ICSE6 Paris - August 27-31, 2012
- Mohammad Arifur Rahman & Md. Munsur Rahman
ICSE6-2012/105
Char Formation Process and Livelihood Characteristics of Char
Dwellers of Alluvial River in Bangladesh
Mohammad Arifur RAHMAN1, Md. Munsur RAHMAN2
1
PhD Fellow/ Institute of Water and Flood Management (IWFM)
Postal address1: IWFM, BUET, Dhaka-1000, Bangladesh - e-mail: [email protected]
2
Professor/ Institute of Water and Flood Management (IWFM)
IWFM, BUET, Dhaka-1000, Bangladesh - e-mail: [email protected]
The present study tries to identify the formative condition of Alluvial Char by the literature review works. It also
focuses the livelihood practices of the char dwellers. The research has been conducted through interdisciplinary
approach. Different socio technical tools are used to analyze the problem. Local people’s participation in the research
process has ensured by using Participatory Rural Appraisal (PRA) tools.
Bangladesh was, and continues to be, formed by sedimentation and accretion of rivers as they flow from the
Himalayas to the Bay of Bengal. Extensive char areas have been created along the bed or basin of big rivers the
Jamuna, the Padma and the Meghna. Char lands are the sandbars that emerge as islands within the river channel or as
attached land to the riverbanks. The Jamuna is basically braided river and produce less stable sand bars within the
river channel. However, Padma shows meandering characteristic and produce stable attached char to the riverbanks.
Stable chars are more resourceful than less stable char. The stability of char has a positive relationship to the stability
of livelihoods of char dwellers. The char dwellers livelihood is more vulnerable in the dynamic char than stable char.
The channel patterns of alluvial rivers have been classified as straight, meandering and braided (Leopold and
Wolman, 1957). Callander (1969) and Parker (1976) developed a two-dimensional flow model to explain the origin of
meandering. They treat the meandering or braiding tendencies of straight channels as a stability problem. Fredsoe
(1978) recommends the stability criteria as: B/h0 <8 (straight); B/h0 >60 (braiding).
The attached char like Char Konabari, about 60 percent people are engaged in handloom activities as labor as their
main source of livelihood. Agriculture is the second highest and about 20 percent people are engaged in such practice;
about four percent people are engaged in small business (broker, small retailer) and rests others are engaged in day
labor activities and others like van driver etc. In the island char like Dakshin Boro-char, about 60% and 30% people
are agricultural farmer and fishermen. On-farm activities are dominant in Dakshin Boro-char. On the other hand both
in off-farming and on-faring activities are equal in attached char.
Key words
Char Livelihood, Alluvial River, Interdisciplinary Approach, Formation Processes.
I
INTRODUCTION
The vegetated landmasses within the riverbanks of Bangladesh, which are commonly known as chars, have
long been inhabited by a large number of people. ISPAN (1995) noted that island chars are defined as land
that, even in dry season, can be reached from the mainland only by crossing a main channel. Attached chars
are accessible from the main land without crossing a main channel during the dry season (crossing lesser
channels may be required), yet is inundated or surrounded by water during the peak of a ‘normal’ flood
shown in Figure 1.
1
Corresponding author
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- Mohammad Arifur Rahman & Md. Munsur Rahman
Figure 1: Char Classification.
The Jamuna is one of the largest braided rivers in the world. Three levels of bars are also present in the
Jamuna River: island char, braid bar and very low level bar associated with dune (Thorne et al., 1993;
Hossain et al., 2000).
When a char emerges, it consists of sand of approximately the same coarseness as the bed material of the
river reach. However, at the lee side of a medial or point bar, fine materials would deposit. When the bar
elevation reaches close to average flood levels, a layer of silt and clay is deposited over the sand layer,
facilitating the development of vegetated islands named as chars. As the chars grow older, their levels
increase and attain the height of the adjacent floodplains. This process might be interrupted by subsequent
lateral erosion of the chars (Sarker et. al, 2003).
Bristow 1987; Thorne et al. 1993 have established that the elevations of active sand bars are less than those
of established chars. A distinction should be made between island chars, which are surrounded by water
year-round and attached chars, which are connected to the mainland under normal flow conditions.
