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River management strategies for flood control and land accretion in coastal belt
Part A: River system, floods and Bangladesh
1. Introduction
Bangladesh is a country of rivers; and the results of delta building process of three major rivers; the Brahmaputra, the Ganges and the Meghna having water catchments areas outside Bangladesh. The total length of the river system is about 22,155 km. During May to October the internal water bodies usually cover a maximum of 1922 square km. (MPO, 1986). The land of the country is divided into three morpho-physiological zones viz. (1) the hills, (2) the terrace and (3) the flood plains. The flood plain zone is again sub-divided into (a) piedmont plains, (b) meander flood plains, (c) tidal flood plains, (d) estuarine flood plains, and (e) basins. Most of these zones are covered almost entirely by quaternary sediments deposited less than 2.4 million years ago. This deltaic country is inhabited by about 160 million people in 2009 and about 60% of the population are engaged in agricultural production activities; therefore, depends mostly on lands, rivers and the climate.
These rivers have their major catchments areas where the water comes from either as snow melts on the Himalayas or from the monsoon rains on the whole region covering Bangladesh and Indias Himalaya, Assam, Meghalaya. The average inundation areas within Bangladesh during flood periods since 1954 are somewhat more than 30,000sq.km/year, which is about 20% of the total area of the country (http://www. climateavenue. com/cl.imp. sealevelk. Bangladesh.htm
_________________________________________________________________ This chapter has been written with one title having two separte parts. The part one is river system management and the second one covers the land accretion in the coastal belt of the country. Bangladesh has only south for increase in her land mass for large popultion. So, there must adequate planning for increasing the land mass on the south.
According to Hofer & Messerli, (2006) the hydro-meteorological processes in the Himalayas are not the main causes for floods in Bangladesh. The combinations of simultaneous discharge peaks of the big rivers high runoff from the Meghalaya hills, heavy rainfall in Bangladesh, high ground water tables and spring tides creates particularly favourable conditions for large-scale flooding.
Lateral river embankments and disappearance of natural water storage areas in the low lands seem to have a significant impact on the flooding process. The frequent inundation of the country due to sudden rush of excess water and its stagnation period cause serious damage to the human lives, crops, livestock and property at scale that becomes difficult for the government alone to handle leading to call for support from different funds and countries. The strategies planned in this article, have more of theoretical base but when used with scientific details, the plans will be effective to control the floods and to the manage rivers system for years to come.
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2.0 The rivers and the lands
The region is located in the lower part of the Ganges, the Brahmaputra and the Meghna. These rivers receive their waters from 600,000 sq.km catchments areas outside the geographical boundaries of Bangladesh. The excessive rainfall and snow melting in India, Nepal and Bhutan cause huge quantum of water to rush through these rivers towards south of the country. Most of the water enters into Bangladesh through the Ganges and the Brahmaputra and it is internally distributed through their tributaries. The rivers Surma and Kushiyara receive water from Indian hills and carry into Bangladesh to form the Meghna. The waters of these major rivers covered most of the areas flooded in 1988. The inland water bodies including rivers (479,735 ha.), “bills”, “haors” and “baors” (114, 161 ha.) cover 593,896 hectares of land of the country. The estuarine rivers of the country covered 551,828 ha., thus the total water bodies is about 11,45,724 ha or about 10% of the total area of the country as per report of 25 years back (MPO, 1986). The delta building process has already reduced many of the water bodies and increased the shoal or char development within the river systems.
The rivers in Bangladesh are very extensive in areas as well as in lengths. The information related to the rivers their lengths and locations are recorded here in the table 6.11. Most of the rivers are carrying the waters towards the Bay of Bengal but the river beds due to siltation over years have risen more than expected. This is more so because the suspended sediments being brought by the rivers Brahmaputra and Ganges every year, close to their entry points to Bangladesh are about 387 and 212 million metric tons respectively (Table 6.1.2). These are in fact sediments from outside. These sediments are the results of deforestation in higher catchments and hilly areas that these river waters carry when passing through India, Nepal and Bhutan to Bangladesh. During the course of their still southward movement towards Bay of Bengal they erode the banks of the rivers and thereby add to the sediments in the lower part of the country. The river Meghna carry considerable lower quantity of sediments and these are also mostly the sediments of eroded banks from the upstream outside & within Bangladesh.
On the basis of the inundation of lands, the land types of Bangladesh have been grouped into five. These are: 1) high land (F0) inundation depth (<30cm) 2) medium high land (F1 30-90 cm) 3) medium low land (F2 90-180 cm) 4) low land (F3 > 180 cm) and 5) low to very low land (F4 > 180 cm continuous water) F1, F2, F3 and F4 are shallow, moderate, deep and very deeply flooded areas respectively of the country. According to present statistics the inundation land types from F1 to F4 cover more than 63% of the total cultivable land area of Bangladesh and the rest is F0 land type. Therefore, this 63% of the land remains under threat of inundation during heavy flood.
