Impact of Bank protection structures on riverine fisheries

13th Bangladesh International Geography Conference

Impact of riverine structures on fish of the Jamuna river

Mahmud Hasan Tuhin1, Rezaur Rahman1, Munsur Rahman1, Tarekul Islam1, M. H. Sarker2, Shahad M. Chowdhury3, Munir Ahmed4

Abstract: The Jamuna is one of the largest rivers in the world. The width of the river varies from 3 km to 18 km but the average width is about 10 km. The river is in fact a multi-channel flow consisting of many different size channels, and of different patterns including braiding and meandering. It also discharges a large volume of water and at the same time brings huge amounts of sediments. Due to high discharge of water and braided nature, the river has a severe flooding and bank erosion problem. Every year, millions of people are affected by flood and erosion that destroys standing crops, farm and homestead land. To protect from these flood and bank erosion, different riverine structures such as embankment, revetment, spur, hard point, groyne and bandal have been installed at different places of the bank of Jamuna. Due to the construction of these riverine structures, the connection with flood plain, natural flow and environment of the river has changed. The ideas of fishermen about the change in species composition for the construction of riverine structures have been collected by using PRA technique. The study identifies the different species found near different riverine structures of the Jamuna River.

Jamuna is a good and important source of natural resource like riverine fisheries. Once upon a time, more than 100 fish species was available in the river. But near the riverine structures, a change in species catch is observed. Flow modification was visually observed and the opinion of local fishermen was collected during survey and it is found that, for construction of the riverine structures, the natural fish habitat and the river flow are modified. Thick layer of sediments are found near CC blocks of revetment which supports fishes like Baila, Baim, Chingri etc. Near spur, scour hole is formed where some infrequent species are found, which were not available before construction of the structure. Fishes like Air, Baghair, Kalbaus are now available near hard point.

KEY WORDS: Jamuna river; structures; flow modification; fish.

1. Introduction

The Brahmaputra-Jamuna River, is one of the world's great rivers. The high water and

sediment discharges are generated by the monsoon-dominated floods and the tectonic

setting, which provides abundant sediment from Himalayan uplift into the subsiding Bay

of Bengal. Structural, climatic and auto cyclic fluvial processes have produced a large

multi-channel river in Bangladesh with individual channels up to 5 km wide that can

scour down to 50 m.

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1Institute of Water and Flood Management - Bangladesh University of Engineering and Technology, 2Center for Environmental and Geographic Information Services, 3Inertnational Union for Conservation of Nature, 4 Technological Assistance for Rural Advancement.


The Brahmaputra-Jamuna has experienced large-scale avulsion at the end of the 18th

century, recent widening and westerly migration and exhibits rapid bank erosion in

response to large floods (Best et al. 2007). The Hydrology Directorate of the Bangladesh

water development board (BWDB) refers to the whole stretch as the Brahmaputra-

Jamuna (Banglapedia, 2009).

The river system has an intensive problem of flood and bank erosion. Its meandering and

braided nature is responsible for bank erosion. Valuable properties, crop land, homestead,

commercial land everything is destroyed by the river bank erosion. For the protection of

valuable properties, different bank protection

and flood control structure have been

constructed in this part.

Jamuna is an important habitat for the fishes.

More than 100 fish species are available in

the river. Riverine and floodplain riverine

migratory species are most common in the

river. For the meandering pattern of the river,

it contain different fish favorable habitats

such as channels, sub channels, oxbow lake

and seasonal pool formed in char, shallow

submersible char land etc. Figure 1 shows a

cross section of the river containing such

habitats. For these suitable environments, annually a huge amount of fish is being

captured from this river. It is estimated that between March 1993 to February 1994 total

5044 tones fish was captured from Jamuna (FAP 17, 1995). From this statistics, it is clear

that, once upon a time the Jamuna River was an important source of fresh water fish for

our country. A good numbers of people lived beside the Jamuna river was involved with

direct fishing and fisheries based economic activities like direct flood plain fishing,

boating, treading, transporting etc. But the riverine structures change the natural flow of

the river and flood control structure stop the connection between the flood plain and river.

