water
bodies.
Importantand their
equivalents
Alpha
index
shows
whetherthe graphdrainstheory
createconcepts
circuit withriverstransport
or not for
free floware:of water.
TheLink:rangeImaginaryof the index
is fromvalue
of 0 for aa finite
minimally
networkbus
to aroutevalue of 1
straight
lineathat
represents
lengthconnectedof road, railway,
forora water
maximally
body.connected one. Where, actual circuit shows the number of existing circuits ofdrains with rivers and maximum circuit shows the number of maximum possible circulation.
Node: Imaginary points where links intersect. Nodes represent road intersections andFrom Table 5.6 it has been shown that, for medium flood zone and low flood zone drains
railway
publicnetworks
nodes also
indicatethe locationof willcreatedno junctions;circuit. Inonward
no.transport
23 the valueof existing
circuitis negative
but there
stationsor bus stops.
remainmaximum
possible circuits of 11 and 151.
5.3.4
in Flood Prone
Areas
At Drainage
the highestConditionlevel of abstraction,
networks
can be represented by a series of vertices
Connectivity
index
areondevelopedin Dhakacity (Appendix
Based on this(representing
nodes
a network)for
andalla wards
set of edges(representing
networkI).linkages),
percentage the drainage condition is analyzed.
together with a relationship of incidence that associates each edge with two vertices.
Analysis of No Flood Zone: The connectivity index for no flood zone is (38-40) %. It means
so defined, the network is a minimal one in terms of its information content- only
thatWhenin noflood zone area the drainage condition is good. The area does not face water
thepresenceor absenceof connection
nodes.
spatiallife
propertiesof theirlogging problem
and floodin Dhaka between
city does
not Measureshamperedofthere
style andinfrastructure.
such a network are structural and deal with the geometrical pattern of the network.
Analysisof Low Flood Zone: The drainage connectivity percentage for low flood zone is2.6.2 Connectivity(30-32) %.It means that the flow of water is moderately good. Drains of this area passed
When a network is abstracted as a set of edges (linkages) that are related to a set ofwater slowly and the area faces less water logging problem.
vertices (nodes), a fundamental question is the degree to which all pairs of vertices are
Analysis of Medium Flood Zone: The area of this zone is flood vulnerable because theirconnectivity percentage is (25-28) %.
Analysis of High Flood Zone: From map 5.4 it has been shown that, no drains are present inhigh flood zone area. So, the area faces the problem of water logging and flood in Dhaka city.

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Map 5.4: Drainage Map of Dhaka City

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Map 5.5: Drainage Map of Ward 23 in Dhaka City