Sl. Rivers Length km Area covered(old districts) 1 Arial Khan 160 Faridpur (102) Barisal (58) 2 Bangshi 238 Mymensingh (198) Dhaka (40) 3 Betna-kholpotua 191 Jessore (103) Khulna (88) 4 Bhadra 193 Jessore (58) Khulna (135) 5 Bhairab 250 Jessore Khulna 6 Bhogai-Kongsho 225 Mymenshingh 7 Brahmaputra-Jamuna (207) 276 Rangpur (140) Pabna (136) 8 Buriganga 27 Dhaka (27) 9 Chitra 170 Kushtia (19) Jessore (151) 10 Dakatia 207 Comilla (180) Noakhali (27) 11 Dhaleshwari 160 Mymensingh, Dhaka 12 Dhanu-Baulai-Ghorautra 235 Mymensingh (126) Sylhet (109) 13 Donai-Charolkata Jamu neshwari Karotoa 450 Rangpur (193), Bogra (157), Pabna (100) 14 Ganges + Padma (258+120) 378 Rajshahi (145), Pabna (98), Dhaka & Faridpur (135) 15 Gorai, Madumati, Baleshwar 371 Kushtia( 37) Faridpur (71), Jessore (92) Khulna (104) Barisal (67) 16 Ghagat 236 Rangpur 17 Karotoa-Atrai-Gur-Gumani-Hurasagar 597 Dinajpur (259) Rajshahi(258) Pabna (80) 18 Krnafuly 180 Chittagong HT, Chittagong 19 Kobadak 260 Jessore (80) Khulna (180) 20 Kumar 162 Jessore Faridpur 21 Kushiyara 228 Sylhet 22 Little Feni-Dakatia 195 Noakhali (95) Comilla (100) 23 Lower Meghna 160 Chandpur to the Bay of Bengal 24 Matamuhuri 287 Chittagong HT and Chittagon 25 Mathabhanga 156 Rajshahi(60) Kushtia (140) 26 Nabagonga 230 Kushtia (26) Jessore (204) 27 Old Brahmaputra 276 Mymensingh 28 Punarbhaba 160 Dinajpur (80) Rajshahi (80) 29 Rupsa-Posur 141 Khulna 30 Sangu 173 Chittagong (80) Cittagong HT (93) 31 Surma-Meghna 670 Sylhet (290) Comilla (235), Barisal (145) 32 Tista 115 Rangpur
The stream flow of the Ganges, the Brahmaputra, the Padma and the Meghna were estimated to be of 71,000 m3/sec., 111,000 m3/sec., and 18,0003/sec. respectively. Table 5.1.1 Major rivers of Bangladesh with their
locations & lengths
Sl. Rivers Length km Area covered(old districts) 1 Arial Khan 160 Faridpur (102) Barisal (58) 2 Bangshi 238 Mymensingh (198) Dhaka (40) 3 Betna-kholpotua 191 Jessore (103) Khulna (88) 4 Bhadra 193 Jessore (58) Khulna (135) 5 Bhairab 250 Jessore Khulna 6 Bhogai-Kongsho 225 Mymenshingh 7 Brahmaputra-Jamuna (207)276 Rangpur (140) Pabna (136) 8 Buriganga 27 Dhaka (27) 9 Chitra 170 Kushtia (19) Jessore (151) 10 Dakatia 207 Comilla (180) Noakhali (27) 11 Dhaleshwari 160 Mymensingh, Dhaka 12 Dhanu-Baulai-Ghorautra 235 Mymensingh (126) Sylhet (109) 13 Donai-Charolkata Jamu neshwari Karotoa 450 Rangpur (193), Bogra (157), Pabna (100) 14 Ganges + Padma (258+120) 378 Rajshahi (145), Pabna (98), Dhaka & Faridpur (135) 15 Gorai, Madumati, Baleshwar 371 Kushtia( 37) Faridpur (71), Jessore (92) Khulna (104) Barisal (67) 16 Ghagat 236 Rangpur 17 Karotoa-Atrai-Gur-Gumani-Hurasagar 597 Dinajpur (259) Rajshahi(258) Pabna (80) 18 Krnafuly 180 Chittagong HT, Chittagong 19 Kobadak 260 Jessore (80) Khulna (180) 20 Kumar 162 Jessore Faridpur 21 Kushiyara 228 Sylhet 22 Little Feni-Dakatia 195 Noakhali (95) Comilla (100) 23 Lower Meghna 160 Chandpur to the Bay of Bengal 24 Matamuhuri 287 Chittagong HT and Chittagon 25 Mathabhanga 156 Rajshahi(60) Kushtia (140) 26 Nabagonga 230 Kushtia (26) Jessore (204) 27 Old Brahmaputra 276 Mymensingh 28 Punarbhaba 160 Dinajpur (80) Rajshahi (80) 29 Rupsa-Posur 141 Khulna 30 Sangu 173 Chittagong (80) Cittagong HT (93) 31 Surma-Meghna 670 Sylhet (290) Comilla (235), Barisal (145) 32 Tista 115 Rangpur Source: Banglapedia 2003, Volume 8 page 430 These rivers carry a huge quantum of suspended sediments every year that has a number of disadvantages with one benefit; that such sediments help increasing land mass, wherever these are settled in the process of being carried down with water towards the sea. This benefit could better be utilized if these sediments could be deposited more towards the southern part of the country than in the upstream. Deposition in the upstream is causing (a) river beds to rise; (b) irregular development of new “Shoal or char lands”, (c) blockade of navigational channels; (d) reduction of water storage area of the river(s); and (e) filling of basin areas or “bills” and “haors”.
