Application of Satellite Based Geoinformation Technology Integrated with GIS for Monitoring and Understanding the Flood Phenomenon in Bangladesh

Salah Uddin | 032013

Application of Satellite Based Geoinformation Technology Integrated with GIS for Monitoring and Understanding the

Flood Phenomenon in Bangladesh

A thesis submitted for the partial fulfillment for the award of

Bachelor of Sciences (B.Sc.) Degree in Information Technology

By

Mohammad Salah Uddin Id: 032013

Supervised by

Prof. Dr. Hafizur Rahman Formaer Head, School of Computer Science & Engineering

And Principal Scientific Officer (PSO) Bangladesh Space Research and Remote Sensing Organization (SPARRSO), Agargaon,

Shere Bangal Nagar, Dhaka-1207, Bangladesh. Cell:+8801715012025 ,Email: [email protected]

Term: Spring 2007

School of Computer Science & Engineering University of Information Technology & Sciences (UITS)

mailto:[email protected]


ACKNOWLEDGEMENT I am very much obliged to many individuals who have contributed

to the development of this thesis.

At first I would like to express thanks to our honorable and

sagacious supervisor, Prof. Dr. Hafizur Rahman, Head School of

Computer Science & Engineering, University of Information

Technology & Sciences (UITS), for his generous help,

encouragement, constant guidance, enthusiasm and wholehearted

support throughout this thesis for its successful completion.

Sincere appreciation to Fida Ashfaq Ahmed, Marufa Tahmid & Ridfa

Rahman, students of IT, for their wholehearted help and

encouragement to complete this thesis.

In addition to the above mention, I am aware of the direct and

indirect contributions of many others towards achieving the success

of this thesis work. I am sincerely thank all them.

Finally, I would like to thank all the teachers of the Schools of

Computer Science & Engineering and all the students of our

Department for their cooperation and support to complete the thesis.


Summary

Bangladesh is a disaster prone country. Cyclone, Tornado, Hailstorm, Drought and the

flood are the most well known issues in terms of disaster. For the last two decades, space

borne remote sensing along with other geo-spatial technology (e.g., GIS) has been

appeared to be as an effective tool for monitoring of such surface events that contributed

significantly to reduce the losses of lives and properties of the people living in the area.

In the present work, multitemporal data acquired by the ScanSar (sensor) on board the

Canadian satellite RADARSAT has been used to monitor flood in Bangladesh. GIS aided

analysis of RADARSAT image coupled with various hydrological data regarding rainfall,

river water level and river water discharge have been performed to study the dynamics of

flood in the spatiotemporal domain. Detailed analysis has been made on the flood

situation in relation to landform, surface topographic characteristics etc. over some

selected districts. Investigation has been made to study the correspondence between

progressive devastation and evolution of flood situation in the country.

Assessment of aerial extent of flood causing damages and casualties to agricultural crops,

land and urban areas has been attempted. Basin-wise investigation on the river

hydrographs in relation to flood extent as derived from time series RADARSAT data

have been analyzed. Analysis of time series Geostationary Meteorological Satellite

(GMS) data has been used to provide the cloud cover condition and possible rainfall over

the region both inside the country and its outside upstream regions during the mentioned

period. Analysis of water level data has been incorporated to the analysis to understand

and interpret the variation of water levels in the river areas including Ganges,

Brahmaputra and Meghna. GIS-based operation has provided area-wise crop under

different damage categories. Comparison of river hydrographs with satellite derived

inundated areas has been made to show the correspondence between the two. GIS-aided

spatial analysis of the pre-flood and post-flood imageries provides area-wise actual

flooded areas.


Contents 1. Introduction ..................................................................................................................... 6

1.1 Introduction ............................................................................................................... 6

1.2 Aims and Objectives ................................................................................................. 7

2. Physical Features of Bangladesh ..................................................................................... 8

2.1 Climatic Condition .................................................................................................... 8

2.2 Topography ............................................................................................................... 8

2.3 Hydrology.................................................................................................................. 9

2.4 Soils ........................................................................................................................... 9

2.5 Land Types .............................................................................................................. 10

3. River System, Statistics of Flood & Cause of Flood of Bangladesh ............................ 11

3.1 Bangladesh River System........................................................................................ 11

3.2 Statistics of Bangladesh Flood ................................................................................ 14

3.3 Causes of flood in Bangladesh ................................................................................ 15

4. Materials & Methods ..................................................................................................... 18

4.1 Data Used ................................................................................................................ 18

4.1.1 Remote sensing data ......................................................................................... 18

4.1.2 Ancillary data ................................................................................................... 19

4.1.3 Agro climatic data ............................................................................................ 19

4.1.4 Agricultural statistics and population census data ........................................... 20

4.2 Software Used ......................................................................................................... 20

4.3 Methodology ........................................................................................................... 20

4.3.1 Preparation of Base Layer ................................................................................ 21

4.3.2 Field data collection and verification ............................................................... 22

4.3.3 Post fieldwork .................................................................................................. 22

4.3.4 Other Processing .............................................................................................. 22

5. Study Area ..................................................................................................................... 25

5.1 Chandpur District .................................................................................................... 26

5.1.1 Geography ........................................................................................................ 26

5.1.2 Subdivisions ..................................................................................................... 26

5.2 Lakshmipur District................................................................................................. 26

5.2.1 Geography ........................................................................................................ 26

5.2.2 Subdivisions ..................................................................................................... 27

5.3 Noakhali District ..................................................................................................... 27


