An SOS From Dhaka
Every year, uncontrolled flooding in the Brahmaputra and Ganges river basins results in loss of life, damage to crops, dwellings and other properties, contamination of water supplies, the spreading of waterborne disease and disruption of orderly social and economic progress. Despite the building of barriers, dikes and levees to protect against flooding, major floods continue to cause extensive damage and prevent full utilisation of the land. Attempts to clear and maintain river channels, to assure the passage of water without obstruction, and to protect river banks and embankments with "river training works" have proven expensive and only marginally effective.
The future trend is likely to be one of increased flooding. Changes in the catchments beyond Bangladesh's northern and eastern borders — caused by deforestation and more intensive land use — are increasing the sediments carried by rivers and leading to bigger and bigger floods. Concurrently with the floods, the south-west monsoon winds raise the mean tide levels in the Bay of Bengal, reducing the slope and, hence, the rivers' discharge. Other factors which contribute to flooding are heavy rainfall, flat topography of the land, siltation of riverbeds and development of the flood plains.
It is clear that flooding is on the increase year by year. There was a severe flood in 1987, followed in 1988 by a flood of catastrophic proportions. It surpassed all previous records in terms of water levels and the extent of inundation (see Nov/Dec Himal). Almost three-fourths of the country, including Dhaka, went under water. Hundreds lost their lives, railways and roads were washed away, and the loss of major crops was nearly total. Bangladesh's economy was crippled.
While flooding in Bangladesh has long been viewed as a natural phenomenon, a combination of human factors appears to have created and exacerbated the country's vulnerability to flooding. Most experts consider that the major manmade cause is deforestation in the catchments of the major rivers lying in Nepal and India. The upstream developments, including the Farakka Barrage on the Ganges about 11 miles upstream from the border, also contribute significantly.
A special feature of the 1988 flood was that the flow in the major rivers peaked within days of each other. Generally, the Meghna is at its highest in May-June, the Brahmaputra in July- August, and the Ganges in August-September — with a time lag of 15 to 30 days between the peaks. In 1988, the Ganges achieved its peak on 31 August and the Brahmaputra on 2 September. The Meghna recorded its highest level on 10 September.
This unusual occurrence may be the result of some upheaval in the Himalayan region. Most probably, it was the result of extensive deforestation in the catchment area. The effect of topsoil washing off the Himalayan slopes is into the rivers is that the carrying capacity of the rivers is drastically reduced. The vegetal and tree cover binds the soil and acts as an absorber of heavy rainfall. When this cover is removed, the torrential which pound the region during the monsoons can cause havoc.
Development of the river channels upstream have further compounded Bangladesh's water problem. The flood embankments constructed along the rivers prevent the rivers from spilling over into natural storage areas. Control structures built on the major rivers and their tributaries add to the problem. The Farakka Barrage, in particular, poses a dual threat to Bangladesh. On the one hand, during the dry season, a large portion of the Ganges water is diverted into the Hooghly, drastically reducing the Ganges' flow into Bangladesh. On the other hand, during the monsoon, there is a sudden rush of water into Bangladesh when it is already facing flooding conditions.
The control of floods requires regulation of monsoon flows. There is no possibility of storing water in the low lying delta of Bangladesh. Storage reservoirs can only be created in the hills, suitable sites for which exist in Nepal, Bhutan and India. Besides controlling floods, such storage dams will also provide for flood control, generate hydropower, augment dry season flows of rivers, allow navigation, and assist in various ways the agricultural, forestry and mineral sectors in the river basins.
About a tenth of mankind lives in the Ganges and Brahmaputra basins, among them a quarter of the world's most poor. This, despite the fact that the two basins have rich alluvial soil and tremendous energy potential in the river flow, as yet almost untapped.
The rising population is putting serious strains on resources and the question of simple survival looms large. Environmental destruction is taking place at a virtually irreversible rate. Unemployment and social tensions are growing rapidly. The time for regional action for water resources development is now.
B.M. Abbas A.T., an engineer by training, has worked on the Ganges-Brahmaputra water system for decades and has served as Bangladesh's Minister for Water Resources. He has represented Pakistan and, after 1971, Bangladesh, as chief negotiator on water talks with India.
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