Table 6.1.2. Annual suspended sediment discharge at selected locations
River/location Annual suspended sediment discharge 1) Brahmaputra river at Bahadurabad 387 million tons 2) Ganges river at Hardinge bridge a> 212 ” 3) Padma river at Baruria a> 563 ” 4) Old Brahmaputra river at Mymensingh 2 ” 5) Dhaleshwari river and Iagir 40 ” 6) Gorai river at Gorai ..... Bridge a> 30 ” 7) Gorai river at Kumarkhali a> 43 ”
a> post Farakka discharge condition Source: MPD 1986, Table 10.2, page 10-16
3.0 Delta building process
According to expert delta building process is a dynamic one and in many cases does not follow a regular pattern that can be used for a permanent solution. But in my opinion a balanced training of the river course is going to pay a good dividend in the long run. There was a programme on training of river courses of not only the major ones, but also their distributaries during the early Pakistani period. But much of the works could not be done in the subsequent years through 1969. Most of the commissions constituted on flood control studies starting from the mission in 1955 to IECO Master Plan (1965-85) in general, suggested river training through dredging and embankment development.
3.0 Floods
So far, there has not been any significant approach in the upstream of the rivers for development of embankment and to train the rivers while unusual meandering increased more rapidly due to heavy siltation every year. We can see the development stage of our delta in figure 1c as drawn by MPO, 1986 (page 10-20).
4.0 The floods
The Bangladesh region is the world’s biggest delta formation of three major rivers of Indian subcontinent. The recorded information indicates that the floods and flooding of the Bengal is almost a regular phenomenon of the area with population being adapted to live-with its furry. The Banglapedia records floods from 1781 to 2000 (page 161-2). These records indicate the nature of the floods and the districts mostly covered with devastating effects. Brief information for readers of this chapter of the book is also given in the tables 3 & 4. This recorded information indicates the severity of the floods in specific areas of the region falls within the geographic areas of Bangladesh today. It is important to note that the information on Cholera outbreak in epidemic form was recorded long back in 1838 and repeated in 1871 in Rajshahi. In case of the 1876 flood there was also records of Cholera Epidemic in Barisal belts.
The distribution of 20 year flood peaks in different major rivers of the country can give us an approximate idea of stream flow in these rivers. However, in my opinion, the 1987, 1988 and 1998 floods were also considerably influenced by high tide in Bay of Bengal that had strong force to keep back the waters following down through the river systems towards the sea. Sufferings of flood hit people knew no bounds. Dhaka was inundated to an extent that many of the developmental approaches taken for this city have been shattered. However, this flood has acted as an eye opener for our planning strategists not only for a city or town but also for the entire river system zones from F1 to F4 which went under water.
According to different experts, the following causes may be attributed to the flood of 1987, 1988 and 1998: 1. 15% rise in water due to Farakka Barrage; 2. 10% due to embankment in upstream; 3. 40% due to deforestation in upland around the upstream; 4. 10% due to silt carried from upstream Ganges and Brahmaputra and deposited inside Bangladesh; and 5. 25% due to raining and local problems in Bangladesh. 6. The additional information should have been due to high tide pressure on the river system resulting into slow downward movement of the river waters causing longer period of water stagnation and thereby inundation of larger areas.
According to the information given in the table 3 & 4, the floods of 1987 and 1988 and 1998 were unprecedented, the 1988 one being the most serious when most of the land mass was inundated. Records also showed that the flood affected areas of the country in 1998 was the highest when 68 per cent of the land mass of the country was affected. But in case of 1988 there were repeated floods also. During 1954 about 36,800sq.km area of Bangladesh went under water; while in 1987 and 1988 the figures rose to 57,300 and 89,970 sq.km. The last two figures were about 39 and 61 per cent of the total area of the country. It can be mentioned here that in 1973 there was 2274 miles of navigable water-ways in Bangladesh which got reduced to only 838 miles in 1975. In 1988 the river beds have risen so much that there is no navigability in 13 rivers of the country. The regression analyses, when made on the magnitude of increase in coverage of flood area in Bangladesh from 1954 up to 1988, the linear positive value of regression coefficient was high and significant. Therefore, the situation has earned an urgency to put the flood under human control. However, the general pattern of flooding that can be seen from the data in table 1 indicate that during 16 years from 1991 to 2007 average flooding area was 30,458 sq.km while that in the previous two series of 16 years(1973-1990 and 1954-1972) were 25,057 or 16.86% and 34,800 sq.km or 23.56% respectively. Thus the average of all these year’s data clearly indicate that the flooding is to the extent of at least 20% of the areas.