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Conclusion
Flood vulnerability assessment for the historical flood event of 1998 in Dhaka City of
Bangladesh was examined using GIS in this study. The study established a simple and costeffective way to use geographical information system for creating flood vulnerability maps
from the available dataset. Although it was very time consuming to derive the GIS databasebecause of the size of the study area, GIS was invaluable in reducing the complexity
associated with vulnerability assessment.
The vulnerability maps showed that a major portion of Dhaka were within low to very highflood zone, especially fringe areas. It is projected that these areas will be fully urbanized by
the year 2015, therefore higher priorities must be paid for the development of apposite flood
countermeasures for areas having higher vulnerability potential. Based on this above analysis
researchers proposed some recommendations which is given below:
Existing natural channels should be kept for flood flow.
Structures must be flood-proofed.
Require preservation of natural drainage systems, existing floodplains.
In order to ameliorate flood induced damage, the developed flood vulnerability map
would be invaluable.
This type of study will provide information about flood protection measure such as
construction and development of infrastructure and preparedness of aid and relief
operation for high vulnerable areas for future flood event.
References
Craciunescu, V., Stancalie, G., Catana, S. and Alecu, C. (2005), Contribution of Earth
Observation Data to Flood Risk Mapping, International conference on innovation advancesand
implementationofflood
forecasting
technology.
(www.actifec.net/conference2005/proceedings/.../Craciunescu_Vasile.pdf)
Dewan, M. A., Kumamoto, T., and Nishigaki, M, (2006), Flood hazard delineation in
greater Dhaka, Bangladesh using an integrated GIS and remote sensing approach.
Geocarto International. 21 (2), 33-38.
Dewan, M. A., Nishigaki, M, and Komatsu, M(2003), DEM based Flood Extent
Delineation in Dhaka City, Bangladesh Journal of the Faculty of Environmental Scienceand Technology, Okayama University Vol.9, No.1, pp.99·110, February 2004.
DMB (1998) Disaster Management Bureau (DMB), 1998, Report on Bangladesh Flood
1998, Dhaka.
FAP-8B (1991), Dhaka Integrated Flood Protection Project, Final Report, p.1.
Georgakakos, K. P., Guetter, A.K., and Sperfslage, J.A. (1997), Estimation of flash floods
potential for large areas, Destructive Water: Water-Caused Natural Disasters, their
Abatement and Control, (Proceedings of the Conference held at Anaheim, California, June
1996). IAHS Publication. no. 239. (www.iahs.info/redbooks/a239/iahs_239_0087.pdf)
http://en.wikipedia.org/wiki/Floods_in_Bangladesh
http://www.vigyanprasar.gov.in/comcom/feature64.htm
Hunter, W.W. (1877), A Statistical Account of Bengal, Vol.V, (Districts of Dacca,
Bakerganj, Faridpur and Maimansingh, London: Trubner & Co. (Reprinted in India by
D.K. Publishing House, Delhi), p.103.
Huq, S., Alam, M. (n.d.), “Flood Management and Vulnerability of Dhaka City” available
at
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http://www.google.com/url?sa=t&source=web&cd=1&ved=0CBkQFjAA&url=http%3A%2F%2Fwww.bvsde.paho.org%2Fbvsacd%2Fcd46%2Fcap9flood.pdf&rct=j&q=Flood%20Management%20and%20Vulnerability%20of%20Dhaka%
20City&ei=DPsWTsjHFInWrQeUnrDPAQ&usg=AFQjCNEcPvte0YDPAl0PnpBJG9Vwt9bsg&cad=rja
Islam, N. (1998), “Flood ’98 and the future of urban settlements in Bangladesh”, CUS
BULLETIN 35, July-December, 1998, p.3.
JICA (Japan International Cooperation Agency). (1987), “Study on Storm Water Drainage
System Improvement Project in Dhaka City.” Supporting Report, Local Government Divisionof Ministry of Local Government Rural Development and Cooperative, Dhaka.
Okoduwa, A. I. (1999) An Application of GIS to Flood Prediction: A Case Study of Benin
City, Nigeria, Unpublished B. Sc. Dissertation, Department of Geography and Planning
University of Benin, Nigeria.
Prathumchai, K, Samarakoon, L, (2006), Application of Remote Sensing and GIS
Techniques for Flood Vulnerability and Mitigation Planning in Munshiganj District ofBangladesh, 4th Annual Mekong Flood Forum, Siem Reap, Cambodia.
(www.geoinfo.ait.ac.th/publications/ACRS2005_Prathumchai_K.pdf)
Rizvi, S. N. H. (1969), East Pakistan District Gazetteers – Dacca, Dacca: East Pakistan
Govt. Press, pp.33-34.
Townsend, P., Walsh, S.J. (1998), Modeling of floodplain inundation using an integrated
GIS with radar and optical remote sensing. Geomorphology, vol. 21, pp 295-312.
(http://www.sciencedirect.com/science/article/pii/S0169555X9700069X)

BNUS Annual Report-2012127PART-XIITRAINING COURSES, SEMINARS AND
WORKSHOPS

BANGLADESH NETWORK OFFICE FORURBAN SAFETY (BNUS), BUET, DHAKA

Prepared By: Mehedi Ahmed Ansary

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A three days training program titled “urban community volunteer training program” was held
on 23rd -25th November, 2012 at IEB seminar room, IEB, Ramna, Dhaka.The training
program was jointly organized by the Occupational Safety Board of Bangladesh (OSBB) andInstitute of Engineers (IEB) with the Fire Service and Civil Defense Directorate. Total
fourteen classes where conducted by the trainers of The Fire Service and Civil Defense
Training Institute, Mirpur during these three days. There were seven theoretical classes andthe other seven were practical classes. The classes were on different issues regarding basic
concepts of fire hazard, firefighting system, use of firefighting equipment, basic earthquake
hazard, earthquake management, basic rescue and evacuation operation system of earthquake
and fire accident , first aid, community level collapse structure, search and rescue(CLCSSR)
operation etc. 45 participants took part in the training program from different professionalgroup.A research engineer (K.M.Khaleduzzaman) of BNUS participated in the training
program. Engr. Kabir Ahmed Vuiya,Vice president of IEB, MostafizurRahman,Chairman of
OSBB, A.B.M. NurulHoque, Principal of Fire Service and Civil Defense Training Institute,were present at the closing ceremony and distributed the completion certificate among theparticipants.

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Interviews on Disaster Information Dissemination
BNUS and ICUS jointly conducted a number of interviews with some officials of different
organizations of Bangladesh from 9th December 2012 to 12th December 2012. They covered
four organizations including Department of Disaster Management (DDM), Bangladesh Red
Crescent Society, Institute of Water Modeling (IWM), Center for Environmental andGeographic Information Services (CEGIS) and Asian Disaster Preparedness Center (ADPC)
to know how the information of a certain hazard is disseminated from concerning authorities
to the local people.