II
METHODOLOGY
The research has been conducted through interdisciplinary approach. Different socio technical tools are
used to analyze the problem. Local people’s participation in the research process has ensured by using
Participatory Rural Appraisal (PRA) tools like Discussion tools (Focus Group Discussion - FGD, Semi
Structure Interview), Mapping Tools (Resource mapping, Transect walk), Diagramming tools (Seasonal
Calendar). This interdisciplinary approach enables the researcher to gain in-depth understanding of the issues
raised through the PRA practices. PRA enables rural people to share, enhance and analyze their knowledge
of life and conditions, to plan and to act (Chambers, 2002). For the study several FGD is conducted with
agricultural farmer, fishermen and handloam worker of different age group (Group 1: Age 18-30 years,
Group 2: Age 31-45 years, Group 3: Age 46-60 years). Secondary data has been consolidated by the
literature review works in order to make a rationale for the formation and growth of sand bars in braided and
meandering rivers.
In addition to this, a formal semi-structure questionnaire is designed in an easy way that is relevant to the
resource and livelihoods practices of the char dwellers for questionnaire survey. Simple random technique
has been applied as sampling procedure. Simple Random Sampling from a finite population refers to that
method of sample selection, which gives each possible sample combination an equal probability of being
picked up and each item in the entire population to have an equal chance of being included in the sample
(Kothari, 1996).
The per capita income noted that the total income divided the total population of the specific region.
Hence, the per capita income of a char is calculated the following equation:
Per capita Income=Total Income from different occupation / Total Population of the specific char.
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II.1
- Mohammad Arifur Rahman & Md. Munsur Rahman
The Study Area
The study area is selected on the basis of stability of the char (less stable char, stable char) as well as
location of the char (attached char and within the river char). Some additional selection criteria also
considered; such as local livelihood pattern and alternative options, household consistency, agricultural
concentration, communication and community responsiveness.
The char Konabari of Rajapur union under Belkuchi Upazila, Sirajganj district and Dakshin Boro-char of
Eklashpur union under Uttar Matlab, Chandpur district is selected for the present study. The char Konabari is
a less stable char and emerged during 1998 flood. However, the Dakshin Boro-char is a stable char and
emerged in the year 1970. The char Konabari is situated on the eastern side of the branch channel of Jamuna
River and the Dakshin Boro-char is placed on the confluence of Padma-Meghna are shown in Figure 2.
Figure 2: Location of the Study Area.
III
FORMATIVE CONDITION OF BARS
The difference between the bars and islands (these are features of braided river morphology) is identified
by different authors (Brice, 1964; Bridge, 1993; Bristow and Best, 1993; Thorne, 1993). Bars are defined as
dynamic features which are unvegetated and submerged at bankfull stage. Islands are more stable features,
emergent at bankfull stage and vegetated.
The formation process and characteristics of these chars are different in braided and meandering rivers,
while within a river the char characteristics may differ in a lengthwise direction. Generally, chars upstream
consist of coarser materials compared to those downstream. Height of the chars above low or average water
levels would depend on the annual water level variations. In a braided river the formation of an island char
would deflect the river flow to both sides, tending to widen the river through bank erosion. This process of
widening of the river and sediments becoming available from the eroding banks would enhance the process
of continued bar-building (ISPAN, 1995).
In a meandering river, two types of reaches exist: bends and crossing. Meandering bends are always
associated with point bars. Point bars are formed through secondary currents, which erode the outer bank of a
meandering bend and deposit the sediments in the inner bend. The topography of this type of chars has a
typical pattern; it is elevated at the upstream part of the inner bend and gradually slopes down in the
downstream and from the bank towards the river. Points bars as attached bars in a meandering rivers are
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different from attached bars in a braided river. In these rivers attached char develop from an island char by
the abandonment of an anabranch near the floodplain. Attached chars in braided rivers would thus have the
same characteristics as a medial bar; in the sense that these will be elevated at the tip of the bar, with the
slope gradually declining in the downstream and toward each of the flanks.
Being both wandering rivers, the Ganges and Padma have similar char formation processes. In these rivers,
large sweeping meandering bend produce point bars. In locations where chute channels remain active in both
the dry and wet seasons, island char are also created. After disappearance of the chute channels, such island
chars become attached chars. In the braided reaches medial bars emerge as island chars, which may become
attached chars if the channel reach becomes meandering or the anabranch near the floodplain is abandoned.