The 1987, 1988 and 1998 floods have also drawn the attention of most of the countries of the world. They have shown interest to help solve this recurrent problem of the country and of the region through internal, regional and international approaches. The author is not an expert in this line, but has over all studies aiming at finding solutions to reduce the adverse effects on agriculture and other economic activities, properties of the people living nearby the river banks and the offshore belts. These are also to share some of the ideas for both long-term and short-term solutions of the problem. It is necessary to understand more about the fearful rivers, the process of delta building, the river flow, the patterns of meandering, the frequency of flood, the drying-up of the rivers, etc. These are mainly to make efforts to solve at least part of problems and to continue to help development of strategies to finally overcome the problems possibility of getting this natural hazard under human control or to live-with over generations. There are numerous irregular char or shoal developed in side the rivers, particularly of the three big ones. These natural structures with silts and sand of various compositions have made the river banks also vulnerable to erosion. The loops are very frequent in the formation, which also creates more obstacles to fast running down of the river water allowing more silt depositions at the upstream than at the end near the sea. These situations indicate that it is necessary to understand the delta building process more in order to be able to direct the rivers in a definite line. It has been observed that the total land coverage during 1954 and 1963 was about46,800 sq.km (31.5%) while that in 1987 and 1988 stood at 73,639 sq.km. (50%) and that of 1998 and 2007 was 81,275 or 55%. This indicates increase in flooded areas over time from 1955 as can be seen from the data given in table 6.1.4.
Table6.1.3. Floods during Bitish period from 1781 to
1904 (Banglapedia, 2003)
Year Information related to floods 1781 Serious flood, more pronounced in western Sylhet cattle suffered 1786 Floods in Meghna, immense destruction on the villages on the banks, followed by famine, Gumti embankment gave way, Sylhet pargana entirely under water 1794 Gumti embankment burst again cause damage around Tippera 1822 Bakerganj division: Barisal, Patuakhali, Bhaola and Manpura were seriously afftected 39,940 people died 19,000 cattle perished & properties more than 130 million taka were destroyed 1825 Bakerganj district and adjoining areas flooded. No important embankments were there. 1838 Heavy rainfall caused floods in Rajshahi and number of other districts. Cholera epidemic took place. 1853 Annusl inundation was more pronounced than usual in Sylhet district 1864 Serious inundation took place embankment was breached and the Ganges water flood major part of the Rajshahi district 1865 Serious inundation took place in Rajshahi district & the town. 1867 Destructive floods in Bakerganj. Crop partially damaged 1871 Extensive inundation in Rajshahi and a few other districts. Cholera epidemic took place. Properties damaged. 1876 Barisal and Patuakhali were severely affected. Meghna out flowed about 6.71km from the sea level. A total of 215,000 people died. Cholera outbreak took place. 1879 Flooding Tista when change in the Brahmaputra began 1885 Serious floods outbreak Satkhira, Khulna area due to damage of Bhagirathi embankment 1890 Serious flood at Sathkhira damage to cattle and people 1900 Serious flood at Sathkhira, bursting of bhagirathi embankment 1902 In Sylhet there was a terrible flood Crops and valuable properties damaged 1904 Crops in some parts of Cox's Bazar & Kutubdia were damaged due to abnormally high tide. This year sever flood was in Mymenshigh which was parallel to that of 1879 when the change in the course of the Brahmaputra began. Table 6.1.4. Flood affected areas of Bangladesh
Year Flood affected areas Year Flood affected areas Year Flood affected areas Sq.km. % Sq.km. % Sq.km. % 1954 36,800 25 1973 29,800 20 1991 28,600 19
1955 (50,500) 34 1974 52,600 36 1992 2,000 1.4
1956 35,400 24 1975 16,600 11 1993 28,742 20
1960 28,400 19 1976 28,300 19 1994 419 0.2
1961 28,800 20 1977 12,500 8 1995 32,000 22
1962 37,200 25 1978 10,800 7 1996 35,800 24
1963 (43,100) 29 1980 33,000 22 1998 100,250 68
1964 31,000 21 1982 3,140 2 1999 32,000 22
1965 28,400 19 1983 11,100 7.5 2000 35,700 24
1966 33,400 23 1984 28,200 19 2001 4,000 2.8
1967 25,700 17 1985 11,400 8 2002 15,000 10
1968 37,200 25 1986 6,600 4 2003 21,500 14
1969 41,400 28 1987 (57,309) 39 2004 55,000 38
1970 42,400 29 1988 (89,970) 61 2005 17,850 12
1971 36,300 25 1989 6,100 4 2006 16,175 11
1972 20,800 14 1990 3,500 2.4 2007 62,300 42.2
Mean 34,800 23.6 X 25,057 16.9 X 30,458 20.7 Highest & 2nd highest flooded area & the averages are given here to compare the periods 1955 50,500 34% 1987 57,309 39% 1998 100,250 68% 1963 43,100 29% 1988 89,970 61% 2007 62,300 42 %
Mean 46,800 31.5 x 73,639 50 x 81,275 55
Source: Bangladesh’s haunting floods (http://www.climateavenue.com/cl.imp.sealevelk.Bangladesh.htm
4.0 The possibilities of reducing flood hazards
The background information’s given in this write-up have taken us to a position where from we can put some analyses and subsequent suggestions for controlling the floods with drainage as a prerequisite through different techniques of river training, construction of barrages and reservoirs of different sizes.