Between 1970 and 1990, around 2.1 million ha of floodplain were removed from river

fisheries production because of the construction of levees (Siddiqui, 1990).

2. Riverine structures

2

Main Channel

Sub Channel

Flood plain connectivity

Channel formed in char

land

Oxbow lake formed in char

land

Figure 1: Different fish habitats in river(Source: CEGIS, 2010)

http://www.banglapedia.org/httpdocs/HT/B_0256.HTM

http://www.banglapedia.org/httpdocs/HT/B_0256.HTM


2.1 Erosion control structures

Different structural measures are adopted by

Bangladesh Water Development Board (BWDB)

for erosion protection. On the basis of river

morphology and flow characteristics the

structures are constructed. Most common

structures for erosion protection are i)

Revetment with Cement Concrete (CC) blocks,

ii) Groyne, iii) Spur, iv) Hard point, v) Bandal,

and vi) Geo bag revetment. Among all,

Revetment with CC blocks is the widely

practiced erosion control measures in our

country. Figure 2 shows the overall bank

protection structures of the Jamuna river.

Revetment protects the bank from direct hit of

water flow, wave and scouring. Scouring creates

a vacant place beneath the toe of the revetment

and for that reason it fails. Hard point is such a

structure, which protect bank from direct hit of

the river water. The head of the hard point is

exposed to the open river. So the water directly hit and diverted. In Sirajganj and both

side of Bangabandhu Bridge, these types of structures are present. Figure 3 shows

different bank protection structures present around the bank of Jamuna.

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Kamarjani Hard point

Bangabandhu Bridge

Sirajgonj Hard point

Figure 2: Bank Protection structures of Jamuna Source: CEGIS, 2010)

Bandal

CC Block revetment Groyne

Spur Geo bag RevetmentSpur

Hard point


Figure 3: Different bank protection structures

Spurs are both permeable and impermeable. But in this study impermeable spurs are

considered. Spurs are constructed in the river for the diversion of the flow. The flow is

diverted for the spurs and a huge land reclaimed on the other side of the spurs. Groynes

are also constructed for the flow diversion. Groynes divert the flow and protect the

downstream side bank. Groynes are also permeable and impermeable types but in our

country impermeable groyne are many in numbers rather than permiable groyne.

Revetment constructed by geo bag is also a kind of erosion protection measures. In Bera

of Pabna district geo bag protection work is observed. Bandal construction is also a new

idea for bank protection by diverting flow by using bamboo pillars and mats. It is very

active in sub channels as erosion protection measures. In Bhuapur of Tangail district such

protection work is present.

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2.2 Flood control structures

Brahmaputra Right Bank Embankment One of

the first embankments constructed in 1960s to

provide flood protection to about 230,000 ha

lying on the western side of the Brahmaputra-

Jamuna and Tista rivers. It is 217 km long and

extends from Kaunia in Rangpur at the northern

end up to Bera upazila in Sirajganj district at the

southern end. Construction of the embankment

started in 1963 and was completed in 1968 at a

cost of about Tk 80 million. The average height is

4.5m, crest width 6m and side slope 1:3 on both

sides. The embankment has been under constant

threat of erosion by the Jamuna river and needs

relocation further away from the riverbank. On

the other hand, no flood control embankment is

constructed on the left bank of the Jamuna river.

Figure 4 shows the Brahmaputra Right Embankment (BRE).

3. Data Collection

The study is based on primary and secondary information.

The primary information is collected form directly field and

the secondary information is collected from detail literature

survey. For primary data collection, PRA a technique of

social survey is conducted. In PRA, FGD and KII is mainly

used for data collection, near different bank protection

structures. FGD was conducted when fishers were back in

bank after fishing. By this way primary data was collected

from the field. The secondary data was collected from

different published journal, reports and from FAP 17 study.

After collection of field data, it was verified with different

literature, analyzed and after that the data are used in the

study.

