The Brahmaputra's Changing River Ecology

Dr AK Das says that we need to learn from the traditional knowledge and wisdom of people while dealing with floods.

The great earthquake of 1950 created havoc, especially in the upper reaches of the Himalaya, in and around the Siang and the Debang river courses as well as in the upper Assam plains. There was considerable impact on the topography on both sides of the Brahmaputra valley. This natural calamity was mainly responsible for abrupt changes in the river ecology. The Brahmaputra and its many tributaries in upper Assam suffered badly due to blockage caused by uprooted trees, boulders and soil erosion.

The first casualty was the small township of Sadiya on the north bank in the North Eastern Frontier Agency, now Arunachal Pradesh. Due to the change of the Digaru river's course, the entire township was eroded in a very short time. This was followed by soil erosion of the Brahmaputra in and around Dibrugarh town on the south bank in upper Assam. About one-third of the total area of the township was eroded, cutting across the horseshoe-shaped bank of the river. A considerable population had to be shifted to safety.

This was a major ecological disturbance faced by the people of Dibrugarh and surrounding areas. There were, however, quick responses to the situation using traditional means without dependance on outside relief measures. Prior to this great earthquake, Dibrugarh town and the neighbouring areas experienced floods a couple of times in the rainy season. On many occasions, low-lying areas adjacent to the river were under waist-deep water. Water usually entered the town from two sides: from the Brahmaputra itself in the north and from the Dibaru, a small channel, in the southeast. The southeastern part of the town was a little higher. These were the outskirts of the town surrounded by tea gardens and paddy fields, while the northwest part of the township was at a lower elevation so floodwaters regularly inundated the houses in the area. As a long-term measure, several houses in this area were built on platforms, including the official residence of the district administration. Such houses were traditionally called changbangla or changghar. A few such houses still exist in the town as an epitaph of the past.

Dibrugarh was a very green town with lots of trees. Kathal, pipal, simalu, bargad, nahar, litchi, mango, ajar and many other valuable trees grew luxuriantly. Wherever there was fallow land, wild herbs, shrubs and bushes were common. Prior to the introduction of the tube-well, there were traditional wells, both kechanad (without a brick lining) and patanad (with a lining). The water was good. There were several privately-owned ponds in the town, as well as marshy land full of meteka (water hyacinth) and other aquatic vegetation, some of which was edible. These ponds were used for fishing in the lean season and were never a health hazard. Malaria occurred occasionally but not on an epidemic scale, unlike recent times, since fish and other aquatic creatures kept the ponds clean and the floods ensured that they were regularly flushed.

The floods which occurred regularly in suburban Dibrugarh due to the Brahmaputra were not considered a threat to local people. Traditional wisdom allowed people to predict their occurrence, magnitude and duration remarkably accurately. Sometimes certain natural signs were taken into consideration such as the movement of ants, the appearance of certain plant species, the behaviour of the gagini insect (a species of locust), some actions of birds and animals, etc. Well before the floods came, people were ready to tackle them with age-old means. If necessary, they moved to an elevated place. Otherwise country boats were used or rafts called bhoor made of the trunk of plantain and split bamboo were quickly assembled. The use of boats and plantain rafts was in fact a pastime for the people of the town during the floods and young children would enjoy swimming in the floodwaters that filled their courtyards!

Another popular pastime connected with the floods was fishing, mostly by a method called dewapata. A barrier is created against the flow with a bamboo dewa (a sort of loose matting) or occasionally by placing boulders across the channel. Fish swimming in with flowing water would jump over the barrier and fall on a net or a piece of cloth which kept hanging just below the dewa. During the floods, plenty of fish were caught with traditional devices such as porangi jal (a lever-operated deep net), jakoi, polo (basket traps), etc.

Once the floods had receded, life returned to normal. There was no panic because of epidemics, no worry about paddy transplantation or kitchen gardens. Nor was there any concern about obtaining clean water because the brick-lined wells remained unpolluted. After the floods, which occurred twice or thrice during the rainy season, the agricultural land in and around Dibrugarh became fertile due to siltation, locally called palash para. After each inundation of the paddy fields, the harvest was invariably good. Vegetables grown after the floods were found to be of good quality, especially leafy vegetables such as cabbage, cauliflower and mustard, as well as carrots, potatoes and turnips. The town was full of wild vegetables such as dhikia (a kind of fern), khutara (a leafy vegetable), matikadene (a medicinal plant), manimuni, videli lata, etc. There were also medicinal herbs which were traditionally used as antiseptics and painkillers, remedies for coughs and colds, stomach diseases, etc.

This was the idyllic ecological situation in and around the Brahmaputra river in upper Assam prior to the great earthquake. There was a natural balance between humans and the river and at no time did people hate the river for its fury. The Brahmaputra was considered both sacred and secular. During Magha Sankranti, people preferred to take a holy dip in the Brahmaputra rather than the Ganga.

