Assessment of Geo-environmental hazards and Natural resources of Sylhet region, Bangladesh

Department of Environmental Sciences Jahangirnagar University

Savar, Dhaka-1342

Assessment of Geo-environmental Hazards and Natural resources of

Sylhet Region, Bangladesh

Assessment of Geo-environmental Hazards and Natural resources of Sylhet

Region, Bangladesh

Submitted By

Bodrud-doza

Exam Roll: 101401

Reg. No: 28863

Session 2009-10

Submitted To

Dr. Mohammad Amir Hossain Bhuiyan

Assistant professor

Date

February 16, 2012

Department of Environmental Sciences

Jahangirnagar University

Savar, Dhaka 1342

Preface

Study Tour is an important part for the students of Environmental sciences.

With the knowledge of theoretical classes, practical knowledge is also

important to get introduced with many unknown subjects. It can be done in

laboratory or field. “Book is not only the store of knowledge” this theme was

in front of us. The necessity and importance of study tour is realized from

the tendency to observing the practical implementation of education while

receiving it theoretically, and from here study tour is initiated. Here our

subject is to observe field and survey related subjects. For this we must

need study tour. In the department of Environmental sciences, we visualized

everything. We analyze everything based on its location and resource. So in

the view of this point, the students of Environmental sciences went in

different places to learn about that place and the people of that community.

We the students of 12th batch of the Department of Environmental Sciences

went out for the2nd year study tour. We had a very nice study tour to the

greater Sylhet region. In this tour we visited the Sunamganj and Sylhet

district. We studied Ponatirtho river, Barikkar tila, Takerghat Limestone

Mining Project, Lakma chora, Flash Flood area, Tanguar Haor in Sunamganj

district and in Sylhet district we studied Amolsidh, Zakiganj Upazila where

Barak-Surma and Kushiyara river met, Madhabkunda waterfall, Haripur

Utlarpar gas blowout area Jafflong-tamabil areas. We started for Sunamganj

on 24th January and after completing our tour we back to Jahangirnagar

campus in 30th January 2012. Our respected teachers helped us by their

direction and experience throughout the study tour and also given us many

surprise fairly in many aspect. And at last we completed our great and

enjoyable study tour. We are grateful to them very much.

Acknowledgement

Practical implementation of analyzed knowledge is very important for developing the problem solving ability of a student. Environmental science, like all other brunches of science requires a proper practical knowledge and ability to implement knowledge in environment to minimize possible adverse environmental degradation and maximizing possible beneficial events. If an environmental scientist doesn’t have a good knowledge about problems and possibilities in implementing environmental knowledge, he/she will have to suffer a lot. By realizing this fact, the department of Environmental Sciences of Jahangirnagar University runs a course on field work as an academic study course each year. This year, with the cordial Co-operation of our three honorable teachers, we have completed our field work in Sylhet region.

First and foremost I offer my deepest gratitude and I’m cordially grateful to my almighty Allah and may His peace and blessings be upon all his prophets for granting me the chance and the ability to successfully complete this field tour in Sylhet region.

I would like to express my best regards to my honorable teacher Dr. Mohammad Amir Hossain Bhuiyan, Assistant professor, Department of Environmental Sciences, Jahangirnagar University for his scholarly guidance, sincere inspiration and generous support.

I want to give special and heartiest thanks and also acknowledge the excellent support from my honorable sir S. M. Nazrul Islam, Lecturer, Department of Environmental Sciences, Jahangirnagar, University.

I would like to express my best regards to my learned guides and respected madam Ms. Fahmida Parvin, Lecturer, Department of Environmental Sciences, Jahangirnagar, University.

I am very much grateful to them all for their precious information and important guidelines and their spontaneous inspiration and friendly discussion about various difficult topics.

And, thanks to Mr.Ataur Rahman(office assistance) of the Department of Environmental Sciences.

I want to express my special thanks to Mahmudul Hasan and Md. Shawon Zoarddar for there extra ordinary and outstanding performance in accommodation and transportation system as well as for well ending of such kind of adventurous field tour.

I also want to give thanks to Imran who gave us shelter and important information, Kashem (Boatman of Tanguar Haor) who gave us proper and fruitful information about Tanguar Haor.

Finally heartiest thanks are extended to my friends who joined with me and helped anyhow to complete the task successfully.

Content

Topic Page n0.

1. Introduction 1.1 Background of the study 01

1.2 Location of the study area 02

1.3 Routes of Our Study Area 03

1.4 Aims and Objectives 04

1.5 Methodology 05

1.6 Preparation 06-07

2. Geology and Geography of the study area 2.1 Geomorphology 08

2.2 Structural geology and Tectonics 08

2.3 Landforms 09

2.4 Sylhet Trough 11

2.5 Rivers and drainage system 12

2.6 Geography and climate 13

2.7 Demography 14

3. Biodiversity 3.1 Flora of the study area 16

3.2 Fauna of the study area 18

4. Natural Resources 4.1 Natural Gas 21

4.2 Crude oil 24

4.3 Limestone 25

4.4 Peat 26

4.5 Silica/Glass Sand 26

4.6 Hard Rock: 26

4.7 Water resource: 27

5. Natural Hazards and Manmade Hazards 5.1 Natural hazards 30

5.2 Vulnerabilities of Tanguar Haor area 33

5.3 Manmade hazards 38

6. Impact Study of Tipaimukh Dam Project of India on Bangladesh

43-53

7. Environmental condition of the eastern folded belt of Bengal Basin 7.1 Environmental condition 54

7.2 Environmental problems 59

7.3 Law and Restriction 61

8. Conclusion and Recommendation 63

9. Appendix 64-65

10. References 66

Chapter One

Introduction

Assessment of Geo-environmental hazards and Natural resources of Sylhet

region, Bangladesh

1 Introduction

1.1 Background of the study

Due to the Environmental significance of Sylhet and Sunamganj District

we have visited this area for our field tour this year.

Sunamganj (Town) stands on the bank of the river Surma. Takerghat(one

of the most important place) Hillocks small low hills. The Takerghat

Hillocks are situated in the Sunamganj district and have a maximum

elevation of about 22m above mean sea level. They consist of Palaeogene

sediments belonging to the Tura and Sylhet Limestone formations.

Although the sandstone of the Tura forms four small hills in the

Takerghat area the top of the formation lies buried under the ALLUVIUM.

Alternating white, pink and brown, fine to coarse grained extensively

crossbedded SANDSTONEs, light-grey, ash-grey shales, mudstones and

streaks of carbonaceous matter make up the Tura Formation in that

area. Outcrops of the Sylhet limestone in Bangladesh are confined to the

narrow strip of the E-W aligned Dauki Fault zone along the southern

spur of the Shillong Massif. The exposed limestone occurrences are

located at the bank of the Dauki Nala, in the Takerghat-Lalghat-

Bhangerghat area and near Bagali Bazar, all in the Sylhet district.

Sylhet Traps the andesitic Sylhet Trap unconformably underlies the

Upper Cretaceous which is considered as the probable continuation of

the Rajmahal Traps. The geological and mineral map of northeast India

published by the Director General of Geological Survey of India in 1973

show 4 areas of Sylhet Traps in the southern part of Khasi Hills, their age

being Lower Cretaceous. In southwest of Shillong Plateau, Sylhet Traps

(Upper Jurassic/Lower Cretaceous) overlies the granitic/ gneissic

Archean basement unconformably which is overlain by the Mesozoic

Tertiary sedimentary sequence. It can be best studied in Jadukata River

gorge. In the south about 150 m of Sylhet Trap was encountered in a well

below 2,390m. It is dark green to greenish-grey, frequently vesicular and

amygdoidal. These are microporphoric with phenocrysts of labradorites

and olivine.

Though this area is full of environmental significance sometimes it

contains different problems so, the authority should take necessary steps

to remove the problem of this area.


region, Bangladesh

2 Introduction

1.2 Location of the study area

Sunamgonj

Jadukata nodi (Ponatirtho river)

Barikkar tila.

Takerghat Limestone Mining Project.

Lakma chora.

Flash Flood area

Tanguar Haor.

Sylhet

Amolsidh, Zakiganj Upazila where Barak, Surma and Kushiyara

river meet

Madhabkunda waterfall

Haripur Utlarpar gas blowout area

Jafflong-tamabil areas


region, Bangladesh

3 Introduction

1.3 Routes of Our Study Area

Kallanpur Bus Counter, Dhaka


Saheb Barir Ghat

Surma River

Sunamganj Bus Counter

Sunamganj

Slyhet, Amborkhana (Base Camp)

Kushiyara River, Zakiganj Upazila

Amalshid

Madhabkunda waterfall


Kallanpur Bus Counter, Dhaka

Base Camp

Haripur, Utlarpar

Jafflong

Sylhet Bus Counter

Monipuri Ghat

Ponatirtho River or Jadukata River

Barikkar Tila

TLMP area and Lakma Chora

Takerghat Limestone Mining Project (Base

Camp)

Base Camp

Lakma gram

Tanguar Haor

Damper Bazar

Patlai River

Tamabil

DAY-2

Day-3

Day-4

Day-5

Day-6

Day-1


region, Bangladesh

4 Introduction

1.4 Aims and Objectives

Geomorphological change detection (river, channel, Shute-cut, bar,

channel shifting process)

Geological structure observation of the study areas

Soil and water condition (constituents of soil, elemental analysis)

Ecological observation (deforestation, types of plants and

biodiversity)

Environmental impact assessment

Vegetation of the study areas

Water resources management

To know and familiar with the Natural resources

Food and agriculture resources

To familiar with environmental condition of the Sunamganj, Sylhet

as well as Tanguar haor.

To know and familiar with the flora and fauna of the study areas.

“Physical, socio economic and cultural aspect, bioderversity of the

study areas

To know the impact of hazardous processes.

Collect the GPS reading of the selected sites.

Listing the characteristics of the different landforms.

Upstream and Downstream observation at pona tirtho nodi

Observation of hilly fountain

Takerghat Limestone Mining Project observation and its

environmental impact assessment

Observation of Flora and Fauna of Tanguar Haor area

Lifestyle and Socio-economic condition of the haor people

Socio-economic condition of the area where surma and kushiara

meet.

Study of probable consequences in Bangladesh which may occur

after building the dam in tipaimukh


region, Bangladesh

5 Introduction

1.5 Methodology

Methodology means the way or manner by which the study is

accomplished, which refers to the full outcome of the process at a glance.

It includes some chronological steps that are necessary to complete the

study successfully. Mode of operation differs with the nature of the

study. Methodology is always a compromise between options and choices

and is frequently determined by the availability of relevant resource and

time. It is very important in the sense that it gives one an idea about how

the study has been conducted. A proper methodology is always necessary

for any report, which helps to organize experiences, observations,

examinations, analysis of data and information and their logical

expression in a systematic process to achieve the ultimate goals and

objectives of the report.

Primary data source: Secondary Data Sources:

1) Observation method 1) Satellite image

2) Field survey 2) Internet

3) Interviewing survey 3) Published and unpublished

document

4) Photography 4) From journals

5) Arranging class 5) From map

6) Group discussion 6) From different organization

7) From related books.

Equipment:

We have used some instruments in study tour. The list of these

instruments given below-

Individual Field Instrument

Haversack, Cap, Sunglass, Box,

Knife, Camera, Trouser, water

bottle etc.

pH meter, DO meter, EC meter,

Acid, Soil sieve, Tape, Binocular,

Hand mike, Sample bag, Sample

bottle etc.


region, Bangladesh

6 Introduction

1.6 Preparation

First of all, our honorable teacher Dr. Mohammad Amir Hossain Bhuiyan

and S. M. Nazrul Islam took a class on the topics of preparation of the

tour. They advised us how we can complete a successful field work. Dr.

Mohammad Amir Hossain Bhuiyan Sir makes some committee. Such as-

Forward team

Medical team

Food committee

Transport committee

Accommodation committee

Banner committee

Instrument management committee

Logistic committee

Our honorable teachers divided the duties and advised to do the duty

according to committee. Within some days all the committees do their

duty sequentially and honorable teachers fixed the date of our field work

on 24th January, 2011.

Activities of different committees:

All the committees had done some duties which explain below-

Forward team:

Forward team started their trip two days before the fixed date of study

tour and ensures our accommodation, location of the study area, and

transport in the local areas. They informed us about the weather

condition and way to the destination.

Medical team:

Medical team managed medicine from J.U medical centre and the

members of this team served that medicine to the sick student .

Food committee:

The duty of Food committee was to manage good food in each abode for

the student. This committee did their duty simultaneously. All the

students and the teachers are pleased above food committee.


region, Bangladesh

7 Introduction

Transport committee:

Transport committee controlled all the transportation systems with the

help of teachers directly.

Accommodation committee:

The duty of accommodation committee was to manage the best

accommodation for the teachers and the students.

Instrument management committee:

The duty of this committee was to carry the instrument carefully and use

them in the field work.

Banner committee:

Banner committee managed two banners for study tour. One banner of

an organization named CHANGE (Committed to Humanitarian

Alternative for Nature and Green Environment) and the other one was the

Department of Environmental Sciences. That banners we used first to

last in the medium of transportation.

Logistic committee:

A lot of duties had done by logistic committee. They produced map and

managed a lot of things for study tour.

Guide Line:

Teachers gave us guide line for every student. The guide line was fulfilling

with the law of study tour. It helps us to complete a successful study

tour.

Chapter Two

Geology and

Geography of the

study area


region, Bangladesh

8 Geology and Geography of the study area

2.1 Geomorphology

Geomorphology is the scientific study of landforms and the processes

that shape them. Geomorphologists seek to understand why landscapes

look the way they do, to understand landform history and dynamics, and

to predict future changes through a combination of field observations,

physical experiments, and numerical modeling. Geomorphology is

practiced within geography, geology, geodesy, engineering geology,

archaeology, and geotechnical engineering, and this broad base of

interest contributes to a wide variety of research styles and interests

within the field

Bangladesh, our country occupies major part of the bengal delta, one of

the largest in the world. The Ganges-Brahmaputra delta basin or the

bengal basin includes part of the Indian state of West Bengal in the west

and Tripura in the east. Geological evolution of Bangladesh is basically

related to the uplift of the Himalayan Mountains and outbuilding of

deltaic landmass by major river systems originating in the uplifted

Himalayas. This geology is mostly characterized by the rapid subsidence

and filling of a basin in which a huge thickness of deltaic sediments were

deposited as a mega-delta outbuilt and progressed towards the south.