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Figure 4: Brahmaputra Right Embankment(Source: Banglapedia)

Figure 5: The study area


For the study, protected and non protected bank of the river was selected. For the

protected bank, revetment and groyne of Shariakandi of Bogura, hard point and

Enayetpur spur of Sirajganj and Geo bag revetment of Bera, Pabna was selected, for non

protected bank downstream of the structures were selected. Figure 5 shows the study area.

4. Flow pattern

4.1 Near bank protection structures

For construction of the bank protection structure, the normal river flow is affected. For

observing the change of the river flow, ADCP (Acoustic Doppler Current Profile) data of

river profile was collected by Nazim et al. (2010). The flow patterns near the bank

protection structure are as follows. Here the Sirajganj hard point is considered as a

protected bank.

1) The flow pattern is continuously changes due to changing morphology of sand

bars, roughness and the configuration of the bank protection structure.

2) During monsoon the return flow become very much stronger than dry season.

3) The magnitude of velocity is relatively higher in the mid-channel.

4) The velocity adjacent to the hard point is amplified up to 2 times of the approach

flow velocity. It is also evident that the deep scour hole is located near the

upstream of hard point.

5) Primary

vortex is formed in the deep scour hole and it rotates anti-clockwise direction. At

the same time a secondary vortex is also developed and it rotates clockwise

direction.

Figure 6, shows the primary and secondary vortex in scour hole around Sirajgang

hardpoint.

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Figure 6: Primary vortex and secondary vortex in scour hole


4.2 Flow pattern near non protected bank

Without bank protection structure, the river flow is its natural state. There is no

disturbance, so there is no turbulence and no high water vortex. Only a slight water vortex

was observer near non protected bank. Less depth scour hole formed. Slight back flow

observer where fish take rest there and collect their food in that place. Some features of

non protected bank are given below.

1) Regular flow of river.

2) Water flow is normal.

3) No water vortex.

4) Near eroded bank, slight back flow found.

5) In deep channel, high velocity water flow and clam wave.

.

Figure 7 and 8 showing the normal flow pattern of river near a non protected bank.

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Figure 7: Flow pattern upstream of a bandal structure

Figure 8: Velocity vectors along vertical planes


4.3 Indigenous knowledge

According to the fisher’s knowledge, fish is less available in high vortex (ghurni) region.

Fishers, who are catching fish near the hard point, informed during KII, that less fish are

available near structure. Some uncommon and previously not available fish species are

found now a day, because of habitat change. And for that reason, fish is less available.

This information match with the above ADCP data.

5. Fish species

5.1 Dominant fish species near riverine structures

Near different riverine structures the following flow and species were observed. The

following Table 1 presents the findings.

Table 1: Species found near different bank protection structure

Name of the

Structures

Habitat

Characteristics

Name of Dominant Species

Revetment Thick deposited

sediments

Chingri, Puti, Kajuli

Hard Point High velocity, high

vortex, Deep scour

hole

Kalbaus, Air, Baghair, Pangas, Boal

Spur Thick deposited

sediments near

dumping cc blocks

Tengra, Baim, Baila, Puti, Kajuli

Groyne Thick deposited

sediments near

dumping cc blocks

Puti, Chingri, Tengra, Baila, Baim

Bandal Simple river flow Chingri, Puti, Baila, Kalbaus, Rui,

Katol.

As seen from the above table, near riverine structures the habitat changes and species

composition also change. The possible reasons are given below.

1) Near revetment, a thick layer of sediment is deposited, where sediment preferring

and bottom dwellers species such as Baila, Baim etc are found.

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2) High water velocity and high vortex observed near revetment, where species like

Air, Kalbaus are common which prefer high velocity.

3) Almost near all structures, deep scour hole and vortex are formed, where bottom

dwellers species are common. As a result, near spur, Tengra, Baim, Baila, Puti are

mostly available. Almost all of the same species are available near groyne.

4) A back flow is formed beside groyne and spurs, where fish is usually available.

5) Bandal dose not affect the river flow too much, so almost normal river flow was

observed and the common species of river are available there.