Given this order of development, it is likely that in the wandering rivers the attached chars are older than the
island chars. This is confirmed by the fact that the area flooded is lower in the attached chars compared to the
island chars.
The channel patterns of alluvial rivers have been classified as straight, meandering and braided (Leopold
and Wolman, 1957). Callander (1969) and Parker (1976) developed a two-dimensional flow model to
explain the origin of meandering. They treat the meandering or braiding tendencies of straight channels as a
stability problem. Fredsoe (1978) recommends the stability criteria as: B/h0 <8 (straight); B/h0 >60
(braiding).
Klaassen and Vermeer (1988a) studied the channel characteristics of the Jamuna River and found that the
relationships between the average depth (in m), width and the discharge (m3/s) for bankfull stages:
h  0.23 Q0.32; B=16.1 Q0.53. The Jamuna is predominantly a braided river, with some anastomosed regions
(Thorne, 2006) and processes an average braided width of 11km, flow depth of 5 m and Brice braiding index
of 4-6 (FAP 24, 1996). The average flood discharge of Jamuna River and Padma River is 70,000 m3/s;
95,000 m3/s respectively. In 1998, river Jamuna and Padma experienced a large flood event which return
period is 100 years (FAP 24, 1996).
Kinoshita (1957) proved that bar formation was independent of the influence of the banks, and proposed a
first rough condition for alternative bar formation: B/h< 5 to 20. Chang, et al. (1971) who mainly
investigated the wavelength of alternative bars in their experiments, found that bars only forms when B/h<
12. Ikeda (1984a) and Jaeggi develop the empirical equation to predict wavelength, and height of alternative
bars :
L  5(Bh/ C f )0.5 , H  0.22B0.85 d 500.15
Here, B  flow width; h  flow depth; L  bar wave length; d 50  mean grain size; H  bar height,
C f  resistance coefficient
The present study also develop equation to predict the wavelength, and height of the alluvial river in
Bangladesh. For this purpose flow width is divided by braiding Index. The present study found that the
height and length of the Jamuna river is 16.6 m and 5km respectively. Braid bars in the Jamuna are typically
up to 15 m high, 1.5 to 3 km long and 0.5 to 1 km wide (Coleman, 1969; Bristow, 1987, Ashworth et. al).
The d50 of bed material of Jamuna River and Padma River is 0.20 mm; 0.12 mm respectively (FAP 24,
1996).
IV
LIVELIHOOD CHARACTERISTICS OF CHAR DWELLERS
Bangladesh was, and continues to be, formed by sedimentation and accretion of rivers as they flow from
the Himalayas to the Bay of Bengal. Extensive char areas have been created along the bed or basin of big
rivers the Jamuna, the Padma and the Meghna. Char lands are the sandbars that emerge as islands within the
river channel or as attached land to the riverbanks. The Jamuna is basically braided river and produce
unstable and semi stable sand bars within the river channel. However, Padma shows meandering
characteristic and produce stable attached char to the riverbanks. Stable chars are more resourceful than semi
stable char. The stability of char has a positive relationship to the stability of livelihoods of char dwellers.
The char dwellers livelihood is more vulnerable in the dynamic char than stable char. The economic status of
island char is poor compare to attached char and the meander river chare is more resourceful than braided
river char. The different characteristics of char within Padma and Jamuna in the study area are described in
Table 1.
Table 1: Characteristics of char.
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Char Konabari
Haulbang
Bamagati
Sharisha bon
Dakhin Boro-char
River Type
Braided
Braided
Meandering
Meandering
Char Type
Attached
Island
Attached
Island
Age of the char
12 years
22 years
12 years
40 years
Stability
Semi stable
Stable
Semi Stable
Stable
Soil Characteristics
50% grain less
than 0.075mm
50% grain less
than 0.075mm
77% grain less
than 0.075mm
71% grain less than
0.075mm
Organic Content
1.68%
1.60 %
2.52%
2.18%
Livelihood
Off-farming
dominate
Farming dominate
Farming dominate
Farming dominate
Resource Extraction
Agriculture
Agriculture
Agriculture
Agriculture
Fishery
Per Capita Income
$0.54
$0.50
$1.24
$0.87
and
In the braided river the soil is coarse than the meander river. The present study shows that there is a
positive relationship between soil organic content and per capita income of the char area. The relationship
between soil organic content and per capita income of the char area is shown in Figure 3.