The delta building is still continuing into the present Bay of Bengal and a

broad fluvial front of the Ganges-Brahmaputra-Meghna river system

gradually follows it from behind. Only the eastern part of Bangladesh has

been uplifted into hilly landform incorporating itself into the frontal belt

of the Indo-Burman range lying to the east. All the above has been the

result of the Indian plate colliding with the Asian plate as explained by

the universally accepted theory of plate tectonics.

The geology of Bangladesh may be discussed under the following

headings: (i) Tectonic framework (ii) Stratigraphy and (iii) Economic

geology.

2.2 Structural geology and Tectonics

Geologically, the region is complex having diverse sacrificial

geomorphology; high topography of Plio-Miocene age such as Khasi and

Jaintia hills and small hillocks along the border. At the centre there is a

vast low laying flood plain of recent origin with saucer shaped

depressions, locally called Haors. Available limestone deposits in different

parts of the region suggest that the whole area was under the ocean in

the Oligo-Miocene. In the last 150 years three major earthquakes hit the

city, at a magnitude of at least 7.5 on the Richter Scale, the last one took

place in 1918, although many people are unaware that Sylhet lies on the

earthquake prone zone of Bangladesh.


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Structural geology is the study of the three-dimensional distribution of

rock units with respect to their deformational histories. The primary goal

of structural geology is to use measurements of present-day rock

geometries to uncover information about the history of deformation

(strain) in the rocks, and ultimately, to understand the stress field that

resulted in the observed strain and geometries. This understanding of the

dynamics of the stress field can be linked to important events in the

regional geologic past; a common goal is to understand the structural

evolution of a particular area with respect to regionally widespread

patterns of rock deformation (e.g., mountain building, rifting) due to plate

tectonics. The study of geologic structures has been of prime importance

in economic geology, both petroleum geology and mining geology. Folded

and faulted rock strata commonly form traps for the accumulation and

concentration of fluids such as petroleum and natural gas. Faulted and

structurally complex areas are notable as permeable zones for

hydrothermal fluids and the resulting concentration areas for base and

precious metal ore deposits. Veins of minerals containing various metals

commonly occupy faults and fractures in structurally complex areas.

These structurally fractured and faulted zones often occur in association

with intrusive igneous rocks. They often also occur around geologic reef

complexes and collapse features such as ancient sinkholes. Deposits of

gold, silver, copper, lead, zinc, and other metals, are commonly located in

structurally complex areas. Structural geology is a critical part of

engineering geology, which is concerned with the physical and

mechanical properties of natural rocks. Structural fabrics and defects

such as faults, folds, foliations and joints are internal weaknesses of

rocks which may affect the stability of human engineered structures

such as dams, road cuts, open pit mines and underground mines or road

tunnels. Geotechnical risk, including earthquake risk can only be

investigated by inspecting a combination of structural geology and

geomorphology. In addition areas of karst landscapes which are

underlain by underground caverns and potential sinkholes or collapse

features are of importance for these scientists. In addition, areas of steep

slopes are potential collapse or landslide hazards.

2.3 Landforms

The Sylhet region may be divided four distinct landforms. These are 1.

Eroded hills; 2. Alluvial fan; 3. Alluvial plain; 4. Basin plain.

1. Eroded hills: The eroded hills are mainly formed by the hill ranges

and hillocks (locally called tila) appearing the north east and south of

Greater Sylhet and also round about the Sylhet town. These hill ranges

attain a low elevation and have gentle slope. To the north of Sylhet town


region, Bangladesh


there are numerous isolated tilas of approximately 70 meters height. The

Khasia-Jainta hills, laying outside the international border in India as

well as some tilas within the districts of Sunamgonj ad Sylhet lie in an

east-west direction. A small part to the tila lands is lying in the north of

Tahirpur. To the north-east of Sunamgonj there is an area of scattered

hills both west and east are Kashimara river. The Chattak hills to the

south-east are continuation of these tilas. Further east, there are two

hills, close to Bhologonj. To the east of Piyain river, there is a five mile

long hills known after Jaflong. To the south-east there is a continuous

hilly area covering Jainatpur and part of Kanairghat. The Jainta series

are mainly composed of sandstone and nummulatic limestone and the

Surma conglomerates, nummulatic limestone and pebble beds of the

Pliocene age (about 10-12 million years B.P) these hills are continuation

of the Chittagong hills running in north-south direction. These hills

gradually slope down to the Sylhet plain with alternating valleys between

them. Form east to west the hill ranges are: 1. The Patharia, 2. Harargaj,

3. Rajkandi-Ita, 4. Bharugaj, 5. Tarap, 6. Raghunandan. The overlying

deposits of these hills are Pleistocene clays and sands over a coarse

ferruginous sandstone, mottled sandy clays and shales of middle Miocene

age.

2. Alluvial Fan: The Alluvial fan, mainly composed of the tipam and

Dupi Tila sediments, occupies the narrow strip of discontinuous low

foothills starting from Jaflong in the east to the Jamuna in the west.

Among these fans, the Jaflong fan attains a maximum height of 61m

above sea level with the elevation decreasing westward. Alluvial valleys

frequently separate the Alluvial fans.

3. Alluvial Plain: the alluvial plain, primarily formed by the river Surma

and the Kushiyara, merges with Meghna to the south. Elevation varies

from 3m to 10m above mean sea level.

4. Basin Plain: A large number of swamps have developed within the

alluvial palin; some of thses are locally called haor. It is believed that the

present saucer shaped depression may be connected with the rise of

Madhupur Tract. These saucer shaped, perennial water bodies covering a

total area of about 6,000 km are considered the largest single inland

depression in the country. Small permanent water bodise within the

haors are called beels which occupy the lowest part of the depressions.

The minor hilly steans like Manu, Khowai, Jaqdukata, Piyain, Mogra and

Mahadao ofrm the dense reainage network of the reaion. The river are

primarily responsible ofr devel0oping low floodplains of Sylhet . the

floodplains remain deeply flooded ofr about 7-8 months. During the rainy

season the haors turn into a vast inland sea, the villages appearing as

islands. Occasional high winds during July to September generate large


region, Bangladesh


waves which cause considerable damage to homesteads. There are 35 big

haors and 475 small haors in Greater Sylhet. The most prominent haors

are: 1. Hakaluki haor, 2. Tenguar haor, 3. Santeer haor, 4.Hail haor, 5.

Dekar haor.

2.4 Sylhet Trough

situated on the southern side of the Shillong Massif and corresponds to

the vast low lands of Surma Valley with numerous swamps (haors) where

absolute elevation marks even below the sea level. It is a sub-basin of the

Bengal Foredeep in the northeastern part of Bangladesh and is

characterised by a very pronounced, vast, closed negative gravity

anomaly up to 84 mgl (Milligal). Shillong Massif forms the northern

boundary of Sylhet Trough while the great Dauki Fault separates the

trough from the Massif. The Trough is bounded on the east and

southeast by the sub-meridional trending folded belt of Assam and

Tripura as the frontal deformation zone of Indo-Burman Ranges.

Indian Platform bounds the trough from the west while it is open in the

southwest to the main part of Bengal Basin. It is an oval shaped trough

about 130 km long and 60 km wide. Sub-meridional trending anticlinal

folds of Chittagong-Tripura Folded Belt gradually plunge northward to

the Sylhet Trough. In cross-section the Sylhet Trough is sharply

asymmetrical with comparatively gentle southern and steep faulted

northern slope. Dauki Fault with 5 km wide fault zone forms the contact

between Shillong Massif and Sylhet Trough. The evolution of Sylhet

Trough includes (i) a passive continental margin (Pre-Oligocene) to (ii) a

foreland basin linked to the Indo-Burman Ranges (Oligocene and

Miolene) to (iii) a foreland basin linked to south-directed over thrusting of

Shillong Plateau (Pliocene-Holocene). The anticlinal folds of Habiganj,

Rashidpur, Bibiana, Maulvi Bazar, Katalkandi, Fenchuganj, Harargaj,

Patharia, Beani Bazar (Mama Bhagna) and Kailas Tila, which occupy the

southern rim of Sylhet Trough have sub-meridional trend in contrast to

sub- latitudinal trending Chhatak, Jalalabad, Sylhet, Dupi Tila and

Jatinga structures. These two structural trends form a syntaxial pattern

at the northeastern tip of Sylhet Trough. The Neogene sediments have

excellent development in Sylhet Trough while the Paleogenes are at

greater depths.

Sylhet Trough is the most prospective petroliferous province of

Bangladesh with 10 gas fields (Chhatak, Jalalabad, Sylhet, Kailas Tila,

Beani Bazar, Fenchuganj, Rashidpur, Maulvi Bazar, Bibiana and

Habiganj) of which Jalalabad, Sylhet, Kailas Tila, Rashidpur and

Habiganj are producing now about 1000 million cubic feet per day

(MMCFD) for generation of power, manufacture of FERTILISER besides


region, Bangladesh


meeting the industrial, commercial and domestic needs to a great extent

thus contributing immensely to the economic development of

Bangladesh.

2.5 Rivers and drainage system

Surma-Kushiyara Floodplain comprises the floodplain of the rivers

draining from the eastern border towards the Sylhet Basin (Haor Basin).

Some small hill and piedmont areas near the Sylhet hills, too small to

map separately, are included within its boundaries. Elsewhere, the relief

generally is smooth, comprising broad ridges and basins, but it is locally

irregular alongside river channels. The soils are mainly heavy silts on the

ridges and clays in the basins. This area is subject to flash floods in the

pre-monsoon, monsoon and post-monsoon seasons, so the extent and

depth of flooding can vary greatly within a few days. Normal flooding is

mainly shallow on the ridges and deep in the basins, with flood depths

tending to the Haor Basin. The basin centres (haors) stay wet in the dry

season

Haor bowl-shaped large tectonic depression. It receives surface runoff

water by rivers and khals, and consequently, a haor becomes very

extensive water body in the monsoon and dries up mostly in the post-

monsoon period. In Bangladesh haors are found mainly in greater Sylhet

and greater Mymensingh regions. During monsoon a haor is a vast

stretch of turbulent water. The word haor is a corrupt form of the

Sanskrit word Sagar (SEA). In Sylhet and northeast Mymensingh,

The haors are of tectonic origin and possibly connected with the rise of

madhupur tract. BEELs do not subside but haor basins do. In its original

form, the haor basin comprising the floodplains of the meghna tributaries

would have consisted of a rich mosaic of permanent and seasonal lakes

and ponds with abundant aquatic vegetation. But through gradual

sedimentation, the basin becomes shallower leading to the formation of

reeds and sedges. This resulted in providing enough food and shelter for

FISH and other aquatic, fauna and attracted the migratory birds which,

in their turn, added to the fertility of the waterbodies by their excreta

promoting rich growth of phytoplankton and macrophytes thus partly

contributing to the process of eutrophication.

The haor basin is bounded by the hill ranges of Meghalaya (India) on the

north, the hills of Tripura and Mizoram (India) on the south, and the

highlands of Manipur (India) on the east. The basin includes about 47

major haors and some 6,300 beels of varying size, out of which about

3,500 are permanent and 2,800 are seasonal. Numerous rivers rising in

the hills of India provide an abundant supply of water to the plains and


region, Bangladesh


cause extensive flooding during the monsoon upto a depth of 6m. Small

permanent water bodies within the haors are called beels, which occupy

the lowest part of the depressions. During the dry season, most of the

water drains out leaving one or more shallow beels which become mostly

overgrown with aquatic vegetation or completely dry out by the end of dry

season exposing rich alluvial soils extensively cultivated for rice.

The Surma and Kushiyara in association with other minor hilly

STREAMs like Manu, Khowai, Jadhukata, Piyain, Mogra and Mahadao

form the dense drainage network of the haors. The rivers are primarily

responsible for providing inputs - rainwater and sediment load to the

plains including haors. The plains remain flooded for about 7 to 8

months. During the rainy season, the haors turn into a vast inland sea

within which the villages appear as islands. Occasional high winds

during July to September generate large waves in the haor, which may

cause considerable damage to homesteads.

The entire Sunamganj district, major portion of Habiganj district, some

parts of Sylhet Sadar upazila and Maulvi Bazar district are covered by

many haors. In greater Sylhet the most prominent haors are Saneer haor,

Hail haor, Hakaluki haor, Dekar haor, Maker haor, Chayer haor, Tanguar

Haor, and Kawadighi haor.

2.6 Geography and climate

Sylhet

Sylhet is located at 24°53′30″N 91°53′00″E in the north eastern region of

Bangladesh within the Sylhet Division, within the Sylhet District and

Sylhet Sadar Upazila. The climate of Sylhet is humid subtropical with a

predominantly hot and humid summer and a relatively cool winter. The

city is within the monsoon climatic zone, with annual average highest

temperatures of 23 °C (Aug-Oct) and average lowest temperature of 7 °C

(Jan). Nearly 80% of the annual average rainfall of 3,334 mm occurs

between May and September.

Sunamganj

Sunamganj is located in the Sylhet Division with the Sylhet District to its

east, Habiganj District to its south and Netrokona District to its west.

TheSurma River and Kushiyara River run through the district. The

annual average temperature of Sunamganj has a maximum of 33.2°C

and a minimum 13.6°C, with annual rainfall of 3334 mm. There are

manyhaors and beels (wetlands ecosystems) in Sunamganj.


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Climate data for Sylhet region, Bangladesh, Source: Weatherbase

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year

Average

high °F (°C)

73

(23)

80

(27)

86

(30)

88

(31)

85

(29)

86

(30)

88

(31)

87

(31)

86

(30)

83

(28)

81

(27)

75

(24)

84

(29)

Average

low °F (°C)

50

(10)

55

(13)

64

(18)

69

(21)

71

(22)

75

(24)

77

(25)

76

(24)

75

(24)

70

(21)

62

(17)

55

(13)

66

(19)

Precipitati

on inches

(mm)

0.4

(10)

1

(25)

4.1

(104)

13.7

(348)

21.9

(556)

32

(813)

31.5

(800)

24.5

(622)

20.2

(513)

9.5

(241)

1

(25)

0.3

(8)

160.1

(4,067)

2.7 Demography

Sylhet

The population of Sylhet within the city corporation, was approximately

427,265 as of 2007 and estimated 463,198 in 2008 (density population is

17,479 per km²). Together with the metropolitan area it has a population

of 2,675,346 as of 2001, constituting 2.06% of the national population.