6. Conceptual framework for fish habitat change due to riverine structure

6.1Habitat change due to Erosion protection structure

Riverine structures damage the spawning, nursery and grazing field for fish. The shallow

char lands are acting as spawning, nursery and grazing fields for fish because fish feed are

available there, but riverine structures divert the flow, which directly hit the char land and

erosion takes place. The construction of spur diverts the upstream flow and down stream

of spur huge land is accreted that disrupt the connection with canals. Figure 9 shows the

erosion and accretion due to construction of bank protection structure.

Figure 9: The morphological and flow changes due to construction of spur

6.2 Habitat change for flood control structure

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Erosion

Spur

Flow diverted for spur

CharLand

Accretion

Bank line

Canal or connection with Flood

plain

Accretion at the mouth of channel

disconnected it from Main River


Flood plain – river migration is very important for the migratory fish. They spend some

important stages of their lifecycle in flood plain and again come back to the river.

Construction of flood control embankment cut off this migration cycle. And this is also a

main cause of decline of fish in Jamuna (FAP 12, 1992). Figure 10 shows the Migration

cycle of floodplain fish and the disruption for embankment.

Figure 10: Before and after construction of embankment (Source: Adpoted from Rahman,

2008.)

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Embankment


6.3 Overall causes of fish decline due to riverine structures

Figure 11 is prepared from the identified causes for fisheries resources declination due to

the bank protection and flood control structure.

Figure 11: Flow chart shows the linkage for fish decline and bank and riverine structure

6. Conclusion

Natural hydrological and morphological characteristics are important constituents of an

ideal fish habitat. But when the natural environment of the river is disturbed by the human

intervention, it become unfavorable as a fish habitat. For the river Jamuna, such situation

is common due to construction of different riverine structures. Due to change in habitat

near riverine structures, new and uncommon species are found. Bottom dwellers such as

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BankProtectionStructures

Flood control

Structure

Groyne

Spur

Hard point

Revetment

Embankment

De links the connection

between flood plain and river

Divert the natural flowof the river,

causes morphological

change

Erosion and accretion in char land, flow type change, high

vortex formed, high turbidity, rising of the river

bed

Migration, spawning,

nursery and grazing place of fish are affected

Fish decline in the Jamuna river


Baila, Baim species are found near spur because of deposition of thick sediment

there,.High velocity preference fish species such as Air, Baghair, Kalbaus are found near

hard point because high water velocity is present there. Such types of change in species

composition are observed near different structures.

7. Acknowledgement

This paper is produced as a part of research project “Hydraulic Profiling of the Important

fish Habitats of the Jamuna River” conducted by IWFM-BUET. The author also praise to

Mohammad Nazim Uddin, PhD student, IWFM-BUET, for providing the ADCP data to

fulfill the research and the paper.

8. ReferencesBest, James L, Ashworth, Philip, Sarker, M.H. and Roden, Julie (2007) “The

Brahmaputra-Jamuna River, Bangladesh” Wiley & Sons Ltd, Chichester.

FAP 12 (1992). FCD/I Agriculture study, Vol. 1, Main Report. Flood Plan Coordination organization, Ministry of Irrigation Water Development and Flood Control, Government of People’s Republic of Bangladesh.

FAP (Flood Action Plan) 17, (1995). “Final report - Main volume” Overseas Development Administration, UK.

Nazim Uddin M., Hoque. M. M., Rahman, M. M. (2010), “Flow Field Around Bank Protection Structures Along the Jamuna River”, 17th congress IAHR APD 2010, Paper no 3d043, 21th to 24th February, Auckland, New Zealand.

Rahman, M.M. 2008. Capture-based aquaculture of wild-caught Indian major carps in the Ganges Region of Bangladesh. In A. Lovatelli and P.F. Holthus (eds). Capture based aquaculture. Global overview. FAO Fisheries Technical Paper. No. 508. Rome,FAO. pp. 127–140.

Siddiqui, M.H. 1990. Flood control and drainage development: Physical Environmental issues. In: A.A. Rahman, S. Huq and Conway, G.R. (Editors), Environmental aspects of surface water systems of Bangladesh. University Press Ltd. Dhaka.

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Impact of Bank protection structures on riverine fisheries

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