5.3.1 Geography ........................................................................................................ 27

5.3.2 Subdivisions ..................................................................................................... 28

6. Flood Reports of the study areas (non-flood period & flood period) ........................... 29

6.1 Non-flood period Report ......................................................................................... 29

6.2 Flood Report, July 7, 1998 ...................................................................................... 31

6.3 Flood Report, September 10, 1998 ......................................................................... 32

6.4 Flood Report, August 25, 1998 ............................................................................... 34

7. Result & Discissions ..................................................................................................... 35

7.1 Vulnerability of Flood ............................................................................................. 36

7.2 Flood affected areas calculation in 25th August 1998 ............................................. 37

8. Conclusion ..................................................................................................................... 38

9. References ..................................................................................................................... 40

10. Appendix ..................................................................................................................... 41

List of Figures ............................................................................................................... 41

List of Tables ................................................................................................................. 41


1. Introduction

1.1 Introduction

Flood and cyclone are the two most common and frequently occurred events in

Bangladesh that cause significant damages and casualties to the lives and properties of

the people. Bangladesh is perhaps the unique country in the world where casualties due to

a cyclone could rise up to hundreds of thousands. Flood can devastate more than half of

the country causing damages to billions of dollars. The rate of visit of all these natural

disaster varies from year to year and the amount of losses and damages depends on the

intensity and the length of occurrence period.

During the last half century at least 9 nos. of extreme flood events occurred affecting

50% of land area. Since early sixties of the last century the country has adopted different

kinds of measures for flood management with mixed experiences.

A location map of Bangladesh is given in fig. 1. Because of its unique geographical

location and topography, flood of different magnitudes and types occurs every year.

Table 1: Important flood events in Bangladesh

Year 1954 1955 1956 1962 1963 1987 1988 1998 2004

Flooded area

(Sq. Km)

36400 49900 35100 39600 42500 56600 818000 83000 57000


1.2 Aims and Objectives

In this section the aims of the research are identified. The primary objectives of the

research is to observe the flood Phenomenon in Bangladesh during summer period. In

detail, the following objectives are set.

Ø Causes of flood in Bangladesh.

Ø Comparision between non-flood period & Flood period by collecting Field data

and verification.

Ø And find the effects of flood

Fig. 1: Location map of Bangladesh


2. Physical Features of Bangladesh 2.1 Climatic Condition

Bangladesh lies between 20o 34. and 26° 38. north, between 88° 01., and 92° 41. east. Its

climate is tropic and humid. It has mainly four seasons, e.g. Pre-monsoon (March to

May), Monsoon (June to September), Post monsoon (October to November), Dry

(December to February). Its climate is influenced by the Indian monsoon. Average

rainfall is 2200-2500 mm but the range of which is between 1200 to 6500 mm. 80% of

the rainfall occurs during monsoon i.e. from June to September. Average temperature is

around 30 C except during the dry season.

2.2 Topography

Topography is mostly flat excepting some part in the northeast and southeast, which are

hilly. Entire country was formed due to sedimentation of the large river systems e.g.

Ganges, Brahmaputra & Meghna. Land Elevation ranges from -3m to 60 m in the plains

and in the hilly areas land elevation varies from100 to 1000 m.


2.3 Hydrology

Bangladesh has unique hydrological regime. It has been divided into 7 hydrological

zones. Hydrological zones are shown in the following figure.

Fig. 2: Hydrological zones of Bangladesh

2.4 Soils

A total of 483 soil series was identified and described in the Soil Reconnaissance Survey

of Bangladesh. It does not include Sunderban, a mangrove forest, and Chittagong Hill

tracts. General soil types are differentiated into three physiographic groups, e.g.

floodplain soils, Terrace soils and Hill soils. Floodplain soils have been formed in

alluvial sediments from a few months to several thousand years. General pattern of

floodplain soils is of sandy or loamy soils on higher parts of floodplain ridges into clay in

the adjoining basins. Terrace soils comprises of a wide range of soils formed over the

Modhupur Clay. Soil differences are due to differences in drainage and in depth and

degree of weathering. Hill soils include a wide range of soils formed over consolidated

and unconsolidated sandstones, siltstones and shale.


2.5 Land Types

In order to understand the flooding and flood management, it is better have look into the

land types. Seasonal flooding regime has been characterized by means of inundation land

types. Usually, it is classified into 5 categories and detailed description of land type with

the area coverage is given in Table 2.

Table 2: Land Types information of Bangladesh

From the land types it is evident that except high lands all other land types are subjected

to flood inundation to different degrees. Normally, 20-25% of the country is inundated

during every monsoon from June to September. In case extreme flood events 40-70%

area can be inundated which was amply proved during the extreme flood events of 1954-

55, 1974, 1987-88 and 1998. All kinds of land type are distributed all over the country.

High lands are situated in some parts of the western, south central, northeastern and

southeastern regions of the country. Excepting very low lands, human settlements can be

found in all other land categories. Of course population density is high in the Medium

High and Medium Low Lands. People live in the Low Lands building earthen mounds.