Figure 1: Interview at DDM

Figure 2: Interview at DDM

DDM is concerned with dissemination of information about any hazard. Three important
personnels of DDM including the Director General Mr. Abdul Wazed, Assistant Director
Mr. Pobil Ghosh and GIS Specialist Mr. Nitai Chanda Dash were interviewed. After
getting the information of hazard from Bangladesh Meteorological Department (BMD),
DDM spreads the news to 230 stakeholders. These 230 stakeholders are different governmentorganizations, NGOs, multinational companies and private firms etc. Then these stakeholders
take necessary steps to disseminate the information about hazard.
Bangladesh Red Crescent Society is one of the stakeholders of DDM. Deputy Secretary
General of Bangladesh Red Crescent Society Mr. K. Jakaria Khaled was interviewed toknow how Cyclone Prepared Program (CPP) responses in case of any cyclone. The CPP
plays an important role in the dissemination of cyclone warning, evacuation, rescue, first aid
and emergency relief work including mobilization of people toward cyclone shelters throughits volunteers in the coastal districts. Currently, CPP has 203 paid employees, 49215
volunteers including 32810 male and 16405 female and 3281 Units covering 321 Unions, 37
Upazilas, 7 Zones and 13 District. Due to global warming, CPP has increased its
preparedness and awareness building functions for the community people living in the coastal
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area of Bangladesh. CPP command area is expanded in more 5 Upazilas of Khulna, Bagerhat
and Satkhira districts with the financial help of Comprehensive Disaster Management
Program (CDMP) Phase I. CPP is a mechanism which relies on technical skills andvolunteers commitment for ensuring that all potential victims of an approaching cyclone are
given sufficient warning to 11 million coastal people so as to enable them to move to safesit. The system starts with the collection of meteorological data from the Bangladesh
Meteorological Department (BMD), which issues bulletins including the designated warning
signals of an approaching cyclone. The bulletins are transmitted to the 6 zonal offices and the
30 upazila level offices (sub-district) over HF radio. The upazila offices in turn, pass it tounions and lower level through VHF radios. The union team leaders then conduct the unit
team leaders immediately. The unit team leaders with his volunteers spread out in the villages
and disseminate cyclone warning signals almost door to door using megaphones, hand sirens
and public address system.

Figure 3: Interview with Bangladesh Red
Crescent Society

Figure 4: Interview with Bangladesh Red
Crescent Society

Institute of Water Modeling (IWM) involves providing flood related information to DDM.
Director of Flood Management Division Mr. Sardar M Shah-Newaz was the key person of
the interview.

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Figure 5: Interview at IWM

Figure 6: Interview at CEGIS

Center for Environmental and Geographic Information Services (CEGIS) also involves about
river related data. Deputy Executive Director (Development) Dr. Maminul Haque Sarker,
GIS Specialist M. Habibur Rahman and R&D and Training Division Specialist Syed
Ahsanul Haque were the key persons of the interview. CEGIS is currently operating 17
gauges in various flood plains of Jamuna and Dhaleswari Rivers in Bangladesh tomonitor water level. This information is disseminated to various organizations including
Union Disaster management Committee (UDMC). The UDMC is the lowest tire of
National Disaster Management Committee. It comprises of 10 members including 1
chairman and 9 members (3 female) from 9 different Wards. They are the secondary
stakeholders where the farmers and local people of the Union are the primary
stakeholders of this information system. As most of the villagers are illiterate so abulletin board is kept in each Union showing the rise and fall of water level by + (plus)
sign and – (minus) sign respectively. Other organizations are provided information by
fax and short message service (SMS). Banglalink, one of the biggest private telecom
companies, helps to distribute SMS without cost in every monsoon.
Asian Disaster Preparedness Center (ADPC) is currently running some projects involving
dissemination of information about landslide at hill tracks areas in Bangladesh. Office in
Charge of Bangladesh office of ADPC Mr. Md. Anisur Rahman, GIS Technical Specialist
Mr. Dr. Renato Forte and Senior GIS Coordinator Mr. Muhammad Murad Billah wereinterviewed.