The population growth rate of the city is 1.73%, which has reduced from

1.93% in 1991. As of 2001, It had average literacy rate of 69.73%. The

highest literacy rate was 84.24% in Ward 22 and the lowest was 48.15%

in Ward 10 (2001). The total number of households in the city was

55,514. The Sylheti language is the main language spoken in the city as

well as throughout the division, and is considered as a dialect of Bengali,

which contains a separate written form that is not widely known, where

in this case Bengali is written, and sometimes spoken. The majority of

Sylhetis are Muslims (85%), other religious groups include Hindus (15%),

and very few numbers of other religions, mainly Buddhists and

Christians (less than 0.1%). Sylhet has high rates of power shortage,

including water shortage. According to the Power Development Board,

Sylhet is only receiving 50MW, which is half than the demand of 100MW.

The city corporation is also supplying only 22,500 gallons of water, far

less than the demand of about 65,000. The major sources of water to the

city is the tube wells and the Surma River. There are also high levels of

arsenic in the water in Sylhet than in most other regions, this is mainly

due to the multiple depth screening in the tubewells. According to the

World Health Organization in 1997, about 61% are highly contaminated

by arsenic, however in 1999, the percentage of boreholes tested where

arsenic levels are above 50 micrograms per litre, was under 25%. There

are about 331 registered restaurants in the city, only 15% maintain

http://en.wikipedia.org/wiki/Precipitation_%28meteorology%29

http://en.wikipedia.org/wiki/Precipitation_%28meteorology%29


region, Bangladesh


sanitary facilities and 85% have unhygienic conditions that are unsafe

for the public. Thousands of foreigners have origins in Sylhet. The largest

numbers of people from Sylhet living abroad is in the United Kingdom,

with a population of about 300,000 (95% of the Bangladeshi population).

Sunamganj

Sunamganj has a total population of 1,968,669; males constitute 50.89%

and females 49.11%.There are also some 6,643 person with ethnic

affiliations of Manipuri, Khasia, Garo and Hajong ethnic groups from

neighbouring countries.

Chapter Three

Biodiversity


region, Bangladesh

16 Biodiversity

Biodiversity is the degree of variation of life forms within a given

ecosystem, biome, or an entire planet. Biodiversity is a measure of the

health of ecosystems. Biodiversity is in part a function of climate. In

terrestrial habitats, tropical regions are typically rich whereas Polar

Regions support fewer species. Biodiversity (jib-baichitra) the wealth of

life forms found on earth including the millions of plants, animals and

microorganisms, the genes they contain, and the ecosystems they form. It

is considered at three different levels genetic diversity, species diversity,

and ecosystem diversity. Genetic diversity is the variability within a

species, measured by the variation in genes within a particular species,

variety, subspecies or breed. Species diversity is the variety of living

organisms on earth, measured by the total number of species in the

world or in a given area. Ecosystem diversity is a measure of the variety

of the ecological complexes of organisms and is related to physical and

ecological variations in an area.

The place we visited that is sylhet region of Bangladesh is very much rich

with biodiversity. Short description of Biodiversity of sylhet region by

dividing in flora and fauna are given below.

3.1 Flora of the study area

Flora is a word of Latin origin referring to Flora, the goddess of flowers.

Flora can refer to a group of plants, a disquisition of a group of plants, as

well as to bacteria. Flora is the root of the word floral, which means

pertaining to flowers. Flora is plant life of an area. More than 6,000 plant

species occur in Bangladesh, of which about 300 are exotic and 8 are

endemic.

Flora of the Takerghat area:

Takerghat area is very much rich area with flora. We observed many

kinds of flora. Some of them were medicinal, hilly, fruity, flower and so

on. A large number of plants are cultivated as fruit crops. JACKFRUIT

and MANGO are the most abundant and popular of these plants. The

other common but economic fruits are blackberry, GUAVA, PINEAPPLE,

litchi, banana, COCONUT, Indian jujube, PAPAYA, sapodilla etc. Some

medicinal plants are Ulatkambal, Muktajhuri, Apang, Basak etc. Various

water bodies and wetland ecosystems provide habitats for diverse kinds

of aquatic plants (hydrophytes), e.g. Potomageton (Ghechu), Lemna

(duckweed), Pistia (Topa pana), Hydrilla, Vallisneria (dog grass), and

various insectivorous plants including Utricularia (Jhanji). Some woody

plants were also present there.


region, Bangladesh

17 Biodiversity

Fig: Flora of the Takerghat area

Flora of the Tanguar haor area:

Aquatic plants: Tanguar Haor is filled with a myriad of aquatic and

semi-aquatic plants and shrubs. Every inch of marshland and open

water is choked with plant life. Many of the herbivorous fishes and birds

owe their survival to this abundance of vegetation. Dense vegetation

provides shelter to many small birds that skulk along the water's edge, as

well as many larger migratory ducks such as these Northern Pintails

(Anas acuta). A cluster of with frilled white flowers Nymphoides indicum.

Singa Paan is one of the most important aquatic plants of that area.

Terrestrial plants: Each year flood waters inundate and destroy these

pink perennial flowers and surrounding grasses. However these

vegetation spring back to life once the water recedes; almost six months

after the onset of floods. A threatened species of plant, theWild Rose of

Bengal (Rosa bengalensis) still thrives in Tanguar Haor. Koroj is one of

the most important terrestrial plants of that area. There was a large

number of Koroj trees with a vast line. Hijal (Barringtonia acutangula),

Karach (Pongamia pinnata), Gulli, Balua, Ban Tulsi (Ocimum

americanum), Nalkhagra (Phragmites karka) and some other important

threatened species of freshwater wetland trees are available in this haor.

Fig: Aquatic plants and Terrestrial plants of the Tanguar haor area


region, Bangladesh

18 Biodiversity

Flora of the Jokigonj, Utlar par and Jaflong area:

Sylhet district is very much rich in various plants. The fruity plants we

have observed are as follows- jackfruit, mango, kool etc. The medicinal

plants we have observed are as follows Ulatkambal, Muktajhuri, Apang,

Basak, neem etc. We also observed bamboo, shim, mehagani etc. Main

crops Paddy, mustered, betel nut. Main fruits Mango, jackfruit, orange,

litchi. We observed a vast line of tea garden. It was an outstanding

experience for us. Main exports Paddy; tea, betel nut. Among them tea is

the best. Some flowers species were also present that was very much nice

to look at. Each year flood waters inundate and destroy these pink

perennial flowers and surrounding grasses. However these vegetation

spring back to life once the water recedes; almost six months after the

onset of floods. The delicate flower is known as Murta. Many of the

aquatic and semiaquatic plants come into bloom with the arrival of the

dry season such as these Polygonum glabrum and Rotala indica.

Fig: Flora of the Jokigonj, Utlar par and Jaflong area

3.2 Fauna of the study area

Fauna can refer to the animal life or classification of animals of a certain

region, time period, or environment. Fauna is also of Latin origin. In

Roman Mythology Fauna was the sister of Faunus, a good spirit of the

forest and plains.

Fauna of Takerghat area:

Takerghat area is very much rich with fauna. Some important fauna of

this area are as follows. Fishes-Rui, Katla etc. Amphibians - frogs and

toads. Birds - shalik, Chorui, balihash, pankouri etc. Domestic fauna -

cow, goat, pigeon. Reptiles – snake. Others fauna includes butterfly,

various insects, foring etc.


region, Bangladesh

19 Biodiversity

Fig: Fauna of the Takerghat area

Fauna of Tanguar Haor area:

Wetlands are some of the most fragile ecosystems and they are extremely

vulnerable to degradation. An entire ecosystem can be destroyed or

changed dramatically by the over exploitation of its natural resources or

changes in land-use such as draining the area for farming. It is vitally

important for animals, plants and the associated communities that

natural environment of areas such as Tanguar Haor remains as pristine

as possible. While safeguarding large areas of grasslands, which emerges

only after flooding abates, may seem unproductive, it is still essential to

be left fallow for the wildlife. Cattle grazing and duck farming, in areas

where huge congregation of water birds gather is a huge risk to both the

wild bird population and domestic flocks from cross contamination of

diseases.

The haor is an ideal place for the migratory birds. Every winter about 200

types of migratory birds come to this haor and make their temporary

habitat here. Once upon a time the zamindars of Sunamganj area used to

make cruise into this haor with large Pansi boats for hunting birds. The

main birds name is kaium, balihash, Boroaal, Pankouri, Kalovodor and

so on.

The haor is an important source of fisheries. More than 140 species of

fresh water fishes are available here. Among them the notables are Air,

Gang Magur, Baim, Tara Baim, Gutum, Gulsha, Tengra, Titna, Garia,

Beti, Kakia,Rui, Katla etc. In the 1999-2000 fiscal year, government

earned Taka 70,73,184 as revenue only from fisheries of the haor. Two

NGOs (IUCN and CNRS) are working in this haor for fishes by taking

lease a fixed area from government.

Birds hunting and trapping of wildlife poses a serious threat to the

survival of many species of water birds. Tanguar Haor is a wetland of

international significance; let it remain a safe haven for the thousands of

wild birds and fishes. So, Tanguar haor is very much in biodiversity.

Everybody should come forward to conserve and save from illegal work.


region, Bangladesh

20 Biodiversity

Fig: Fauna of Tanguar Haor area (Birds and Fishes)

Fauna of the Jokigonj, Utlar par and Jaflong area:

Jokigonj, Utlar par and Jaflong area is the main sub area of Sylhet

district. This district is full of various kind of fauna some of them are

available and some of them are in indanger. Some important fauna of

this area are as follows. Fishes-Rui, Katla etc. Amphibians - frogs and

toads. Birds - shalik, Chorui, balihash, pankouri etc. Domestic animal -

cow, goat, pigeon. Reptiles – snake. Others fauna includes butterfly,

various insects, foring etc. In this area we found different types of

animals. We found both primary secondary and tertiary animal in our

field tour. Some of them were unknown.

Chapter Four

Natural

Resources


region, Bangladesh

21 Natural Resources

The grater Sylhet region is the most enriched area of Bangladesh in

mineral resources. A large quantity of the total proven gas reserve and

the only oil field of the country are located here. The area has also vast

deposit of limestone, peat, glass-sand hard- rock grave. But the economic

values of hydrocarbon reserves are overwhelmingly dominant. The region

is geologically known as the Surma Basin and covers the north-eastern

parts of the foredeep and Folded-Belt division of the Bengal Basin which

happens to be one of the most prominent tectonically-active sedimentary

basins of the world. Parts of the Sylhet region which are apparently flat

having are within the foredeep division while the hilly areas are called

folded Belt. Thickness of the sedimentary pile with the foredeep area is in

excess of 15 kilometers; the Folded Belt representing the uplifted parts of

this sedimentary pile. This huge sedimentary body is dominantly

composed of sand and mud with subordinated limestone which started

depositing in a deep-basement (bottom of the basin being composed of

igneous-metamorphic complex) basin about 5o million years ago with the

gradual rise of the Himalayas due to collision between Indian and

Burmese Plates and subsequent erosion. The sand-mud composition of

the sedimentary body, along with technically-developed favorable

structural set up (exposed and covered folds and faults mainly) have

made the Sylhet region highly potential for occurrence of natural

resources. Muds act as sources, sands as reservoirs, while folds

(anticlines) act as traps for hydrocarbons (gas and oil). Age of the

sediments, local geothermal gradient, pressure of the overburden etc.

have been sufficient for the source materials to be "cooked" to from

hydrocarbon.

4.1 Natural Gas:

There are eight gas fields located in Sylhet region. Also the first 3 gas

fields of the country were discovered in this region between mid-1950s

and early 60s – Sylhet gas field in 1955, Chatak in 1959 and Rashidpur

in 1960. These predate the discovery of Titas gas field which is at present

the largest natural gas supplier of the country. Other gas fields of the

region according to their year of discovery are Koilastila 1962, Hobigonj

1963, Beanibazar 1981, Fenchugonj 1988 and Jalalabad 1989. All these

reserves have been discovered in structural traps formed by mild folds

(anticlines) that occur in the subsurface and have no direct surface

expressions. The intensity of these folds increase west to east in the

direction of the Folded Belt region; which relates to the development of

grater thrust in that direction due to tectonic activity. However, the

discovery gas fields are mostly located in the nearly-plan lands of along

the western fringe zones of the intensively folded areas. Gas is discovered

within sandstone layers of Bhuban and Bokabil formations in the


region, Bangladesh


subsurface, which is about 35 million years old. Sandstone act as good

reservoirs because of their high porosity; however, the gas is generated in

some neighboring clayey layers with high organic contents and lager

migrates to the sandy units, which are sealed by impervious sedimentary

layers. Impervious layers prevent further migration of the gas. Total

reserve of the gas fields of the Sylhet region is about 14 trillion cubic feet

with a recoverable reserve of about 8.5 tcf.

Fig: Natural Gas Blow Out and Gas Field


region, Bangladesh


Table 1: Gas in Place and Reserve of Different Gas Fields As Declared By Petrobangla

S.

No

Fields Year of

Discovery

Reserve

Estimated by

Company... Year

GIIP

(proven +

probable)

Recoverable

proven +

probable)

Cumulative

Production

(Dec. 2000)

Net

Recoverable

A. Producing

1 Bakhrabad 1969 IKM 1992 1432 867 586.568 280.432

2 Habiganj 1963 IKM 1992 3669 1895 818.315 1076.685

3 Kailashtilia 1962 KM 1992 3657 2529 231.820 2297.180

4 Rashidpur 1960 IKM 1992 2242 1309 194.920 1114.080

5 Sylhet 1955 HHS 1986 444 266 166.084 99.916

6 Titas 1962 IKM 1992 4138 2100 1783.400 316.600

7 Narsingdi 1990 IKM 1992 194 126 29.205 96.795

8 Meghna 1990 IKM 1992 159 104 23.278 80.722

9 Sangu 1996 Cairn/Shell 1997 1031 848 91.026 756.974

10 Saidanadi 1996 Bapex 1996 200 140 14.816 125.184

11 Jalalabad 1989 Unocal/PB 2000 1195 815 52.298 762.702

12 Beanibazar 1981 IKM 1992 243 167 4.681 162.319

Total A 18604 11166 3996.411 7169.589

B. Non-Producing

13 Begumganj 1977 Welldrill 1991 25 15 0 15

14 Fenchuganj 1988 Bapex 1988 350 10 0 210

15 Kutubdia 1977 Welldrill 1991 780 468 0 468

16 Shahbazpur 1995 Bapex 1995 514 333 0 333

17 Semutang 1969 HHS 1991 164 98 0 98

18 Bibiyana 1998 Unocal 2000 3150 2401 0 2401

19 M’bazar 1999 Unocal 2000 500 400 0 400

Subtotal B 5483 3925 0 3925

Subtotal

A+B)

240087 15091 3996.4 11094.59

C. Production Suspended

20 Chattak 1959 Niko/Bapex 1998 447 268 27 241.5

21 Kamta 1981 Niko/Bapex 1998 33 23 21.1 1.9

22 Feni 1981 Niko/Bapex 1998 178 125 40 85.49

Grand Total (A +B+ C) in BCF 24745 15507 4083.52 11423.48

Grand Total (A +B+ C) in Tcf 24.745 15.507 4.08 11.42

Source: Marketing and Production Division, Petrobangla (Revived on 15/02/2001)


region, Bangladesh


4.2 Crude oil:

The only oil field of the country is located in Haripur of the Sylhet

district, which, was discovered in 1986. Although a relatively large

quantity of gas has been discovered in the county, the amount of oil

discovery is very small. This is in a sharp contrast to many hydrocarbon

provinces of the world where large volumes of both gas and oil co-exist.