Land Type Description Area in ha % Area

High Land Land above normal inundation 4199952 29

Med. High Land Land normally inundated up to 90 cm deep 5 039 724 35

Med. Low Land Land normally inundated up to 90-180 cm

deep

1 771 102 12

Low Land Land normally inundated up to 180-300 cm 1 101 560 8

Very Low Land Land normally inundated deeper than 300 cm 193 243 1

Total Soil Area 12 305

581

85

River, Urban etc. 2 178 045 15


3. River System, Statistics of Flood & Cause of Flood of Bangladesh 3.1 Bangladesh River System

The Ganges originates near the Gangotri Glacier of the Himalayes with an elevation of

over 23,000 ft and has a length of about 1600 miles. It receives the flow of a number of

major tributaries namely Gogra, Gandak and Kosi originates in Nepal and Tibet. Another

tributary of the Ganges, the Mohananda, which flows through Bangladesh, originates in

India. The catchments area of the Ganges is about 3,50,000 square miles spread over four

countries namely China, Nepal and Bangladesh.

The Brahmaputra originates in Tibet and has a length of about 1800 miles upto its

confluence with Ganges. It flows under the name of Tsangpo in Tibet north of the

Himalayan range for a distance of 700 miles. It turns south under the name of the Dihang

and is joined by its main tributaries the Dibang, the Lohit and the Dihing. It then flows

westwards down the Assam valley as Brahmaputra, thereafter it enters Bangladesh

(where the main flow is known as Jamuna) and is joined by Dharala at Kurigram and

Tista at Chilmari. The catchment area of he Brahmaputra is about 2,24,000 square miles

and is spread over China, India, Bhutan and Bangladesh.

The Meghna is formed by the confluence of the Surma and Kushiara together with other

streams from hills in the northeast. The Surma is fed mainly by the tributaries from Jainta

Hills while Kushira is fed by tributaries from Tripura hills. The Meghna system is about

500 miles long of which about 260 miles lies in Bangladesh and the rest in India. The

total catchments area of the Meghna above Bhaira Bazar is about 25,000 square miles of

which about 32% lies in Bangladesh.


Fig. 3: River system of Bangladesh


Rivers of different morphological characteristics e.g. meander, braided, incise etc. are

found in this country. Major rivers having length of 500 to 2500 km and width range

from 1km to 20 km can also be found in this country. Water surface slopes of the major

rivers are also very flat e.g. av. slope of Ganges is 5-6 cm/km, av. slope of Brahamaputra

is 8-9 cm/km and av. slope of Meghna is 4-3.5 cm/km. Annual flow volume of the rivers

is to the tune of 1200 billion cum. Rivers of Bangladesh carries huge sediment annual

amount of which is between 1.8 to 2.0 billion tons. A picture of annual flow cycle of

three major rivers at three selected locations e.g. Ganges at Hardinge Bridge,

Brahmaputra at Bahdurabad and Meghna at Bhairab Bazar are presented in the fig. 4, fig.

5, fig. 6 respectively.


3.2 Statistics of Bangladesh Flood

Bangladesh is very much affected by flood. The following table provides information on

important flood events in Bangladesh along with inundated areas.

Table 3: Statistics of Flood events in Bangladesh

Year Thousand Sq. Km.

1954 36.4

1955 49.9

1956 35.1

1960 28.2

1961 28.4

1962 36.9

1963 42.5

1964 30.7

1965 28.2

1966 33.2

1967 25.3

1968 36.3

1969 41.0

1970 42.0

1971 35.8

1972 20.5

1973 29.4

1974 52.0

1975 16.4

1976 27.9

1977 12.3

1978 10.8

1980 32.5

1982 3.1


1983 11.0

1984 27.9

1985 11.3

1986 3.1

1987 56.6

1988 81.8

1989 6.1

1990 3.5

1991 28.6

1992 2.0

1993 28.7

1994 0.42

1998 85.0

3.3 Causes of flood in Bangladesh

The primary cause of flood in Bangladesh is rainfall in the catchments areas of the rivers

of Bangladesh. Situated in the monsoon belt with the Himalayes in the north, Bangladesh

falls in the region of very heavy rainfall. About 80 percent of the rainfall occurs during

the 5 months period from May to September.

The annual rainfall varies from about 60 inches in the western part of the country to about

200 inches in the northeastern part. At Cherepunje in Assam very near our Sylhet Border

the average annual rainfall is about 500 inches, which is highest in the world. But the

average rainfall in Bangladesh generates annually only 100 million acre to water whereas

1100 million acre feet of water comes from outside Bangladesh. Thus about 90 percent of

the water carried by our river system, the Brahmaputra, the Ganges, the Meghna and

other smaller rivers is brought from outside the country. These rivers carry water from an

area of about 6000000 sq miles of which only 7.5 percent lies in Bangladesh. Water

enters in Bangladesh through three major channels but the discharge takes place through

one major channel. The river system has evolved to carry the normal flow of water

generated in the catchments area. Whenever the inflow of water is greater than the


carrying capacity of the rivers flood results. The magnitude of the flood depends on the

magnitude of excess water that is generated.

It must be remembered that flood in Bangladesh is caused by rainfall in the catchment

areas of the river systems of Bangladesh, 92.5 percent of which lies outside it, namely in

India, Nepal, Bhutan and Tibet (China). Thus though there may not be mush rainfall

locally, there may be heavy rainfall in the catchment area causing flood. In these days,

with the help of weather satellite imagery, rainfall in the whole year that is responsible

for flood catchment area can be monitored. Again it is not the rainfall for the whole year

that is responsible for flood. The rainfall for the whole month or the year may be normal

but if a whole month’s rainfall in the whole catchment area occurs over a matter of few

days and if the soil is already satured because of previous rainfall, severe flooding may

result. It is difficult to imagine the nature of rainfall in hilly areas where most of the

catchment areas of Bangladesh rivers lie. Whereas the average annual rainfall at Dhaka is

about 80 inches, that at Cherapunjee is 500 inches and the maximum rainfall at

Cherapunjee is 900 inches a year. That means in hilly areas rainfall could be as much as

ten times that in the plains of Bangladesh.