The question is, can we control the natural hazards of floods or to be adjusted to and live-with? The answer is yes we can reduce the impact of such hazards through scientifically developed sustained programmes. In such attempts the relative degree of positive impact on the economy of the country is enormous so is on the environment. The veteran irrigation and flood control expert of Bangladesh Late Mr. B.M. Abbas, suggested the following points for keeping the floods under control:
1. To construct dams in the upstream of the rivers flowing through Bangladesh. This will help create water reservoirs to hold the excess water during monsoon and to distribute it in dry season. 2. So much sedimentation has taken place in river beds that it is not possible to dredge the rivers and distributaries of the main rivers. 3. Unplanned constructions of railroads, roads, embankments, etc. are preventing the water channels and there is no regulators also on embankments, there should be adequate provisions for drainage. 4. The embankments on either side of the rivers must be maintained properly. 5. Penetration of sea water must be checked in the coastal areas by embankments. It is also necessary to prevent entry of high tide water through embankments. 6. For drainage & irrigation, canal digging is a good programme. (However, it should be well planned and beyond the influence of politics) 7. It is not possible to control flood in Bangladesh, but it is possible to reduce its furry through different techniques, good irrigation and drainage channels would contribute significantly to the control of floods.
These suggestions of those days are still applicable with appropriate modifications, which can be seen from the recommendations of the Flood Action Plan (FAP) as guidelines for any future programmes developed finally by the Bangladesh government in around 1998-2000. The most important messages that we can translate from those are only a few and are still valid for discussion and taking appropriate actions. A close look at the guide lines recommended based on FAP studies one can correlate the relevance of the expert opinion of the past years with the present situations.
Eleven guiding principles of FAP (Banglapedia Volume-4 p164)
1. Phased implementation of a comprehensive flood plain development aimed at: protecting rural infrastructure and controlled flooding to meet the needs of agriculture, fisheries, navigation, urban flashing annual recharges of surface and ground water resources;. 2. Effective land and water management in protected & unprotected areas. 3. Measures to strengthened flood preparedness and disaster management. 4. Improvement of flood forecasting and early warning. 5. Safe conveyance of the large cross-border flows to the Bay of Bengal by channeling it through the major rivers with the help of embankments on both sides. 6. River training to protect embankments and urban centers. 7. Reduction of flood flows in the major rivers by diversion into major distributaries and flood relief channels. 8. Channel improvement and structures to ensure efficient drainage and to promote conservation and regulations. 9. Flood plain zoning where applicable and possible. 10. Coordinated planning and construction of all rural roads, highways, railways and embankments with provisions for unimpeded drainage. 11. Encourage popular support by involving beneficiaries in the planning, design and operation of flood control and drainage works.
In addition to the immediate necessity indicated above, the most important decision has to be taken by the government whether it wants effective solution of both increasing water reserving capacity within country as well as to reduce the hazards of the floods and the incursion of salinity. Every government of the country should think seriously that the area of Bangladesh can get increased only in the south and the potentiality is high. This is due to carrying of huge silt loads through Ganges/Padma and Brahmaputra/Jamuna rivers. These points to my opinion or hypothesis whatever one calls are: 1. water flow from the upper riparian beyond Bangladesh is at a low level and will continue to be so in future, therefore, the present planning of increasing future water reserve within country is very urgent, particularly to reduce or delay the desertification process;
2. the water catchments areas within Bangladesh must be re-excavated with whatever resource we have not only for increasing flood water containment but also to irrigate from surface water sources to reduce possible incursion of heavy metals into our agricultural products and finally to the human body system;
3. increase in water reserving capacity in the upstream as well as close to saline belt or even within the belt will keep a continuous pressure on the upward incursion of saline water in the coastal belt and can be used for flushing out the river beds to increase navigability; and
4. government should, plan and execute excavation of water bodies and re-excavation of silted up water bodies of both upper-mid to down river areas faster than other areas, and appropriately protect even with involvement of armies as their duties. It is necessary that all citizens of the country know about the political decision of the government to address these problems as far as practically possible and as fast as possible, and not to give leap service only. In order to address this issue, I have considered some cases and described individually so that the planners can take the steps after studying the details of the ideas described here.