Geologists of our country are somewhat confused by this reality and most

opine that exploration into even deeper sedimentary layers then those

producing gas may help discover oil. The Horipur oil is discovered in

sandstone layers within a subsurface fold called Sylhet Anticline which is

about 13 kilometers long and 3 kilometers wide; producing horizons are

around 2000 meters depths and two closely spaced oil-horizons have

been detected. Maximum oil reserve is estimated to be around 21 million

barrels. Oil production under natural pressure was 400 barrels per day

in 1987 which dropped to about 100 barrels in 1994 and since then it

has remained suspended due to necessity of further development of the

field. Between 1987 and 1994, a total of 0.56 million of crude oil have

been produced. The quality of the Haripur oil is similar to that discovered

in Assam.

Fig: Crude oil in Haripur oil


region, Bangladesh


4.3 Limestone:

Limestones of Eocene time are exposed on or close to the surface in the

Takergaht-Lalghat areas of the north-western part of the Sylhet region

along its border with the Indian state of Meghalaya. Reserve is about 30

million tons and it is the second largest discovered limestone in the

country after the Jaipurhat. Preliminary reserve estimation was done in

the sixties and seventies while the Geological Survey of Bangladesh in

1982 ascertained the reserve by putting 5 depths of about 30 to 100

meters below the surface, the deposit has a thickness of 152 meters and

the reserve is estimated to be 17 million tons. In Lalghat and Takerghat

areas limestone deposits occur at much shallow depths and their reserve

are estimated to be about 10 and 2 million tons respectively. In these

areas, limestone deposits are also sporadically exposed. The limestone

body has brought to the surface by upliftment due to techtonic activity;

most of its parts fall within the Indian Territory and Bangladesh sharply

disappear under the alluvium cover in the south with a very high angle of

dip. The Takerghat limestone deposit is being extracted since the

Independence of Bangladesh and it’s reserve is fast diminishing.

Fig: Takerghat Limestone Deposit


region, Bangladesh


4.4 Peat:

Peat, Glass-sand, hard rock Gravel: about 2.5

million tons of peat reserve was discovered in the

Maulvibazar area in the early fifties. The deposit

occurs 1.5 meter from surface, 1.6 meter thick

and extends over an area of about 10 square

kilometers. Peat deposits also exist in the Pagla

and Chorka areas of the Sunamgonj district, has

an estimated reserve of about 3 million tons and

at comparable thickness and deposits occur as

modern sediments within valleys and floodplains.

4.5 Silica/Glass Sand:

Shahzibazar of the Hobigonj district has

Glass-sand reserve of about 1.41 million

tons which discovered in the early fifties

is dominantly composed of silica (over

95%) and occur in centimeter scale

lenses that appear within 1-2 meter

from the surfacee.

4.6 Hard Rock:

Hard-rock gravels of up to 1 meter in diameter are found on the stream

beds that drain the hilly areas of Meghalaya and fall on the flat land

within Bangladesh territory along the northern parts of the Sylhet region.

This is particularly prominent in Jadukata river and Jafflong-tamabil

areas where total estimated reserve is about 45.6 million cubic meters.

Gravels occur both on the present streambeds and up to several meters

depth.

Fig: Hard-rock of Jadukata river and Jafflong area


region, Bangladesh


4.7 Water resource:

A river is a natural watercourse, usually freshwater, flowing towards an

ocean, a lake, a sea, or another river. In a few cases, a river simply flows

into the ground or dries up completely before reaching another body of

water. Small rivers may also be called by several other names, including

stream, creek, brook, rivulet, tributary and rill. River long water course

that flows down a slope along a bed between banks. It originates from a

'source' and culminates to a sea or lake at its 'mouth'. Along its length it

may be joined by smaller rivers called 'tributaries'. A river and its

tributaries form a 'river system'.

The main river of Sylhet region are surma and kushiyara. Trere are 82

haors in Syhlet region; Shingua Beel (12.65 sq km) and Chatla Beel

(11.86 sq km) are notable; Tanguar Haor a large haor lies within

Sunamganj district. Tanguar Haor lies in the floodplain of the Surma

River, one of the main tributaries of the Brahmaputra in Bangladesh, at

the base of the Meghalaya Hills (in adjacent India). It is one of the last

remaining (semi-) natural floodplain wetlands of Bangladesh, as only a

few minor dikes and canals have been constructed. Locally, these

floodplain depression wetlands are called haors, and the deeper sections

that retain water in the dry months are called beels.

Here, an attempt has been made to present list of rivers in Sylhet region-

Description of the main Rivers and Haor are given below-

Surma River:

The Surma River is a major river in Bangladesh, part of the Surma-

Meghna River System. It starts when the Barak River from northeast

India divides at the Bangladesh border into the Surma and the Kushiyara

rivers. It ends in Kishoreganj District, above Bhairab Bazar, where the

two rivers rejoin to form the Meghna River. The waters from the river

ultimately flow into the Bay of Bengal. The River surma, the right bank

tributary of the Barak originating from Manipur and Mizoram of India,

passes along Sylhet town and joins the kushiyara west of Baniachong,

Surma, Piyain, Sharigoyain, Bagra Gang, Noiya Gang, Shawla,

Dhamalia, Manai Bardal, Juri, Manu, Dhalai, Langla (Karangi),

Khowai, Sutang, Kushiyara, Madhabpur, Mahasing, Khajanchi,

Vattakhal, Kalni, Jamalpur, Boraba, Lova, Hari, Bogapani, Dhariana,

Dhoai, Jadukata, Dhala-Dhalai Gang, Gopla-Langla, Mogai-Chalti,

Rakti, Poiyanda, Vera, Mohana, Dhanu-Baulai: (36 rivers).


region, Bangladesh


the combined flow of which is the mighty meghna river. The average

depth of river is 282 feet (86 m) and maximum depth is 550 feet (170 m).

Kushiyara River:

The Kushiyara River is one of the many rivers in Bangladesh that crosses

international boundaries. It is a branch of the Barak River, which

originates in the state of Manipur in India and runs along the border of

the Indian states of Manipur & Mizoram before getting split into Surma

and Kushiyara prior to entering Bangladesh. The total length of the

Kushiyara is about 161 km. The average width of the river is 30 feet (9.1

m) and in the rainy season the mean depth of the Kushiyara reaches up

to 33 feet (10 m), the maximum depth of river is 40 feet (12 m). The river

carries a huge amount of water as well as sediments from Karimganj in

Assam and the hilly areas of Hill Tripura. The highest and lowest

discharges have been measured at Sherpur amounting to 3,700 cubic

metres per second and 33 cubic metres per second respectively.

Tanguar Haor:

Tanguar Haor a large haor lies within Sunamganj district extending over

10 mauzas of Dharmapasha and Tahirpur upazilas of the district. The

mauzas covering the Tanguar haor are (1) Jagadishpur, (2) Bhabanipur,

(3) Lamagaon, (4) Ramsinhapur, (5) Mahajampur, (6) Maindag, (7)

Mayajuri, (8) Bhangachara Purba, (9) Noagaon, and (10) Tanguar Haor.

The haor consists of 120 beels of various sizes. The area of Tanguar haor

including 46 villages within the haor is about 100 sq km of which

2802.36 ha is wetland. Waters in Tanguar haor consist mainly of water

backing up in the Baulai-Surma river system, although some water is

received from streams flowing from the Meghalaya hills, in India, to the

north. Although rich in nutrients, waters are generally clear, especially in

the dry season. The Jadukata River, to the north-east, brings large

amounts of silt to this part of the haor. The entire area is flooded during

the summer monsoon (June-September) and waters may 6-10 metres

deep in the beels; in the dry winter months, water depth in the beels

ranges from 2-6 metres. Small submersible dikes have recently been

constructed to the north-west and north of the haor, to protect rice

crops. Villages are constructed on artificial hillocks called kandas, which

rise 3-6 metres above the haor plain. Tanguar Haor buffers floodwaters

from the Baulai/Surma system, and from the Meghalaya Hills in India,

mitigating peak floods and maintaining water levels in dry months. It also

acts as a sediment retention area for vast amounts of silt from the

Meghalaya Hills (esp. via the Jadukata River). Deep flooding has always

been a season event with which the local community has had to cope.

The small submersible dikes constructed to the north-west and north,


region, Bangladesh


only serve to prolong the growing period by several weeks, thereby giving

a limited amount of crop protection.

Fig: Surma and Kushiyara River

Fig: Origin of Surma and Kushiyara River

Fig: Tanguar Haor

Kushiyara Surma

Chapter Five

Natural Hazards

and Manmade

hazards


region, Bangladesh

30 Natural Hazards and Manmade hazards

5.1 Natural hazards

Flash flood

A flash flood is a rapid flooding of geomorphic low-lying areas washes,

rivers, dry lakes and basins. It may be caused by heavy rain associated

with a storm, hurricane, or tropical storm or melt water from ice or snow

flowing over ice sheets or snowfields. Flash floods may occur after the

collapse of a natural ice or debris dam, or a human structure such as a

man-made dam. Flash floods are distinguished from a regular flood by a

timescale less than six hours. The temporary availability of water is often

utilized by foliage with rapid germination and short growth cycle, and by

specially adapted animal life.

Tekerghat area: The area is situated beside the Meghalaya hilly zone

and over the Shilong plate. As we have observed the area is recently

flashed flooded that comes from the hill. During the hazard the area is

heavily inundated with mud and limestone. That causes massive

destruction and the flood gives a trail of stones and boulders along its

pathway. During flood coal, peat, sand stone and even the trees from the

hill is washed to the plain area. That disrupts the natural agricultural

process by disturbing the soil condition, disrupting the equilibrium of the

natural systems of soil. This flash flood brings tipam sand to the

agricultural field that destroys the crops and delays the harvesting

season.

Tanguar haor: The greater haor basin in the northeastern part of the

country covering vast area is a flash flood zone. In the haor areas, flash

flood comes from the very steep uplands in Meghalayan hills causing

immense damage to the standing crops and properties. The flash flood of

the region of tanguar haor erodes calcium carbonate to the water of the

haor that increases the basicity of the water and make nutrition for the

fish species. But on the contrary the flood carries huge amount of mud

and pollutants to the water that destroys the breeding system of the fish

species. Thus there may occur some poisonous submerged plants that

disrupt the natural environment and quality of water.

Jaflong: In Jaflong, flash flood hits the bank area beside the river

Jaflong. It carries huge amount of stones, mud, boulders and the speedy

water that damages the structures of the area, washes the vegetation and

destroys life. The extreme flashy character of the hilly rivers and sudden

excessive rainfall in the region causes frequent flash floods.


region, Bangladesh


Fig: Map of Flash Flood area of Bangladesh and Flash Flooded area

Land slide

A landslide or landslip is a geological phenomenon which includes a wide

range of ground movement, such as rockfalls, deep failure of slopes and

shallow debris flows, which can occur in offshore, coastal and onshore

environments. Although the action of gravity is the primary driving force

for a landslide to occur, there are other contributing factors affecting the

original slope stability. Typically, pre-conditional factors build up specific

sub-surface conditions that make the area/slope prone to failure,

whereas the actual landslide often requires a trigger before being

released. Landslides are a major cause of erosion, causing the strongest

degradation known, often exceeding 10,000 tons per sq km in a year.

Tekerghat, Tahirpur: Landslides are common in the hilly areas of

Bangladesh. These areas have a long history of instability. Although

written records of landslide incidents are very rare, they have been a

hazard to people ever since they have been living there. In fact, every year

especially in the rainy season landslides take place in both natural and

man-induced slopes. As we have observed that the area of Tekerghat,

Tahirpur is laid beside the Meghalayan hilly range and the area shows

the trace of landslide that occurred during the time. The local people cut

the hill or make slopes for collecting coal and limestone. As a result

during the rainy season landslide occurs. There are also geological

reasons behind this hazard. Certain plate movement is also responsible

for it. Deforestation is one of the major causes for landslide in the area.

Because trees helps to make slopes stable and absorbs or reduce the

risks.

Jaflong: In a landslide or rock falls, movements of the materials depend

on the slope. In most cases, material movement happens because of the


region, Bangladesh


slope instability. Several geological, morphological, and human induced

changes cause these slope instabilities. Presently indiscriminate hill

cutting is one of the major causes of landslide in this area. For collecting

stones from the hill, people cut hill and makes unstable slopes. When it

rains, water dissolves the minerals of the soil of the hills that loosen its

compaction. Soils of the hills also become heavy by absorbing rainwater.

If rain intensity is too high, minerals of soil dissolve very quickly and the

soil turns into mud and becomes very heavy. The steep slope of the hill

cannot bear the mass weight of the wet soil or mud that results the

landslide. Deforestation in the hill areas is another major reason of

landslide in Chittagong. Deforested areas are more prone to landslide

than a forested area. Vegetation protects the soils and makes slope stable

which reduce the risk of landslides. Large trees provide strong root

structures into the earth that anchor the soil and protect it from any

erosion.

Fig: Sample image of Landslide in our study area

Erosional hazard

Major cause of erosion is the land slide which is caused by the geological

and morphological reasons. Soil erosion brings worst effects for the

locality and over all for the total environmental condition. Erosional

hazards causes agricultural loss and the loss of habitate of the certain

area.

Tekerghat, Tahirpur: From our field observation it can be said that the

area is a victim of erosional hazards. The landslides and the flash flood

erodes the top soil and causes sedimentation on the agricultural fields

and carries tipum sand that endeavors the whole area. Due to this

erosional process the environmental quality is disrupted. Water pollution,

air pollution etc are occurred for the process. Dust particle percentage is

abruptly high than the normal condition.

Tanguar haor: Water quality of tanguar haor is hampered due to this

erosional process. Sedimentation process can lessen the depth of the


region, Bangladesh


haor and cause disruption of the haor ecology. Erosional hazard is a

curse for the haor ecology. Local hydrophytic species may be extinct in

the long run. It may confirm total economy and environmental loss for

our country.