Besides the primary cause, namely rainfall in the catchment area, there are other factors,

which may aggravate the floods. They are:

Ø Snow melting in the Himalayes can also contribute towards flood. However,

maximum flooding occurs in Bangladesh during August-September whereas

maximum snow melt occurs probably during May-June and as the snow melting

process is normally quite slow, this alone may not be a great factor in causing

flood in Bangladesh. However, as rainfall itself accelerates the process of snow

melt, the contribution of snow-melting as a factor in flood may not be entirely

negligible. More research needs to be done in this field.

Ø It is understood that considerable hydrographic changes have taken place in the

region specially in the Brahmaputra basin as a result of 1950 earthquake in

Assam. This has resulted in the rise of the bed of Brahmaputra river in the upper

reaches, thus reducing the carrying capacity of the river. This may be one of the

reasons for increase of flood frequency in Bangladesh after 1950.


Ø It is estimated about 2.4 billion tons of sediments are carried by the river system

of Bangladesh every year and part of this sediment is deposited in river beds. This

the rivers, which worsen the flood. As a matter of fact many of the past active

rivers have ceased to be active in the dry season.

Ø The catchment areas of the rivers of Bangladesh are being denuded of forests at

an alarming rate. The soil in the catchment area which was covered by forests

previously is becoming bare. Forest covered soil absorbs part of the rain water but

bare soil absorbs less water and consequently run off is more. Thus deforestation

in the catchment area tends to aggravate the flood.

Ø Constructions of unplanned roads, railways, barrages, embankments etc. may also

create obstacles to the flow of water and may, to a certain extend, aggravate the

flood.

Ø Because of the southwest monsoon wind, the mean sea level rises by about two

feet during summer. If there are depressions in the Bay of Bengal and the

magnitude of the wind is more, the sea level may rise further creating obstacles to

the river flow thus aggravating the flood.

Ø High tide occurs new and full moon twice every month. Of the flood peak occurs

during high tide time, aggravation of the flood may result. Moreover, if the moon

is at perigee that is at the nearest distance from the earth, tide could be more and

flood could further worsen.


4. Materials & Methods

4.1 Data Used

In the present study, remote Sensing (RS) and Geographical Information System (GIS)

have been used for monitoring flood in Bangladesh. The aim of this study is to assess the

land qualities, land characteristics and land requirements of various land utilization types

for optimal land use planning. For the present study following data set are used.

4.1.1 Remote sensing data

Sensor characteristics are very important in the utilization of satellite data for a particular

purpose. The interaction of solar radiation with plant and other earth’s surface materials

are very important. The spectral, temporal and radiometric properties play significant role

in determining the signal at satellite altitude.

Characteristics of Landsat TM

Table 4 provides the basic characteristics of Landsat TM. It has a total of seven relatively

narrow spectral bands.

Table 4: Basic sensor characteristics of Landsat TM

Channel Description Band widths (um) Spatial resolution

1 Blue 0.45 – 0.52 30m

2 Green 0.52 – 0.60 30m

3 Red 0.63 – 0.69 30m

4 Near-Infrared 0.76 – 0.90 30m

5 Middle Infrared 1.55 – 1.75 30m

6 Thermal Infrared 10.4 – 12.5 120m

7 Infrared 2.08 – 2.35 30m


Landsat travels along a sun synchronous orbit over the North and South poles, at roughly

right angles to the equator, at an altitude of about 700km. They circle the earth 15 times a

day, and return to their starting point every 16 days. Observed data are provided in 185

kmX170 km scenes.

Satellite Imagery

i. Satellite/ Sensor : Landsat Thematic Mapper (TM)

Projection : Lambert Conformal Conic (LCC)

Path/Row : 136/043

ii. RADARSAT / NOAA Data

4.1.2 Ancillary data

- Topographic Map: Prepared by Survey of Bangladesh (SOB), Topo sheet No. 78

P/4, 78 P/8, 78 P L/16, Scale 1:50,000.

- Administrative map of Bangladesh, Scale 1:1000000.

- Soil map prepared by Soil Resources and Developed Institute (SRDI), Dhaka,

Bangladesh, Scale: 1:50,000.

- Soil nutrient from Soil Resource Development Institute (SRDI)

- Land reconnaissance map of 1967.

4.1.3 Agro climatic data

- Rainfall and temperature data supplied by the Bangladesh Metrological

Department (BMD), Bangladesh.


4.1.4 Agricultural statistics and population census data

- Historical crop yield data and population census supplied by the Bangladesh

Bureau of Statistics (BBS), Dhaka, Bangladesh.

4.2 Software Used

The methodology adopted for this study involves both the Digital Image Processing

(DIP) and GIS based analysis. DIP was carried out in the computer system having the

following software configuration.

- PC-based ERDAS IMAGING Image Processing Software.

- PC-based Arc Info Software.

- Microsoft Excel.

- MGI Photo Suite.

4.3 Methodology

The whole work has been performed according to the following phases:

- Phase 1: Pre-processing and preparation of satellite data

• Geometric Correction of Satellite images.

• Geo-referencing.

• Cloud screening of digital images

• Digital mosaic and subset operation

- Phase 2: Preparation of reference raster layer for pre-flood and flood conditions

• Spatial characteristics and identification of different object classes in digital

images.

