August 13, 1955 THE ECONOMIC WEEKLY Are Rivers in the Siliguri-Amingaon Section of N E Railway a Challenge to Engineers?

Kumud Bhushan Ray

NORTH-EAST India's ordeal by area of the river basins in Bihar, basins is not always restricted to water begins with the beginning Bengal and Assam, lying between the any one loop channel. Sometimes of the floods in July. The Assam foot-hills of the Himalayas and the the water flows through one chan­ Rail Link has again been snapped outfalls of the rivers into the Ganga nel and sometimes through another; in more place? than one. (Fig. 1). and Brahmaputra. Watershed ma­ the flow through these several loop The Assam Access Road has also nagement and afforestation in such channels is seldom kept under obser­ suffered a .similar fate (Fig. 2). desolate and sparsely inhabited re­ vation. It may happen that the How As flood damage has become an gions, would encounter colossal diffi­ through one channel goes on im­ annual phenomenon, the public ap­ culties and involve enormous costs. proving and consequently the flow through another, which was so long pears to be under the impression that Breaches and Loop Channels engineers do not fully realise the carrying the main discharge of the It may now be studied why breach­ river basin, goes on diminishing. great force of a river, which they es occur in the Assam Rail Link. try to harness. It is widely believed When the improving loop channel Fig. 2 shows in greater detail the becomes the main river of the river that deforestation in the upper Torsa and Kaljani Rivers, which catchments of the rivers in the Hima­ basin, the bridge over it may not cross the Assam Rail Link and the have sufficient waterway to pass layas is the cause of flood and that Assam Access Road. It will be seen the Governments of Tibet, Nepal, the total discharge of the river basin. that the Torsa River has developed, There is then damage to the bridge, Sikkirn and Bhutan, where these by erosion of banks, in its upper catchments lie, should be persuaded or the approach embankments are reach a channel about half a mile overtopped and breached. to take up and maintain watershed wide. From the point where it management and afforestation works emerges from the foot-hills of the The usual procedure, while re­ and only if this is done, India can Himalayas in Bhutan on to the be spared this annual ordeal. building the breached bridge, or plains, it has many loop channels— making up the breached embank­ The Hood damages this year in Mujnai, Burhi Torsa, Chhota Torsa, ments, is to provide additional spans Uttar Pradesh from rivers, whose Burha or Sili Torsa, etc. The Mujnai, to the bridge. But it is found that catchment area lies in the alluvial Burhi Torsa and a few smaller loop this does not provide a permanent plains, show that the deforestation channels have their outfalls into the safeguard. In course of time, an­ in the upper catchments of the river Jaldhaka, while the Chhota Torsa, other loop channel starts improving, cannot be the real cause of the flood. Burha Torsa and some smaller ones and ultimately the whole discharge Fig. 1 will show that the area of have their outfalls back into the of the River Basin may pass through the catchment basins in the Hima­ Torsa. The Kaljani has also many it in which case similar flood dama­ layas, lying in Tibet, Nepal, Sikkim loop channels. ges will occur. Considering that all and Bhutan, is more than twice the The flow of water in these river the rivers crossing this section of