Jokigonj: Due to the erosional process the normal flow of the Surma and

Kushiara River is disturbed. The river bank area is disrupted, the local

vegetation is hampered. River bank area in Bangladesh portion is

breaking in a great extent and that is causing land loss and decreasing

the boundary area of Bangladesh.

Jaflong: Erosion of soil and embankment causes devastation for the

area. During the rainy season the Jaflong river fills to the brim and the

heavy flow of water associated with stones and boulders hits the flowing

area that causes loss of structures and damages the systems of soil

formation.

Fig: Flash flood and landslide causes erosion in hilly region and River

bank erosion

5.2 Vulnerabilities of Tanguar Haor area

Vulnerabilities (Climatic and Non-climatic) of Tanguar Haor areas:

Siltation of Haor:

Rate of siltatoin of sand and alluviam is high

Erosion of suface soil in hilly area for cultivation of Pine-apple

Destruction of forest

Cuttinng down of hills

Reduction of fish species:

Overharvesting because of increase in number of fishermen and

Haor-leasing


region, Bangladesh


Using improper and destructive fishing technique like, dewatering

the entire Haor, applying poison, using of small geared net

destroying the spawning of fish because of poison

late or early arrival of rainfall in monsoon

In addition,

Breakinng law in case of fising and leasing

uncertainity of rainfall

catching fish by destroying aquatic herbs with poison (Bishlata)

fishing practices in breeding season

peticides which are used in tea garden mix with water cause

reduction of fish

Removal of gas from Urea-fertilizer in upstream

Fising practice is done yearly in case of leasing

Destruction of Haor-biodiversity:

Due to population pressure and thus over extraction

Siltation of Haor

Destruction of swamp forest by the ranching of domestic animal

and using as fuel wood

Leasing of Haor

Water flow is reduced in stream due to destruction of vegetation

Maximum streams are getting closed

Less amount of sanctuary

By using of small geared net a lot of planktons are captured

Vulnerabilities (Climatic and Non-climatic) of Agricultural Land:

Reduction of land fertility

limited availability land for cultivation in contrast of increasing

population pressures


region, Bangladesh


dividing of land in too many small pieces and excessive use of

fertilizer and chemicals for getting higher production

Additional climatic or non-climatic (developmental or socio-

economic) threat to Agricultural Land are:

Early flash flood that is very risky for Boro crop

Rate of destroying crop for flash flood is very high than previous

Reduction of water retention capacity of soil

Invasion of insect is increased

Vulnerabilities (Climatic and Non-climatic) of River:

Decrease in water flow

Siltation due to the destruction of upstream vegetation and erosion

Outlet of river is becoming narrow day by day

Vulnerabilities (Climatic and Non-climatic) of Kanda:

Cattles eat herbs

Birds do not come for the cattles

Increased insects and use of insecticides

Total ecosystem is disrupted

Fishing Communities Vulnerabilities:

Reduction in the availability of fish species

Increasing cost of fish catch

Limited availability of fishing ground

Cause of Vulnerabilities

Leasing of Haor restricted the common fishing grounds to the poor

and marginal fishermen (but beneficiary for powerful people)

Haor lessee use improper fishing technique (like, dewatering of

entire haor, poisoning, using small mesh size net) and thus

destroys the present, as well as future stock of fish, fry and egg

Late arrival of monsoon interrupt the spawning of certain fish

species


region, Bangladesh


Siltation of beels due to excessive erosion reducing the habitat of

fish species

Destruction of beel vegetation destroys the food and habitat of fish

species

Population pressure, unemployment and low tendency of livelihood

mobilization put a pressure on the fish resources

Additional (developmental or socio-economic) threat to the Fishing

community are:

Lobour cost is comperatively high in local area

In breeding season marginal fishermen have no capital for doing

another work

No available alternative livelihood

Farmer Communities Vulnerabilities:

Water unavaibality for irrigation

Increasing temperature

Fallow land, Kanda and wet land are becoming agricultural land

Mitigation

Probable Ecosystem-base Adaptation to reduce these

vulnerabilities: Haor

Leasing should be stopped

using of small geared net should be stopped

Fish conservation act should be maintained

Proper monitoring and enforcement should be needed

Identify the proper place for making dam

In making dam proper hydrological survey should be needed

Tree plantation is necessary in the bank of the Beels

Legal protection and help is necessary from govenment

Besides these Major Ecosystem Based Adaptation are listed below:

Good management plans or integtrated management plans

Digging Beels as wel as outlet


region, Bangladesh


Management for extraction of water

Long timed sanctuary should be establised

Bank of the large Beels should be got bound

Co-management based ecosystem conservation

Probable Ecosystem-based Adaptation to reduce these

vulnerabilities: (Agricultural Land)

Horizontal plantation may be done instead of vertical plantation in

case of pine-aple cultivation in hilly area.

Joint environmental commission can be made with India

Proper land use policy should be made

Crop varity may be introduced that can stand in flood

People can depend in altenative cash crop

Probable Ecosystem-base Adaptation to reduce these vulnerabilities:

(River)

To protect the rivers from silting up due to excessive erosion in

upstream or dam construction and consecutively dying, Integrated

Water Resources Management (IWRM) should be practiced through

the negotiation of Joint watershed management committee.

To prevent excessive siltation, silt control measures should be

taken with the suggestion and discussion of multidisciplinary

committee and experts to minimize any environmental impact.

In addition;

In case of water shed management water development board

should have concern about environment

Probable Ecosystem-base Adaptation to reduce these

vulnerabilities: Environment

For conservation of threatened fish species captive breeding may be

done

Copies of swamp forest should be protected

Coservation can be done by local protection practices


region, Bangladesh


In addition

Leasing should be stopped, using of small geared net should be stopped,

fish conservation act should be maintained strictly, proper monitoring

and enforcement should be needed, identify the proper place for making

dam, in making dam proper hydrological survey must be needed, tree

plantation is necessary in the bank of the beels, legal protection and help

is necessary from government.

The steps that should be done for the sustainable use of Haor:

Good management plans or integtrated management plans

Digging Beels as wel as outlet

Management for extraction of water

Long timed sanctuary should be establised

Bank of the large Beels should be got bound

Co-management based ecosystem conservation

Sanctuary sustainability should be made by group-fisheries

5.3 Manmade hazards

Water pollution

Water pollution is the contamination of water bodies (e.g. lakes, rivers,

oceans and groundwater). Water pollution occurs when pollutants are

discharged directly or indirectly into water bodies without adequate

treatment to remove harmful compounds.

Water pollution affects plants and organisms living in these bodies of

water. In almost all cases the effect is damaging not only to individual

species and populations, but also to the natural biological communities.

Tekerghat, Tahirpur: Due to the collection process of limestone in the

Tekerghat area the surface area is polluted. The local collection process

for coal disturbs the water quality of the river Patlai and Jadukata. On

the other hand the surface water is also polluted by the unwise activites

of the people. Wastes and oil from the boat engine decreases the water

quality and make the poisonous environment for the species of the water.

Tanguar haor: Wastes from the locality and polluted materials flow to

the haor area and make water quality unstable. On the other hand coal


region, Bangladesh


transportation causes pollution to the haor water. Unplanned sanitary

system also polluting water of haor area.

Alamnagor, Jokigonj: Borak river enters into Bangladesh and divided

into surma and kushiara river. From the upstream wastage is carried to

the downstream and thus water is polluted in the downstream and that

affects the surrounding area.

Jaflong: Stone collection process and the crushing system creates dust

and other pollutants that pollutes the river water and hampers the

natural system of the area.

Fig: Image of Water pollution

Health hazards

Tekerghat, tahirpur: Air pollution is one of the major problems of this

area. Here coal is collected by traditional methods and reserved in open

place. Thus the air is polluted by the dust of the coal. Inhabitants of this

area are affected by mainly air borne diseases. The surface water of this

area is polluted by the indigenous pollutants. Malnutrition is one of the

health problems of this area. Respiratory system of the people of this

area is hampered largely. Skin problem is another problem of this area.

Utlarpar, Horipur gas field: As we observed that Utlarpar is an area

from where continuously gas with slight oil is coming out naturally after

an accident in 1965 during extraction process. From that day till now

natural gas and a few amount of crude oil is coming out through seepage

space in a pond. Here gas is going to the atmosphere for a long time and

disrupting the spheres quality. Nobody is concerned about the air quality

of this area but it is confirmed that local environment is polluted by

uncontrolled gas come out. And that affecting the local people who are

not concerned at all about their health and the hazard by which they are

affecting till now.

Jaflong: Dust is a major problem of this area. Air is polluted at a large

extent of this area. On the other hand jaflong is a tourist place and for

this reason human wastage also causes pollution in this area. The local


region, Bangladesh


people of this area are affected by the polluted air and their respiratory

system is hampered. Pure drinking water is scarce here. For this the

people of this area have to take polluted water and they are attacked by

the water borne diseases as a result.

Fig: Impact of Coal and Gas on Human Health

There are some other Manmade Hazards which will turn into more

devastating in near future. These are discussed below-

Sand extraction:

We observed sand extraction at Ponatirtho river. It is one kind of

manmade hazard. It causes a great extent of air pollution at the area. It

also causing problem for the natural movement of the river.

Limestone extraction:

We studied the area of Ponatirtho river. Here we saw that local people

extracting limestone from the river. These limestones come from the

Meghalaya hilly area with many natural water falls. These extractions are

not maintained in a controlled manner. It may cause problem for the

natural depth of the river.

Hill cutting:

We observed hill cutting at the Takerghat area. This accelerates the

landslides from the hills.

Peat extraction:

We saw peat extraction at the Takerghat area. It causes severe soil

pollution. Extraction of peat causes the pure sulfur content to be

dissolved within the soil. It also causes a grat health hazard.


region, Bangladesh


Peat transportation:

At Takerghat area we studied the Dumper bazar area. This is the place

which has been used for peat transportation. Here we saw the color of

the soil and the river water is black. Pure sulfur content get mixed with

soil and river water. It causes a great amount of pollution.

Temporary sanitation:

We observed many temporary sanitation systems within the Patlai river

bank. These causes the river water to be get polluted.

Fishing at the haor:

Excess and nonseasonal fishing at the Tanguar haor is another kind of

manmade hazard. It causes the extinction of fish species.

Bird hunting:

Bird hunting at the haor is another kind of hazard. Birds are very

important for the balane of haor ecosystem. But people are illegally

hunting birds and causing problems.

Deforestation at the haor:

Deforestation at the haor is another major manmade hazard. It

imbalances the natural ecosystem.

Waste dumping:

We saw a great amount of waste dumping at the Patlai river. This causes

problem for the river water quality.

Gas seepage:

We observed gas seepage at the Utlarpar area. Pure methane released at

the atmosphere. That causing a great pollution of environment. This

seepage is a result of gas explosion which was caused at the moment of

gas extraction at 1965.

Dust pollution:

We observed a great extent of dust pollution at the Dawki river of Jaflong.

This is caused by the limestone transportation vehicles.


region, Bangladesh


Some Image of Manmade Hazards

Chapter Six

Impact Study of

Tipaimukh Dam

Project of India

on Bangladesh


region, Bangladesh

43 Impact Study of Tipaimukh Dam Project of India on Bangladesh

Bangladesh and India is sharing as many as 54 trans-boundary rivers

with each other. Being a lower riparian country of the Ganges-

Brahmaputra-Meghna (GBM) Basin, Bangladesh receives as much water

as it is ‘allowed’ to enter into Bangladesh through these rivers. The

question of ‘allowance’ is used to bring the fact to the surface once again

that out of those 54 trans-boundary rivers, annual flow of 48 rivers are

now heavily modified by the respective Indian water management

authorities. In this epoch of modification, there remain in one hand,

rivers like the mighty Ganges on the western part of the country, ever-

unpredictable Teesta on the northeastern part, violent Gumti on eastern

part, flashy Manu on the northeastern, and on other hand, many other

small river courses entering into Bangladesh. The nature of modification

varies from storage and withdrawal to regulate the seasonal flows to

sudden opening the gates of those regulators to release out the extra

water holding upstream of those regulators. The very consequences of

those modifications, as we now understand, are unprecedented. The

impacts bear numerous dimensions – eco-hydrological, morphological,

geological, biodiversity and environmental, climatic change and

desertification, socio-economical, and finally political. We have already

experienced those very badly in the northwest and southwest region of

Bangladesh due to Farakka Barrage on Ganges River, we are going to

observe more and more in future for the other rivers also. Currently

Central Water Commission of India is planning to divert, control, and

withdraw more and more water from those common rivers between

Bangladesh and India. Barak River flow alteration and withdrawal by

constructing a hydroelectric dam at Tipaimukh and Fulertal Barrage is

one of those planning. The last havoc that Bangladesh can ever imagine

is about to come when it is being strongly believed that India is planning

to divert the Brahamaputra flow to the water ‘deficit’ states of India. This

report though is on the study to understand the most probable scenario

that will be seen in the northeast region of Bangladesh in near future, in

terms of hydrological change if there is a 168.5 meter rock-filled earthen

dam constructed on the Barak River at Tipaimukh. The Tipaimukh Dam

on the Barak River is now neither a concept nor just a mere proposal of

the Central Water Commission of India. It is very much on its way to be

constructed with an aim to produce an estimated 1,500 MW electric

power with firm power generation of 401 MW.

The proposed Tipaimukh Dam- a 162.8 m high rock-filled earthen dam is

going to be constructed on the Barak River at 500 m. downstream of the

confluence of the Barak and Tuivai River near Tipaimukh village in

Manipur state, where the Barak River takes a 2200 bend from southwest

ward direction to northerly direction and flows through a stretch of more

than 24 km. downstream of Tipaimukh. It has been confirmed that the


region, Bangladesh


whole project would submerge nearly 311 sq. km. of land permanently in

India, of which around 229.11 sq. km. areas are reserve forest, remaining

are agricultural and settlement land. The local and indigenous people of

Manipur and Mizoram state of India, eminent engineers, geologists, and

environmentalists have opposed the dam proposal right from the

beginning of its conceptualization. It is being claimed from their side that

this project would result in a massive socio-economic, ecological and

environmental disaster, at both riparian of upstream and downstream of

the dam.