• Digital classification of raster image

• Threshold operation to climate statistically insignificant sized object clusters.

• Regrouping operation to climate statistically large number of object classes into a

limited number of meaningful thematic classes.


• Finalization of pre-flood raster layer.

- Phase 3: Generation of various thematic layers containing information on road network,

infrastructures, settlement, agricultural areas etc. from satellite data and existing maps of

the area.

- Phase 4: GPS (Global Positioning System) based field survey operation for field data

collection, verification, and correction of interpreted thematic raster layer.

- Phase 5: Generation of class statistics

4.3.1 Preparation of Base Layer

Base map preparation: Using topographic maps and satellite images of different physical,

cultural and thematic information have been depicted for the preparation of spatial layers.

And the thematic layers provide information about major communication network,

agricultural pattern, river & canal, settlement etc.

Preparation of base maps

Base map of the study are has been prepared using SPOT data. Visual interpretation of

the images was performed using the most important diagnostic characteristics, including

shape, size, tone/color, texture, contrast and pattern. The drainage system and land cover

of the study area is also considered during interpretation. The geographic references and

gradients are taken from top sheets 1:50,000 scales prepared by Survey of Bangladesh

(SOB).

The general techniques used to obtain macro-structure land use classes in vector from

were:

- Unsupervised classification of merged image as well as Landsat TM image.

- Merging the classes to the desired number of classes.

- Elimination of non-homogeneity and noise using 7X7 majority spatial filter.

- Raster to vector: transformation.


- Combination of vector layers obtained from all the images.

- On-screen editing of the vector data.

- On-screen editing of the vector layer was needed to correct classification error, as

well as to well shape the structures of he features, Micro-structured features were

digitized on-screen from the images, as well as from the base maps.

Interpretation of landsat/land cover map

Using temporal Landsat TM digital data landuse/land cover were recognized through

digital processing.

4.3.2 Field data collection and verification

Initially to understand the broad landforms and landuse a reconnaissance survey was

under taken. Through the fieldwork the landuse map of the study area were corrected. To

do the fieldwork easily topographical map at the scale 1:50,000 were used.

4.3.3 Post fieldwork

After the fieldwork digitally classified Rabi and Kharif seasons landuse/land cover maps

were corrected and for final analysis the above maps were brought in the ARC/INFO GIS

environment.

4.3.4 Other Processing

i) Digital Image Processing

Remotely sensed imagery data in suitable format is freely accessible for digital

processing, Spatially the data is composed of discrete picture elements or pixels, and

radiometrically it is quantized into different discrete brightness levels. The numeric value

of a pixel represents the average brightness of surface of pixel area. Digital image


processing procedures are categorized into the following types of computer-assisted

operations.

A) Image processing: This involved the initial processing of the image to correct for

geometric distortions, to calibrate the data rediometrically and eliminate the noise

present in the data. All the images were projected to Lambert Conformal Conic

(LCC) system. The images were almost cloud free over the Bangladesh area and

have reasonably good contrast.

B) Image Enhancement: This procedure is applied to image data in order to increase

the visual distinction between features in an image. The objective is to create new

images from the original images so as to increase the amount of information

extracting that can be interpreted or used for further analysis by computers. Three

broad classes of problems to be considered in image enhancement are: i) Contrast

Manipulation ii) Spatial features manipulation iii) Multi image manipulation.

C) Image Analysis and Identification: The interpretation of digital imagery may be

quantitative or qualitative. In quantitative analysis much of the interpretive work

is left to the computer, such as in image classification. In qualitative analysis, an

analyst uses the computer to improve the interpretability of the image. The

objective of this operation is to replace visual analysis of the image data with

quantitative techniques as for automating the identification of features in the

image by computer. Image analysis techniques require extraction of certain

features that aid in the identification of the object. Segmentation techniques are

used to isolate the desired object from the scene.

In the present work, both supervised and unsupervised techniques of classification have

been employed. An image has been classified into different categories depending on the

interest of surface features or different zones of the study area. Classification has been

performed using ERDAS IMAGINE interpreter modeler where signature editor is the

primary step that helps to been conducted and chooses maximum likelihood for

parametric rules to get the desired classes. Then recoding has been done and different

land features classes were assigned after studying the spectral profile.

ii) GPS Based Ground Survey


The present study has been supplemented by extensive field investigation over some

selected locations in the study areas. The purpose of the survey was to verify the results

of classification and regroup the classified areas into a limited number of significant

classes representative of major surface classes of the area.

In this step, areas belonging to different class categories have been selected from the

classified image and have been taken as a basis for field investigation. A global

positioning system (GPS) (GeoExplorer 11, Trimble) has been used to locate each of

these selected areas with a good precision. Then detailed observations on the locations

have been made over each of these selected areas. Such a step based on a limited number

of ground observations provided an interpretation key to classify the study.

iii) Application of GIS

In the present study, various thematic information have been used in the analysis of land

suitability. Spatial data on land type distribution, surface elevation etc. have been

incorporated into Geographic Information System (GIS) database. A district boundary

vector layer has been generated from a 1:1000000 administrative map of Bangladesh

using the GIS. This vector layer is used for the calculation of district crop statistics from

the classified images. Finally, all these data are combined with the thematic information.

The objective analysis much of the interpretive work is left to the computer, such as in

image classification. In qualitative analysis, an analyst uses the computer to improve the

interpretability of the image. The objective of this operation


5. Study Area

Fig 7 : Map of Study Areas

NORTH


5.1 Chandpur District

Chandpur is a district in east-central Bangladesh. It is located at the mouth of the

Meghna River. It is a part of the Chittagong Division.