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Figure 7: Interview at ADPC

Figure 8: Interview at ADPCBNUS and ICUS also conducted a field trip to a small village of 3000 people named Boro
Boinna on 10 December 2012. The village is situated at Daulatpur Upazila of Manikganj
District and only 1.5 km away from the mighty River Jamuna. So flood is a common
phenomenon of the village. The village is the study area of a project conducted by CEGIS.
The project is a flood early warning system that basically forecasts the possible change ofwater level of nearby river for the next 48 hours. This information is disseminated to somekey persons of the village through short message service (SMS) to their cell phones. After
getting information they spread it to the local people by raising flag at the main bazaar. 1 flag
indicates 6 inches increase of water level at the river. The project was started on the month ofDecember 2003 and ended on December 2008. The project was a great success and thepeople still have been benefitted of the outcome of the project.

Figure 9: Interview with the villagers

Figure 10: Interview with the villagers

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Figure 11: 2 Flag indicates 12 inches rise of Figure 12: Community Office of Climate Changewater level.
Adaptation Project

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Seminar on Current Trends in Earthquake Resistant Design of Structures
Dr. S. K. Ghosh, President, S. K. Ghosh Associates Inc., USA and an internationally reputed
earthquake engineer made a presentation on Current Trends in Earthquake Resistant Designof Structures on 09/02/2013 (Saturday) at 4:30 PM at Environmental Seminar room, Civil
building, BUET. This presentation discusses the significant changes that have taken place inrecent times in the way seismic design is done in accordance with U.S. codes and standards.
Some of the most important changes are: (1) two, rather than one, ground motion parameters
are used in seismic design – a short-period and a long-period parameter; (2) the parameters
are spectral quantities (specifically, spectral accelerations), rather than peak groundacceleration, as in the past; (3) site soil characteristics play a more important role in seismic
design than ever before; (4) seismic design criteria are determined not on the basis of seismic
zones, which do not exist any longer, but on the basis of seismic design categories, which arefunctions of: seismic hazard at the site, occupancy of the structure, and the characteristics ofsoils at the site. An idea of U.S. codes and standards will be given in the beginning. Risktargeted and maximum-direction ground motion, introduced in very recent times, will also be
briefly discussed.A question and answer session will be an important part of the presentation.
Forty participants took part in this seminar from different professional group.

Dr. Ghosh delivering the lecture

Dr. Ghosh with Head of Civil Engg.

Participants at the lecture
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GLOBAL EARTHQUAKE MODEL (GEM)
SOUTH ASIAN EXPERT MEETING AND GEM TECHNICAL TRAINING
Kathmandu, Nepal: 1-3 March 2013
A One day expert meeting and two days technical training on Global Earthquake model(GEM), jointly organized by National Society for Earthquake Technology (NSET)–Nepal
and Global Earthquake Model (GEM) Foundation and supported by USAID, was hold in
Dhulikhel Lodge Resort, Nepal in 1-3 March 2013.A number of earthquake experts andyoung professionals from India, Bangladesh, Pakistan, Nepal, Bhutan and Maldives took partin it. Mr. Khishore Thapa, Secretary of the Ministry of Urban Development (MUD), Nepal
was the chief guest in the opening ceremony.

Fig: Delegation leaders from different countries on the dais and Group Photo session of theparticipants
The expert meeting involved participatory sessions geared firstly towards introducing GEM’s
tools, methods, metrics and secondary to have a detailed round –table discussion related totechnological and methodological needs within the South Asia Region pertaining to theassessment of socio-economic vulnerability and resilience, to identify relevant contextual
factors and variables for measurement, to prioritize the ranking of certain factors andvariables.

Fig: Group discussion at expert meeting

Fig: Prof. Ansary presenting the summaryof the findings

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The GEM Technical Training (GEMTRAIN) was held in 2nd and 3rd March, 2013. There
were 3 sessions at the first day that covered the Probabilistic Seismic Hazard Analysis
Method, demonstration and exercise using the open Quake-Engine and using tools for PHSA
input Model. The second day covered the using method of GEM science tools for seismic risk
assessment, an introduction to risk features of Open Quake Engine, Scenario risk andscenario damage distribution calculations and plotting output maps. The training sessions
were conducted by officials of GEM foundation.

Fig: GEM Technical Training (GEMTRAIN)
There was a field trip titled “Earthquake walk” and observation of a retrofitted schoolbuilding named tri-Padma Vidyasgram Higher secondary School in Lalitpur, Nepal. Ms.
VidyaPanday, principal of that school welcomed the participants at her school.

Fig: Observing the retrofitted schoolbuilding and evacuation plan

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Then the Earthquake walk was done from PatalDarbar Square to Dau-Baha with a view tofeel the earthquake risk of Kathmandu Valley through guided walk along the streets in a coreurban area by observing existing and continued build up seismic vulnerabilities and learns
about the existing capacities and resources in Kathmandu Valley communities. The walkwas expected to assist the need and possibilities of reducing earthquake risk in
KathmanduValley.

Fig: Observation of some existing buildings of Kathmandu Valley.

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