Fig: Location of Tipaimukh Dam, India

However, overruling those claims the Central Water Commission of India

and NEEPCO (North Eastern Electric Power Corporation Limited), the

assigned organization for carrying out the project, have asserted that the

project would moderate the annual flood in the Barak sub-basin along

with potential power generation facilities of 1500 MW. They have also

enforced their statement in favor of the dam by saying that it would make

feasible the proposed pick up barrage near Fulertal, about 100 km.

upstream from Amalshid (Bangladesh-India border) and 95 km

downstream of the dam to develop the Cachar Irrigation Project and

enhance the navigability of the Barak and its tributaries during the dry

season as a complementary benefit of the Tipaimukh Dam Project.

However, overruling those claims the Central Water Commission of India

and NEEPCO (North Eastern Electric Power Corporation Limited), the

assigned organization for carrying out the project, have asserted that the

project would moderate the annual flood in the Barak sub-basin along

with potential power generation facilities of 1500 MW. They have also

enforced their statement in favor of the dam by saying that it would make

feasible the proposed pick up barrage near Fulertal, about 100 km.


region, Bangladesh


upstream from Amalshid (Bangladesh-India border) and 95 km

downstream of the dam to develop the Cachar Irrigation Project and

enhance the navigability of the Barak and its tributaries during the dry

season as a complementary benefit of the Tipaimukh Dam Project.

Meanwhile, this is the brief introduction of the Tipaimukh Dam Project

on which so many claims and counter claims are continuing on both

sides of the project, by pro-dam side and anti-dam people of India. But

this is only the one side of the whole issue. The other side lies on the

much concerned perspective of potential hydro-morphological, ecological,

socio-economical impacts of the dam project on the Barak River which

are likely to be happened in the downstream region, particularly in the

northeast region of Bangladesh in future. Some of the impacts may be

realized within a very short time as an immediate impact, while some of

the environmental effects of the dam may not be realized for hundreds of

years after construction. That’s why it has been claimed, as Patrick

McCully said in his book Silenced Rivers, The Ecology and Politics of

Large Dams that, ‘A dam can thus be regarded as a huge, long-term and

largely irreversible environmental experiment without a control’. This

type of apprehension has not been aroused for not only that Bangladesh

is the downstream riparian of the Meghna Basin but also for the core

hydrological misconception of how we understand and characterize the

river basin and the eco-hydrological system it produces. How natural

phenomena like rivers and its flood have been conceptualized – in

psychologically, materially and the symbolically – in an era of supremacy

of ‘modern science’ and how this supremacy can be maneuvered to meet

the nationalistic development goal of a modern country that is also a

question to ponder about. So there are many dimensions of such a mega

project aiming to exploit the natural resources like water.

Meghna Basin and Northeast Region of Bangladesh

Location and Geography:

Bangladesh is the site of the world’s largest alluvial delta, and the

formation of this delta is solely associated with the very distinguished

water and sediment carrying features of the mighty Ganges-

Brahamaputra-Meghna (GBM) Basin. The total drainage area of these

river systems is more than 1.55 million sq.km. of which about 0.12

million sq.km. (7.5 per cent) lies within Bangladesh. GBM river system is,

therefore, a continental system stretching across five countries: India,

Nepal, Bhutan, China and Bangladesh, of which Meghna Basin is the

smallest but one of the most unpredictable and chaotic basins in the

world by hydrologic means. About 10 percent of the world’s humanity

lives in GBM region, which contains only 1.2 percent of the world’s


region, Bangladesh


landmass. The region is characterized by endemic poverty-being home to

about 40 percent of the total number of poor people residing in the

developing world.

Larger portion of the northeast region of Bangladesh falls within the

Meghna Basin. Meghna Basin, on the other hand, bounded by Indian

Shield on the west, by Madhupur tract on southwest, by Meghalaya

Foothills, Shillong Plateau and North Cachar Hills on the north, by

Tripura Hills on the south; and the basin extends towards the

northeastern states of India comprising western part of Manipur and

northern part of Mizoram and Tripura. The total basin area of Meghna is

82,000 sq.km. out of which 47,000 sq.km. and 35,000 sq.km. lie in India

and Bangladesh, respectively. The northeast region of Bangladesh

encompasses 2.42 million hectares of land. The topography is irregular,

falling from the piedmont hills near India across gently sloping plains to

the Sylhet Depression near the geographic center of the region. The

region is a triangular shaped wedged, roughly 250 km east to west and

120 km north to south. The region is bounded by the Old Brahamaputra

River on the west, by the Meghalaya Foothills and Shillong Plateau on the

north, and by the Tripura Hills on the southeast. It consists of two

portions, the larger comprising 20,261 sq.km. or 83.5 per cent of the

region, lying within the Meghna Basin. The smaller portion comprising

4,004 sq.km. or 16.5 per cent of the region, lies on the left bank of the

Old Brahamaputra and Lakhya River.

Fig: Ganges-Brahmaputra-Meghna (GBM) Basin

Although the two portions of the region experience essentially the same

climate and are similar geologically, they differ significantly in the

number and nature of their cross-boundary inflows. The Meghna portion

receives many flashy inflows from the adjacent Indian states of Tripura,

which lies south of the region, and Meghalaya to the north. It also

receives the substantial outflow of the Barak River Basin, which lies to

the east and occupies parts of the Indian states of Assam, Mizoram and

Manipur. In contrast, the Old Brahamaputra and Lakhya portion receives

only floodwaters spilling into the Old Brahamaputra from the Jamuna

and Brahamaputra River.


region, Bangladesh


The Contemporary State of the Hydrologic System:

The Meghna Basin comprises five main river sub-basins: Sylhet Basin

(Surma-Kushiyara river system) within the northeast region of

Bangladesh and on the western part of Meghna Basin, Barak Basin on

the eastern part, Meghalaya Foothills Basin and Susang Hill on the north

and Trpira Hill Basin on the south.

Sylhet (Surma-Kushiyara) Basin: Sylhet sub-basin actually comprises

larger portion of northeast region of Bangladesh (83.5 per cent). The

basin is bordered by floodplain land from the Old Brahmaputra River on

the west and from the Barak River on the east, by uplands of the

Meghalaya Foothills on the north and by uplands and Piedmont

floodplains along the south. As it has been mentioned earlier discussing

on the northeast region, the topography is of the basin is irregular, falling

from the piedmont hills near India across gently sloping plains to the

Sylhet Depression near the geographic center of the region.

Fig: Meghna Basin and northeast region of Bangladesh

The interfluvial depressions, commonly known as the Haor are the

dominant features of this basin. The large saucer shaped haor region

covering an area of 8,000 sq.km., which is the largest single inland

depression in the country. There are as many as 47 major haors in the

whole haor region. The main streams traversing the Depression include

Surma, Kalni, Kushiyara, Baulai and Dhanu River. Highly sinuous,

meandering sand-bed channels with cohesive banks characterize the

streams. Between May to October the entire central portion of the basin

becomes deeply flooded in most years. Across the Sylhet Basin, rainfall

during the southwest monsoon ranges from around 1400 mm (about 65

per cent of annual total in this particular region) in southwest to around

4100 mm (69 per cent) in the northeast at the border of Meghalaya. In

contrast, the northeast monsoon brings dry air into the region basin


region, Bangladesh


China and rainfall in this season ranges from around 85 mm (4 per cent)

in the southwest to around 220 mm (4 per cent) in the northwest. The

spring reversal from around 493 mm (23 per cent) in the southwest to

around 1287 mm (21 per cent) in the northeast, and the autumn reversal

by decreasing sporadic rainfall, the rainfall ranging from around 171 mm

(8 per cent) in the southwest to around 316 mm (6 per cent) in the

northeast. All the surface water originating in the Barak, Meghalaya

Foothills, Tripura Hills sub-basin actually enter to the Sylhet (Surma-

Kushiyara River) sub-Basin, flow towards the outlet of the whole Meghna

Basin. Bhairab Bazar is considered as the outlet, which is 20 km.

downstream of Bilapur, the joining point of the Surma and Kushiyara

river system after being bifurcated at Amalshid from the Barak River. The

recorded maximum discharge of the Meghna Basin at Bhairab Bazar was

19, 800 m3/s.

Barak Basin: The Barak River drains 25,260 sq.km. of land in the states

of Assam, Manipur and Mizoram in India. The basin has a relief of over

3,000 meter and much of the land is extremely mountainous. The Barak

River is the main channel of this basin, originates from the hill complex

near Mao at the border of Nagaland and Manipur, southeast of Japvo

peak. It runs westward for some distance forming the boundary of

Nagaland and Manipur and then suddenly turns southward and flows

through Manipur until it reaches Tipaimukh at the southwestern corner

of that state. It then takes a sharp northward turn, forms firstly the

boundary of Manipur and Mizoram and then Manipur and Cachar

district of Assam. Thus, flowing northward for about 60 km, it again

sharply turns westward at Jirimukh and flows through Cachar Plain

sluggishly. In the western part of the Cachar plain the river gives out two

branches near Indo- Bangla border, close to Amalshid of Sylhet district.

The northern branch is known as the Surma, the southern branch is

called the Kushiyara. The river system of both the branches again join

together at Bilapur on the Upper Meghna River in Bangladesh. The total

length of the Barak-Surma-Kushiyara River is about 902 km. of which

403 km. is in Bangladesh. Its important right-bank tributaries include

Makru and Jiri in Manipur and Labak, Madhura , Dalu, Jatinga and

Larang in the Barak Plain. The major left-bank tributaries are Irang and

Tuivai (Tipai) in Manipur and Sonai, Rukni, Katakhal, Dhaleswari, Singla

and Langai in Cachar Plain. Mean annual rainfall varies from about

3,000 mm in the western part of the basin to about 1,700 mm in the

east. The river sedimentation and morphological study carried by FAP 6

suggests that roughly 1,440 tonnes/km2 of sediment is yield in the

Barak River and the corresponding annual sediment inflow from the

Barak River at Amalshid is 36.5 million tones/year. The study also

mentioned that the presented figure is estimated using the regional


region, Bangladesh


analysis of Jansen and Painter, while it includes both the wash load and

suspended material load components. The description on the

hydrological process involved in the Meghalaya Foothills, Susang Hills

and Tripura Hills watershed have been reproduced here briefly from the

discussion presented in the report of ‘River Sedimentation and

Morphology’, Northeast Regional Water Management Project (FAP 6).

Fig: Discharge hydrograph of Amalshid on the Barak River

Meghalaya Foothills Basin: Streams draining the Meghalaya Foothills

include Lubha River, Hari River, Dauki River, Ohalai gang, Chela River,

Jhalukhali River, Jadukata River, Lengura River and Someswari River.

The watersheds are all located in the Shillong Plateau, a large elevated

block of Pre-Cambrian Basement rock that has been draped over by late

Mesozoic and Cenozoic sediments. The total Meghalaya catchment area

amounts to 13,466 sq.km. which represents 20.4 per cent of the regions

external catchment area. The two largest catchments are the Jadukata

River catchment (2,500 sq.km.) and Someswari River catchment (2,480

sq.km.). The average annual rainfall tends to increase with elevation,

reaching up to 12,000 mm/year near the headwaters of the Cheala River

catchment. In general, rainfall amounts decrease towards the eastern

and western limits of the Foothills. Even so, annual rainfalls still exceed

10,000 mm over the headwaters of the Jadukata River and Jhalukhali

River. Runoff generated from the Meghalaya Foothills streams is very

flashy and of very high intensity. Published records indicate peak daily

discharges reached around 2,800 m3/s in 1988 and 1991 on the Ohalai

Gang (8.2 m3/s/km2), and around 3,150 m3/s on the Someswari River

in 1988 (1.5 m3/s/km2).

Daily discharges exceeded 5,000 m3/s twice on Jadukata River in 1991,

with the maximum discharge intensity being 2.07 m3/s /km2. These

flows are more than twice the highest daily discharge recorded on the

Surma River at Sylhet. Given the huge flood flow volumes that can be

generated, steep catchment slopes and the presence of relatively erodible


region, Bangladesh


sedimentary rocks, it is expected that the sediment yields from these

basins would be extremely high. Site observations and air photo

interpretation indicate the Someswari River, Jadukata River, Jhalukhali

River are indeed transporting huge quantities of predominately sand-

sized sediments. Sediment yields from the Dhalai gang and Dauki River

are also very large, although the sediment is much coarser, being

composed of a mixture of coarse sand, gravel, cobbles and boulders.

Susang Hills Basin: The Susang Hills are drained by three main rivers:

Bhogai River, Chillikhali River, Malijhee River. These catchments range in

size from 453 sq.km to 118 sq.km. The Chillikhali and Malijhee

catchments are of low relief (150 meter) while the Bhogai River catchment

is more mountainous. Rainfall volumes range between 2,700 - 3,500

mm/year, generally decreasing to the west. Runoff intensities, although

lower than the Meghalaya streams, are still high. For example,

measurements on the Bhogai River indicated maximum daily discharges

have reached 1,240 m3/s, which corresponds to a runoff intensity of

2.74 m3/s/km2. The long-term mean discharge between 1964-1991 was

38 m3/s, which corresponds to a depth of runoff of 2,645 mm. No

information is available on the sediment yields from these streams.

However, given the lower relief and lower rainfall over the basins it is

believed that the sediment yields would be relatively low. Using the

regional sediment yield data, a figure of 1,000 tonnes/km2 was adopted

as a preliminary estimate for these streams. This implies the three

catchments supply in the order of 700,000 tonnes/year of sand load.

Tripura Hill: Streams draining the Tripura Hills include the Juri River,

Manu River, Dhalai River, Karangi River, Khowai River and Sutang River.

The catchment areas are defined by five prominent north-south trending

ridges that project from India into the region. These long linear ridges are

plunging anticlines composed primarily of sandstone, siltstone and shale.

The intervening basins are long and narrow and have wide, flat valley

floors. Relief is relatively low; typically less than 1,000 meter. Rainfall

averages around 2,300 mm/year in the headwaters. There have been

several extreme floods in the 1980's and comparatively lower flood

discharges in the 1960's and 1970's. However, the runoff rates are

substantially lower than the catchments draining the Meghalaya or

Susang Hills catchments. For example, the flood of record on the Khowai

River was reported to reach 1,050 m3/s in 1988, which corresponds to a

runoff of 0.94 m3/s/km2. This is less than half of the runoff intensity

from recent floods on the Jadukata River. A review of satellite photos and

topographic maps from the 1950's suggests the sediment yields from the

headwaters of the Tripura watersheds has increased substantially in

recent years. Land clearing for agriculture and plantations is one likely


region, Bangladesh


cause of the changes. Estimated annual loads are approximately 1.2

million tonnes/year on Khowai River and 3.5 million tonnes/year on

Manu River. The year-to-year variation in sediment loads was found to be

particularly high on the Khowai River. For example, the load in

transported during five days of high flows in 1988 exceeded the sediment

load supplied during the previous five years! This illustrates the critical

effect that extreme flood events can have on the sedimentation processes

in the region.