5.1.1 Geography

Chandpur district has a total area of 1704.06 square kilometers. It is bounded by

Munshiganj District and Comilla District on the north, Noakhali District, Lakshmipur

District and Barisal District on the south, Comilla District on the east, and Meghna River,

Shariatpur District and Munshiganj District on the west.

Chandpur is the confluence of two of the mightiest rivers of Bangladesh .. the Padma

River (the main branch of the Ganges River) and the Meghna River, which meet near

Chandpur Town. Important tributaries of the Meghna River flowing through Chandpur

are Dakatia River, Dhanagoda River, Matlab River and Udhamdi River.

5.1.2 Subdivisions

Chandpur has 6 municipalities, 60 wards, 195 mahallas, 7 upazilas, 1 thana, 87 union

parishads and 1226 villages. The municipalities are Chandpur Sadar, Shahrasti, Matlab,

Changer Char and Hajiganj. The administrative subdivisions called upazilas are

Chandpur sadar, Hajiganj, Kachua, Faridganj, Matlab, Haimchar and Shahrasti.

5.2 Lakshmipur District

5.2.1 Geography

Lakshmipur District with an area of 1455.96 km², is bounded by chandpur district on the

north, bhola and noakhali districts upazilas on the south, Noakhali district on the east,

barisal and Bhola districts and the meghna and on the west. Maximum temperature

34.3°C, minimum 14.4°C; annual rainfall 3302 mm. Main rivers are the Meghna, dakatia,

Katakhali, Rahmatkhali and Bhulua.


5.2.2 Subdivisions

It consists of 4 upazilas, 3 municipalities, 30 wards, 55 mahallas, 47 union parishads, 445

mouzas and 536 villages. The upazilas are lakshmipur sadar, raipur, ramganj and ramgati.

Land use Cultivable land 1 25466 hectares, fallow land 9704 hectares, forest area 9604

hectares; single crop 25.85%, double crop 59.03%, triple crop 15.12%.

Population 1479371; male 49.21%, female 50.79%; Muslim 95.31%, Hindu 4.66%,

Christian 0.01%, Buddhist 0.01% and others 0.01%.

5.3 Noakhali District

Noakhali is a district in South-eastern Bangladesh.

Noakhali District

Division: Chittagong

Area (km²) 3,600

Population:

Total:25,33,394

Male: 48.91%

Female: 51.09%

5.3.1 Geography

Noakhali District ( part of Chittagong division ) with an area of 3600.99 km², is bounded

by Comilla district on the north, the Meghna estuary and the Bay of Bengal on the south,

Feni and Chittagong districts on the east, Lakshmipur and Bhola districts on the west.

Annual average temperature: maximum 34.3 °C, minimum 14.4 °C; annual rainfall 3302

mm. Main rivers are Bamni and meghna.


5.3.2 Subdivisions

Noakhali district, whose earlier name was Bhulua, was established in 1821. It consists of

eight upazilas, 5 municipalities, 45 wards, 90 mahallas, 83 union parishads, 909 mouzas

and 978 villages. The upazilas are Noakhali sadar, Subarna Char, Kabirhat, Begumganj,

Chatkhil, Companiganj, Hatiya and Senbagh; the municipalities are Begumganj

(Chawmuhani), Companiganj (Bashurhat), Noakhali Sadar, Chatkhil, Kabirhat (Sadar).


6. Flood Reports of the study areas (non-flood period & flood period) 6.1 Non-flood period Report

Figure 8: Image of Non-flood period

Legend

Water Vegetation1 soil vegetation2

NORTH


The following tables (Table 5, Table 6 & Table 7) shows the informations about Non-

flood period of Chandpur, Lakshmipur & Noakhali districts respectively.

District Name: Chandpur

Class Name Count % Hectares

Water Area 376440 18.83 33879.600

Land Area 1279565 64.01 115160.850

Vegetation 343135 17.17 30882.15

Total 1999140 100 179922.600

Table 5 : Information about Non-flood period of Chandpur district

District Name: Lakshmipur


Water Area 442846 26.28 39856.140

Land Area 855054 50.74 76954.860

Vegetation 387347 22.98 34861.23

Total 1685247 100 151672.230

Table 6 : Information about Non-flood period of Lakshmipur district

District Name: Noakhali


Water Area 2261076 48.88 203496.840

Land Area 1814516 39.22 163306.440

Vegetation 550522 11.9 49546.98

Total 4626114 100 416350.260

Table 7 : Information about Non-flood period of Noakhali district


6.2 Flood Report, July 7, 1998

The following tables (Table 8, Table 9 & Table 10) shows the informations about flood

period of July 7, 1998 of Chandpur, Lakshmipur & Noakhali districts respectively.



Water Area 824267 41.23 74184.030

Land Area 1174873 58.77 105738.570

Total 1999140 100 179922.600

Table 8 : Information about flood period of July 7, 1998 of Chandpur district



Water Area 532406 43.82 47916.540

Land Area 682699 56.18 61442.910

Total 1215105 100 109359.450

Table 9 : Information about flood period of July 7, 1998 of Lakshmipur district



Water Area 508638 39.87 45777.420

Land Area 767046 60.13 69034.140

Total 1275684 100 114811.560

Table 10 : Information about flood period of July 7, 1998 of Noakhali district


6.3 Flood Report, September 10, 1998

Legend

Water

Soil

Figure 9 : Image of flood period September 10, 1998

NORTH


The following tables (Table11, Table 12 & Table 13) shows the informations about flood

period of September 10, 1998 of Chandpur, Lakshmipur & Noakhali districts

respectively.