970 THE ECONOMIC WEEKLY August 13, 1955

As the Manas Loop Channel could and breached. Successive bridges not accommodate and drain away with larger waterways were then the discharge of the Manas Basin, provided over the Beki Loop Chan­ there was backing up and rise of nel, from 1909 to 1945 ; water level in the channel upstream, (i) 4 x12' (ii) 4 x20' (iii) 9 x 20' so that a part of the water found its (iv) 1x50', 1x30', 6x19' (v) 1 x 50', way through the shallow but 2 x 40', 6 x19' (vi) 2 x 40', 3 x100', straighter Beki Loop Channel to its (vii) 7 x150'. outfall at T (Fig. 1). A cataract As a result of increasing flow action started at T, which dug back through the Beki Loop, less and less and back along the Beki Loop T S water flowed through the Manas until it reached E, the railway cross­ Loop, so that in 1945, water flowed ing, and further upstream to A where through only 4 x 100' out of the a cut-off channel was established. 10 x 100' spans, while the river bed More and more water flowed through had risen 14 feet in the Manas Loop this cut-off channel in the Beki Loop, Channel. which went on. improving, while less and less water flowed through the In the Beki Loop Channel, there Manas Loop, which went on deterio­ was also erosion of river banks and rating. development of a tortuous channel C D E F G, lengthening its course As the Beki Loop gradually im­ and flattening its S W S while the proved, and its channel became widening and shallowing of its chan­ the N E Railway and the Assam deeper, the 4 x 12' span bridge with nel gradually decreased the HMD. Access Road have several loop chan­ shallow foundation was undermined With consequent decreasing velocity, nels, breaches are likely to go on occurring, in the process of improve­ ment of one loop channel and the consequent deterioration of another. Vagaries of Rivers The cause of these variations in a river channel may now be studied. Fig. 3 shows the several loop chan­ nels in the Manas Basin—Manas, Bholukadoba, New Hakua, Old Hakua, Beki, etc. At the time of railway construction in Assam in 1909, the main flow in the Manas River Basin was through the Manas Loop Channel. The bridges provided at the time over the three Loop Channels were: Manas 10 x 100' Bholookadoba 2 x 75' Beki or Mara (dead) Manas 4 x 12' Between the years 1901) and 1945, more and more water started flow­ ing through the Beki Loop Channel and consequently less and less water flowed through the Manas Loop Channel. It may now be examined why this happened. The Manas had a more or less straight channel between A and K in 1948, (See Fig. 3). Below K, due to erosion of river banks, a tortuous channel K L M N developed, which continued below the railway bridge. The channel also became wider and shallower and had islands and sand banks. The greater length of the tortuous channel flattened the Slope of Water Surface (S W S), while the wider and shallower channel de­ creased the Hydraulic Mean Depth (HMD). Thus the velocity of flow and consequently the discharging capacity of the Manas Loop Channel gradually decreased 971 August 13, 1955 THE ECONOMIC WEEKLY