5.0 The case 1: The Brahmaputra
The Brahmaputra entered Bangladesh from the north and was previously flowing towards south-east forming Old Brahmaputra flood plain. The river in its entry point on eastern bank is flanked by terrace soil zone and is much older and stronger than the subsequently developed soils. The present Jamuna Channel of the Brahmaputra river is believed to have taken place due to catastrophic earthquakes of 1862 and 1882. Still the entry point of the river is in high risk zone of earthquake. The western bank of the river Brahmaputra (Jamuna channel) has an embankment starting from the north (Teesta confluence with Brahmaputra) going down to the confluence of this river with the Ganges. This embankment has been found to be threatened by flood water at many points particularly near Sirajgonj and Sariakandi and is a recurrent problem almost every year. This embankment needs to be strengthened, raised and stabilized. Stabilizing the embankment is even more important than its construction only. Afforestation of such embankments with deep rooted, long duration, thickly grown tree species appears to be a positive approach than to keep barren and allow nearby inhabitants to use in their own ways. It is therefore, necessary to do such works even now. In addition, widening of the embankment is also necessary so that the stabilizing process is effectively implemented and can serve multi-purpose needs in the long run. The eastern side of the river should have a similar, but wider and higher elevation embankment. Sufficient regulators will be required to regulate the water during flash flood. The embankment on this side should be planned for at least 15m. wide at the top and 10 meter height having sufficient slopes. This will help less damage in the embankment, but will be costly. The reduction of cost is possible by using the river dredged soils and through its use in economic activities of different nature when fully stabilized. In the stabilization attempt there should be densely seeded only Acacia plantations. This is suggested as because at least for a number of years there will be no human entry into the thorny dense trees and there should be punishment rule for damaging the plantation by any one of the nearby villagers or inhabitants. Such a wide embankment will help developing a parallel road links after a stabilization period of at least 5-8 years. The plantation on the river banks will be the “shared property” and investment forestry of the locally organized groups.
The embankment should be developed following more or less the present river course. In addition, there should be a number of regulators in the emergence point of Old Brahmaputra and other small rivers/canals wherever present. One important consideration has to be given on the southward direction of the rivers and wherever necessary excavation of small to big canals should be under taken to link the bigger rivers and basins taking the water-flow southwards. The barriers of south directions through roads etc. must be removed wherever necessary.
The dredging of the river Brahmaputra and using the soils in the embankment will serve three important purposes; viz.; 1) increase the capacity of water storage within in the river; 2) reduce the use of inside soil by digging long channels making the embankment vulnerable to flash flood pressure; and 3) increase the bottom pressure of the rushing water for clearing the river beds; at least near the vulnerable points created through dredging. 4) Near the upstream of the Jamuna bridge point excavation or dredging of the rivers must not take place. But on the down stream of the bridge keeping sufficient space dredging of the river should again start. The embankments established on the river banks will act as multipurpose communication & development areas resulting into more activities of the people around the areas for socio-economic development.
There are a number of big “shoals” or “chars” developed inside the rivers due mostly to the silt deposition and these are more in the Brahmaputra than in other rivers. These chars are having different shapes and sizes and some are quite old; while many others are fairly new and can be removed through effectively planned dredging. The dredging technique should be planned in such a fashion so that maximum hydraulic pressure of the river stream can be used for eroding the soils creating obstruction in the river beds. Again this dredging has to be done during the early period of the monsoon or when the stream flow is high. The fanning out or denting process of dredging will help more use of stream-flow energy for flashing out of the chars and thereby reducing the cost involvement. It will however, not be possible to clear the lands of this type by one stroke in one year. But a continuous attempt for two-three years will make the river beds clear for more speedy discharge of water. The Teesta barrage is completed as suggested previously and it is time, we take up the works of Brahmaputra barrage also. It is to be remembered that a nation can not remain under pressure from outside for all time to come.
6.0 The case 2. The Ganges
The southward movement of the flow of the proposed trained Brahmaputra (Jamuna channel) will face obstacles at its confluence with the Ganges. The area has been shown in figure 1a. it is an area which certainly requires correct decision and timely action. The second case has therefore, been analyzed here. The total volume of the flow of the Ganges is less than that of the Brahmaputra. It carries less suspended sediments than that of the other river. It again carries sediments of more degraded nature than that of the other. There is an embankment in some part of this river on its north bank in Rajshahi.