Water Area 1105353 44.79 80580.234

Land Area 1362728 55.21 99342.871

Total 2468081 100 179923.105

Table 11 : Information about flood period of September 10, 1998 of Chandpur district



Water Area 1061685 51.03 77396.837

Land Area 1018879 48.97 74276.279

Total 2080564 100 151673.116

Table 12 : Information about flood period of September 10, 1998 of Lakshmipur district



Water Area 3353664 58.72 244482.106

Land Area 2357504 41.28 171862.042

Total 5711168 100 416344.147

Table 13 : Information about flood period of September 10, 1998 of Noakhali district


6.4 Flood Report, August 25, 1998

The following tables (Table14, Table 15 & Table 16) shows the informations about flood

period of September 10, 1998 of Chandpur, Lakshmipur & Noakhali districts

respectively.



Water Area 1321570 66.11 118941.300

Land Area 677570 33.89 60981.300

Total 1999140 100 179922.600

Table 14 : Information about flood period of August 25, 1998 of Chandpur district



Water Area 1293941 76.78 116454.690

Land Area 391306 23.22 35217.540

Total 1685247 100 151672.230

Table 15 : Information about flood period of August 25, 1998 of Lakshmipur district



Water Area 3768664 81.47 339179.760

Land Area 857450 18.53 77170.500

Total 4626114 100 416350.260

Table 16 : Information about flood period of August 25, 1998 of Noakhali district


7. Result & Discissions

The first phase of the study was carried out with objectives such as, monitoring floods as

accurately as possible

For this study, we use the radar images of July 7, August 25, September 10 and a non-

flooded period, 1998. The full extent of the images, that covered almost the whole of

Bangladesh, was used to map open water flooding in successive image dates.

From the Statistics of Bangladesh Flood and fig. 4, fig. 5 & fig. 6 (Bangladesh River

System), we can see that the 1998 flood in Bangladesh has been characterized as one of

the most catastrophic deluges on record. Water levels in all the rivers exceeded danger

levels with local rainfall occurring in catchments of small rivers. The consequent bank

overflow and drainage congestion resulted in a flood that extended over most of the

country for months causing heavy loss of human lives, and damage to crops and

infrastructures.

My study areas are Chandpur, Lakshmipur & Noakhali districts of Bangladesh. These

three districts are situated on the bank of the river Meghna. Their land type are Medium

Low Land. That’s why from the non-flood period data, we can see their water areas are

18.83%, 26.28%, and 48.88% respectively. And Flood Repor July 7, 1998 the water areas

were 41.23%, 43.82% and 39.87% respectively.

But these three districts has been characterized as one of the most catastrophic deluges on

record in August , 1998. Because (fig. 6, Bangladesh River System) water level of river

Meghna at Bhairab Bazar in August exceedded danger level with local rainfall. Then

water level become little low in september but again it goes high in November.The

consequent bank overflow such a level resulted catastrophic flood. The flood effected

areas was 66.11%, 76.78% and 81.47% respectively in August 25, 1998 and 44.79%,

51.03% and 58.72 % respectively in September 10, 1998.


7.1 Vulnerability of Flood

Comparision between non-flood period & Flood period data

In non-flooded period the water areas of my study areas are like the following table 17

and Figure 6.10 shows the daily water discharge in m3/sec of the river Meghna at the

Bhairab Bazar measuring station near the present study areas. The water discharge was

less than 2,000 m3/sec in April to May 1998.

District Name % of Total Area Hectares

Chandpur 18.83 33879.600

Lakshmipur 26.28 39856.140

Noakhali 48.88 203496.840

Table 17 : water areas of non-flood period of the study areas

25th August 1998, it was one of the devastating flood in our country. Water level of the

rivers begins to rise steadily at the onset of the moonsoon and reach tjeir paek level in

July, August and September. Flash floods occur in the northeastern and northern areas of

the country at any time during the monsoon. Wide spread overland flooding become

severe and devastating when the peak of the Ganges, the Brahmaputra and the Meghna

syschronize and remain at high stage for longer period.


Fig: 6 shows the daily water discharge in m3/sec of the river Meghna at the Bhairab

Bazar measuring station near the present study areas. The water discharge attained a very

high value of about 12,000 m3/sec in August 1998. That’s why it was the most

devastating flood of the recorded history.

The water areas of flood period in 25th August 1998 are flows-

District Name % of Total Area Hectares

Chandpur 66.11 118941.300

Lakshmipur 76.78 116454.690

Noakhali 81.47 339179.760

Table 18 : water areas of flood period in 25th August, 1998 of the study areas

7.2 Flood affected areas calculation in 25th August 1998

So, if we subtract the data from flood period 25th August 1998 to non-flood period and

flood, we can easily find out the flood-affected areas in 25th August 1998.

The flowing table shows the flood-affected areas in 25th August 1998

District Name % of affected Area Hectares

Chandpur (66.11-18.83)= 47.28 (118941.300-33879.600)=85061.7

Lakshmipur (76.78-26.28)=50.5 (116454.690-39856.140)=76598.55

Noakhali (81.47-48.88)=32.59 (339179.760-203496.840)=135682.92

Table 19 : flood-affected areas in 25th August, 1998 of the study areas

The application of remote sensing in flood monitoring is a tested technology and is

suitable for flood monitoring.