972 THE ECONOMIC WEEKLY August 13, 1955 the discharging capacity of the Beki Channels exist not only in the Manas nel, which will improve and become Loop decreased, there was backing River Basin, but also elsewhere. the NEW KOSI. up and rise of water level in the Beki Mention has already been made The Yellow River Basin Loop Channel upstream, and water of Loop Channels in the Torsa and It has been mentioned that in the found its way through the Bholuka- Kaljani River Basins in Bengal. Manas River Basin, a former aban­ doba Loop Channel to its outfall at Similarly in Bihar, there are several doned eastern Loop Channel—the V (Fig 1). A cataract action from loop channels in the Kosi River Beki or the Mara (dead) Manas— V upstreamwards gradually improved Basin. Loop Channels also exist in became the New Manas, while the the Bholukadoba Loop, deepening its the Yellow River Basin in China. Old Manas Loop Channel gradually channel. Successive bridges with Can all these River Basins be classed deteriorated from 1909 to 1945. larger waterways had to be provided as undeveloped? in the Bholukadoba Loop Channel: Similarly in the Yellow River Basin The Kosi River Basin in China, a former abandoned loop (i) 2 x 75', (ii) 3 x 75', (iii) 1 x 250', The Kosi has several loop channels channel has at present become the 2 x 150'. (Fig 1). There is considerable ero­ main river. A careful record is kept After the breaches in the bridges sion of river banks in the alluvial of the many loop channels in the over the loop channels in the Manas plains of Bihar, resulting in the deve­ Yellow River Basin, as shown in River Basin, it was decided to stop lopment of a tortuous course and a Fig. 4. The water of the Yellow the How of water through the Beki wide and shallow channel. The velo­ River Basin (lowed through the loop Loop Channel, by the construction city and consequently the discharg­ channel A from 2278 B C to 602 of the Motaguri Bund at A (Fig. 3). ing capacity in such a channel gra­ B C, through B from 601 B C to The aim was that there would be no dually diminishes. There is backing 11 A D, C from 12 A D to 1048 A D, flow through the Beki Loop Channel, up and rise in water levels and over­ D from 1049 A D to 1194 A D, E so that the waters of the Manas flow away from the channel, so that from 1195 A D to 1494 A D, F from River Basin would have to river-side lands are submerged and 1495 A D to 1855 A D, G from flow through the Manas Loop there is flood damage. 1856 A D to 1938 A D and Channel, which had a bridge H from 1939 A D to 1946 A D. From The choked up and abandoned east­ 1947, the Yellow River is again flow­ over it of 10 x 100' spans. ern loop channels in the Kosi River As expected, the upper reach A H of ing through its former loop channel Basin are not. able to accommodate G: Such vagaries of rivers arc the Manas Loop improved But as and drain away the overflow water. the tortuous, wide and shallow length explained by uncontrolled erosion of Hence practically the whole of the river banks. K L M N of the Manas Loop was not­ overflow water finds its way into a able to accommodate and drain away parallel western river. A cataract Erosion of River Banks the increased flow, there was back­ action starts at this point, which digs As already explained, erosion of ing up and rise of water level, en­ back and back, establishing a cut­ river banks by the development of abling it to find its way through the off channel. More and more Kosi a tortuous alignment and by the shallow but straighter channel of the water flows through the western widening and shallowing of chan­ New Hakua Loop, having an outfall river, which goes on improving, while nel, gradually decreases the velocity into the Beki Loop, avoiding the tor­ less and less writer flows through of flow, and consequently the dis­ tuous part of the Beki Loop Channel the Kosi Channel, which is ultimate­ charging capacity of a loop channel C D E F (Fig 3), The cataract ly choked up and abandoned. The gradually decreases. Overflow water action at F dug back and back, im­ western river thus becomes the New finds its way into another loop chan­ proving the New Hakua Loop Chan­ Kosi. nel, which is thus improved. If this nel. Manas water thus continued improvement goes on, the latter be­ Erosion of river banks continues to flow through the Beki Loop Chan­ comes the main channel of the River in the New Kosi. The same process nel Bridge of 7 x 150' spans. The Basin. object of diverting the flow of water is repeated. Another western river The flood damages from the livers of the Manas River Basin through is improved and becomes the Newer Gomti, Tons etc. in the U P the Manas Loop Channel, having a Kosi, while the New Kosi channel is are due to the deterioration of their bridge of 10 x100' spans, was thus choked up and abandoned. The west­ channels, caused by the development frustrated. ward movement of the Kosi has gone on in this manner. of tortuous alignments and widening Belief in Undeveloped River Basins and shallowing of channel by ero­ It will be seen from Fig 1 that the sion of river banks. This frustration gave rise to the Kosi now flows through the lower belief that the Manas River Basin is reach of the Tilajuga and Balan Similarly flood damages from the still undeveloped and that vagaries of Rivers, and that there is no longer Teesta, Brahmaputra and other rivers in such a river basin cannot a parallel western river. With in­ rivers in N. K. India are due to the be stopped. This caused so much creasing deterioration of the present very wide and consequently shallow pessimism that there was a proposal Kosi Loop Channel, in the process of channels developed by these rivers, to abandon the railway line between erosion of river banks, with no west­ as a result of erosion of river hanks. Bongaigaon and Amingaon, to have ern river to drain away the overflow A Challenge to Engineers a diversion railway line from Bon­ water from the Kosi Channel, flood The challenge to engineers from gaigaon to Joghighopa, to cross the water level in the Kosi will become rivers cannot be met by building Brahmaputra by a bridge, and to progressively higher, causing- sub­ additional spans to the waterways have a new railway line to Gauhati mergence of greater areas of river­ in bridges in the Assam Rail Tank, along the left or south bank of the side lands to greater depths and for or in the Assam Access Road or by Brahmaputra (Fig. 1). longer periods. In this process, the having Watersheil Management in That the belief in an undeveloped higher level of Kosi water is likely Upper River Catchments by Affore­ River Basin is unfounded, will be to find its way through a former station etc. or by building check evident from the fact that Loop abandoned Eastern Kosi Loop Chan- dams across the rivers in the hills. 973 August 13, 1955 THE ECONOMIC WEEKLY