Impact of Tipaimukh dam on downstream co-riparian Bangladesh

The construction of Tipaimukh dam will have serious adverse impact on

the downstream part of the Barak river basin, which is in northeastern

part of Bangladesh, and known as Surma-Kushyiara-Meghna river basin.

Institute of Water Modelling (IWM), an autonomous research institute in

Bangladesh has recently conducted a study on the impact of Tipaimukh

dam on Bangladesh . The study predicts that, the dam, once operational,

will change the hydrological pattern of the Barak River. According to the

report, the overall nature of impact can be summarized in six broad

categories, like hydrological impact, impact on flooding pattern and on

river-floodplain-wetland ecosystem, impact on morphology, impact on

water quality, dam-beak and general.

Impacts on Hydrology:

The IWM study estimate that once the Tipaimukh dam is fully functional,

average annual monsoon inflow from the Barak River at Amalshid point

to the Surma-Kushiyara-Meghna River system would be reduced around

10% for month June, 23% for month July, 16% for month August and

15% for month September. Water level would fall by more than 1 meter

on average during the month July at Amalshid station on the Kushiyara

River, while this would be around 0.25 meter, 0.15 meter and 0.1 meter

at Fenchuganj, Sherpur and Markuli station, respectively. On the other

hand, at Kanairghat and Sylhet station on the Surma River, average

water level would drop by 0.75 meter and 0.25 meter, respectively in the

same month. During relatively drier monsoon year, dam would have more

impact on the availability of monsoon water in the Barak-Surma-

Kushiyara River than the average annual monsoon year. Like for the

month July, August and September, flow would be reduced as much as

27%, 16% and 14%, respectively, 4%, 2% and 2% higher than the volume

reduction found for average monsoon year.


region, Bangladesh


Impact on Inundation Pattern and River-Floodplain-

Wetland Ecosystem:

Sylhet and Moulvibazar district in northeastern part of Bangladesh will

be effected more due to the Tipaimukh Dam operation regarding their

natural monsoon-flooding pattern. For Sylhet district, total inundated

area would be reduced by 30,123 ha. (26%) during post-dam scenario

than it actually happens in pre-dam average monsoon season. For

Moulvibazar district, this would be around 5,220 ha. (11%). 71% of the

Upper Surma-Kushiyara Project area would no longer be flooded during

average monsoon season for post-dam condition. The Kushyiara River

would cut its connection with its right bank floodplain for around 65 km.

reach. As a result the river at this part will become ‘reservoir river’; rather

than a most valuable ‘floodplain river’. The Kushiyara-Bardal haor

(wetland) on the left bank of the Kushiyara River would become

completely dry during average monsoon year dry due to Tipaimukh dam

operation. The Kawardighi haor (wetland) would also lose around 2,979

ha. (26 %) of its usual inundated land during average monsoon year.

Impact on Damrir haor and Hakaluki haor would be relatively less in

comparison to other haors of the Sylhet and Moulvibazar district. The

above impacts on the river-floodplain-wetland would destroy the natural

integrity of the ecosystem involved within these physical system, thereby,

the consequences of that will be the loss of riverine habitat and species,

lack of enrichment of land with the nutrient full silt leading to the

ultimate decline in the natural productivity of the two most abundant

resources of Bangladesh – land and water.

Impact on Morphology:

The erosion just downstream of the Tipaimukh Dam would be excessively

high and this erosion would continue as long as hundred kilometers

downstream or more. This excessive erosion in the first 100 or 150 km. of

Barak River downstream of the dam would increase the overall deposition

in the lower Barak River, thereby, in the Surma- Kushiyara River system.

Low flow during late monsoon and post-monsoon will accelerate this

deposition in the region.

The probable deposition during late monsoon and post-monsoon season

will raise the overall bed level of the rivers, and for an extreme case it

would block the mouth of certain tributaries originating from the

Kushiyara River. Bed level would rise and that will induce the average

monsoon flood to become a moderate to severe flood in the floodplain of

the Surma-Kushiyara. There would be possibility of increasing erosion in

the upper Kushiyara River, and this will cause more deposition in the

downstream of Kushiyara River and in Kalni River.


region, Bangladesh


Dam Break and Its Consequences:

The communities living in the downstream of any dam remains in a

constant threat of catastrophe being occurred by dam-bursts and dam

induced other floods. The apprehension like this is intensified further

when the very seismic characteristics, its activities as well as the

instability of the Tipaimukh Dam site and the region as a whole is taken

into the consideration. The claimed Reservoir Induced Siesmicity (RIS) is

another important feature of any large dam project that should be

considered in the analysis of safety ground of Tipaimukh Dam Project .

Construction of Tipaimukh dam is violation of co-riparian rights:

India and Bangladesh share many rivers and water resources. The rivers

that flow across the northern parts of India are mostly international

rivers or their tributaries. In the North Eastern region, the Brahmaputra

River and the Barak River are both international rivers. The joys and

sorrows that these two rivers mean for the peoples of Bangladesh and

northeastern India are shared. This issue has been well recognized and

many efforts are in place to address this unhappy state of affairs.

International water treaties have been made and even a Joint Rivers

Commission was set up to examine and settle disputes . The Tipaimukh

Dam project was entirely developed and approved without once informing

the government of Bangladesh or involving its people in any meaningful

exercise to assess the downstream impacts of the dam. This is clearly a

gross violation of co-riparian rights of Bangladesh. The unilateral

construction of Tipaimukh dam on an international river is also violation

of UN Convention on the Law of Non-navigational Uses of International

watercourses.

Chapter Seven

Environmental

condition of the

eastern folded

belt of Bengal

Basin


region, Bangladesh

54 Environmental condition of the eastern folded belt of Bengal Basin

7.1 Environmental Condition

Regional geology

Bangladesh constitutes the eastern continuation of the central broad

Indo–Gangetic plains of India, which serve to physiographically divide the

Peninsular (shield) area to the south from the extra-Peninsular region

(Himalayan mountain ranges) to the north and northeast. The Bengal

basin is located primarily in Bangladesh, with a lesser part in the West

Bengal State of India. The basin is surrounded by India on three sides.

The Shillong Plateau of Assam lies to the immediate north, and the

Himalayas to the distant north. The Indo–Burmese Arakan-Chin uplifts

lie to the east and the Indian shield to the west.

Fig: Map showing major tectonic elements in and around the Bengal

basin. The Dauki fault separates the Sylhet trough from the uplifted

Shillong Plateau at the north.

The area is open toward the south and drains into the Bay of Bengal in

the northern Indian Ocean. Sediment carried by three major rivers, the

Ganges, the Brahmaputra, and the Meghna, is distributed to the Bengal

deep-sea fan by turbidity currents through the ‘Swatch of No Ground’, a

submarine canyon. The Bay of Bengal has beenidentified as a remnant

ocean basin because the basin has been closing by easterly subduction

beneath the Indo–Burman ranges and the Andaman and Sunda Arcs.

Stratigraphy

The stratigraphy of the basin is incompletely known because of thick

sequences of alluvium cover and relative paucity of fossils. Comparative

lithologic studies have been the only means to establish and to interpret


region, Bangladesh


the stratigraphy. The nomenclature and classification of the stratigraphy

of the Bengal basin is established on the basis of type sections in the

Assam basin (northeast India). Stratigraphically, only the Tertiary rocks

are exposed in the folded flank of the Bengal basin (Chittagong Hills and

flanks of the Sylhet trough; and the Permo– Carboniferous Gondwana

coals are the oldest Phanerozoic sediments at the holes drilled into the

Precambrian ‘Indian platform’ tectonic zone in northwest Bengal basin.

These intracratonic, faultbounded Gondwana coal deposits are exposed

at the western fringe of the Bengal basin, in the Bihar State of India.

There are also subsurface occurrences of volcanic rocks, equivalent to

the Rajmahal traps of India, followed by trap-wash sediments present

above the Gondwana coal formations at the NW of the Bengal basin.

Repeated submergence and emergence of the Bengalbasin must have

taken place in the shelf region during Late Cretaceous–Middle Eocene

time, whenthe deeper parts of the Stable shelf of West Bengal,

Bangladesh and Assam were invaded by the sea, whereas freshwater

sedimentation of sandstone and carbonaceous mudrocks continued in

most of the shallow shelf regions. In the Bengal foreland and Indo–

Burman ranges, sedimentation took place in a marine environment and

turbidites probably played an important role in sedimentation.

The Eocene interval is marked by an extensive marine transgression

caused by conspicuous basin-wide subsidence. Clastic sediment input on

the ‘Stable shelf’ was reduced and the shelf became the site of deposition

of shallow, clear water, open marine, limestone. These limestones,

commonly known as the Sylhet Limestone, are very rich in fossil

nummulites. This limestone is exposed at the northern fringe of the

Sylhet trough on the south slope of the Shillong plateau.

Fig: Stratigraphic framework of the Bengal basin.


region, Bangladesh


The Oligocene to Earliest Miocene time was characterized by a major

marine regression exposing most of the ‘Stable shelf.’ The Bengal basin is

bounded from the Burma basin to the east by the Indo–Burman ranges.

The Oligocene clastic rocks (Barail Group) are exposed in part of the

Sylhet trough and drilled in some holes. The Miocene Surma Group is a

diachronous unit consisting of a succession of alternating mud rock,

sandstone, siltstone and sandy shale with occasional thin conglomerates.

Overlying the Surma Group, the Upper Marine Shale represents a

regional marine transgression in the region. By Early Miocene time, a

major phase of sedimentation started and huge amounts of clastic

sediment were funneled into the basin from the northeast and the major

Mio–Pliocene delta complex started to build from the northeast. A

considerable amount of sediment was also coming into the basin from

the northwest and small deltas were building on the western side of the

basin. Sedimentation was in deltaic and open-shelf environments along

the basin margins, whereas turbidities were controlling the

sedimentation in the central and southern areas. Deltaic sedimentation

during the Miocene has been documented based on extensive studies of

lithofacies, and fossil assemblages (mostly palynology; as cited in,

confirmed by studies of seismic reflection character. Many investigations

of lithofacies have reported mainly coastal to shallow water deposits, with

some reports of deep marine strata in SE Bangladesh. Tests of

foraminifers and hystrichospherids from the more shaky sequences in

the Chittagong Hills also indicate brackish to marine environments.

Remains of gastropods, lamellibranchiate, echinoids and burrows

discovered in cross-bedded sandstone of the Bhuban Formation indicate

nearshore depositional environments. A paleogeography reconstruction of

the Bengal basin in the Miocene shows several deltaic complexes

programing from the northeast, east, west and northwest into the basin.

Strata of the overlying Tipam Formation were laid down under

continental fluviatile conditions. During this time, strata along the

eastern margin of the Bengal basin began to be actively deformed.

The stratigraphy of Bangladesh is somewhat problematic because the

greater part of the country is covered by thick alluvium and almost all

the strata are devoid of faunal fossils. The works leading to the

establishment of stratigraphy in Bangladesh are mainly based on

lithological interpretation. The lithostratigraphic units are defined and

described in terms of their lithological composition and geographical

location only. Bangladesh occupies most of the Bengal Basin - a major

geotectonic element of the Assam -Himalayan region and is considered

apparently the largest depositional feature in the world today. The Bengal

Basin is the site of the world’s largest delta (about 60,000 km2) formed

by rivers (Ganges,s Brahmaputra/Jamuna, Padma, Meghna) that drain a


region, Bangladesh


large proportion of the Himalayas. Structural architecture of the Bengal

Basin has been strongly controlled by the collision pattern of the Indian

plate with the Burma and Tibetan plates. The eastern fold belt (EFB) of

the basin, comprising a series of north–south-trending curvilinear

anticlines and synclines, represents a fold-and-thrust belt that

constitutes the westward continuation of Arakan–Chin fold system of the

Indo–Burman Ranges. The present study is mainly concerned with the 2-

D modeling of the anticlinal structures in order to develop an

understanding about the process–response relationships between the

structural style and tectonic evolution of the eastern fold belt. The

dominant fold-generating mechanism is believed to be the east–west-

directed compressional force arising from oblique subduction of the

Indian plate beneath the Burma plate that resulted in the growth of fault-

propagation folds above a detachment or decollement at depth, giving rise

to the Neogene accretionary prism complex development. A prominent

feature of the region is the major east-dipping thrusts separating

successive accretionary wedges. In seismic sections, evidence for several

phases of compressional deformation suggests that multiphase stress

conditions were responsible for the structural expression of the fold belt.

Deep seismic sections reveal that the base of folding is characterized by a

low-interval velocity horizon that represents a detachment separating the

upper folded zone from the lower, seismically coherent, nearly unfolded

zone. This detachment coincides with the under compacted pressured

shale unit, which is thought to have played an important role in the

structural development of the eastern fold belt. Clay mineralogical

analysis reveals the presence of a low-density shale horizon within the

dense and thick shale sequence that is thought to be an under

compacted pressured shale during the geological past, and was

responsible for the initiation of decollement and incipient diapirism

involving thin-skinned tectonics. It is suggested that the salient

structural features of the eastern fold belt, e.g. multiphase fold

development, series of east-dipping thrusts and a basal zone of

detachment or decollement, are the products of thin-skinned tectonics

resulting from the Indo-Burmese plate convergence.

The eastern fold belt (EFB) of the Bengal Basin, also known as the

Chittagong–Tripura fold belt (CTFB) represents the Neogene post collision

tectonic element that developed due to oblique convergence of the Indian

plate with the Burma and Tibetan plates. Tectonically, the EFB is

regarded as the western part element of the compressional Arakan–Chin

fold system of the Indo–Burman Ranges that migrated westward from the

early Miocene, and reached Bangladesh territory in late Miocene/ early

Pliocene times. The EFB is bounded on the west by the present-day deep

basinal part of the basin and on the east by the thrust sheets of the


region, Bangladesh


Indo–Burman fold system that extends linearly from the Arakan Hills of

Myanmar (Burma) in the south to the Naga Hills of India in the north.

The Neogene sedimentary succession of the EFB, consisting

predominantly of thick clastic sequences of shale, sandy shale, and

sandstone, remains relatively less deformed in comparison with the rock

strata in the adjacent Indo– Burman fold belt to the east. The structural

style in the EFB is commonly expressed as a series of overall north–

south-trending elongate anticlines and synclines, the former commonly

associated with faults. The intensity of tectonic deformation is relatively

severe in the east and gradually diminishes towards the west of the EFB.