8. Conclusion

This thesis work has been carried out for the partial fulfillment of the requirements for

Bachelor of Sciences degree in Information Technology. Chandpur, Lakshmipur &

Noakhali districts have been taken up as the study areas for understand the flood

phenomenon in Bangladesh.

Proper management and monitoring of natural resources is an important pre-condition for

sustainable development of an area. Management through appropriate land evaluation

supported by efficient monitoring system can yield maximum benefit. The urgency of a

potential tool accomplishing such objectives has directed to carry out the present study.

The study has been supplemented by a number of GPS-based surveys to verify the result

of digital analysis and classification. Through the limited number of ground observation

an interpreted key to classify the study have been evolved and the GPS-based reference

point used to correct the spatial mismatching.

A comprehensive database has been generated in GIS platform containing information

various flood-periods information, comparison between non-flood period & flood-period

and its characteristics and reasons.

Monitoring the flood-period for the study areas have been studied with the aid of

RADARSAT data in associated with GMS, Landsat TM data and hydrological data.

The study indicates that remote sensing technology integrated with GIS is very effective

for land evaluation. But, at the same time availability of real time data is a major

constrains in this regard. In some cases real time data is supplemented by other ancillary

data but it increases the possibility of degradation in respect of accuracy. GIS have wide

range of scope for dealing with spatial and non-spatial data. As the data extracted from

different sources, the question of accuracy is so common. But, through the manipulation

of problematic attributed along with the data GIS support to maximize as high as

possible. In the present study application of GIS is remarkable found as effective,

sophisticated and useful tool.


In the following a number of specific remark has been made:

Ø The study areas (Chandpur, Lakshmipur & Noakhali) are the flood-affected areas.

Because of the mid low lands & water level of Meghna river become high in the

summer season.

Ø In 25th August 1998, the food-affected areas of Chadpur, Lakshmipur & Noakhali

districts were 47.28% (85061.7 hec), 50.5% (76598.55 hec) & 32.59 (135682.92

hec) as respectively.

After analysis & monitoring the Flood Phenomenon in Bangladesh ensuing suggestions

have been made:

Ø Satellite Remote Sensing and GIS techniques are established as most powerful

tools to study the flood monitoring system.

Ø From these techniques we can easily compare flooded and non-flooded areas

favorably with ground information collected simultaneously to the radar data.

Ø We can use multi-temporal data for watching changes in flood extent

Ø The satellite imagery provides an understanding of complex land use practices,

which vary greatly between the dry season and the monsoon flood period.


9. References

Ø Information for Flood Management in Bangladesh: Main Report, Riverside

Technologies Inc. and Environment and GIS Support Project for Water Sector,

2000

Ø Summary Report Based on Studies carried out under the Flood Action Plan,

FPCO, 1995

Ø S. M. Humayun Kabir- “Integrated Use of Satellite Remote Sensing and GIS in

Optimal Land Use Planning for Agricultural Development” 2003

Ø Water and Power Development Master Plan, EPWAPDA, 1964

Ø National Water Plan, MPO, 1986

Ø A.N.H. Akhter Hossain- “BANGLADESH: FLOOD MANAGEMENT” 2003

Ø Water Sector Study Report, IBRD, 1972

Ø Flood and Water Management Strategy, FPCO, 1996

Ø Chandpur District – From Wikipedia, the free encyclopedia.

Ø Lakshmipur District – From Wikipedia, the free encyclopedia.

Ø Noakhali District – From Wikipedia, the free encyclopedia.


10. Appendix

List of Figures

Fig. 1: Location map of Bangladesh

Fig. 2: Hydrological zones of Bangladesh

Fig. 3: River system of Bangladesh

Fig 4: 10-daily Discharge at Hardinge Bridge on the Ganges

Fig 5: 10-daily Discharge at Bahadurabad on Brahmaputra

Fig 6: 10-daily Discharge at Bhairab Bazar on Meghna

Fig 7: Map of Study Areas

Fig 8: Image of Non-flood period

Fig 9 : Image of flood period September 10, 1998

List of Tables

Table 1: Important flood events in Bangladesh

Table 2: Land Types information of Bangladesh

Table 3: Statistics of Flood events in Bangladesh

Table 4: Basic sensor characteristics of Landsat TM

Table 5 : Information about Non-flood period of Chandpur district

Table 6 : Information about Non-flood period of Lakshmipur district

Table 7 : Information about Non-flood period of Noakhali district

Table 8 : Information about flood period of July 7, 1998 of Chandpur district

Table 9 : Information about flood period of July 7, 1998 of Lakshmipur district

Table 10 : Information about flood period of July 7, 1998 of Noakhali district

Table 11 : Information about flood period of September 10, 1998 of Chandpur district

Table 12 : Information about flood period of September 10, 1998 of Lakshmipur district

Table 13 : Information about flood period of September 10, 1998 of Noakhali district

Table 14 : Information about flood period of August 25, 1998 of Chandpur district


Table 15 : Information about flood period of August 25, 1998 of Lakshmipur district

Table 16 : Information about flood period of August 25, 1998 of Noakhali district

Table 17 : water areas of non-flood period of the study areas

Table 18 : water areas of flood period in 25th August, 1998 of the study areas

Table 19 : flood-affected areas in 25th August, 1998 of the study areas

Education

Application of Satellite Based Geoinformation Technology Integrated with GIS for Monitoring and Understanding the Flood Phenomenon in Bangladesh