Based on the information given above, it is necessary to construct embankments on both sides of the river and the present one should be renovated and the new ones should be planned more carefully. The situation is similar to that of case 1, and similar action plans are suggested. Bringing in the water down to the confluence with more or less straightened river beds will cause a tremendous stream flow and hit the newly developed chars in the confluence area. The actions have to be completed during the period starting from the pre-early flash flood to the period before water starts receding. However, a vast quantum of the Ganges water will require to be diverted to Bhairab and Madhumati rivers through regulators. Coming to the confluence, the rivers will find a series of small and big “chars” in their ways of flashing those out to the sea. Now, it is a question of extremely technical details of hydrological engineering aiming at washing out of a big portion of these chars making channels for the easy flow of the water of major two rivers of the country. As a layman again, my suggestion is to find out the areas of char lands and dredge it in angles not more than 25o on either sides of the char keeping provisions for 40o to be hit by stream flow of the two rivers. It is also necessary to dredge these types of “chars” by V shape denting, which may help easy flashing out of the rest soils. It is to be mentioned here that the embankment on the northern bank of the river Ganges is close to the river. Such embankments are subject to more strong water force at the top and scouring/ eroding force at the bottom. So, the embankments on the other bank should be planned keeping sufficient distance from the present river bank. Also there should be dredging of the river sufficiently away from the north bank. Afforestation of the embankment is a must and should be strictly maintained for a period of at least 10 years through a mechanism developed in such a fashion that, after this period the benefits may be given to the land owners of the embankment and road communication be developed along the embankments.
7.0 The Case 3: The Padma
The river Padma from the confluence of the Brahmaputra and the Ganges is flowing down to a course of eastward direction to meet the course of Meghna in its confluence near Chandpur. This does not allow the river gain more speed in its stream flow. The river outlet (distributaries) towards south from this river is again not very straight or clearly big. The river Arial Khan distributing water towards southern direction, is flowing southwardly in a zigzag fashion resulting into low speed. The position of the river Kumar is also like that. Beds of both these rivers have seriously been raised due to siltation and non-dredging. The river banks are considerably strong and if flow speed is regulated at the entry point with lowering the bed of all distributaries by dredging; sufficient water can be stored in these rivers.
It is important to note that a sizable portion of the stream flow of 111,000m3/sec. of the Padma be diverted before it reaches Meghna which has a peak stream flow of 18,000m3/sec. This may be possible through straightening the rivers Kumar and Arial Khan and reactivating a number of canals of southern direction and regulating their flow from the entry point. The low-laying areas nearby these rivers will not be flooded to a very high depth, if the river embankments are high and regulators are set. When the river Padma has limited southward outlets and when under control from the upstream, water pressure will be tremendous and will hit the Meghna course, such pressure will be very high and will try to wash away part of the Chandpur town. This is not at all desirable. In order to save it, it is again necessary to partly influence the pressure of Meghna where the flows of all the three major river of the country have joined together.
8.0 Case No. 4: The Meghna
Coming to the case No. 4 the Meghna, it is possible to train this river again in a fashion shown for other rivers. Any one looking to the upper Meghna will see a number of developed char lands, these are obstructing the stream flow and allowing the river to take its own direction. In order to save the Chandpur area what has been done is an embankment which is threatened for erosion in many forms. This is because the up streams have not been trained rather an embankment has been put close to the area of the river system where maximum water flow is found. The river course of Meghna should be slowly pushed down in the same fashion as in other two rivers. This will in fact leave a breathing space for Chandpur town that should fully be exploited to get the embankments established more effectively. Is it not possible to construct groins using tall RCC pillars slowly down the shore? It is not a job of one year but boulders inside these pillars can help more than boulders in the open river. Is it not possible to start pilling angles that faces minimum pressure from the flash flood? It is possible to strengthen the new char developed very close to Chandpur and extend it further down to act as a direct resistance to the water pressure. Well it is a question of how sincere and dedicated we are to get rid of this chronic problem. Even a vast area of the land east of the present town should be developed slowly to push back the town. This is also because the Meghna river is in high risk zone of earthquakes and may change its course any time.
9.0 The case 5: The beels, haors & baors
I think, I have written much about the rivers. I will now give my readers some ideas about the Bills/haors and Baors of the country. These are in fact perennial water reservoirs. In the past, these bills used to hold a large quantum of waters annually. The present area of these ‘beels’ are about 114,000 hectares. Now a day many of these areas are put under cultivation of rice in Boro season. This F4 type of land should be kept as the natural water bodies. Excavation works should be under taken to make them more & more deep every year as far as possible. The increase in water storability in these basins will help upland irrigation in dry season more economic resulting into much production of not only crops but also fish. At the same time will contain a large quantity of water during the flood period & rainy season which also will help better recharging of the aquifers.
There are a number of natural depressions in many areas of the country under a good planning and implementation of the plan these areas could be developed into natural water bodies to store excess water not only for fish culture and irrigation but also to reduce pressure of floods. In the red soil areas of Mymensingh, Dhaka and Tangail large areas of depressions locally called ‘bydh’ may be developed as water holding bodies. This will also increase aquifer re-charging capacity in these areas where the water reserve capacity is low and the ground water table is being lowered every year with more and more suctions for water use in the cities and towns and intensive cropping in winter season. Similarly, creation of new & large water reservoirs in the northern and southern parts of the country will help increased irrigation coverage including better drainage for increase in agricultural production.