The earthquake caused a topographical disturbance in the riverbed due to the deposition of soil, gravel, tree trunks and branches from the badly damaged mountain. A strong undercurrent started cutting the soft soil of the bank on the Dibrugarh side, taking houses and trees into the turbulent river. Engineering measures were taken to stop the soil erosion. Several dykes of boulders were built across the river to divert the dangerous undercurrent along the riverbank covering the entire eroded zone. This measure saved the town but created problems for areas outside the protective cover of the dykes. Because of the flood control and soil erosion measures, there was a gradual change in the river ecology in and around Dibrugarh town. Its impact on day-to-day life was evident at a later stage.

Dykes protected the township yet created problems for areas outside the protective cover. Fishing, which was a regular feature near the riverbank, became impossible.
A whole village of fisherfolk living on the bank was displaced and had to change their lifestyle.
With engineering success in controlling erosion, attention was given to flood control. The embankment constructed along the riverbank across the length of the town stopped floodwaters, but in a few years, the results of the flood control measures were reflected in the changing riverine ecology and the corresponding impact on the lifestyle of the people. The river's fury became a nightmare with breaches during peak flood times and the possibility of flash floods.
Since Dibrugarh lies in a heavy rainfall zone, during the rainy season, water started accumulating inside the town and the low-lying areas, as the embankment interfered with natural drainage. This became the source for health hazards, especially in the northwestern part of the town. To solve this new problem, a drain was dug through the length and breadth of the town. The canal served its purpose for some time but gradually became more of a repository for polluted water due to the deposition of debris and frequent blockages.

We have seen two contrasting realities when we take into account the pre-earthquake and post-earthquake ecology in Dibrugarh. In the pre-earthquake period, there was complete harmony between the people and the river. Floods were tackled indigenously and were not considered a menace. The recurring floods were responsible for the fertility of the soil, for flushing out stagnant water and also resulted in an enhanced fish catch. In the post-earthquake period, because of engineering measures, there was a gradual change in the river's ecology in and around Dibrugarh, which resulted in socio-economic problems, such as:

The embankment which was erected to protect the town from floods has become a source of fear for people in the recent past. It has created a constant threat of flash floods during heavy rains due to a possible breach in the embankment. People living adjacent to the river have had to be shifted to multi-storied buildings or to higher ground several times in the past.
The stoppage of the annual silting action of the floodwaters has been reflected in falling productivity in the agricultural sector. This has led to an increased use of chemical fertilisers with resultant adverse impacts on human health and the environment.
Fish have become more expensive and rare because of the dykes and the natural drying of the ponds.
The drain across the length of the town has become a health hazard and is now a constant source of water pollution.
In pre-earthquake times, Dibrugarh was a green town. Due to the change in the river ecology, there are now fewer trees, shrubs and medicinal herbs.

Though there are many other observations relating to the changing river ecology in and around Dibrugarh, the primary objective of this article is to show that there is a need for understanding the traditional wisdom of the people and infusing their traditional knowledge into ecological and natural crisis management. The lifestyle of the people of Dibrugarh, once attuned to the river ecology has been alienated by engineering measures and other development work without considering need-based long-term planning.

This is an example of modern ecological management in which the significance of the cultural dimension has been totally neglected while tackling changing river ecology. In modern scientific parameters, the cultural component is peripheral to the planning process and ignoring this results in disastrous after-effects. In such an approach, the short-term results overshadow long-term holistic requirements. This is quite apparent in the case of the Brahmaputra's changing river ecology in the Dibrugarh region.

Keeping in view the traditional knowledge and experience of the people who have lived their lives in harmony with the river, the following long-term ecological management measures would have been the right prescription for this particular region:

Soil erosion by the Brahmaputra is a natural process. This has happened in the past as and when there were disturbances in the riverbed and is continuing today.
Natural erosion should have been allowed to continue till it reached a stage of saturation.
Instead of constructing an artificial embankment to prevent river water from overflowing the bank and into low-lying areas, the natural process of flooding should have been allowed to continue. With the gradual removal of debris either naturally or by mechanical means, the fury of the floods would have eased in the course of time.

There are lessons in the experience of Dibrugarh. Planners need to study traditional ecological crisis management systems in further depth and with more respect, to make these methods more effective in dealing with recurring floods and soil erosion.

Dr AK Das is the Maulana Azad Chair Professor (ICCR endowment) with the National Museum Institute of History of Art, Conservation and Museology, New Delhi. This article was first presented during the conference on the 'Cultural dimension of education and ecology', held in New Delhi on October 13 to 16, 1995 as a part of the UNESCO Chair activities organised by the Indira Gandhi National Centre for the Arts (IGNCA). This has been subsequently published by IGNCA in 'The Cultural dimensions of ecology'.