The Bengal Basin, especially the EFB, has been the focus of geological

investigation over the past few decades owing to its hydrocarbon

potential. Significant contributions have been made by several workers in

relation to the regional geology, hydrocarbon prospects, sedimentology,

and tectonic evolution of individual parts of the basin and adjoining

areas. However, very few studies relate the structural style of the EFB to

the tectonic evolution of the Bengal Basin. Accordingly, there remains a

major gap in our understanding regarding the structural evolution and

development of the EFB.s

Fig: Regional tectonic setting of the Bengal Basin showing its tectonic

elements

Tectonic setting

The Bengal Basin is located between the Precambrian Indian Shield

platform to the west and the mainly Tertiary and partly Mesozoic Indo–

Burman fold belt to the east, and bounded by the Precambrian Shillong

Plateau in the north. To the south, the basin extends into the Bay of

Bengal with its present-day shelf edge near the 200-m bathymetric

contour. The basin is believed to have evolved largely over a remnant

ocean basin and rifted continental margin of eastern India, with at least


region, Bangladesh


its northern and northwestern portion underlain by continental crustand

the southern and southeastern part underlain by oceanic crust. From a

regional perspective, the tectonic elements surrounding the Indian

subcontinent are thought to have started developing with northward drift

of the Indian plate since Cretaceous and its collision with the Tibetan

landmass by early/middle Eocene. Several independent geological and

geophysical evidences suggest that the Indian plate has been subducting

beneath both the Tibetan and Burma plates during the greater part of the

Tertiary. Towards north, the collision between the Indian and Tibetan

plates has led to development of the east–west-trending Himalayas, and

towards east, the subduction process developed the roughly north–south-

trending Indo–Burman fold belt with the EFB as its westward extension.

The Indo–Burman Ranges and the Andaman Islands form a tectonically

continuous belt displaying various geological elements of an arctrench

system, and the development of the EFB is closely related to the easterly

subduction of the Indian plate within this arc-trench setting.

7.2 Environmental Problems

There are various environmental problems is the eastern folded belt of

Bengal basin which are described in the various chapter of this report.

Among them acute environmental problems are described here.

Environmental problems with coal, oil, and gas

This problem is severe in various areas of eastern folded belt of Bengal

basin. Over the past quarter century, we have come to realize that there

is more to life than material goods and services, that "some of the best

things in life are free." The pleasure we derive from breathing fresh air,

drinking pure water, and enjoying the beauty that nature has provided is

priceless and must not be sacrificed. Moreover, losing them will lead

directly or indirectly to incalculable economic losses. We have come to

appreciate the importance of our environment. Wide variety of

environmental problems in burning fossil fuels — coal, oil, and gas. They

probably exceed those of any other human activity. The ones that have

received the most publicity in recent years have been the "greenhouse

effect," which is changing the Earth's climate; acid rain, which is

destroying forests and killing fish; and air pollution, which is killing tens

of thousands of people every year, while making tens of millions ill and

degrading our quality of life in other ways Coal, oil, and gas consist

largely of carbon and hydrogen. The process that we call "burning"

actually is chemical reactions with oxygen in the air. For the most part,

the carbon combines with oxygen to form carbon dioxide (CO2), and the

hydrogen combines with oxygen to form water vapor (H20). In both of

these chemical reactions a substantial amount of energy is released as


region, Bangladesh


heat. Since heat is what is needed to instigate these chemical reactions,

we have a chain reaction: reactions cause heat, which causes reactions,

which cause heat, and so on. Once started the process continues until

nearly all of the fuel has gone through the process (i.e., burned), or until

something is done to stop it. Of course, the reason for arranging all this

is to derive the heat. The carbon dioxide that is released is the cause of

the greenhouse effect we will be discussing. A large coal-burning plant

annually burns 3 million tons of coal to produce 11 million tons of

carbon dioxide. The water vapor release presents no problems, since the

amount in the atmosphere is determined by evaporation from the oceans

— if more is produced by burning, that much less will be evaporated from

the seas.

Environmental impact of fishing

This problem is acute in Tanguar Haor area. The environmental impact of

fishing can be divided into issues that involve the availability of fish to be

caught, such as overfishing, sustainable fisheries, and fisheries

management; and issues that involve the impact of fishing on other

elements of the environment, such as by-catch. These conservation

issues are part of marine conservation, and are addressed in fisheries

science programs. There is a growing gap between how many fish are

available to be caught and humanity’s desire to catch them, a problem

that gets worse as the world population grows.

Similar to other environmental issues, there can be conflict between the

fishermen who depend on fishing for their livelihoods and fishery

scientists who realise that if future fish populations are to be sustainable

then some fisheries must reduce or even close.

Effects on habitat: Some fishing techniques also may cause habitat

destruction. Dynamite fishing and cyanide fishing, which are illegal in

many places, harm surrounding habitat.

Overfishing: Overfishing has also been widely reported due to increases

in the volume of fishing hauls to feed a quickly growing number of

consumers. This has led to the breakdown of some sea ecosystems and

several fishing industries whose catch has been greatly diminished. The

extinction of many species has also been reported.

Ecological disruption: Fishing may disrupt food webs by targeting

specific, in-demand species. There might be too much fishing of prey

species such as sardines and anchovies, thus reducing the food supply

for the predators. It may also cause the increase of prey species when the

target fishes are predator species such as salmon and tuna. Fisheries

can reduce fish stocks that cetaceans rely on for food.


region, Bangladesh


Possible remedies:

Many governments and intergovernmental bodies have implemented

fisheries management policies designed to curb the environmental impact

of fishing. Fishing conservation aims to control the human activities that

may completely decrease a fish stock or washout an entire aquatic

environment.

Fish farming has been proposed as a more sustainable alternative to

traditional capture of wild fish. However, fish farming has been found to

have negative impacts on nearby wild fish. Further, farming of predatory

fish like salmon can rely on fish feed that is based on fish meal and oil

from wild fish.

7.3 Law and Restriction

Environmental recourses are limited. It should be kept in mind that it is

our duty to keep the environment free from pollution. Usually the Sylhet

area is full of recourses. The dwellers maintain their daily basis

depending on the natural recourses. At takerghat we saw a very

significant pollution from extracting natural recourses. Limestone

extraction causes an outstanding amount of air pollution. This kind of

operation should maintained in a controlled manner. Government should

make a strict rule to minimize the pollution. The N.G.O should be more

careful about this type of mining. The general people who do not know

much about this kind of pollution but suffering from it should be

concerned about this pollution. Takerghat area containing a massive

amount of peat in the soil. It spoils the normal properties of soil.

Extraction should be maintained more carefully. Government can control

the peat extraction. The area is surrounded by Meghalaya hilly region.

The main problem of this area is flash flood from Meghalaya hill.

Government should follow a more planned way to free the area from

pollution. The use of natural water should be in a planned manner. For

cultivation and drinking the water has been used. But the pollution from

Dumper bazaar area causing a vulnerable situation. Government should

take a great measure to minimize the pollution from peat. The Tanguar

haor is one of the most resourceful area. There are government based

rule to preserve biodiversity. But dishonest people are causing problem.

So there should be strict rule for the conservation of biodiversity. The

CNRS and IUCN are working for the conservation. But general people

should also be more aware about the situation. Government based

awareness campaign should be made for welfare of the environment. It is

not possible for the local authority to maintain the balance of haor.

N.G.O can make this tusk easy for the government. So N.G.O based

activity should be accelerated to maintain the natural balance. The


region, Bangladesh


people who are extracting limestone from the Ponatirtho river do not

know about the consequences. This people should be taught well to make

aware about the natural depth and current of the river. Sand extraction

from this river should be done at a controlled wayGovernment should

make people aware about the pollution of the river. When we studied the

Alomnogor area of Jokiganj we saw Kushiyara river. We saw that the

portion of Bangladesh has been erosional. Government should make a

solution about the erosion the river. There are many problems within the

pollution at Utlarpar, Horipur. It was the first gas and crude oil

exploration project. But the drilling equipments were destroyed because

of the high pressure beneath the surface. So for this kind of mining

project the workers should be appointed who are more potential. We

observed a massive amount of air pollution at jaflong area beside the

Dawki River. Government should be more aware this pollution. Stone

containing vehicles can be finned if it is causing pollution above an

optimum level. This environment is ours. And its resources are limited.

The utilization should be done in such a way that doesn’t harm the

natural balance of the environment.

Bangladesh Environment Conservation Act

Bangladesh Environment Conservation Act (BECA) is set of laws enacted

by the government of Bangladesh in 1995.

The Act gives operational definitions of terms that historically did not

exist in the legal regime of the country, including ecosystem, pollution,

waste and hazardous substance. Seven areas in Bangladesh are defined

as Ecologically Critical Areas under this law beyond the scope of the

Forest Act of 1927 enacted by the British Raj. Other major preservation

laws enacted by the government of Bangladesh include the Bangladesh

Wild Life (Preservation) Order of 1973, the Marine Fisheries Ordinance of

1983 and the Brick Burning (Control) Act of 1989. Other major

preservation laws enacted before the independence of Bangladesh include

the Public Parks Act of 1904, the Agricultural and Sanitary Improvement

Act of 1920, the Protection and Conservation of Fish Act of 1950.

In September 2009, the four rivers around the capital city Dhaka -

Buriganga River, Shitalakshya River, Turag River and Balu River -- have

been declared by the Department of Environment as ECAs.

The Act followed the establishment of the Ministry of Environment and

Forest in 1989 and the National Environment Management Action Plan

(NEMAP) in 1992, as well as the Forest Policy in 1994 and the Forestry

Master Plan (1993–2012) in 1993. Despite the Act and its supporting

laws and policies the environmental degradation of Bangladesh continues

principally under the population pressure.

Chapter Eight

Conclusion and

Recommendation


region, Bangladesh

63 Conclusion and Recommendation

The Sylhet Division with its hills and basins constitute one of the most

distinctive regions in Bangladesh. The physiography of Sylhet comprises

mainly of hill soils, encompassing a few large depressions known locally

as "beels" caused by tectonic subsidence. It is flanked by the Indian

states of the Meghalaya in the north, Assam in the east, Tripura in the

south and the Bangladesh districts of Netrokona, Kishoregonj and

Bramanbaria in the west. At the center there is a vast low laying flood

plain of recent origin with saucer shaped depressions, locally called

Haors. Available limestone deposits in different parts of the region

suggest that the whole area was under sea in the Oligo-Miocene. Earlier

we crossed the Surma river. We studied the features of the river. We

studied that how iron content is coming out from the river bank. We

observed a hilly region along with river and drainage system. Sylhet

division consists of a great amount of natural gas, lime stone. The most

resourceful area is the Tanguar haor. We observed the Ponatirtho

river(Jadukata river). Which is evoluted from the natural falls from

Meghalaya hills. We observed a massive flash flood hazard at

Shunamgonj area. The river system of total sylhet area is interlinked with

Meghalaya hilly area, tanguar haor, and rivers entering into Bangladesh

from India. We observed many mineralogical resources in Takerghat.

Such as (limestone, peat etc). the Tanguar Haor is one of the most

important for biodiversity in Bangladesh which we also studied.

Takerghat area is also significant for air pollution and health hazard. We

observed the area called jakiganj which area is beside India. The Barak

river entered Bangladesh from India through this upazilla. We studied

Alomnagar area. Kushiyara river is flowing alongside of the area within

India. This river showed the erosional hazard. This river is one of the

trans-boundary river of Bangladesh-India. The Borak river entering point

at Amolshid area is the most important for Bangladesh now a days. We

observed the evolution of kushiara and Surma from Barak river. We can

understand the consequences if Tipaimukh dam is built. We observed

how a river converts into multiple number of rivers. Barak river entered

Bangladesh as a river, but it is a distributary river of Surma and

kushiara. There we studied the impact of erosion and deposition. If

Tipaimukh dam is constructed then surma and kushiara will be no more.

Total Sylhet region will turn into a desert land. We went to the Haripur

area where we observed the Utlarpar gas explosion area. Release of free

methane is very significant for the destruction of ozone layer. Here we

also observed the layer of Tipum sand at the side wall. We observed the

Madhobkunda eco-park. Where we observed Madhobkunda natural water

fall, geologic feature and many flora. At jaflong we studied the Dawki

River and some portion of dawki fault. The most important thing is that

we can now understand the lifestyle of such area. Finally we can say that

Sylhet area is very significant for environmental study.

Chapter Nine

Appendix


region, Bangladesh

64 Appendix

Appendix

GPS Location of the Study Area

Area GPS Location

Barikkar tila, laurer gor 23°15´20´Ń, 90°14´45´É

Lakma chora 25°11´18´Ń, 91°09´47´É

Base camp : TLMP, tahirpur 25°11´40´Ń, 91°10´15´É

Lakma village 25°11´40´Ń, 91°09´57´É

Dumper baazar 25°10´44´Ń, 91°09´31´É

Dumper ghat 25°10´37´Ń, 91°09´28´É

Row of koroch tree 25°09´38´Ń, 91°08´01´É

Poncho haor dam 25°09´34´Ń, 91°07´06´É

Chiragao village 25°08´44´Ń, 91°06´36´É

Tanguar haor entering route 25°08´21´Ń, 91°06´13´É

Laowa bill 25°08´19´Ń, 91°05´53´É

Loichchamara khanda bill 25°08´17´Ń, 91°05´31´É

Roa bill 25°08´14´Ń, 91°05´25´É

Chordynna bill 25°07´38´Ń, 91°05´03´É

CNRS project area 25°08´10´Ń, 91°08´29´É

Hatikada chor 25°08´57´Ń, 91°08´08´É

Water seepage in lakma chora 25°09´26´Ń, 91°06´50´É

ICP, Alamnagar, jokigonj 29°52´23´Ń, 92°21´54´É

Meeting point of borak-surma-

kushiyara

24°52´33´Ń, 92°29´16´É

Madhabkunda, Moulovibazar 24°38´15´Ń, 92°13´24´É

Utlapukur gas accident zone 24°58´51´Ń, 92°01´44´É

Oil drilling pipe, Haripur 24°58´55´Ń, 92°01´56´É


region, Bangladesh

65 Appendix

Chemical Properties of Water Body of Tanguar Haor

pH

7.8

9.1

8.6

DO

6.18 mg/l

7.50 mg/l

7.06 mg/l

7.80 mg/l

EC

90 Micro siemens

78 Micro siemens

TDS

10.6 mg/l

8.3 mg/l

11.0 mg/l

9.5 mg/l

Salinity 0.03%

Chapter Ten

References


region, Bangladesh

66 References

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Documents

Assessment of Geo-environmental hazards and Natural resources of Sylhet region, Bangladesh