A survey has to be made of all alignments joined by flat curves. to straighten the river alignment up­ the Loop Channels, whether flowing Such an improved flowing Loop stream of the railway bridge, by as­ or choked up and abandoned, in a Channel in a River Basin will then sisting the river to reclaim an em- River Basin. Action should be taken be able to accommodate and drain bayment 3000 feet long, with a maxi­ in the main flowing Loop Channel away quickly the maximum flood mum width of 1000 feet and a maxi­ in the River Basin, so that its wide discharge through its channel. With mum depth of water of 40 feet, by and shallow channel with a tortuous adequate waterway, provided in the laying a line of improved "bandall- alignment is guided to a single, nar­ bridge over an improved Loop Chan­ ing". Fig. 5 shows photographic row and deep channel, having nel, there can be no unexpected in­ prints of "bandalling" used in the straight alignments, joined by fiat crease in discharge, likely to damage Beki River. curves. Such a channel maintains a the bridge or the bridge approaches. stable alignment in good order. The challenge to Engineers by "Bandalling" has been used by rivers in the Siliguri-Amingaon Sec­ This may be done by assisting a Steamer Companies to maintain tion of the N. E. Railway can be met river to utilise the great force of its navigable depth in wide and shallow by assisting a flowing Loop Chan­ current of water—its power of trans­ rivers in Northern India. As this nel in a River Basin to improve its portation of silt and of erosion of type of "bandalling" is liable to be the channel surface to deposit silt undermined in the flood season, an channel by the use of "Bandalling". to form new parallel river banks, improved type known as "permeable The cost per running foot varies having a single narrow and deep screens" was used in 1049 by the from Rs. 20 to Rs. 40 depending on channel in between, with straight author in the Beki River in Assam, the depth of water. Agricultural Labour I — Pattern of Occupation and Employment ( Continued from last Issue )

THE general rural occupational cultural adult male labourers were of both the tables is the relative pattern and the employment sta­ fully unemployed were collected stability of unemployment from tus of agricultural labourers have month to month for a period of one month to month. That is to say, been discussed in the last issue. An year. In doing so, only those labour­ in zones where a large part of agri­ attempt is made below to analyse ers were taken into account in any cultural labour is unemployed, quite the findings of the Agricultural month who reported wage-paid em­ a substantial part of it is unemploy­ Labour Enquiry, regarding the extent ployment for at least one day in that ed during the whole year. The of unemployment and self-employ­ month" (emphasis ours). Here number of clays in a month that ment among agricultural labourers "fully unemployed" is deceptive as labour is unable to get employment and to examine how far these find­ labour unable to secure wage-paid shows as great, if not greater stabi­ ings answer some of the issues posed employment may yet get part-time lity, The picture of agricultural em­ earlier in the article. work or be self-employed. ployment that emerges from these tables is quite different from the ac­ Naturally, the most difficult part cepted picture of rural agriculture of the investigation was the measure­ viz that or long spells of uninterrupt­ ment of the extent of unemployment ed idleness alternating with short and under-employment. The Enquiry spells of brisk activity. The assump­ does not go into conceptual difficul­ tion, therefore, on which the case for ties. It takes the working day as supplementary rural industry is the unit of measurement of labour usually supported as part time occu­ time. Thus, variations in the hours pation for agricultural labour as of work during different agricultural well as the basis of much of current seasons are ignored; but that is not thinking on agricultural problems so important as the distinction be­ would be seriously shaken by these tween employment and under-employ­ findings. ment which the Enquiry found so difficult to measure precisely. Con­ Unemployment is well spread over fining itself, first, to wage-paid agri­ the month. Where it is high, it is cultural and male labour only, it set fairly high even in the peak em­ out the number of days such labour ployment period. Again, the num­ was unemployed. That is to say, the ber of days in a month that labour information was collected only about is unable to get job is larger in some visible unemployment which is de­ states, and comparatively small in fined, as lack of wage-paid employ­ others. But whatever it is, it is ment. It is recognised that unem­ the inter-zonal variations which are ployment defined thus also includes pronounced rather than the varia­ under-employment. But it is not An idea of the volume of un­ tion in the same zone as between quite clear whether this is always employment, subject to above quali­ one part of the year and another. borne in mind; for instance, the fications, can be gathered from opening paragraph in the section Table VI which gives in the all-India Equally striking is the extent of "Unemployment of men workers", averages. Zone-wise figures (Table unemployment even at the peak reads as follows: "Data on the num­ VII) show wider variations, but period of agricultural activity. Tak­ ber of days during which the agri- even so, the most striking feature ing India as a whole, 13 per cent 974