10. Other considerations
It may seem likely that suggestion about embankments and dredging of rivers all over the country, partly it is yes, partly it is no. This is because we need to train the rivers and lead them to the seas. Starting from Krug mission and the FAP all have recommended for embankments and training of the rivers to take them down to the sea as very important ones. In order to prevent flood & protect East Pakistan there was plans like this where in the map produced on 8.12.1969, one will find embankments, dams and barrages all over the country. But it was not implemented. However, parts of the plan have been implemented with variable modifications resulting into more difficult situation than expected.
Flood control and drainage through training & dredging the rivers and using their hydraulic force for cleaning the river beds has the biggest advantage of low cost involvement nd time saving. Use of reservoir system through two dams/ barrages one on Brahmaputra and one on Ganges will increase reserve waters for dry season. We can flash-out our river system whenever required. But all these will require huge fund. And every one will agree that we don’t have so much money. In my opinion we have money or we can have money provided we are sincere and honest in utilizing the same. Citizens of Bangladesh and Government of outside countries are donating crores of taka, but these are not being used for a permanent solution. We are about 160 million people now. 10 taka each will create a fund of more than 1600 million a day a day or a week. This is an example. There are people who can and should contribute in millions and tens of millions and they will do it when requested for. Only issue is honest expenditure with honest and sincere people designing and executing the works.. There are countries, which can extend technical and financial assistance for handling such programmes step-wise. We have armed forces and we can use their organized service for executing the programmes in a more disciplined way. We have also a number of programme oriented organizations like BWDB, IWTA and others to execute the programmes of dredging with added funds and manpower under a central command of sincere and honest people with powers to handle the issues as it come along without having political stooges to interfere. However, I am not suggesting the fattening of these organizations, if the works can not be handled by them. In that case there should be alternatives too. We do not have large number of dredgers for use, but we can get those on loans from friendly countries provided we don’t burn the oil for nothing. The Chinese river Hoangho is no more designated as the sorrow of China. Can we not do something which will recreate Bangladesh, help us getting more and more lands in the Bay of Bengal, and make our efforts successful for future generations? We are trying for flood control with India, Nepal, Bhutan, and China mostly with India. Well, it is possible. But what we have seen from the handing over of Tin bigha corridor for Dahagram and Angorpota to Bangladesh. Today we are 40 years old and have not been able to get this land leased other than getting only the right to use 24 hours a day. This had been instead of all possible efforts. Have we been able to get the due share of Ganges water? To my opinion we must stand on our own to have our decent living. A disaster control council has been constituted on 30th September, 1988. Well a body like this with the President/Prime Minister as its Chairman should have gone a long way in collecting fund and directing the bodies responsible for execution of plans but not to interfere with the technical programmes once finalized by the technical experts on the political plea of one or the other issu. But we have not seen something tangible till to date? Had there been any effective plan and execution programme of the same other than consultancy service/for FAP and like others we could possibly do a lot more for solving the problems of river systems, recurrent floods, loss of lives and properties of millions taking shelter in bastis of big cities like Dhaka?
11.0 Conclusion
Recurrence of flood must be checked. Coordinated and Integrated approach is a need of the time. River training is a basic need to minimize the possible hydrological and ecological imbalance created otherwise. (i) In order to do so, it is necessary to start dredging and embankment construction in the full length of rivers. There is strong possibility of using the hydraulic force for dredging/ clearing the river beds using dredgers in serial line applying a system to use highest force of the water current for flushing out the chars towards the downstream. (ii) In course of the dredging of rivers one has to identify the most vulnerable points of the river beds never close to the banks but certainly at a distance from banks that will not increase bank erosion. (iii) Construction of embankment is essential but maintenance is more important. Therefore, the breadth and the elevation of the embankment and the tires should be well designed and must be afforested with deep rooted, rapidly grown easily non-usable trees. (iv) There should be honest planning execution of the plans where the Armed forces should serve as a catalytic agent in getting the works done in time. Punishment should be given for week construction of embankments and regulators. Fund generation for the programmes should be well planned and not to be burnt out in diesel, petrol and hifi vehicles to use by project people and other-wise. The straight canal digging programmes should be well planned and executed. The canal digging should be free of local influence that usually results into zig zag path way for water. The one bank of the canal should serve as the embankment as well as roads. The help from friendly countries for dredging the lands more than money alone may be sought for. Minimum costs for consultants should be allowed for their work. If required the whole population of 20 years and above may be mobilized for different works over a fixed period, but should be well-planned and to be used regionally. There should be a clear-cut political will for solving problems of flood control, drainage development and maintenance of internal water bodies.