Figure 3: Relationship between Soil Organic content and Per capita Income of the char area
Household survey revealed that the total population of Char Konabari is about 969 in numbers in which
478 are male and 481 are female; however the total population of Dakshin Boro-char is about 2745; among
them 1355 are male and 1390 are female. About 215 households live in the Char Konabari of which about 60
% people are engaged in handloom activities as labor, which are their main source of livelihood. Agriculture
is the second highest and about 20% people are engaged in such practice; among the agricultural farmers,
50% have their own land and rests of them are landless. About 4% people are engaged in business (petty
business) and rests of the people are engaged in day labor activities, van driver and others (boats men) are
shown in Figure 5. On the other hand about 586 households live in Dakshin Boro-char of which about 60%
and 30% people are agricultural farmer and fishermen. On-farm activities are dominant in Dakshin Borochar. Most of the farmers have their own land as well as they also cultivate khas (public) land. The rest of the
people are engaged in day labor activities, petty business and others (boats men) are also shown in Figure 4.
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Figure 4: Livelihood practices of Dakshin Boro-char and Char Konabari
IV.1
Char Livelihood Development Process
The vegetated landmasses within the riverbanks of Bangladesh, which are commonly known as chars, have
long been inhabited by a large number of people. Newly formed char consists of sand of approximately the
same coarseness as the bed material of the river reach. First two or three years erosion or accretion of the
char is the natural phenomena. Char dwellers cultivated Ground nuts and Dhaincha/Catkin if fine materials
deposited on the bed of the char. These processes would continue more or less five years until the land
enriched with minerals like nitrogen and silt/clay. Dhaincha (sesbania aculeata) and Ground nuts are
leguminous plant those can fix nitrogen directly from air into the soil by their special roots. In addition due
to Catkin (Saccharum spontaneum) grown every year a layer of silt and clay is deposited over the sand layer
when the char elevation reaches close to the average flood level. After ten to twelve years, the char land
make suitability for cultivation of rice as well as people have been migrated from adjacent char and inhabit
in the fertile land due to resource availability. They make their house in the barren land in the char area. The
coordination among people and fertile land with the influence of river formed a complete char land. The
entire process would be completed within twelve to fifteen years. At the final stage the newly formed char
turned into a stable char. Table 2 and Figure 5 shows the six-step development process of char livelihood and
four-step development of agricultural practices respectively.
Table 2: Six –step Development of Char Livelihood.
Step
Age of Char
1
1-3 yrs
2
3-5 yrs
3
5-10 yrs
4
5
10-15 yrs
15-20 yrs
6
20+ years
Livelihood
Natural resource collection such as: Catkin for house
making and fodder of cattle.
Start migrating of mainland people to the char as well as
farming activities especially Ground nuts and
Dhaincha/Catkin and different type of cereal (Local), Corn,
Maize.
Start settlement and social activity (Agricultural farmer and
Day labor).
Start Economic activity (Small businessmen, broker).
Broker, trader, boatman, rickshaw puller.
Start development/ Administrative activity (Teacher, GOs
and NGOs official).
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Bush
Catki
Legume (Dhoincha,
Ground nut), sweet
potato)
Cereals, Pulses (Lentil), Maize,
Pepper, Mustard, Wheat, Rice, Jute, Potato
Figure 5: Four steps Development of Agricultural Practices.
V
CONCLUSION
Bangladesh was, and continues to be, formed by sedimentation and accretion of rivers as they flow from
the Himalayas to the Bay of Bengal. Extensive char areas have been created along the bed or basin of big
rivers the Jamuna, the Padma and the Meghna. Char lands are the sandbars that emerge as islands within the
river channel or as attached land to the riverbanks. The entire process of char formation would be completed
within twelve to fifteen years. After fifteen years it is turn into stable char. The present study explore six-step
development process of char livelihood and four-step development of agricultural practices. The resources of
the less stable attached char like Char Konabari is agricultural dominated but most of the char dwellers are
engaged in off farm activities. The bulk amount of yearly income comes from on farming activities rather
than off farming activities. However off farming activities is also popular in an attached char dwellers due to
easy communication but their contribution is not remarkable in respect to on farming activities. The present
study shows that the char dwellers’ economic status stands below the poverty line compared to the present
poverty data.
VI
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